Issued by NWS Pocatello, ID
000 FXUS65 KPIH 222059 AFDPIH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE POCATELLO ID 200 PM MST SUN NOV 22 2009 .SHORT TERM...TONIGHT THROUGH WEDNESDAY. LEADING EDGE OF UPPER TROUGH WORKING THROUGH REGION EARLY THIS AFTERNOON WITH ASSOCIATED PRECIPITATION BAND EXTENDING FROM REXBURG WSW THROUGH JACKPOT AND MOVING AT A GOOD CLIP TO THE EAST. EXPECTATION IS THAT THIS BAND WILL EXIT EAST INTO THE ERN HIGHLANDS BY LATE AFTERNOON/EARLY EVENING WITH LINGERING SHOWERS AND BREEZY WEST-NW WINDS CONTINUING OVER THE REGION AS UPPER TROUGH WORKS EAST INTO WYOMING OVERNIGHT. HEAVY SNOWFALL HAS ALL BUT ENDED BEHIND THE MAIN PRECIP BAND AND THUS HAVE CANCELLED THE WINTER STORM WARNING FOR SAWTOOTH MOUNTAINS AND DROPPED THE ADVISORY FOR THE LOST RIVER REGION AND SOUTH CENTRAL HIGHLANDS. UPPER RIDGE EXPANDS ACROSS REGION MONDAY AS A SECONDARY SHORT-WAVE TOPS RIDGE AND SHEARS EAST THROUGH CANADA. THUS DRIER CONDITIONS SHOULD PREVAIL MONDAY AND ON INTO WEDNESDAY AS RIDGE DOMINATES. TEMPERATURES WILL BE SOMEWHAT TRICKY WITH CLEARING SKIES ALLOWING OVERNIGHT LOWS THE NEXT COUPLE OF NIGHTS TO DROP SHARPLY WHILE DAYTIME HIGHS STRUGGLE TO BURN THROUGH THE COLD AIR TRAPPED IN THE VALLEYS. THUS AM TRYING NOT TO STRAY TOO FAR FROM GUIDANCE THROUGH THE PERIOD. HUSTON .LONG TERM...WEDNESDAY NIGHT THROUGH NEXT SUNDAY. STRONG UPPER LEVEL RIDGING STARTS THIS PERIOD...BUT BREAKS DOWN AT THE 36 HOUR POINT. HOW MUCH IT BREAKS DOWN IS THE MAIN FORECAST PROBLEM. GFS KEEPS A DRIER FORECAST WITH THE STORM TRACK FARTHER NORTH...BUT MORE STABLE ECMWF KEEPS A STEADY STREAM OF SHORTWAVES CLIPPING THE NORTHERN HALF OF THE FORECAST AREA. HAVE GONE WITH THE NCEP-PREFERRED ECMWF AND THUS HAVE HIGHER THAN GFS POPS AND COLDER TEMPERATURES FOR AFTERNOON HIGHS. DO NOT SEE ANY SIGNIFICANT WIND EVENTS DURING THIS PERIOD. THE FRI/FRI NIGHT STORM IS THE HEAVIEST PRECIPITATION MAKER...AND MAY NEED SOME LOW-LEVEL ADVISORY HIGHLIGHTS EVENTUALLY. MESSICK && .AVIATION...FRONT IS PASSING THROUGH THIS AFTERNOON WITH ISOLATED TO WIDELY SCATTERED LIGHT SHOWERS BEHIND. MAIN PROBLEMS WILL BE THE WIND SHIFT AND THE RISK OF FOG AND STRATUS IN THE MORNING. WITH STRONG WIND CONTINUING ALOFT...DO NOT EXPECT FOG...BUT VERY LIKELY CEILING WILL BE AFFECTED...MAINLY IN THE SNAKE RIVER PLAIN AIRPORTS. KSUN APPEARS TO BE FAIRLY DRY ONCE THEY RE-OPEN MON MORNING. DRYING TREND THROUGH THU...SO ONLY THREAT IS MORNING STRATUS AND FOG. MESSICK && .PIH WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 5 AM MST MONDAY FOR IDZ019-023-025. && $$
