761
FXUS65 KPIH 202227
AFDPIH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
327 PM MST WED NOV 20 2024
SHORT TERM
TODAY THROUGH THURSDAY.
AN ATMOSPHERIC RIVER EVENT STARTED THIS MORNING FOR THE WESTERN
CENTRAL MOUNTAINS AND THE SAWTOOTH MOUNTAINS. PACIFIC MOISTURE IS
MOVING INTO THIS AREA DUE TO AN UPPER LEVEL LOW JUST OFF THE
WASHINGTON COAST. A WINTER STORM WARNING IS STILL IN EFFECT FOR
HEAVY SNOW THROUGH FRIDAY MORNING FOR THE WESTERN CENTRAL
MOUNTAINS AND THE SAWTOOTH MOUNTAINS.
MODELS SHOW THIS MOISTURE STREAM FOR THE NORTHERN AND WESTERN
CENTRAL MOUNTAINS AND SAWTOOTH MOUNTAINS TO CONTINUE THROUGH
EARLY FRIDAY, IF NOT LONGER. STILL LOOKING FOR SNOW AMOUNTS IN THE
WOOD RIVER VALLEY AROUND 2 TO 8 INCHES THROUGH FRIDAY MORNING.
LOOK FOR 14 TO 20 INCHES OF SNOW FOR GALENA SUMMIT AND UP TO 2
FEET (POSSIBLY HIGHER UP TO 3 INCHES) FOR EXTREME WESTERN SLOPES
FOR CENTRAL MOUNTAINS AND SAWTOOTH MOUNTAINS. MODELS CONSISTENTLY
SHOW SNOW LEVELS RISING FROM 5000 FEET TO AROUND 6500 TO 7000 FEET
BY FRIDAY. SOME MODELS SUGGEST SNOW LEVELS COULD GO AS HIGH AS
7500 TO 7800 FEET IN THE NORTHERN CENTRAL MOUNTAINS AND SAWTOOTH
MOUNTAINS BY FRIDAY. THESE RISING SNOW LEVELS WILL MAKE IT HARD TO
KNOW EXACTLY HOW MUCH SNOW WILL HAPPEN IN LOWER LEVELS THROUGH
THE PERIOD, ESPECIALLY FOR CITIES LIKE STANLEY, KETCHUM, AND
HAILEY. THERE IS A 10 TO 20 PERCENT CHANCE FOR HAILEY TO GET 3
INCHES OF SNOW THROUGH FRIDAY MORNING. THERE IS A 30 TO 40 PERCENT
CHANCE OF KETCHUM TO GET 3 INCHES OF SNOW. AND THERE IS A 60 TO
70 PERCENT CHANCE FOR STANLEY TO GET 3 INCHES OF SNOW THROUGH
FRIDAY MORNING. THE NBM MODEL SHOWS A 100 PERCENT CHANCE FOR
GALENA SUMMIT GETTING 8 INCHES OR MORE OF SNOW THROUGH FRIDAY
MORNING.
OUTSIDE OF THE CENTRAL MOUNTAINS AND THE SAWTOOTH MOUNTAINS, NOT
MUCH RAIN AND SNOW IS EXPECTED FOR OTHER AREAS UNTIL THE WEEKEND.
ONLY THE BIG LOST AND MONTANA DIVIDE WILL GET LIGHT PRECIPITATION
THE NEXT COUPLE OF DAYS. SNOW LEVELS WILL START AT VALLEY FLOORS
AND RISE TO AROUND 7000 FEET FOR THE BIG LOST RANGE AND AROUND 6000
FEET FOR THE MONTANA DIVIDE BY FRIDAY MORNING.
MORE RAIN AND SNOW IS EXPECTED FRIDAY AND OVER THE WEEKEND.
PLEASE SEE LONG TERM DISCUSSION FOR MORE DETAILS.
WYATT
LONG TERM
FRIDAY THROUGH NEXT WEDNESDAY.
ACTIVE AND UNSETTLED WEATHER WILL CONTINUE FRIDAY AND THROUGH THE
WEEKEND AS ATMOSPHERIC RIVER MOISTURE AND A H5 TROUGH CONTINUE TO
BUILD INTO IDAHO FROM THE PACIFIC, BRINGING SEVERAL ROUNDS OF RAIN
AND SNOW SHOWERS WITH IT. FOR FRIDAY, A WARM FRONT LIFTING NORTH
WILL LEAD TO PREDOMINANT SW FLOW AND WILL BRING SNOW LEVELS UP TO
8000-9000 FEET WITH ABOVE NORMAL HIGHS IN THE MID 40S TO UPPER 50S.
STARTING FRIDAY NIGHT INTO SATURDAY, A COLD FRONT WILL WORK THROUGH
THE PACNW WITH WIDESPREAD PRECIPITATION OF WHICH COULD BE MODERATE
TO HEAVY AT TIMES ESPECIALLY IN THE MOUNTAINS. HERE IS WHERE WE WILL
SEE SNOW LEVELS GRADUALLY FALL TO VALLEY FLOORS THROUGHOUT THE DAY
SATURDAY INTO SATURDAY NIGHT. WHILE MOST FOLKS WILL HAVE REMAINED
FAIRLY DRY AHEAD OF THIS COLD FRONT, WE ARE LOOKING AT PRECIPITATION
TOTALS FRIDAY THROUGH SATURDAY NIGHT TO THE TUNE OF 0.20-0.50" OF
QPF/RAIN ACROSS THE SNAKE RIVER PLAIN AND SRN/ERN HIGHLANDS WITH
0.50-1.50" IN THE WRN-CNTRL MOUNTAINS AND ISLAND PARK REGION. GIVEN
W/SW MOISTURE TRANSPORT WITH THIS SYSTEM, THIS SYSTEM WILL FAVOR
THOSE AREAS IN THIS REGIME WITH EFFICIENT UPSLOPE OROGRAPHICS AT
PLAY LEADING TO SIGNIFICANT MOUNTAIN SNOW POTENTIAL, ESPECIALLY IN
THE MOUNTAINS UP AROUND THE NRN WOOD RIVER VALLEY AND SAWTOOTH
VALLEY.
WINTER STORM WARNINGS REMAIN IN EFFECT FOR THE NRN WOOD RIVER VALLEY
AND SAWTOOTH VALLEY REGION THROUGH 5 AM MST FRIDAY AND GIVEN A
WARMER AIRMASS BUILDING IN, MAY NEED TO BE DROPPED TO A WINTER
WEATHER ADVISORY AS SNOW LEVELS CLIMB TO 7000-8000 FEET. ELSEWHERE,
THE ONLY OTHER POTENTIAL FOR WINTER WEATHER ADVISORIES FRIDAY NIGHT
INTO SATURDAY LOOKS TO BE AROUND ISLAND PARK AND THE BIG HOLES/BEAR
RIVER RANGE WHICH WILL NEED TO CONTINUE TO BE MONITORED IN FUTURE
FORECAST UPDATES. SNOW TOTALS ELSEWHERE WITH THIS COL DIFFERENT WILL
REMAIN IN THAT T-2" RANGE IN THE VALLEYS AND AN ELEVATION DEPENDENT
2-6" WITH LOCALLY HIGHER TOTALS IN THE LOST RIVER AND LEMHI RANGES.
CLOSING OUT THE WEEKEND INTO EARLY NEXT WEEK, A COLDER AIRMASS WILL
SETTLE BACK INTO PLACE WITH HIGHS RETURNING TO THE 30S/40S STARTING
SUNDAY. DRIER AIR WILL ALSO BUILD IN BEHIND THIS COLD FRONT FOR
SUNDAY WITH BOTH THE ECMWF/GFS ENS/DETERMINISTIC MODELS FAVORING A
BRIEF RIDGE OF HIGH PRESSURE BUILDING IN AS A COLD FRONT DEPARTS
EAST OVER THE CONTINENTAL DIVIDE. WE WILL STILL LIKELY SEE SOME SNOW
SHOWERS CONTINUE SUNDAY INTO EARLY NEXT WEEK AS A MOIST ZONAL/NW
UPPER LEVEL FLOW PATTERN KEEPS MOISTURE BUILDING IN. INCREASED
UNCERTAINTY SURROUNDS EXACTLY WHAT HAPPENS EARLY NEXT WEEK WITH BOTH
THE GFS/ECMWF SHOWING SOME SORT OF ORGANIZED OR SPLIT TROUGH MOVING
ONSHORE. GIVEN THE INCREASED UNCERTAINTY AT THIS TIME, WILL KEEP
WITH A COLDER FORECAST AND ISOLATED TO SCATTERED PRECIPITATION
CHANCES AND WE WILL NARROW DOWN THE DETAILS WE GET CLOSER TO SEE
WHERE THE BULK OF MOISTURE ENDS UP. CASE IN POINT, IT IS CERTAINLY
STARTING TO FEEL MORE LIKE NOVEMBER IN THE PACNW!
MACKAY
AVIATION
18Z TAFS THROUGH 18Z THURSDAY.
WIDESPREAD CLOUD COVER AND A MIX OF RAIN/SNOW SHOWERS AT TIMES WILL
BE THE GOING TREND OVER THE NEXT SEVERAL DAYS AS AN ATMOSPHERIC
RIVER CONTINUES TO BRING MOISTURE INTO IDAHO FROM THE PACIFIC. GIVEN
THE ORIENTATION OF MOISTURE TRANSPORT FAVORING THE CENTRAL MOUNTAINS
INTO THURSDAY, KSUN WILL CONTINUE TO BE THE MOST AFFECTED SITE WITH
MVFR/IFR CIGS/VIS POTENTIAL AT TIMES DUE TO BANDS OF MODERATE TO
HEAVY SNOW. PREDOMINANT VFR CONDITIONS ARE EXPECTED ELSEWHERE AT
KPIH, KIDA, KBYI, AND KDIJ WHERE DRIER CONDITIONS ARE EXPECTED TO
PREVAIL OUTSIDE OF ISOLATED SHOWERS/VIRGA.
WHILE KSUN WILL SEE BREAKS IN THE SNOW THIS AFTERNOON, CONDITIONS
LOOK TO DETERIORATE OVERNIGHT TONIGHT INTO THURSDAY MORNING AS
ANOTHER WIDESPREAD PLUME OF MOISTURE WORKS INTO THE WOOD RIVER
VALLEY. WHAT THIS MEANS FOR OTHER TERMINALS WILL BE AN INCREASE IN
ISOLATED TO SCATTERED RAIN/SNOW SHOWER POTENTIAL ON THURSDAY AT ALL
OTHER TAF SITES. CAMS REMAIN MORE UNCERTAIN ON EXACTLY WHERE THESE
SHOWERS WILL DEVELOP BUT CEILINGS WILL DROP FURTHER ON THURSDAY AS
MOISTURE CONTINUES TO BUILD IN. WINDS THROUGH THE TAF PERIOD WILL
REMAIN LIGHT, REMAINING LESS THAN 12 KTS AT ALL TERMINALS.
MACKAY
PIH WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL 5 AM MST FRIDAY FOR IDZ072>074.
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