Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 230147
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
646 PM MST SAT NOV 22 2014

.SHORT TERM...TONIGHT THROUGH THURSDAY. QUICK UPDATE THIS EVENING TO
EXPIRE WARNINGS/ADVISORIES. THE THREAT FOR HEAVY SNOW HAS ENDED
ALTHOUGH A WEAK SYSTEM PASSING OVERHEAD TONIGHT WILL LIKELY BRING AN
ADDITIONAL 1 TO 3 INCHES TO ISLAND PARK/TETON AREA LATE TONIGHT AND
1 TO 2 INCHES TO THE SOUTH CENTRAL HIGHLANDS THIS EVENING. WINDS
SPEEDS HAVE ALSO DROPPED BELOW ADVISORY CRITIERIA. THUS HAVE EXPIRED
THOSE ADVISORIES. SEE PREVIOUS DISCUSSION BELOW. HUSTON

STRONG ZONAL FLOW CONTINUES TO STREAM INTO THE PAC NW...WITH THE
BULK OF THE PRECIP ACROSS THE SOUTHERN AND EASTERN HIGHLANDS. PRECIP
DIMINISHES TONIGHT TO SCATTERED MTN SNOW SHOWERS AND ISOLD SNOW
SHOWERS IN THE VALLEYS. A FEW MORE INCHES OF SNOW ARE POSSIBLE IN
THE MTNS OVERNIGHT...WITH AROUND A HALF INCH POSSIBLE IN THE
VALLEYS. STRONG WINDS WILL CONTINUE INTO THE EVENING
HOURS...DIMINISHING SOMEWHAT BY LATE EVENING. WITH THE PASSAGE OF
THE UPPER TROF...WINDS TURN TO THE NW. WITH PAC MOISTURE STILL IN
THE FLOW... LIGHT SNOW REMAINS POSSIBLE OVER THE MTNS DUE TO UPSLOPE
FLOW. PRECIP DIMINISHES ON MON AS UPPER RIDGING BUILDS OVER THE W
COAST. ANOTHER MINOR WAVE IN THE NW FLOW ON TUE WILL BRING MORE
LIGHT SNOW MAINLY TO THE MTNS. HEDGES

.LONG TERM...TUE NIGHT THROUGH NEXT SAT NIGHT. 500MB LONG WAVE PROG
INDICATES HIGH AMPLITUDE RIDGE TO REMAIN IN THE EASTERN
PACIFIC...KEEPING A MEAN NORTHWESTERLY FLOW UNTIL THE LAST 36 HOURS
OR SO AS THE UPPER LEVEL RIDGE DE-AMPLIFIES. SO THE FIRST PART OF
THIS PERIOD SHOULD BE COLD AND SOMEWHAT DRY...BUT THE LAST 26 HOURS
OR SO HAS A BETTER POTENTIAL OF MOIST STORMS BREAKING DOWN THE
WEAKENED RIDGE AND PUSHING THROUGH THE GEM STATE. AND THAT IS
EXACTLY WHAT GUIDANCE HAS...ALTHOUGH THE GFS BRINGS IN MORE
PRECIPITATION IN MINOR WAVES THAN A VERY DRY ECMWF. THERE IS ONE
EXCEPTION.  EARLY IN THE PERIOD...TUE NIGHT...A SHORTWAVE IS
FINISHING UP JUST BRUSHING EASTERN IDAHO WITH SOME LIGHT TO MODERATE
PRECIPITATION THAT NIGHT...AND THE ECMWF IS WETTER.

THURSDAY IS THE CRITICAL DAY AS IT IS THANKSGIVING. IN EITHER
GUIDANCE PRODUCT...IT CURRENTLY LOOKS VERY GOOD FOR SOUTHERN
IDAHO...ALTHOUGH TRAVEL THROUGH WESTERN MONTANA MAY HAVE ITS
PROBLEMS. EXPECT DRY CONDITIONS AND PROBABLY THE WARMEST DAY OF THE
WEEK. MESSICK
&&

.AVIATION...TWO FRONTAL BOUNDARIES EXPECTED TO PASS THROUGH TODAY IN
THE NEXT FEW HOURS...MAKING A COMPLICATED AND LOW-CONFIDENCE
FORECAST. A BRIEF BREAK DURING THE EARLY EVENING WONT ALLOW MUCH
RELIEF...BUT THE SECOND ONE WILL DEFINITELY TURN KSUN WINDS TO THE
NORTHWEST AND ALLOW THIS AIRDROME TO SCATTER OUT WITH LITTLE
PROBLEMS EXPECTED SUNDAY WITH STRONG SUBSIDENCE AND CONTINUED
NORTHWEST FLOW. THESE FRONTS ARE DEFINITELY DISPLAYING THEIR POWER
AS THE SOUTHEAST WINDS ARE OCCURRING IN THE MORNING AT KSUN WHILE BY
LATE AFTERNOON THEY SHOULD HAVE AT LEAST A WESTERLY IF NOT
NORTHWESTERLY COMPONENT...THE EXACT OPPOSITE OF WHAT HAPPENS ON A
SUNNY SUMMER DAY. BUT UNTIL THE WIND SWITCH...KSUN WILL BE CLOSED
WITH SNOW AND LOW CIGS.

FOR THE VALLEY AIRDROMES THE HEAVY PRECIPITATION EXPECTED TO
CONTINUE AT LEAST UNTIL 23/00Z. THE MARGINAL VFR CIGS THOUGH SHOULD
CONTINUE LONG AFTER THAT. AND EVEN LATER KBYI...KIDA...AND KPIH ARE
ALL EXPECTED BY THE NAM TO HAVE IFR CONDITIONS ONCE THE WIND
SUBSIDES AND THE MOIST BOUNDARY LAYER COOLS DURING THE OVERNIGHT
HOURS IN TIME FOR MORNING OPENING. GFS AND NAM ARE AT ODDS ON THE
CIGS...WITH THE NAM BEING THE USUAL PESSIMIST COMPARED TO THE GFS.
WITH THE ABUNDANT RAIN SO FAR...AND THE BETTER TEMPERATURE
VERIFICATION THIS MORNING ON THE NAM...HAVE DECIDED TO BELIEVE THE
CIG CRASH FOR THE MORNING HOURS. FINALLY...WHILE WIND IS
STRONG...LITTLE IMPACT AS IT IS RIGHT DOWN THE RUNWAYS FOR THE THREE
VALLEY AIRPORTS. MESSICK
&&

.PIH WATCHES/WARNINGS/ADVISORIES...NONE.
&&

$$










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