FXUS64 KHUN 291453 AAA AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 853 AM CST SUN DEC 29 2013 .UPDATE... MORNING FORECAST UPDATE. LOWERED MEASURABLE POPS AREAWIDE AND ADJUSTED SKY COVER, TEMPERATURES, AND DEWPOINTS. && .DISCUSSION... MORNING WATER VAPOR IMAGERY SHOWS THAT THE DRIVING SHORTWAVE RESPONSIBLE FOR MUCH OF THE RAIN OVER THE LAST 24 HOURS HAS NOW PIVOTED JUST NORTHEAST OF THE AREA, RESULTING IN A GOOD AMOUNT OF MID AND UPPER-LEVEL DRYING. ON VISIBLE SATELLITE IMAGERY, THIS MANIFESTS ITSELF AS A CHANGE IN CLOUD DEPTH, AND ACTUALLY RESULTS IN SOME CLEARING OVER PORTIONS OF MISSOURI, ARKANSAS, AND TENNESSEE. NORTHWEST OF THAT, LOW CLOUDS QUICKLY FILL BACK IN BEHIND AN ARCTIC COLD FRONT THAT HAS PUSHED ACROSS ST. LOUIS AND TULSA. AREA RADARS ARE STILL PICKING UP ON A LITTLE BIT OF DRIZZLE/MIST OUT THERE, SO THE FORECAST WILL BE UPDATED TO LOWER POPS FOR THE REST OF THE MORNING. IT IS NOT CERTAIN THAT THE CLOUDS WILL COMPLETELY SCATTER OR CLEAR OUT THIS AFTERNOON, BUT SOME SUNSHINE STILL LOOKS LIKE A GOOD BET, SO HIGH TEMPERATURES WILL BE LEFT ALONE. THE MAIN CHANGE WILL BE TO TWEAK HOURLY TEMPERATURES TO SHOW STEADY TRENDS THROUGH THE MORNING HOURS, THEN MORE WARMING FOR THE AFTERNOON. THE RELATIVELY-BALMY WEATHER WON'T LAST LONG, HOWEVER, AS THAT ARCTIC FRONT WILL ARRIVE IN THE AREA TONIGHT. BCC && .AVIATION... /ISSUED 523 AM CST SUN DEC 29 2013/ FOR 12Z TAFS... MVFR CONDITIONS SHOULD PREVAIL THROUGH 17Z WITH SOME BREAKS IN THE CLOUD COVER LIKELY. RAIN IS QUICKLY ENDING FROM WEST TO EAST AS THE UPPER LOW RESPONSIBLE FOR THE PRECIP MOVES OFF TO THE NORTHEAST. DROPS BELOW ALT MINIMUMS ARE POSSIBLE BTWN 13-17Z (TEMPO GROUP) AS A LOW DECK OF CLOUDS (BKN005) MOVES ACROSS THE AREA FROM THE SW. VFR CONDITIONS ARE THEN EXPECTED BTWN 17-23Z. THEN, A COLD FRONT IS EXPECTED TO PASS OVER THE REGION BTWN 23-06Z BRINGING A WIND SHIFT AND ANOTHER DROP IN CATEGORY TO MVFR. SL.77 && .PREV DISCUSSION... /ISSUED 158 AM CST SUN DEC 29 2013/ THE FIRST WIDESPREAD AREA OF RAINFALL WHICH WAS DRIVEN BY GOOD ISENTROPIC LIFT/WARM ADVECTION HAS EXITED TO THE NE. THE 850 MB LOW PRESSURE SYSTEM WAS ALSO MOVING NEWD INTO EASTERN TN ALONG WITH ITS ATTENDANT TROF. A 50+ KT LLJ WAS DEPARTING IN ADVANCE OF THIS WAVE. IN ITS WAKE, WIDESPREAD DRIZZLE AND AREAS OF -RA DUE TO SHALLOWER LIFT AND MOISTURE WAS OCCURRING IN ADVANCE OF THE UPPER LEVEL SHORTWAVE CROSSING THE MS RIVER. THIS WAS PRODUCING A SOLID BAND OF RAINFALL RAPIDLY ADVANCING TO NEAR THE I-65 CORRIDOR AT THIS HOUR. EXTRAPOLATION AND SHORT RANGE MODELS INDICATE THIS WILL EXIT THE FORECAST AREA BETWEEN 12-15Z. STRONG SUBSIDING AIR WILL LIKELY ERODE CLOUD COVER BY THIS AFTERNOON, SO HAVE FORECAST HIGHS NEAR THE WARMER MET/NAM GUIDANCE. 07Z SFC CHART SHOWS THE ARCTIC FRONT JUST ABOUT TO EXIT SOUTHEAST IA THRU CENTRAL MO AND SOUTHEAST KS. THE FRONT WILL ARRIVE IN NW AL JUST AFTER 00Z, AND REACH THE I-59 CORRIDOR AROUND 09Z. THE LATEST MODEL RUNS ARE A BIT WARMER THAN PREVIOUS WITH THIS SURGE OF COLD AIR. THE MODELS STILL SHOW GENERAL LACK OF MID LEVEL MOISTURE TONIGHT INTO EARLY MONDAY BEHIND THE FRONT. WHETHER THE SHALLOW UPSLOPE FLOW ALONG THE CUMBERLAND PLATEAU IN TN WILL BE ENOUGH TO PRODUCE FLURRIES OR -SN IS QUITE UNCERTAIN, SO HAVE OPTED TO KEEP IT OUT OF THE FORECAST ATTM. WE HAVE REMOVED PRECIP AREAWIDE THRU MIDDAY MONDAY UNTIL THE NEXT UPPER SHORT WAVE ARRIVES. HOWEVER, -DIVQ SIGNAL APPEARS RATHER WEAK. SOUNDING PROFILES SHOW WARMER LOW LEVELS THAT ARE NOT SUPPORTIVE OF WINTRY PRECIP AT THIS POINT AND HAVE GONE WITH -RA AFTER WFO COORDINATION. ALSO, THERE IS NO MOISTENING BELOW -10C THRU MONDAY AFTN/EVENING WHICH WOULD FAVOR ICE CRYSTALS NEEDED FOR SNOW GROWTH. NO SIGNIFICANT CHANGES WERE MADE TO THE EXTENDED FORECAST. A STRONGER NW FLOW SHORTWAVE AND CLIPPER SYSTEM ARRIVES THURSDAY WITH THE NEXT MODEST PUSH OF COLD AIR. THIS SHOULD BE A DRY FRONT WITH THE SFC LOW TRACK THRU THE UPPER OH VALLEY. A MORE ZONAL PATTERN WILL FOLLOW THRU NEXT WEEKEND. AK && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.  FXUS64 KHUN 122207 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 407 PM CST Mon Feb 12 2018 .NEAR TERM...(Tonight) Issued at 340 PM CST Mon Feb 12 2018 Just did a quick forecast update to address the rain showers moving through far southern portions of the area. An elevated front around 925 mb is moving northward into the area and along with sufficient moisture is producing a small area of showers in far southern portions of the HUN CWFA. The showers will largely be relegated to Cullman, Marshall and DeKalb Counties, but POPs were raised a little in adjacent areas to address uncertainty with regards to the extent of the shower activity. The showers will move across the area mainly during the late afternoon and evening. Rainfall amounts will mostly be under one tenth of an inch. Otherwise, extensive cloudiness is expected to linger tonight, especially for about the southeastern half of the area, while some breaks in cloud cover may appear in the west. Winds and clouds may be sufficient to prevent fog from developing in most locations, but will need to be watched late tonight as winds lighten and if some breaks in the cloud canopy appear in the west. Additionally, we will be watching and updating river forecast flood products as necessary. The only TN River tributaries that remain in flood at this hour are the Big Nance Creek and the Paint Rock River, both of which are falling. It looks as though the Big Nance may fall below flood stage here in the next few hours. An updated FLS for that river may be coming out soon. .SHORT TERM...(Tuesday through Wednesday night) Issued at 158 PM CST Mon Feb 12 2018 At the beginning of the short term, a surface high will be moving into the northeast US and models are all consistent in developing some cold air damming along the eastern side of the Appalachians. This should result in a wedge front sneaking into NE AL early Tuesday. Localized convergence along this feature could result in light rain developing over the higher terrain and have kept low end PoPs in the forecast out east. About the same time this is occurring an upper level ridge begins to build over the central Gulf of Mexico. Winds shift to the E/SE Tuesday and warmer air returns to the TN Valley. Despite the cloud cover guidance have highs Tuesday in the lower 60s for the western half of the area. The wedge front keeps temps in NE AL and in TN in the 50s. A disturbance moving N/NE out of the SE TX/LA area Tuesday night into Wednesday will accompany an influx of 50 to 60 degree dewpoints. This system is forecast to move over the TN Valley Wednesday, providing another round of moderate to heavy rainfall. The GFS/ECMWF differ in where the heaviest rainfall tracks and have gone with a blend of guidance for QPF values. In either case, rainfall totals won't be as high as what we saw this weekend. So, even with the max rainfall of 0.75 inches, do not believe those values would result in any additional flooding concerns. Lows Wednesday night into Thursday won't fall very far from the highs Wednesday afternoon with values dropping to around 60 degrees. .LONG TERM...(Thursday through Sunday) Issued at 158 PM CST Mon Feb 12 2018 A rather unseasonably warm and moist weather pattern will continue in the day 4-7 period. The subtropical anti-cyclone will be in place aloft over the Gulf of Mexico keeping the TN valley in the midst of brisk westerlies aloft. The center of the ridge shifts east through day 6-7 through the FL peninsula and Bahamas, while the surface-850mb highs become positioned off the east coast. A shallow cold front will be able to push southeast on Friday producing widespread showers and a few thunderstorms. Some of these could be post-frontal through Friday evening. At this time, near surface temperatures look to remain above freezing through Saturday morning for our area, so precipitation should not freeze. The GFS brings a more amplified shortwave east through the OH/TN valleys on Saturday, while the ECMWF is not nearly as amplified. Will keep the suggested low blended PoP in for Saturday. The blended highs on Saturday around 50 degrees may in fact be too warm, but will assess this trend in coming model runs. As the aforementioned ridges shifts east, a rather quick transition back to south-southwest flow in low levels will commence by day 7. This will bring a substantial wing of theta-e advection with PWs jumping rapidly well above one inch again. Cannot rule out elevated instability and thunderstorms, but will just go with showers for now on Sunday until this becomes a bit more certain. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1124 AM CST Mon Feb 12 2018 The low stratus deck between 1,000-2,000 feet is expected to remain over the area through the TAF period. Just to the NW in western TN drier air has allowed for some clearing and we could see this clearing line make it the MSL terminal but confidence is low. Winds remain out of the N/NE with speeds of 9 to 12kts currently but should taper off this afternoon and finally become light and variable overnight. Cigs could briefly drop to IFR overnight but have left out of the current package due to low confidence. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...KDW SHORT TERM...Stumpf LONG TERM...17 AVIATION...Stumpf For more information please visit our website at weather.gov/huntsville.