964
FXUS65 KPIH 212353
AFDPIH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
453 PM MST SUN DEC 21 2025
KEY MESSAGES
- HIGH ELEVATION SNOWFALL EVENT THROUGH EARLY MONDAY. WINTER
STORM WARNINGS AND WINTER WEATHER ADVISORIES IN EFFECT FOR
PORTIONS OF EAST IDAHO.
- WEATHER PATTERN REMAINS ACTIVE THROUGH CHRISTMAS WEEK.
- CONTINUED WELL ABOVE NORMAL TEMPERATURES THROUGH CHRISTMAS.
SLIGHT COOLING BUT STILL ABOVE NORMAL NEXT WEEKEND.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 116 PM MST SUN DEC 21 2025
ATMOSPHERIC RIVER EVENT ONGOING ACROSS EAST IDAHO PER SATELLITE
AND RADAR IMAGERY, AND SURFACE OBSERVATIONS. TEMPERATURE AND
SNOW LEVEL GRADIENT IS QUITE TIGHT ACROSS THE REGION, WITH THE
RAIN/SNOW LINE HAILEY TO ISLAND PARK. SURFACE FREEZING LINE IS
GRADUALLY SHIFTING NORTH AS EXPECTED, ALBEIT SLIGHTLY SLOWER
THAN PREVIOUSLY EXPECTED. HEAVIEST ACCUMULATIONS STILL EXPECTED
ABOVE 7500 FT THROUGH TONIGHT, WITH MODEL MEANS STILL SUPPORTING
24-HR LIQUID AMOUNTS EXCEEDING 1.5" AND 10TH PERCENTILE AMOUNTS
EXCEEDING 1.0" LIQUID ACROSS HIGHER ELEVATIONS OF THE CENTRAL
MOUNTAINS AND THE HIGHEST ELEVATIONS ALONG THE WY BORDER NEAR
AND NORTH OF THE BIG HOLES. CURRENT RANGE OF WINTER HEADLINES
REMAIN WELL SUPPORTED, THOUGH COULD SEE SOUTHERN ZONES
CANCELING EARLY OVERNIGHT AS THE WARM AIR MASS BECOMES MORE
ENTRENCHED AND SNOW LEVELS CONTINUE TO RISE.
MAIN SHORTWAVE DRIVES EAST OF THE REGION DURING THE DAY ON
WEDNESDAY, LEAVING A BROKEN DEFORMATION ZONE OF PRECIPITATION
ACROSS THE REGION. ANY OROGRAPHIC PRECIPITATION THAT CAN
CONTINUE DURING THE DAY SHOULD BE MUCH LIGHTER, SO A RELATIVE
BREAK IS EXPECTED. NEXT WARM SURGE LATE IN THE DAY RE-
CONSOLIDATES THE BAND INTO A NEW WARM FRONTAL FEATURE, AND LIFTS
NORTH DURING THE OVERNIGHT MONDAY NIGHT. TEMPERATURES REMAIN
WELL ABOVE NORMAL FOR THE BEGINNING OF CHRISTMAS WEEK WITH
OVERNIGHT LOWS AROUND OR ABOVE WHERE NORMAL HIGHS SHOULD BE.
LONG TERM /MONDAY THROUGH SUNDAY/
ISSUED AT 116 PM MST SUN DEC 21 2025
WE ARE STILL LOOKING AT A BAND OF RAIN AND SNOW TO LIFT NORTHWEST
OUT OF OUR ARE TUESDAY AS ANOTHER LOW HELPS RELOAD THE PATTERN
TO OUR WEST. FOR CHRISTMAS EVE DAY AND NIGHT, WE SEE A QUICK BUT
POTENTIALLY HEALTHY SHOT OF RAIN AND SNOW ACROSS CENTRAL AND
EASTERN IDAHO. WITH STRONG SOUTHERLY FLOW INTO OUR AREA, WE ARE
LOOKING AT FAIRLY STRONG UPSLOPE INTO PLACES LIKE THE WOOD RIVER
VALLEY, ARCO, MONIDA PASS, AND ISLAND PARK. MEANWHILE,
DOWNSLOPE IS LIKELY ALONG AND SOUTH OF THE SNAKE RIVER INTO THE
TETON VALLEY. WE DID KNOCK DOWN THE PRECIPITATION AMOUNTS A BIT
AS IT APPEARS THE NUMBERS MIGHT BE INFLUENCED BY SOME
UNREALISTIC AMOUNTS COMING FROM THE GFS. THE LATEST
PRECIPITATION AMOUNTS ARE IN THE 0.30-0.70" RANGE WHERE THE BULK
OF THE MOISTURE FALLS. PLACES LIKE THE CHALLIS AND PAHSIMEROI
VALLEYS ARE LOOKING AT A MAJOR SHADOW EFFECT AND CLOSER TO 0.10"
OR LESS. HIGHER ELEVATIONS ARE LOOKING AT UPWARDS OF 1" IN
FAVORED AREAS. THERE ARE A FEW POCKETS OF 1.0-1.25" CURRENTLY IN
THE FORECAST, WHICH IS SOMEWHAT BACKED UP BY PROBABILITY
FORECASTS THAT HAVE A 20-40% CHANCE OF MORE THAN 1.0". IF YOU
TOOK THE GFS AT FACE VALUE, WE COULD HAVE ANOTHER 0.20-0.50"
ACROSS THE AREA. DO EXPECT THESE NUMBERS TO CHANGE AS WE GET
CLOSER, BUT JUST BEWARE THAT THIS TIME PERIOD COULD BE ANOTHER
WET AND IMPACTED TRAVEL PERIOD FOR US. THE ECMWF IS A BIT SLOWER
THAN OTHER MODELS, AND ACTUALLY HOLDS ON TO HEAVIER
PRECIPITATION ESPECIALLY ACROSS THE CENTRAL MOUNTAINS FOR
CHRISTMAS. THE REST OF THE MODEL NUMBERS POINT TO KEEPING SOME
SHOWERS AROUND BUT NOTHING TOO CRAZY AMOUNT-WISE. OUR BLEND OF
MODELS IS NOT FOLLOWING THE ECMWF'S PLAN AT THE MOMENT. THE
LATEST TRENDS IN THE EXTENDED MODELS AND BLEND OF MODELS IS TO
DRY THINGS OUT BY THE END OF THE EXTENDED HOLIDAY WEEKEND. THE
GFS, EARLIER RUN OF THE ECMWF AND BLEND OF MODELS CLOSE A LOW
OFF WELL TO OUR SOUTHWEST OVER THE WEEKEND AND PULLS ALL OF THE
MOISTURE OUT OF IDAHO. TEMPERATURES THROUGH CHRISTMAS REMAIN
WELL ABOVE AVERAGE, WITH COOLER TEMPERATURES RETURNING AS EARLY
AS FRIDAY. EVEN THEN, THE CURRENT FORECAST HAS HIGHS AT OR JUST
ABOVE AVERAGE.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 425 PM MST SUN DEC 21 2025
MODELS SHOW THE ATMOSPHERIC RIVER MOISTURE CURRENTLY OVER OUR
AREA TO SHIFT SOUTH SLIGHTLY AND TO CONTINUE TO BRING OVERALL
SOUTHERLY MOIST FLOW TO THE AREA. AS A RESULT, ALL TAF SITE
HAVE WARMED UP, AND ALL REMAINING PRECIPITATION WILL BE ALL
RAIN. MODELS SHOW MAXIMUM WINDS OF AROUND 20KTS SUSTAINED FROM
THE SOUTH FOR MAINLY PIH AND IDA WILL OCCUR AROUND 12Z. EXPECT
CONTINUED SHOWERS FOR ALL TAF SITES EXCEPT BYI. SHOWERS LOOK TO
REMAIN JUST SOUTH OF BYI. SUN MAY SEE A BRIEF BREAK IN SHOWERS
WITH JUST VICINITY SHOWERS FOR A SHORT PERIOD THIS EVENING.
HOWEVER, SHOWERS SHOULD CONTINUE BY LATE MORNING AND CONTINUE
THROUGH TOMORROW EVENING WITH SOUTHERLY, MOIST UPSLOPE FLOW INTO
SUN. MODELS SHOW PIH WITH MVFR CIGS BY THE MORNING. HOWEVER,
DOWNSLOPE WINDS COULD KEEP SHOWERS LIGHTER AND CIGS HIGHER THAN
THE CURRENT FORECAST. MODELS SHOW MVFR/IFR CONDITIONS WITH RAIN
SHOWERS AND GUSTS OF 20 TO 25KTS FOR IDA AND DIJ FOR THIS
EVENING INTO TOMORROW AFTERNOON.
PIH WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 11 AM MST MONDAY FOR IDZ060-064-
066-075.
WINTER STORM WARNING UNTIL 11 AM MST MONDAY FOR IDZ071>074.
SHORT TERM...DMH
LONG TERM...KEYES
AVIATION...TW
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