FXUS65 KPIH 250939 AFDPIH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE POCATELLO ID 239 AM MST WED DEC 25 2013 .SHORT TERM...TODAY THROUGH SATURDAY. MODIS FOG/LOW CLOUD IMAGERY DOING A FAIR JOB THIS MORNING AT PICKING UP THE STRATUS IN THE UPPER SNAKE HIGHLANDS AND EXTENDING DOWN TO REXBURG. NAM LOW LEVEL RH SHOWING THIS AREA SHOULD EXPAND ACROSS THE SNAKE PLAIN THROUGH ABOUT SUNRISE. WITH UPPER RIDGING BUILDING IN WE SHOULD SEE MOSTLY CLEAR SKIES THROUGH THE DAY AND COLD TEMPERATURES AT NIGHT. THERE WILL ALSO BE A POSSIBILITY OF SOME PATCHY FOG...SO HAVE KEPT THAT IN THE FORECAST TONIGHT AND TOMORROW NIGHT. POPS WILL REMAIN LOW UNDER THIS PATTERN. THE MAIN STREAM OF MOISTURE ALONG THE UPPER JET AXIS REMAINS WELL TO THE NORTH THROUGH THE PERIOD...BUT THE RIDGE SHOWS SIGNS OF SHIFTING EASTWARD FRIDAY NIGHT AS AN UPPER TROUGH DIGS IN ALONG THE WA/OR COAST. GFS/NAM KEEPING THINGS RATHER DRY WITH THIS TROUGH AS IT PASSES THROUGH EASTERN IDAHO. HINSBERGER .LONG TERM...SATURDAY THROUGH TUESDAY. MODELS MAINTAIN A HIGH PRESSURE RIDGE IN THE EASTERN PACIFIC WITH DOWNSTREAM FLOW FROM THE NORTHWEST OVER SOUTHEAST IDAHO AND ALONG THE DIVIDE. THERE IS GOOD AGREEMENT IN BRINGING A DISTURBANCE OVER THE TOP OF THE RIDGE SATURDAY...BRUSHING THE LOST RIVER RANGE AND UPPER SNAKE HIGHLANDS. MOISTURE AT THIS TIME LOOKS MOSTLY LIKE HIGH LEVEL CLOUDS. THEREFORE TRIMMED POPS IN THE UPPER SNAKE PLAIN BACK SOME...FAVORING THE HIGHER PEAKS. THERE IS A SECOND DISTURBANCE DROPPING ALONG THE DIVIDE ABOUT NEXT WEDNESDAY. OTHERWISE...THE MAIN DIFFERENCE IN MODELS IS THE ECMWF KEEPS A BIT MORE MOISTURE ON THE DOWN STREAM SIDE OF THE RIDGE THROUGH THE UPPER SNAKE HIGHLANDS TO SUPPORT ISOLATED MOUNTAIN SHOWERS EACH DAY. LITTLE CHANGE IN TEMPERATURES THE NEXT FEW DAYS...COLD DRAINAGE OFF THE MOUNTAINS WILL KEEP THE ARCO DESERT AREA IN THE 10-15 DEGREE RANGE AT NIGHT. RS && .AVIATION...LOW STRATUS TRIES TO REDEVELOP OVER NIGHT IN THE UPPER SNAKE PLAIN NEAR OR NORTH OF KIDA. THE DOWN PLAIN NORTHEASTERLY SURFACE WINDS ARE ACTING TO THIN OUT THE LOW LEVEL STRATUS WITH TIME...SO THERE IS A SMALL CHANCE OF A 2000-3000 FT AGL DECK SHOWING UP. KPIH...KSUN....AND KBYI SHOULD BE LARGELY VFR THE NEXT 48 HOURS. RS && .PIH WATCHES/WARNINGS/ADVISORIES...NONE. && $$  FXUS65 KPIH 251547 AFDPIH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE POCATELLO ID 847 AM MST WED DEC 25 2013 .UPDATE...SAT IMAGERY/AREA WEBCAMS PUT FAIRLY WIDESPREAD AREA OF LOW CLOUDS/FOG THROUGH PORTIONS OF THE SNAKE PLAIN AND STRETCHING INTO THE UPPER SNAKE HIGHLANDS. MODELS MAINTAIN HIGH BOUNDARY LAYER HUMIDITY AT SURFACE UNDER INVERSION LAYER 750-700MB THROUGH THURSDAY MORNING. SOME BREAKUP/EROSION OF THE LAYER EXPECTED FROM THE EDGES THROUGH THE MORNING THOUGH NEW 12Z NAM GUIDANCE KEEPING UPPER SNAKE PLAIN IN THE SOUP THROUGH THE DAY. MODEL SOUNDINGS SUPPORT THIS IDEA AS WELL. WILL MAKE MINOR ADJUSTMENT TO WX/SKY GRIDS TO MAINTAIN PATCHY FOG AND HIGHER CLOUD PERCENTAGE THROUGH THAT REGION. NO OTHER UPDATES ANTICIPATED. DMH && .PREV DISCUSSION... /ISSUED 239 AM MST WED DEC 25 2013/ SHORT TERM...TODAY THROUGH SATURDAY. MODIS FOG/LOW CLOUD IMAGERY DOING A FAIR JOB THIS MORNING AT PICKING UP THE STRATUS IN THE UPPER SNAKE HIGHLANDS AND EXTENDING DOWN TO REXBURG. NAM LOW LEVEL RH SHOWING THIS AREA SHOULD EXPAND ACROSS THE SNAKE PLAIN THROUGH ABOUT SUNRISE. WITH UPPER RIDGING BUILDING IN WE SHOULD SEE MOSTLY CLEAR SKIES THROUGH THE DAY AND COLD TEMPERATURES AT NIGHT. THERE WILL ALSO BE A POSSIBILITY OF SOME PATCHY FOG...SO HAVE KEPT THAT IN THE FORECAST TONIGHT AND TOMORROW NIGHT. POPS WILL REMAIN LOW UNDER THIS PATTERN. THE MAIN STREAM OF MOISTURE ALONG THE UPPER JET AXIS REMAINS WELL TO THE NORTH THROUGH THE PERIOD...BUT THE RIDGE SHOWS SIGNS OF SHIFTING EASTWARD FRIDAY NIGHT AS AN UPPER TROUGH DIGS IN ALONG THE WA/OR COAST. GFS/NAM KEEPING THINGS RATHER DRY WITH THIS TROUGH AS IT PASSES THROUGH EASTERN IDAHO. HINSBERGER LONG TERM...SATURDAY THROUGH TUESDAY. MODELS MAINTAIN A HIGH PRESSURE RIDGE IN THE EASTERN PACIFIC WITH DOWNSTREAM FLOW FROM THE NORTHWEST OVER SOUTHEAST IDAHO AND ALONG THE DIVIDE. THERE IS GOOD AGREEMENT IN BRINGING A DISTURBANCE OVER THE TOP OF THE RIDGE SATURDAY...BRUSHING THE LOST RIVER RANGE AND UPPER SNAKE HIGHLANDS. MOISTURE AT THIS TIME LOOKS MOSTLY LIKE HIGH LEVEL CLOUDS. THEREFORE TRIMMED POPS IN THE UPPER SNAKE PLAIN BACK SOME...FAVORING THE HIGHER PEAKS. THERE IS A SECOND DISTURBANCE DROPPING ALONG THE DIVIDE ABOUT NEXT WEDNESDAY. OTHERWISE...THE MAIN DIFFERENCE IN MODELS IS THE ECMWF KEEPS A BIT MORE MOISTURE ON THE DOWN STREAM SIDE OF THE RIDGE THROUGH THE UPPER SNAKE HIGHLANDS TO SUPPORT ISOLATED MOUNTAIN SHOWERS EACH DAY. LITTLE CHANGE IN TEMPERATURES THE NEXT FEW DAYS...COLD DRAINAGE OFF THE MOUNTAINS WILL KEEP THE ARCO DESERT AREA IN THE 10-15 DEGREE RANGE AT NIGHT. RS AVIATION...LOW STRATUS TRIES TO REDEVELOP OVER NIGHT IN THE UPPER SNAKE PLAIN NEAR OR NORTH OF KIDA. THE DOWN PLAIN NORTHEASTERLY SURFACE WINDS ARE ACTING TO THIN OUT THE LOW LEVEL STRATUS WITH TIME...SO THERE IS A SMALL CHANCE OF A 2000-3000 FT AGL DECK SHOWING UP. KPIH...KSUN....AND KBYI SHOULD BE LARGELY VFR THE NEXT 48 HOURS. RS && .PIH WATCHES/WARNINGS/ADVISORIES... NONE. && $$  FXUS65 KPIH 110937 AFDPIH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE POCATELLO ID 237 AM MST MON JAN 11 2016 .SHORT TERM...TODAY THROUGH THURSDAY. SAT IMAGERY...INCLUDING MODIS NIGHTTIME MICROPHYSICS...SHOWS EXTENT OF FOG/STRATUS ACROSS MUCH OF THE SNAKE PLAIN THIS MORNING AND EXTENDS INTO THE EASTERN HIGHLANDS UP TO THE WYOMING BORDER. OBSERVATIONS AND WEBCAMS SHOW GENERALLY IMPROVED VISIBILITY OVER LATE EVENING. STILL EXPECT TO SEE POCKETS OF DENSE FOG OVER THE UPPER SNAKE PLAIN THIS MORNING...SO KEEPING DENSE FOG ADVISORY OUT TIL 16Z. NAM/GFS PRODUCE SOME LIGHT SNOWFALL COMING OUT OF THIS LOW CLOUD DECK. FORECAST SOUNDINGS DROP TEMPS TO -12C TO -15C WITHIN THE MOIST LAYER...PROVIDING A CHANCE FOR ICE FORMATION...BUT ATMOSPHERE LACKS ANY LARGE-SCALE LIFT TO SEE ANY SIGNIFICANT ACCUMULATION. MODELS TRACK A WEAK SHORTWAVE ACROSS THE TOP OF THE UPPER RIDGE CURRENTLY IN PLACE OVER THE WEST. MEAN UPPER RIDGE SHIFTS EAST WEDNESDAY WHILE MODELS PUSH IN UPPER TROUGH ALONG THE WA/OR COAST WEDNESDAY NIGHT. SNOW SHOULD BEGIN OVER THE CENTRAL MOUNTAINS SOMETIME IN THE AFTERNOON AND SPREAD ACROSS THE REST OF THE FORECAST AREA LATE THAT NIGHT. HINSBERGER .LONG TERM...THURSDAY THROUGH MONDAY NIGHT. MODELS FINALLY COMING TOGETHER ON THU...WITH BOTH GFS AND ECMWF ON THE SAME PAGE WITH LIGHT SNOW ACROSS MUCH OF THE AREA LINGERING INTO FRI. MODELS BEGIN TO DIVERGE ON SAT WITH THE ECMWF MAINTAINING THE RIDGE OVER WESTERN ID WHILE THE GFS KNOCKS IT DOWN. THIS RESULTS IN THE GFS SPREADING LIGHT SNOW ACROSS THE AREA ON SAT WHILE THE ECMWF IS ABOUT 12 HRS SLOWER. COMPARED TO MODEL DIFFERENCES THE PAST FEW DAYS...THIS IS AN IMPROVEMENT. PRECIP DIMINISHES SUN NIGHT PER ECMWF...BUT THE GFS AGAIN FLATTENS THE RIDGE AND SPREADS SNOW ACROSS THE AREA. WILL JUST KEEP LOW CHANCES IN THE EAST SUN NIGHT AND GO DRIER ON MON THRU MON NIGHT WHICH IS MORE IN LINE WITH THE ECMWF. NOT SEEING ANY MAJOR CHANGES IN TEMPS. HEDGES && .AVIATION...LOW CIGS AGAIN PLAGUE THE SNAKE RIVER PLAIN/EASTERN MAGIC VALLEY THIS MORN AS LOW LEVEL MOISTURE REMAINS TRAPPED. MAY SEE SOME IMPROVEMENT THIS AFTN...BUT WITH NOTHING TO SCOUR OUT THE MOISTURE...LOW CIGS WILL BE WIDESPREAD AGAIN TONIGHT. ONLY KSUN SEEMS TO ESCAPE THE LOW CIGS...BUT SAT IMAGERY SHOWS THE NORTHERN EDGE OF THE CLDS TO BE JUST TO THE SOUTH. KSUN COULD SEE THE LOW CIGS EDGE IN BRIEFLY. HEDGES && .PIH WATCHES/WARNINGS/ADVISORIES... DENSE FOG ADVISORY UNTIL 9 AM MST THIS MORNING FOR IDZ019-020. && $$  FXUS65 KPIH 090907 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 207 AM MST Sat Dec 9 2017 .SHORT TERM...Today through Tuesday. Blocking upper high continues to be the dominant feature for the short-term period. Surface weather will be most influenced by the surface inversion. Fog and stratus will continue to be the norm under these conditions. MODIS nighttime microphysics imagery very similar to 24 hours ago with fog/stratus trapped in the Snake Plain and adjacent valleys. Freezing fog is present at a couple observation sites, but road conditions have not responded as yet. Thus holding off on any headline issuance for freezing fog. Main strategy for temps/RH was to incorporate some persistence and carry it through Tuesday. Hinsberger .LONG TERM...Tuesday night through next Friday. High pressure ridge will continue to support inversion conditions through next Thursday night. Models are then showing support and agreement on finally breaking down the ridge and letting disturbances come in off the Pacific, the first being Friday afternoon or night. Until then, will continue to favor colder temperatures in the Snake Plain and some valley areas, with potential for some fog and low stratus. RS && .AVIATION...Inversions continue to be problematic with low stratus and areas of fog. KBYI is still on the edge of the stratus and has the best potential for clouds scattering out in the afternoon. The other location where skies may well remain VFR is KDIJ. Confidence in low stratus at KDIJ in the early morning hours is marginal. The NAM12 model continues to support the development of easterly winds at the surface and in the boundary layer tonight and Sunday morning. The inversion has been pretty strong, but this could transport some of the status towards the west side of the state. RS && AIR STAGNATION...Inversions continue to hold and reduce air quality, particularly for Franklin County where and Air Stagnation Advisory remains in effect. Saturday night and Sunday morning, looking for development of more persistent easterly winds at the surface and near the top of the low level stratus in the Snake Plain. Both the NAM and GFS models have supported this idea the past two days. It probably will not get rid of the inversion completely, but it can transport some of the low stratus out of the Snake Plain and towards the west side of the state. RS && .PIH WATCHES/WARNINGS/ADVISORIES...None. && $$