FXAK68 PAFC 051419 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 519 AM AKST Fri Jan 5 2018 .ANALYSIS AND UPPER LEVELS... It is a tale of two domains this morning. In the east, high pressure is building in. This is resulting in offshore gaps winds in the usual locales (Seward, Whittier, Valdez). It is also making for a fairly wide swath of fog and low stratus across much of South Central. This fog shows up very well on POES Satellite imagery and it is banked up along the Chugach and Kenai Mountains in addition to filling in many of the valleys of the Kenai Peninsula. Out west, it is quite a different story. A potent 80 kt finger of the subtropical jet is pushing a strong warm front through the Eastern Aleutians and the Alaska Peninsula. Winds along this front are approaching warning-level (75 mph) in places like Cold Bay, but we expect those strong gusts to be limited in extent and frequency. Nonetheless, very gusty southeast winds will continue from the Alaska Peninsula and into SW AK courtesy of this front. Several other surface low pressure centers are developing along this boundary. The one that will eventually emerge as the dominant low into the weekend is over the west central Bering Sea bringing its own swath of gale-force winds along with it. && .MODEL DISCUSSION... Models continue to come into better agreement with the upcoming pattern. Thus, forecast confidence going into the weekend is moderate to high. The most challenging part of the forecast is when the fog and low stratus will ultimately lift around the Anchorage Bowl and the rest of Southcentral. With an increasing offshore gradient and drier air moving in, we are still thinking it will dissipate by later this morning. Otherwise, the only other significant change to the forecast was to continue to increase winds and PoPs along the Gulf Coast this weekend. All models continue to trend a bit stronger with this feature, so we utilized the GFS to add some more detail. The GFS also came into better agreement with the other solutions in handling the parent low over the Bering, so it was used for forecast adjustments out there as well. Yet another storm-force low will make its way towards the Aleutians on Sun. While there are some minor differences with this system, there is a strong general consensus it will bring another round of wind and rain. && .AVIATION... PANC...The fog/stratus continues to lurk around the Anchorage Bowl. As northerly winds continue and usher in drier air, it should continue to dissipate. However, there is still a fair chance it could "slosh" off the Chugach and back over the terminal during the morning hours. Once the fog threat is over, VFR conditions will persist with light northerly winds. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... Upper level high pressure over southern Alaska will slowly drift north today. Gap winds will decrease today as the associated surface high weakens. Some fog and low stratus will linger this morning, then dissipate in the afternoon as the ridge moves away. A front will move into the southwest Gulf today, with precipitation and winds reaching southern Kodiak by late morning and Kodiak City by early afternoon, and then to the north Gulf Coast tonight. A triple point low will develop along this front just southeast of Kodiak Island around midnight tonight. This low will move into the northern Gulf Saturday, setting up south of Seward Saturday evening and remaining nearly stationary through Saturday night while slowly weakening. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)... A potent low is looming down range from Southwest Alaska. A front will push eastward today with robust southeasterly winds across the southern Alaska Peninsula. The low has already bottomed out and the winds for the most part will stay below warning thresholds, with perhaps just a few isolated peak wind gusts up to 75 mph. The front stalls but will still bring precipitation into the coastal areas. The biggest impact will be strong southeasterly winds, particularly in the Bristol Bay area and into the Kuskokwim Delta. As the forecast period unfolds, the front will decay and the remnants of the upper trough will lift northward across Southwest. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)... A pair of lows will impact the Bering. A 950 mb low north of Adak will continue to push north and later wobble northwestward and bring unsettled conditions to the Central and Western Bering. A second low south near Unalaska will trek northeastward and become an open wave. The tight pressure gradient will continue to deliver more gusty conditions today with a peak wind of 64 knots recorded at Cold Bay early this morning. Expect storm/gale force winds for much of the Bering into tomorrow. In association with the aforementioned lows, warm air has advected into the Bering Sea and multiple locations along the chain will see max temperatures in the 40s today and tomorrow. Additional shortwave energy will be ejected from the vortex which will later be in the Western Bering, bringing a shot of cooler temperatures as the trough propagates across the Aleutians. && .LONG TERM FORECAST (Days 4 through 7)... The weather looking into early next week will be dominated by continued storminess over the Bering Sea/Aleutians with a ridge of high pressure over the Mainland. The most impactful system in this period will begin late Sunday with a storm force low that will move it the Central Bering. This system looks to bring widespread gales to much of the Bering Sea region to the Southwest coast, but likely will not move much further inland as high pressure over the Mainland holds. This should allow for temperatures to remain at or below normal for most of the Mainland with clear skies through Tuesday with impacts largely confined to possibility of outflow winds to the Gulf Coast. This pattern then looks to break down slightly towards the middle of next week as the high pressure begins to slide eastward into the Yukon. This would allow storminess to return to the Southwest Mainland and possibly the Western Gulf, however confidence in this pattern shift is low as the models are typically too quick to break down Mainland ridging in the extended forecast. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...None. MARINE...Storm Warning 150 155 160 165 180 181 185. Gale Warning 119 120 127 130 131 132 136 138 139 170 173 174 175 176 177 178 179. && $$ SYNOPSIS AND MODEL DISCUSSION...MSO SOUTHCENTRAL ALASKA...BL SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PS LONG TERM...DEK  FXAK68 PAFC 031334 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 434 AM AKST Thu Jan 3 2019 .ANALYSIS AND UPPER LEVELS... There is a vortex of cold air over Eastern Siberia, with this frigid air pushing over the Bering. The models and the ASCAT/advanced scatterometer data have detected several weak and decaying surface lows over the Bering but the most organized lows are well south of 50N. Not surprising, the jet core is also south of 50N. The longwave trough clearly spans from Russia across the Bering and into Western Alaska. Looking at the temperatures aloft and at the surface, there is a blanket of Arctic air south of the Aleutians, albeit slightly modified and a brutal cold airmass over the interior. The radars at Bethel (PABC), Kenai (PAHG) and Middleton Islands (PAIH) have snow showers on them early this morning. && .MODEL DISCUSSION... The NAM, GFS and ECMWF are in decent agreement with the placement of the synoptic features over the AKPEN, Southcentral and the Gulf Of Alaska. By 00z Saturday, the same models rapidly bring a strong low in the Western and Central Aleutians but there is no consensus for the placement of the surface low on Saturday. The GFS and the ECMWF have more similar tracks, but the NAM is an outlier. This divergence in solutions is already present at 36hrs which does not bode well for the remainder of the forecast package especially for the zones west of 170W as the timing of the gale/storm force winds and precipitation shield is a function of the accuracy of the low. && .AVIATION... PANC...A band of light snow has moved into the region and the ceiling dropped below 5,000 feet over night. Generally expecting VFR conditions however, cannot rule out the possibility of brief MVFR conditions based on the presence of low clouds on the AVHRR satellite image over Knik Arm and portions of the northern Cook Inlet. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... The upper level trough is over the Talkeetna Mountains and into Prince William Sound early this morning. It will continue to move eastward today allowing the much colder air to the west to move into the area. Temperatures will drop though the day over northern Cook Inlet through the Susitna Valley as cloud cover decreases. Some embedded short waves over the next few days may bring in some periods of high clouds which could bump the temperatures up a little as they are overhead, but it will be a generally cold period. Outflow winds will increase today but the pattern is not conducive for extremely strong winds since there is no strong low in the Gulf of Alaska. This will also keep the Matanuska River winds that often occur during cold periods from occurring, at least for the next few days. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2: Today and Friday)... Parts of Southwest Alaska are getting a little bit of snow this morning as a weakening front moves into the coast. The front is producing snow showers over the Kuskokwim Delta near Bethel and south alon gthe coast to Dillingham this morning. Continued weakening is expected for the rest of the morning which will result in the snow showers diminishing as well as the move inland. Otherwise, expect mostly cloudy skies and mainly dry conditions across Southwest Alaska today as temperatures stuggle into the single digits and teens along the Kuskokwim Valley and 20s along the coast. Tonight, another weak low and associated front will restart the snow showers, once again mainly at the coast, though some may drift inland, especially Friday morning. Once again none of the snow showers are expected to be heavy or long in duration. The snow showers will diminish into Friday evening. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2: Today and Friday)... As expected, the Bering remains mostly quiet this morning, however a few small, weak systems are producing snow showers in localized areas, including the Pribilofs this morning. Those snow showers will slowly weaken as they move into the eastern Bering today. Otherwise, scattered snow showers are expected for the rest of the Bering through tonight. More active weather will begin across the Western and Central Aleutians Friday morning in advance of a strong area of low pressure approaching the islands. While at least a mix of snow and rain is expected, temperatures should remain above freezing, so any accumulations of snow will be minor. The primary weather hazard with this storm are strong winds, which will be sustained above 35 mph, especially the closer to the low you get. By Friday evening, the center of the low will have crossed the chain into the Western Bering. Cold advection to the south of the low will cross the Aleutians, producing winds nearing 50 kt as the low peaks in intensity Friday night. Gusts will near hurricane force, and have been included in the forecasts at 60 kt by Saturday morning. The leading front will approach the Pribilofs early Saturday morning. While winds are likely to be at or above 35 kt as it passes, for now it seems enough warm air will be present to at least have a mix of rain and snow, and should it stay all snow, temperatures will be in the mid 30s, which will limit any of the snow being resuspended. Finally, the front will be through the Pribilofs in 6 hours or less, so any reduced visibilities and potential heavy snow will be brief. && .LONG TERM FORECAST (Days 4 through 7)... Beginning the extended period forecast on Saturday evening, there will be a strong storm force low over the western Bering Sea and associated upper low with a developing high amplitude blocking high over Eastern Siberia. Over Southern Alaska, there will be a series of weak upper level waves merging into a consolidated trough. With time, the upper trough over the mainland will deepen in response to the building blocking high over the high latitudes, so this will keep a storm track over the Bering Sea with cold and dry high pressure forming over Southern Alaska. This pattern will last through Tuesday until high uncertainty develops with the development and placement of an arctic low over Alaska. The ECWMF and GFS both show a low, but the GFS favors a quicker transition to southwest progressive flow from the Pacific which would eventually bring in more precip threats as early as Tuesday whereas the ECMWF favors a much colder and longer lasting dry spell, through at least Wednesday. Due to the anomalous ECMWF upper level pattern, and overall high uncertainty with developing arctic lows, this forecast will trend in more precip threats beginning Tuesday. Precipitation threats will likely be all snow given the cold air which will be in place, but for now, there is no strong signal. && .MARINE (Days 3 through 5)... Beginning the extended period marine forecast, the main impacts will be a developing storm force low over the western Bering Sea on Friday. The low track is now highly certain with a general track moving along and then north of Attu Island. The front will extend northward into the Bering on Saturday and may reach storm force as the low tracks north. With an easterly component to the winds, heavy freezing spray may become an issue closer to the ice edge. Another powerful storm force low is on track to move into the western Bering again on Sunday and Sunday night. Confidence with this second low is quite good, and model trends have remained consistent. In the Gulf of Alaska waters, with the storm track over the Bering Sea, there is high confidence that winds will remain well below gale force through the period. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...413 411 175 176 177. FIRE WEATHER...NONE. && $$ SYNOPSIS AND MODEL DISCUSSION...PJS SOUTHCENTRAL ALASKA...EZ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JPW MARINE/LONG TERM...DL  FXAK68 PAFC 041342 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 442 AM AKST Fri Jan 4 2019 .ANALYSIS AND UPPER LEVELS... The longwave pattern features a broad trough from Eastern Siberia to Western Alaska. There is a ridge axis which spans from Hawaii to the Central Aleutians which will serve as a break between storms. There is a strong jet core south of 50N but a sliver of the jet is breaking off and curving towards the Bering. The remnants of a decaying low has brought some moisture into portions of southwest AK and the radar at Bethel (PABC) has pinged into a band of snow. Looking at the temperatures aloft and at the surface, there is a cold airmass in place which has originated from the Siberian vortex but the arctic intrusion is being displaced away from the Western Aleutians as the next occluded system moves in from the North Pacific. Looking at Southcentral, specialized satellite imagery has detected several areas of fog over portions of the Anchorage Metro Area and the Kenai Peninsula. Last but not least, the Copper River Basin continues to stockpile brutally cold and dense air. && .MODEL DISCUSSION... The models have converged on a solution for the Western Bering and North Pacific for today and Saturday. The consensus is mirrored over the Alaskan Interior through to the Gulf Of Alaska. Model divergence begins to creep into the domain on Sunday morning but its predominately with the decaying low near Kamchatka. The other low near Attu and the frontal boundary pushing across the Aleutians looks well-synced through Sunday. Other than the pesky fog issues in Southcentral, above normal confidence with the sensible weather highlights through the weekend. && .AVIATION... PANC...On the Nighttime Microphysics and AVHRR (which are both satellite products) there is a bank of fog over portions of Knik Arm, Turnagain Arm, in the Anchorage Bowl and down to PAEN. The metars around the area all have light to calm winds which supports the notion that its pretty stagnate in the boundary layer. The fog situation is being actively monitored. Degraded flight categories due to reduced visibilities and low cigs likely at PANC this morning. The other very plausible possibility is that the bank of fog may just remain in the vicinity. Amendments will be made as needed. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... With high pressure over Southcentral Alaska the only issues to look into for today are the outflow winds and fog potential. The low level northerly flow over Cook Inlet and the Susitna Valley caused fog to pack up along the Chugach and Kenai Mountains overnight. Nighttime microphysics imagery from the GOES 17 satellite is showing this fog through Knik Arm and most of Anchorage and engulfing Turnagain Arm and part of the Kenai Peninsula. This fog may be a little stubborn to completely clear out as the light northerly flow will persist. However, some high clouds from a weak short wave may help to disrupt the fog as it moves over the area later today. Fog has also developed in the Copper River Basin and it increasing in coverage early this morning. This fog may also be difficult to get rid of today into tonight. There are some outflow winds along the North Gulf coast bringing some gusty conditions to Seward and Whittier as well as through passes such as Thompson Pass. With the overall pattern remaining the same though tomorrow, these winds should persist. The winds that often develop which are not developing yet are the Matanuska River winds. The pressure gradient shifts very slightly tonight which could allow some to develop, but even if they do the gradient will not be strong enough for them to be very strong. Even so, it will be worth keeping an eye on as they can sometimes develop even without a very tight pressure gradient. This is especially true when the Copper River Basin temperatures are well below zero which they already are, and will be getting colder. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today through Sunday)... Diminishing of the snowfall rates across the Kuskokwim Delta is already underway as a front moving into the area from the Bering shears apart. Nevertheless due to a bit of upsloping, the snow may persist east of Bethel along the mountains through the rest of the morning. Further south, as the front moves through Bristol Bay this morning, a similar effect of some upslope may allow some snow showers to develop near King Salmon this morning and slowly drift eastward towards the Iliamna area this afternoon. Elsewhere, some patchy fog may develop in some of the same areas that will get snow earlier in the day due to the extra moisture added to the atmosphere from the snow and light and variable winds. All precipitation will end tonight with continued seasonably cold temperatures persisting. On the way behind it is another front that looks to be an interesting example of meteorological de ja vu all over again. The front will approach the Kuskokwim Delta from the west Saturday night, potentially causing briefly moderate snowfall rates around Bethel overnight. Then the front will rapidly weaken as it tracks eastward, but lingering snow showers along the west sides of the mountains may persist into the day on Sunday. Thus, it appears to be nearly a repeat of the event going on right now for most of the area. Elsewhere, winds look to remain light and variable for nearly all of Southwest Alaska through Sunday with the exception of some gustier conditions along the coast Saturday evening as the front moves in from the Bering. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Today through Sunday)... Not much is going on across the vast majority of the Bering this morning as high pressure over the eastern two-thirds of the Basin keeps weather conditions quiet. However, the first of two storm systems is quickly approaching the western and central Aleutians that will keep the area active for the next several days. The strengthening storm system will produce widespread gale force winds with storm force gusts over most of that area as it tracks to the west of the Date Line this afternoon. Behind the low, a "sting jet" is already appearing on satellite, which itself is expected to produce storm force winds and gusts approaching hurricane force over the Western Aleutians starting tonight and persisting into the day Saturday. The storm weakens and moves to the northwest, nearing the Kamchatka Peninsula Saturday night. The leading front associated with this low will be the one approaching mainland Alaska Saturday night as well with that front shearing apart as it moves into Southwest Alaska. Even as this first low weakens, the second one will be right on its heels on Saturday night. Currently the center is expected to track over or near Shemya early Sunday morning. Most of the strongest winds with this system will be east of the low in the warmer southerly flow out ahead of the center. This means the strongest winds which currently also look to get to storm force will take aim mainly on the central Aleutians, including Adak and Atka, late Saturday night into the day on Sunday. The low center will slowly continue moving into the northwestern Bering Sunday night as its leading front sweeps across the Bering, bringing gusty southeasterly winds to the Pribilofs and Eastern Aleutians Sunday night, then rapidly weakens and shears apart beyond that as it approaches the Kuskokwim Delta coast and Alaska Peninsula Monday morning. && .LONG TERM FORECAST (Days 4 through 7)... An Arctic high over northern AK and Canada will continue to bring cold dry conditions and offshore flow to Southcentral and Southwest AK through early next week. Expect temperatures to be below climo normal for the first time this winter for most of Southcentral. The last few runs of the GFS and EC have positioned the axis of the high over the Yukon, indicating very cold conditions in the Copper River Basin. Meanwhile, models continue to indicate a storm force, or high end gale force low impacting the Aleutians and western Bering Sea Sunday then winds should diminish and precipitation will transition to a showery pattern Monday as the low shifts northward into the central Bering Sea. Expect a series of weak fronts associated with the low to bring onshore flow and potential for precipitation to the AKPEN, Bristol Bay, and Y-K Delta areas early next week. There's uncertainty with the timing of these waves given the dependence on the exact progression of that main low, which has differed between various models and runs. High pressure over Southcentral will erode by mid next week, bringing increasing chances for precipitation by the second half of the week. && .MARINE (Days 3 through 5)... A storm force low will move into the western Bering Sea Sunday then track north toward Eastern Siberia by Monday. The front will bring a swath of southerly gale/storm force winds to the Central Bering Sea before the front exits the north Bering Sea Monday night. Much quieter weather moves into the Bering Tuesday as the storm track shifts south. Over the Gulf waters, the weather regime will remain quiet as north/northwest offshore winds remain below gale force. A weak front moves into the Gulf waters on Tuesday, but the front will be weakening and also currently looks to remain below gale force. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...Gale 165 170 171 172 173 174 175 176 177 179 181 411 412 413 414. Storm 178 185. && $$ SYNOPSIS AND MODEL DISCUSSION...PJS SOUTHCENTRAL ALASKA...EZ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JPW MARINE/LONG TERM...JA  FXAK68 PAFC 051412 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 512 AM AKST Sat Jan 5 2019 .ANALYSIS AND UPPER LEVELS... There is a deep surface low northwest of Adak with an occluded front extending from it. And there is a triple point low that has formed south of Nikolski. In the latest ASCAT/advanced scatterometer pass there is a large area of high pressure at the surface from the Gulf Of Alaska to south of the AKPEN. There is a fierce jet core south of the chain and the longwave pattern is becoming more amplified. The radars at King Salmon, Middleton Island and Kenai are all clear. There does appear to be one shower on the Bethel radar but it isn't anything impressive. On the GOES Nighttime Microphysics and the AVHRR (which are both satellite products) fog and low clouds have been detected again over portions of Knik Arm, Turnagain Arm and in the Anchorage Metro area. The coldest area for the southern tier of Alaska remains the Copper River Basin where temperatures are handily into negative territory. && .MODEL DISCUSSION... Models continue to remain in sync with the synoptic features through the short-term forecast period. Overall, forecast confidence remains above normal for the Bering/Aleutians and SW AK. The only fly in the ointment remains the fog issues over Southcentral Alaska. && .AVIATION... PANC...Looking at Southcentral Alaska, specialized satellite imagery has detected several areas of fog and low clouds over portions of the Anchorage Bowl and the Kenai Peninsula. Compared to 24 hrs ago, the fog bank is smaller. Looking at the metars the bases of these clouds are under 500 feet in some places. More fog and LIFR conditions are possible this morning for PANC. The boundary layer is generally stagnate based on the light winds and the presence of an inversion on the skew-t for Anchorage. There are discernible breaks in the clouds and fog but it difficult to pinpoint when VFR conditions will materialize over PANC. The situation is actively being monitored and amendments will be made when necessary. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... The overall pattern over Southcentral is similar to yesterday with a weak upper level ridge over the area and a weak surface trough in the northern Gulf of Alaska. A weak short wave is washing out as it crosses over the upper level ridge and bringing in a few higher clouds to the Cook Inlet region and Susitna Valley. This is helping to diminish the extent of the fog around Cook Inlet though patchy fog is likely to move in and out throughout the day. The Copper River Basin will likely remain with some fog/low stratus in the lower elevations as there is just not much mixing of the air to dissipate it. A difference from yesterday is that instead of significant fog in the Glennallen area with lows in the single-digits below zero, the fog has lifted to a stratus ceiling and temperatures have plunged to more than 20 below zero. This is indicating that there is a chance the stratus diminishes and clears out today, however think it is more likely to wait until tomorrow so forecast reflects that. Outflow winds along the north Gulf coast will persist through the weekend. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3/Saturday through Monday)... A low level stratus deck currently sits over southwest Alaska, along with some fog and light snow showers. This stratus deck is the result of a cold air intrusion from the north, whose flow is clearly depicted on satellite. These conditions are expected to persist today as there are no real kickers to change the pattern. What will be the kicker comes in tonight through tomorrow in the form of the frontal system currently moving across the Aleutian Islands. When it reaches southwest Alaska, it will bring a shift in the wind direction and a band of precip that should dispatch the stratus deck in place. After this front moves through, there will be some brief clearing in the weather before the next front moves in late Monday. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3/Saturday through Monday)... Two large low pressures systems with storm force winds will work their way through the Bering Sea and Aleutian Island chain the next couple of days. The first storm is currently moving through the Western Aleutians, with an elongated front that is well removed from the low center. This front moving through the Central and Eastern Aleutians today and will produce snow/rain and gusty winds. The storm force winds with this system are more associated with the low center and in the Western Aleutians and Central Bering. Tomorrow into tomorrow night the next low will move north across the western edge of the Aleutians. A band of storm force winds will push through the western Aleutians in association with frontal system with this low, which is a bit different than the low currently moving through the area. It will also bring a strong band of precipitation with it. After this low pushes through the region, the Bering and Aleutian Island Chain will be quiet for the remainder of the short term. && .MARINE (Days 3 through 5)... Monday evening, the Bering Sea will be "quieting down" behind a two strong storm force lows. The remnants of the last storm force low will be moving into the Bering Strait. This period of time from Monday night through Wednesday will be characterized by very broad low pressure with a couple of weak fronts moving in from the North Pacific. At this juncture, these lows look rather weak and will likely remain below gale force. The next front of interest comes late Wednesday night as it moves north into the western Bering Sea and east toward the Central Aleutians. This front will likely support strong gales to low end storm force winds. Over the Gulf waters, a weak front will move onto the North Gulf Coast Monday night, but winds will continue to remain below gale force as the storm track remains well south of the area. && .LONG TERM FORECAST (Days 3 through 7)...An Arctic high over northern AK and Canada will continue to bring cold dry conditions and offshore flow to Southcentral and Southwest AK through mid to late next week. Monday into Wednesday, several shortwaves will rotate around a low situated over the Bering Sea, bringing periods of precipitation and increased winds to the Aleutians. These waves will push weakening fronts toward the mainland resulting in onshore flow and potential precipitation over the AKPEN, Bristol Bay, and Y-K Delta areas. Southcentral will remain mostly dry during this time period, as any approaching boundary will dissipate by the time it reaches the Alaska Range. Late Wednesday into Thursday, a potent low from the southwest will approach the western Aleutians. Models have been fairly consistent with the basic pattern, but there's uncertainty as to how strong winds will get in the Aleutians...the low is expected to rapidly deepen with potential storm force winds, however a slight southerly shift in its track would indicate primarily gales for the Aleutians. On that note, models continue to point to the potential for wetter conditions in Southcentral late next week, but this will be contingent on the progression of the low upstream. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...Heavy Freezing Spray 185 181 160. Gale 414 165 170 171 172 173 174 179 181. Storm 411 412 413 175 176 177 178 185. && $$ SYNOPSIS AND MODEL DISCUSSION...PJS SOUTHCENTRAL ALASKA...EZ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BJB MARINE/LONG TERM...JA  FXAK68 PAFC 061347 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 447 AM AKST Sun Jan 6 2019 .ANALYSIS AND UPPER LEVELS... There is a weakening surface low north of Attu Island that is vertically stacked and has the remnants of a decaying occlusion wrapped into it. There is a mature low south of Unalaska and a second mature low that is rapidly intensifying southwest of Attu Island. In the latest ASCAT/advanced scatterometer image there is a large area of high pressure at the surface south of the AKPEN and Kodiak. The jet stream is south of 50N. There are two distinct jet cores supporting the aforementioned matures cyclones. The radars at King Salmon and Kenai are barren and both in clear air mode. Meanwhile, the Middleton Island and Bethel radars have a few light returns on them but nothing ominous or sinister. On the GOES Nighttime Microphysics and the AVHRR (which are both satellite products) fog and low clouds have been detected again over portions of Southcentral, more specifically Anchorage, Wasilla and Hope. The satellite has also pinged into areas of freezing fog and low stratus in the Copper River Basin. There is a another area of fog in Southwest Alaska over portions of the Kuskokwim River north and east of Aniak. The coldest region again for the southern tier of Alaska remains the Copper River Basin where temperatures are ranging from the negative teens to negative twenties. However, at 4 AM this morning the METAR at Talkeetna was -21F which was a function of pure radiational cooling. && .MODEL DISCUSSION... Models are in good agreement with the major synoptic features through Tuesday. The caveat being the decaying low in the extreme Western Bering. But the model consensus with the train of cyclones south of 50N in the short term forecast period looks good. Weather models in high latitude environments in general don't handle microscale features such as localized fog very well. Which is the case right now for the fog and stratus in the Anchorage Metro Area. This is the portion of the forecast is where the level of uncertainty is bumped up a skosh. && .AVIATION... PANC...The nighttime microphysics images from GOES have detected an area of fog/low stratus over Knik Arm, Turnagain Arm and over portions of the Cook Inlet. The metars near the Knik Arm suggest that the base of that batch of stratus is at 200 feet. The stratus over Cook Inlet ranges from cigs of 600 to 1000 feet. There has not been a lot of mixing and the forecast for the ensuing 30 hr period still looks pretty stagnant in the boundary layer. The best chance for VFR flight conditions at PANC will be this afternoon but its not a guarantee. The fog/stratus situation is actively being monitored. Amendments will be made as required. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... The same forecast issues from the past two days will remain again today across Southcentral...areas of fog around Cook Inlet and the Copper River Basin and winds through channeled terrain. The fog and low stratus does look to mostly remain again today and through tonight in these areas. This has led to the low temperatures tonight being adjusted upward some as skies should not clear out. Tonight, a short wave will move over Kodiak Island and then progress over the Cook Inlet area for Monday and Monday night. While this is not a strong short wave it will be enough to increase mid and higher level clouds which may help break up the persistent fog and stratus over Cook Inlet. The trough along the northern Gulf of Alaska coastline has helped increase some of the outflow winds from Seward through the Prince William Sound area. These winds and colder temperatures have decreased the wind chill in Thompson Pass to around 45 below zero this morning. Since the temperatures will continue and winds will persist near those levels through Monday morning, a wind chill advisory has been issued for that area through Monday morning. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3/Sunday through Tuesday)... The first of two fronts forecasted to impact southwest Alaska is currently coming ashore from the Bering Sea. It is producing some light snow and windy conditions along the coast as it does so. This is reducing visibility to a mile or so, but those conditions are localized. Additionally, the low stratus that has been in place is slow to move out of inland areas of the southwest. It is clearly evident on the nighttime microphysics satellite. As the front pushes inland, it should clear out the remaining stratus. After this front pushes through, it will pretty much be a repeat of the setup we have had the past couple of days. A brief break in the weather will occur later today with the strong possibility of stratus/fog setting up again over the area. Being that stratus has been slow to dissipate and there is a broad deck of it throughout western Alaska, would not be surprised to see it return after the front moves through. These indicators show conditions are primed for it to redevelop. The next front will then approach the coast tomorrow night, bringing about the same weather for Tuesday. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3/Sunday through Tuesday)... The low center with the first in succession of two lows is pushing out of our forecast area in the Western Bering. Its slowly decaying front is leaving the eastern Aleutians and moving into southwest Alaska. Behind this low center, some cold core cumulus is moving through the Bering and Aleutian Islands. It is in association with cold air being entrained into the low. The next low that will be moving through the Bering and Aleutians is starting to appear in our forecast area on satellite imagery and is entering the western Aleutian Islands. Storm force winds with a few hurricane force gusts are still forecasted with this low. However, as the previous discussion mentioned, these stronger wind gusts will be brief so still steering away from issuing any hazard products associated with them. The front still looks to detach from the low center and lose its dynamic support as it moves east. This means little change in the forecast for the area. && .MARINE (Days 3 through 5)... Beginning Tuesday evening, conditions are expected to improve across the Bering Sea as a storm system tracks north out of the area while weakening. Winds and waves are likely to subside quite a bit through Wednesday night before the next storm system approaches from the south by Wednesday night. The storm is expected to be quite strong with central pressures potentially bottoming out below 950 mb, though the system is expected to weaken as it approaches the Western/Central Aleutians and stay south of the island chain. This would bring upper end gale force winds to most of the Western Bering Thursday night into Friday. Models have been fairly consistent with this storm so far, thus confidence is above average in the track and strength. Though, if the low takes a more northward track and maintains its strength, winds will likely increase into the storm force category. Over the Gulf of Alaska, high pressure will continue to keep the storm track to the south and west, thus expect generally good conditions through the week. Localized higher winds may develop out of bays and passes along the North Gulf Coast due to northerly outflow winds. && .LONG TERM FORECAST (Days 4 through 7)... The long term forecast begins Wednesday with high pressure over most of Southcentral and a cold Arctic upper level low over the northern mainland. This will keep cold and dry conditions with offshore flow over Southcentral and most of Southwest AK through the end of the week. A few shortwaves rotating around a low south of the AKPEN and the Arctic low will bring some snow showers to parts of southwest AK on Wednesday but should diminish by the end of the day. The Arctic low is expected to shift south some allowing even colder air to filter in over the southern mainland on Thursday. At the same time, a strong North Pacific low will move north towards the Aleutians, but should stay south of the island chain as a strong polar high over Siberia will prevent the system from pushing further north. Regardless, the system will bring very wet and windy conditions to the Aleutians and spread further east towards the AKPEN by the end of the week. Models are now beginning to show the low complex spreading east into the Gulf of Alaska by Friday as high pressure shifts east at the same time. This would bring a pattern change to the southern mainland with a return to warm and wet southerly flow as we head into the weekend. There is still a fair amount of disagreement between models as to how far east the North Pacific low gets, so a lot could change between now and then. Best to keep track of the forecast for updates through the week as the details are worked out. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...Wind Chill Advisory 131. MARINE...Heavy Freezing Spray 185. Gale 414 412 170 172 173 174. Storm 413 411 175 176 177 178 179 185. && $$ SYNOPSIS AND MODEL DISCUSSION...PJS SOUTHCENTRAL ALASKA...EZ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BJB MARINE/LONG TERM...KVP  FXAK68 PAFC 111327 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 427 AM AKST Mon Feb 11 2019 .ANALYSIS AND UPPER LEVELS... There is a surface low in the southern Gulf Of Alaska and a deep surface low near Attu Island with an approximate intensity of 958 mb. Additionally, there is a dome of high pressure over the Central Pacific with a ridge nosing its way towards Southwestern Alaska. The low in the West Bering has an occluded front north of the chain with the warm front bisecting the Aleutians and the associated cold front extends back towards Japan. This juggernaut is producing hurricane and storm force winds and wave heights greater than 40 feet near the Western Aleutians. The core of the jet has curved into the Bering and is steering this system. Meanwhile, the radars at PAHG/Kenai, PAIH/Middleton Island, and PAKC/King Salmon are all in "Clear Air Mode" early this morning. While the leading edge of the precipitaton shield from the next Bering system has moved into Nightmute and Kipnuk and has been detected by radar at Bethel/PABC. && .MODEL DISCUSSION... The global models are in good agreement through 72 hrs with the placement synoptic features. This pattern where the longwave trough has dominated the western/central Bering and NW Pacific has been going on for weeks now. The persistence of this pattern may be impacting the performance of the global models. There are some minor differences with the intensity of the jet core associated with the current Bering storm and with the 1000-850 thickness values past 24 hrs which could be a red herring for p-type for the AKPEN and SW AK. But otherwise the confidence level for this forecast package is above average especially considering that it is February. && .AVIATION... PANC...Fog has again developed over the Anchorage Bowl this morning. As of 1253Z or 3:53 AM local the visibility at PANC was reduced to 1/4 SM freezing fog and the ceiling at PAMR was 100 feet. Looking at other spots around the Cook Inlet, fog was observed at the metar for PAEN and fog was detected on the AVHRR south of Anchorage. Generally expecting light winds and VFR conditions at PANC for the ensuing 30hr forecast period. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2/Today through Tuesday night)... As a very weak short-wave trough exits this morning a ridge will build right back overhead of Southcentral. Local areas of fog will linger through the morning hours, especially from the western Kenai Peninsula northward to Anchorage. A weakening surface front will then approach from the west this afternoon, leading to increasing mid to high clouds. With the parent low far away over the northern Bering Sea, there will be very little in the way of upper level forcing. Thus, front will cross Southcentral tonight with very little precipitation. Deep and strong low level southwest flow will produce upslope along the west side of the Kenai, Chugach, and Talkeetna Mountains. Thus, best chance of some light snow accumulation will be right along the mountains. Cold air advection behind the front will kick up winds across the western Gulf as well as the bays and passes of western Prince William Sound overnight tonight into Tuesday. A strong upper level short-wave tracking along the Aleutians Tuesday will lead to cyclogenesis south of the Alaska Peninsula. This low will track south of Kodiak Tuesday night then exit across the southern Gulf Wednesday. This scenario is similar to what occurred in this same area Saturday night and Sunday. A building ridge upstream of the low will help tighten pressure gradients and lead to pressure rises along the Alaska Peninsula. When combined with cold air advection, this will lead to another round of strong winds across the western Gulf and Kodiak Island on Wednesday, with the typically much stronger gusts out of bays and passes of the Alaska Peninsula. && .MARINE (Days 3 through 5)... The period begins early Wednesday with a low around 960 mb southwest of the Bering Sea and another strong low south of Kodiak Island. The track and intensity of both of these lows is not changing much from run-to-run on the computer models and the overall solution looks very reasonable, so the forecast confidence is above normal as compared to other lows recently. The low south of Kodiak should pull southeastward and bring in some north-to-northwesterly storm force winds south of The Alaska Peninsula and near Kodiak Island Wednesday then move out of the area by Thursday. The low approaching the Bering Sea and the front associated with it will bring periods of gales to most of the Bering/Aleutian region with a significant area of storms in the western Bering/Aleutians on Wednesday. && .LONG TERM FORECAST (Days 3 through 7)... The long term forecast period starts early Wednesday with the very active storm track over the western and northern Bering Sea where it will generally remain through next weekend. A strong frontal system will cross the west and central Aleutians on Wednesday and then continue across the Bering Wednesday night and Thursday to reach the Southwest Alaska coast Thursday afternoon. This front will then shear apart and dissipate Thursday night as it tries to swing inland to be replaced by a high amplitude ridge. The next strong front will move into the central Bering Thursday night and continue east to push across Southwest Alaska Friday night. Another frontal wave will follow behind it, crossing the Alaska Peninsula Saturday and then lifting northeast into Southern Alaska Saturday night through Sunday. Yet another strong front will approach the western Aleutians late Saturday night. Its powerful parent low will track into and across the Bering Sunday through Sunday night with its associated frontal system swinging east across the Aleutians and Alaska Peninsula to reach Southwest Alaska Monday. For Southcentral Alaska, the long term forecast period will begin with a low track from west to east across the southern Gulf Wednesday with a cold upper level trough to the north digging into Southcentral Alaska behind it. The result will be a rapid strengthening of offshore flow Wednesday afternoon through Wednesday night, particularly through channeled terrain gaps. Upper level ridging will build in from the west Thursday and Friday bringing a gradual easing of the offshore flow and steady warming aloft. By Friday night the axis off the upper level ridge will push east to be centered over Southcentral Alaska with a weakening frontal system following behind on Saturday. A second, better organized frontal wave will push into Southcentral Alaska Saturday night and Sunday. Ridging will briefly rebuild Sunday night ahead of another front coming in from the southwest. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...High Wind Warning 191 195. Winter Weather Advisory 155. MARINE...Heavy Freezing Spray 185. Storms 414 413 412 411 175 177 178 179 181 185. Gales 165 170 173 176 180 351 131 120. && $$ SYNOPSIS AND MODEL DISCUSSION...PJS SOUTHCENTRAL ALASKA...SEB SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA MARINE/LONG TERM...JR  FXAK68 PAFC 261334 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 434 AM AKST Tue Feb 26 2019 .ANALYSIS AND UPPER LEVELS... There is a potent surface low near the coast of NE Russia south of Anadyr with an elongated occlusion bisecting the north and east Bering and pushing eastwards. There is a plume of moisture along this occlusion and the radars at Nome/PAEC and Bethel/PABC are picking up returns. As of 1319z or 4:19 AM AST the radar at King Salmon/PAKC was dry as a bone. The pressure gradient is still really tight with this system and the latest ASCAT/Advanced Scatterometer pass has detected both storm and gale fore winds in the Bering with this feature. The remainder of the frontal boundary extends more than 1500 nautical miles south of the chain into the North Pacific. There is a developing low southwest of Adak. There is a dome of high pressure at the surface over the Central Pacific and the upper level ridge is bisecting eastern Alaska and the Gulf Of Alaska. With those clear skies in place yesterday, the temperatures began to plummet once the sun set. Numerous locations are in single digit or in below zero territory this morning. && .MODEL DISCUSSION... With the prolonged residence of the longwave trough over the NW Pacific and the Bering, the initialization parameter of choice has been the ASCAT/Advanced Scatterometer wind field. Both the GFS and NAM initialized well when comparing the placement of the surface low near the NE coast of Russia and placement of the anticyclone over the Gulf Of Alaska. The global models are in good agreement with the major synoptic features through Thursday morning which includes the domes of high pressure over the Gulf of Alaska and Central Pacific, the new low impacting the Aleutians and the remnants of Wutip in the East Pacific. The only potential pitfall in the forecast package remains the fog prognostics over southcentral. The models attempt to grapple with the microscale features over Southcentral, but in reality there is a fair amount of "nowcasting" that occurs with fog and low stratus. && .AVIATION... PANC...As of 1253z or 3:53 AM AST the sky conditions at PANC were FEW002 and the VSBY was unrestricted. Once again, the Baldy Webcam has detected an area of fog/low stratus near Knik Arm. Additionally, the AVHRR/Advanced Very High Resolution Radiometer (which is a satellite instrument) has detected fog and low status over Cook Inlet west of Fire Island. The potential for fog or low stratus moving over PANC is actively being monitored. For the 12z TAF package, hedged with VCFG and a TEMPO for fog developing near the aerodrome and the potential for low cigs or intermittent low cigs this morning. If fog moves over PANC, conventional wisdom is that conditions would improve early afternoon as the temperature begins to climb. Other than fog or low stratus potential, expect light winds and VFR conditions. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)... (Tonight through Wednesday night) The upper ridge entrenched over the Gulf and Southcentral is the dominate synoptic feature. To a lesser degree, but still noteworthy, is an inverted surface tough lingering near the North Gulf Coast. In regards to the upper ridge, it shifts east some over the next day or so. As it does so, flow in the low to mid levels becomes southerly and will help push stratus up Cook Inlet. So we are expected increasing low clouds to spread as far as north as the Anchorage Bowl tonight and perhaps the extreme southern Susitna Valley. The late February sun will likely help break up the cloud deck over land areas during the day, but cooling at night may allow low clouds to redevelop during the overnight hours. Some fog will likely accompany the stratus field. The main contribution of the coastal surface trough will be to enhance outflow conditions over the North Gulf and eastern Kenai Peninsula tonight and Wednesday. So look for gusty outflow conditions in favored locals (Copper River Delta, Thompson Pass, Whittier, etc.). && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)... (Today through Friday) A persistent pattern will remain in place, with a strong omega block ridge centered to the east of the region, and a series of troughs moving from the western Bering into central portions of it. In between these two features is a surface front that is currently stalled along the Kuskokwim Delta south towards the AKPEN. A few weak waves passing through will provide some burst in ascent aloft. This combined with modest surface convergence along the front will continue to foster showery type precipitation near it. Further inland, drier conditions will continue as these locations will experience more subsidence (sinking air) and drying from the ridge of high pressure to the east. The stalled front will try to make progress further inland as an upstream storm tries to "kick" it eastward. However, the high pressure to its east will spell a quick death for it as frontolysis (the dissipation of a front) ensues. Then, a pair of lows moving through the Bering looks to send a couple of fronts towards the coast through Friday, with re-newed precipitation potential. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)... (Today through Friday) As our current storm force low departs the region for eastern Siberia, more of the same is on the way, as a pair of surface lows race north from the Pacific. The first of which will enter the west central portion of the chain later this evening, reaching a position west of Saint Matthew Island by late Wednesday morning. As it does so, a surface front will surge eastward towards the coast before stalling. Widespread precipitation will accompany both of these features, with sustained gale force winds accompanying it, with the low dropping into the ~986-990 mb range. The second system, which will be the stronger of the two, will cross the chain near Adak (like its predecessor) during the mid to late afternoon hours on wednesday, passing through around 980mb. This storm looks to have some tropical origins with its moisture source, which will interact with a strong disturbance in the base of a trough exiting the Sea of Okhotsk. This mid-level storm will then get absorbed into the Bering trough, bringing the tropical moisture northward. Typically when this occurs, strong low level theta advection getting positioned under a cold Bering trough tends to lead to strong surface cyclogenesis (low pressure development), as indicated by the GFS and ECMWF models, which show the storm bottoming out just under 970mb in the northwestern Bering. As it does so, another surface front will move towards the coast. Given the increased potential instability with this storm, and from a pattern recognition standpoint, we substantially increased the winds to storm force. There's fairly high confidence as virtually all models showed similar synoptic patterns at the surface and in the mid levels, with the weaker NAM (9 mb weaker) being discounted. This also was coordinated with the Fairbanks office (AFG) after a good in house discussion. That said, additional forecast refinements are likely over the next day or so. && && .MARINE (Days 3 through 5)... We begin Wednesday with a strong pressure gradient in the Bering Sea east of 175W. There remains a good amount of uncertainty as we progress into Wednesday night and Thursday with the strength and location of the low centers. This translates to some wind direction and intensity uncertainty. At this point expect gale to storm force wind over much of the Bering east of 175W much of Wednesday and Thursday. Following this storm is a break in the action as the next strong storm is not expected to impact the western Aleutians and Bering Sea until late Friday. There is a significant difference in model solutions for this storm, though there is agreement that we will likely see gales, and possibly storm force winds, over the western Bering Sea and western Aleutians late Friday. Persistent high pressure over mainland Alaska into the Gulf of Alaska equates to generally benign conditions, sub gales Wednesday through Friday. && .LONG TERM FORECAST (Days 3 through 7)... The strong upper high will continue to be the dominant feature over mainland Alaska into the Gulf of Alaska while the Bering Sea and Aleutians remain very active. Models and ensembles are in good general agreement with this overall pattern. Beginning Wednesday, the ridge will persist over eastern Alaska as the broad deep upper trough is entrenched over the Bering Sea Thursday through Saturday. A strong surface low treks north through the central Bering Sea Wednesday leaving a broad weak trough of low pressure across the Bering Thursday and Friday. This is followed by a weak ridge poking into the eastern Bering Sea late Friday into Saturday while yet another strong low moves into the picture over the western Aleutians. Here the models diverge on the location and intensity of this storm, but do agree on a tight pressure gradient moving into the central to western Bering Sea. This prefrontal pressure gradient then moves to the eastern Bering Sea through the weekend, bringing with it gale to storm force wind along with warmer low level air. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...Storm 170 173 174. Gale 172 411 412 413 414 165 175 176 179 180 181 185. && $$ SYNOPSIS AND MODEL DISCUSSION...PJS SOUTHCENTRAL ALASKA...BC SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD MARINE/LONG TERM...BJB