877
FXUS65 KPIH 200814
AFDPIH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
114 AM MST WED NOV 20 2024
SHORT TERM
TODAY THROUGH THURSDAY.
ATMOSPHERIC RIVER EVENT BEGINS THIS MORNING ACROSS THE CENTRAL
MOUNTAINS. HEAVIEST SNOWFALLS ARE ABOVE 7500-8000 FEET WHERE 1 TO 2
FEET OF SNOW WILL LIKELY FALL BETWEEN 12Z THIS MORNING AND 12Z
FRIDAY. SNOWFALL AMOUNTS DROP OFF QUICKLY IN THE WOOD RIVER VALLEY
AND STANLEY BASIN BECAUSE OF WARM AIR. HERE SNOW AMOUNTS RANGE FROM
2 TO 8 INCHES. THESE VALLEYS WILL STILL SEE A HEALTHY AMOUNT OF
RAINFALL WITH AN INCH POSSIBLE THROUGH 12Z FRIDAY. OUTSIDE OF THE
CENTRAL MOUNTAINS, NOT MUCH IS HAPPENING. AN ISOLATED SHOWER IS
POSSIBLE TODAY, BUT NOT MUCH IN TERMS OF ACCUMULATIONS. BETTER
CHANCES OUTSIDE OF THE CENTRAL MOUNTAINS ON THURSDAY AS A STRONGER
PUSH OF MOISTURE HEADS TOWARDS THE REGION. HOWEVER STILL LOOKING AT
LIGHT QPF AMOUNTS. TEMPERATURES WILL BE WARMING TOO WITH 40 DEGREE
TEMPERATURES PUSHING INTO THE LOWER SNAKE PLAIN TODAY WITH MOST OF
THE SNAKE PLAIN IN THE 40S ON THURSDAY. HEADLINES STILL LOOK
APPROPRIATE, MAIN IMPACTS EXPECTED TO BE NEAR GALENA SUMMIT.
13
LONG TERM
FRIDAY THROUGH WEDNESDAY.
BIG PICTURE REMAINS UNCHANGED, HOWEVER LOTS OF DEVILS IN THE
DETAILS. FIRST QUESTION, SOME MODELS ARE SHOWING THE PLUME OF
MOISTURE ASSOCIATED WITH THE ATMOSPHERIC RIVER NOT LETTING UP ON
FRIDAY ACROSS THE CENTRAL MOUNTAINS BUT CONTINUING INTO THE WEEKEND.
THE GFS AND ECMWF DETERMINISTIC IN PARTICULAR KEEP THE TRAIN
ROLLING, WHILE THE NAM DOES LIFT IT NORTH SOME. IN ADDITION, WARMER
AIR WILL BE PUSHING INTO THE REGION SENDING SNOW LEVELS HIGHER.
POTENTIALLY EVEN ABOVE GALENA SUMMIT. SO, WILL LEAVE THE WARNING
CONTINUING THROUGH 12Z FRIDAY STILL BUT LATER SHIFTS MAY NEED TO
EXTEND IT.
STILL LOOKING AT THE COLD FRONT MARCHING THROUGH EAST IDAHO ON
SATURDAY. THIS WILL BRING WIDESPREAD PRECIPITATION TO THE REGION.
SNOW LEVELS GENERALLY LOOK TO BE ABOVE 6000 FEET AND DO NOT FALL TO
VALLEY FLOORS UNTIL LATE SATURDAY NIGHT. SNOW AMOUNTS FOR SATURDAY
THROUGH SATURDAY NIGHT LARGELY LOOK SUB-ADVISORY EXCEPT ALONG A FEW
MOUNTAIN PASSES SUCH AS GALENA, THE ISLAND PARK AREA, AND EMIGRATION
SUMMIT.
THE NEXT QUESTION COMES INTO PLAY SUNDAY INTO MONDAY WHEN SOME
MODELS SHOW A WEAK LOW MOVING THROUGH NORTHERN UTAH AND SOUTHERN
IDAHO. RIGHT NOW, MODELS SHOW 1 TO 3 INCHES IN THE VALLEYS WITH UP
TO 8 INCHES ON THE RIDGE TOPS. BUT THIS IS THE TYPE OF PATTERN THAT
OFTEN OVERACHIEVES ACROSS SOUTHEAST IDAHO AND IS SOMETHING TO KEEP
AN EYE ON.
FINALLY, THE MAIN LOW WILL MOST LIKELY WORK THROUGH THE REGION
TUESDAY. CURRENTLY THE FORECAST HAS HIGH PRECIPITATION CHANCES BUT
LOW QPF, MOST LIKELY BECAUSE OF HIGH SPREAD ACROSS MODEL MEMBERS AS
TO HOW MUCH MOISTURE THERE IS TO WORK WITH. BUT POTENTIALLY, THIS
COULD BE ANOTHER OPPORTUNITY FOR SNOWFALL IN THE VALLEYS. LOOKS LIKE
WE MAY BEGIN TO DRY OUT AFTER WEDNESDAY, BUT WE GET NOTICEABLY
COLDER AS WELL. BUNDLE UP FOR THANKSGIVING WITH MOST AREAS HAVING A
GOOD CHANCE OF NOT EVEN REACHING 32 DEGREES FOR A HIGH.
13
AVIATION...20/12Z TO 21/12Z
AN APPROACHING FRONT HAS DEVELOPED OR
WILL SHORTLY DEVELOP CIGS FOR THE THREE VALLEY AIRPORTS AT
600MB/10000AGL, KBYI, KPIH, AND KIDA. SOME LOW CLOUDS DEVELOP, AT
VARIOUS COVERAGES, BELOW 700MB/6000AGL, BUT ONLY KIDA HAS A RISK OF
SOME VERY TEMPORARY MARGINAL VFR FOR CIG DURING THE DAY TODAY. THOSE
LOW CLOUDS ARE AT KBYI AT 20/15Z, THEN AT KPIH AT 20/18Z, THEN KIDA
AT 20/21Z. KDIJ IS PROGGED TO GET THOSE LOWER CLOUDS AT 21/00Z, AND
IT IS POSSIBLY A CIG. THESE FOUR AIRDROMES HAVE VERY LITTLE CHANCE
OF PRECIPITATION DURING THE DAY AND EVENING, WITH ONLY KBYI
QUALIFYING FOR A VCSH WITH SOME 20 PERCENT-PLUS POPS FOR DURING THE
DAY. IN ALL CASES, THE CIG RETURNS TO MID-LEVELS.
KSUN IS A DIFFERENT KIND OF FLYING, ALTOGETHER. A WALL OF MOISTURE
ARRIVES AT 19/15Z. THE TEMPERATURES ARE COLD ENOUGH FOR SN, BUT THE
GUIDANCE WANTS TO KEEP CIGS VFR AND VSBY UNLIMITED WITH NEAR ZERO
CHANCE OF EVEN MARGINAL VFR FOR THE VSBY. THIS IS DESPITE HIGH
PROBABILITIES OF PRECIPITATION, ABOVE 50 PERCENT FOR THE FIRST TWO
SIX HOUR PERIODS IN THIS TAF. AND IT IS ONLY MARGINALLY HIGHER
THREAT, APPROACHING 10 PERCENT, FOR THE PERIOD BEYOND 21/04Z. THIS
DOESN'T SEEM TO GO TOGETHER TOO WELL. HOWEVER, THE HRRR INDICATES
ONLY WEAK PRECIPITATION THIS FAR SOUTH IN THE CENTRAL IDAHO
MOUNTAINS, SO WILL STICK WITH THE VFR CONDITIONS. THERE IS SOME RASN
CHANCES AS TEMPERATURES WARM DURING THE AFTERNOON AT KSUN, BECOMING
NEARLY ALL RA BY 20/20Z TO 21/03Z. THIS WOULD HELP VSBY STAY UP, AND
WOULD AID SLIGHTLY FOR CIG.
WIND-WISE, THE FRONT IS EXPECTED TO BRING WIND ON THE ORDER OF
15G25KT TO KBYI AND KPIH, FROM THE SOUTH. MESSICK
PIH WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING FROM 5 AM EARLY THIS MORNING TO 5 AM MST
FRIDAY FOR IDZ072>074.
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