720
FXUS65 KRIW 171908
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1208 PM MST WED DEC 17 2025
KEY MESSAGES
- HIGH WIND WARNINGS ARE IN EFFECT THROUGH TODAY FOR WIDESPREAD GUSTS
OF 50 MPH OR GREATER.
- MODERATE SNOW CONTINUES ACROSS PORTIONS OF THE WESTERN
WYOMING MOUNTAINS, WHICH LESSENS THROUGH THE AFTERNOON.
COMBINED WITH GUSTY WINDS, EXPECT VERY IMPACTFUL WINTER TRAVEL
CONDITIONS ACROSS MOUNTAIN PASSES.
- ANOTHER WEATHER SYSTEM BRINGS GUSTY WINDS AND HEAVY WESTERN
MOUNTAIN SNOW THURSDAY AFTERNOON THROUGH FRIDAY.
UPDATE
ISSUED AT 1206 PM MST WED DEC 17 2025
STRONG WINDS HAVE BEEN OBSERVED ALREADY ACROSS THE AREA, WITH HIGH
WIND WARNINGS IN EFFECT FOR THE AREA THROUGH AT LEAST THIS EVENING.
HAVE EXTENDED THE HIGH WIND WARNING FOR THE BUFFALO AREA THROUGH
EARLY TOMORROW MORNING FOR THE PROLONGED THREAT OF DOWNSLOPING
MOUNTAIN WINDS, AND A NORTHERLY WIND SHIFT WHICH FAVORS STRONGER
WINDS THERE. WINDS BEGIN TO DECREASE LATE AFTERNOON AND INTO THE
EVENING, THOUGH REMAINS GUSTY THROUGH TONIGHT.
FOR THE NEXT SYSTEM, WHICH IS QUICK TO FOLLOW, SNOW CHANCES BEGIN
OVER THE WESTERN MOUNTAINS AS EARLY AS ABOUT SUNRISE, WITH THE MAIN
PUSH ARRIVING EARLY THURSDAY AFTERNOON. PERIODS OF HEAVY, WET SNOW
ARE EXPECTED OVER THE WESTERN MOUNTAINS THROUGH FRIDAY. TO AVOID ANY
CONFUSION, HAVE HELD OFF ANY WINTER HIGHLIGHTS (WIND OR SNOW) WITH
THIS NEXT SYSTEM SO THE CURRENT HIGHLIGHTS CAN EXPIRE LATER TODAY
OR TONIGHT.
DISCUSSION
ISSUED AT 258 AM MST WED DEC 17 2025
RECORD BREAKING WARMTH CONTINUED ACROSS THE COWBOY STATE ON MONDAY.
IF YOU WERE TO LOOK AT THE HIGH TEMPERATURES ACROSS MANY LOCATIONS
EAST OF THE DIVIDE OVER THE PAST TWO WEEKS, YOU WOULD THINK ITS
CURRENTLY MID OCTOBER. HIGH TEMPERATURES HAVE BEEN NEARLY 20 TO
30 DEGREES ABOVE NORMAL FOR A PROLONGED PERIOD AND THAT
CONTINUES TODAY. TEMPERATURES ONCE AGAIN WILL BE VERY MILD WITH
HIGHS IN THE MID 50S EAST OF THE DIVIDE AND LOW TO MID 40S WEST
OF THE DIVIDE. FRANKLY, WE MAY SEE SOME LOCATIONS EAST OF THE
DIVIDE NEAR 60 ONCE AGAIN, ESPECIALLY ONCE WINDS PICK UP AND MIX
DOWN DURING THE AFTERNOON TODAY.
TEMPERATURES WHILE BEING WELL ABOVE NORMAL ARE GOING TO BE THE LEAST
CONCERN TODAY. THE NEXT DISTURBANCE WILL BRING WIDESPREAD IMPACTFUL
WEATHER TO THE STATE STARTING THIS MORNING. THE MAIN CATALYST IS A
POTENT UPPER-LEVEL LOW CURRENTLY DEVELOPING OVER THE PACNW. THIS LOW
WILL MAKE ITS WAY EAST REMAINING WELL TO THE NORTH OF THE STATE.
HOWEVER, A POTENT JET STREAK ASSOCIATED WITH THIS DISTURBANCE
WILL MAKE ITS WAY SOUTH BRINGING WITH IT WIDESPREAD STRONG GUSTY
WINDS. MODELS HAVE AND CONTINUE TO REMAIN VERY BULLISH WITH
700MB WINDS OF 60 TO 80 KNOTS ACROSS MUCH OF THE REGION. THESE
WINDS START EARLY WEDNESDAY MORNING AND INTENSIFY THROUGH THE
MID TO LATE MORNING INTO THE AFTERNOON. SURFACE WIND GUSTS OF 60
MPH WILL BE COMMON (60-80%) OVER MOST OF THE CWA WITH STRONGER
GUSTS POSSIBLE IN WIND PRONE AREAS. DOWNSLOPING ACROSS EASTERN
SLOPES MAY CREATE STRONGER GUSTS EXCEEDING 60 MPH IN SOME
LOCATIONS, ISOLATED GUSTS NEARING 70 MPH CANNOT BE RULED OUT AT
TIMES. FAVORABLE LOCATIONS THAT MAY POSSIBLY SEE THESE WIND
GUSTS OF 70 MPH OR MORE INCLUDE CODY, LANDER, AND BUFFALO WITH
PROBABILISTIC CHANCES RANGING FROM 40 TO 70%. WINDS LOOK TO
GRADUALLY DECREASE OVER MUCH OF THE STATE AFTER SUNSET. HOWEVER,
THERE IS SOME EXCEPTIONS TO THIS AND THAT LOOKS TO BE ALONG THE
EASTERN SLOPES OF THE ABSAROKAS AND BIGHORNS. HI-RES MODELS
HAVE PICKED UP ON A LINGER PUSH OF STRONG WINDS AROUND 60 MPH
MOVING THROUGH THESE AREAS DURING THE EARLY MORNING HOURS
THURSDAY. AS A RESULT OF THIS HIGH WIND WARNINGS HAVE BEEN
EXTENDED TO 5 AM MST ON THURSDAY. NO FURTHER CHANGES HAVE BEEN
MADE TO PREVIOUS HIGH WIND WARNINGS.
THE OTHER ASPECT OF THIS SYSTEM WILL BE PERIODS OF HEAVY SNOWFALL
ACROSS THE HIGHER ELEVATIONS OF WESTERN WY MOUNTAINS. PRECIPITATION
WILL CONTINUE TO SPREAD IN COVERAGE EARLY THIS MORNING.
STRENGTHENING WESTERLY 700MB WINDS WILL ENHANCE OROGRAPHIC DYNAMICS
DURING THE MID TO LATE MORNING AND EARLY AFTERNOON WEDNESDAY. THIS
PERIOD WILL LIKELY SEE THE HEAVIEST SNOWFALL FOR WESTERN MOUNTAINS
WITH SNOWFALL RATES OF 1 TO EVEN 2 INCHES POSSIBLE. THE HEAVIEST
SNOW IS EXPECTED TO BE LIMITED TO THE HIGHEST ELEVATIONS ABOVE 8,500
FEET DUE TO WARM TEMPERATURES. A NEARING COLD FRONT AND ITS PASSAGE
WILL BEGIN TO CUTOFF THE HEAVIEST PRECIPITATION OVER WESTERN WY. THE
TIMING LOOKS TO BE IN THE LATE AFTERNOON ON WEDNESDAY WITH IT
GRADUALLY SPREADING OVER CENTRAL WY BY THE LATE EVENING WEDNESDAY
INTO THE EARLY MORNING HOURS THURSDAY. STORM TOTAL SNOWFALL AMOUNTS
HAVE REMAINED FAIRLY CONSISTENT OVER THE PAST 24 HOURS WITH NOT MUCH
CHANGE TO NOTE. THE HIGHER ELEVATIONS ABOVE 8,500 FEET ACROSS THE
TETONS, GROS VENTRE AND WIND RIVER RANGES CURRENTLY LOOK TO SEE
ANYWHERE FROM 6 TO 12 INCHES. HIGHER PEAKS MAY SEE AMOUNTS NEARING
14 TO 18 INCHES. OTHER LOCATIONS SUCH AS THE WESTERN ABSAROKAS, THE
SALT RIVER/WYOMING, AND HIGHER ELEVATIONS OF YNP CAN SEE AMOUNTS OF
6 TO 12 INCHES. LOCALLY HIGHER AMOUNTS OF 8 TO 14 INCHES ARE
POSSIBLE OVER SOUTHWESTERN YNP SPECIFICALLY PITCHSTONE PLATEAU. WARM
TEMPERATURES WILL GREATLY LIMIT SNOW ACCUMULATIONS ACROSS LOWER
ELEVATIONS AND WESTERN VALLEYS. STORM TOTAL AMOUNTS FOR THESE AREAS
ARE LOW RANGING FROM A WET SLUSHY COATING TO AN INCH OR TWO. NO
CHANGES HAVE BEEN MADE TO WINTER RELATED HIGHLIGHTS AND AS A RESULT
WINTER STORM WARNINGS REMAIN IN PLACE FOR WESTERN MOUNTAINS THROUGH
LATE WEDNESDAY EVENING.
PRECIPITATION IS FORECAST TO REMAIN MOSTLY CONFINED TO PORTIONS OF
WESTERN WY AND HIGHER ELEVATION MOUNTAINS. HOWEVER, SOME SHOWERS
WILL BE POSSIBLE AHEAD OF THE COLD FRONTS PASSAGE. THE TIMING FOR
THESE SHOWERS EAST OF THE DIVIDE LOOKS TO BE AROUND LATE MORNING
THROUGH THE EARLY AFTERNOON. TEMPERATURES WILL BE TOO WARM FOR ANY
SNOWFALL SO IF ANY PRECIPITATION DOES FALL EAST OF THE DIVIDE IT
WOULD LIKELY BE IN THE FORM OF RAIN. OVERALL, ONLY LIGHT
PRECIPITATION LOOKS POSSIBLE EAST OF THE DIVIDE AND WILL BE
ISOLATED. THERE IS ONE CAVEAT THOUGH AND THAT IS THE SMALL
POSSIBILITY FOR A VERY ISOLATED THUNDERSTORM. THIS WILL ALSO BE
POSSIBLE WEST OF THE DIVIDE WITH THE CHANCE FOR A FEW STRIKES OF
LIGHTNING AND RUMBLES OF THUNDER NOT COMPLETELY OFF THE TABLE.
THURSDAY WILL SEE TEMPERATURES THAT ARE COOLER BUT STILL ABOVE
NORMAL. WHILE IT MAY NOT FEEL LIKE OCTOBER ON THURSDAY IT STILL WILL
NOT BE FEELING LIKE DECEMBER. HIGHS ARE FORECAST TO RANGE IN THE LOW
40S EAST OF THE DIVIDE AND MID TO UPPER 30S WEST OF THE DIVIDE. SO
INSTEAD OF DECEMBER TEMPERATURES WILL BE MORE LIKE NOVEMBER, WHICH
IS A SLIGHT IMPROVEMENT TOWARDS NORMALCY THAT SAYS A LOT ABOUT
HOW THE MONTH HAS GONE SO FAR. OTHERWISE, ANOTHER DISTURBANCE
TAKES AIM AT THE STATE WITH VERY SIMILAR IMPACTS AS THIS CURRENT
DISTURBANCE. WET HEAVY SNOW LOOKS INCREASINGLY LIKELY FOR
WESTERN MOUNTAINS WITH WIDESPREAD STRONG GUSTY WINDS RETURNING
TO THE AREA AS WELL. CURRENTLY THE TIMING FOR PRECIPITATION
WOULD BE THURSDAY AFTERNOON WITH WINDS GRADUALLY INCREASING LATE
THURSDAY INTO FRIDAY. THE GREATEST IMPACTS ARE LIKELY TO BE
LIMITED TO THE WESTERN MOUNTAINS AND PASSES DUE TO THE
COMBINATION OF STRONG WINDS AND HEAVY SNOW. WINDS THANKFULLY DO
NOT LOOK AS INTENSE BUT SOME STRONG GUSTY WINDS DO LOOK
POSSIBLE. WINTER RELATED HIGHLIGHTS MAY NEED TO BE ISSUED DUE TO
INCREASING CONFIDENCE IN SNOW AMOUNTS.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1055 AM MST WED DEC 17 2025
WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI TERMINALS
VIGOROUS SHORTWAVE TROUGH DRIVEN BY AN APPROACHING 130-150KT JET IS
MOVING ACROSS THE REGION LATE WEDNESDAY MORNING. UPSTREAM
INSTABILITY IS EVIDENCED BY THUNDERSTORMS ACROSS SOUTHEAST
IDAHO. ONGOING IFR/MVFR SNOW TO PERSIST INTO THE AFTERNOON AT
KJAC WITH OCCASIONAL RAIN/SNOW SHOWERS AT KPNA/KBPI AND
EVENTUALLY KRKS BETWEEN 20Z-22Z/WEDNESDAY. PRECIPITATION
GENERALLY DECREASES IN COVERAGE AND INTENSITY FROM WEST-TO-EAST
BETWEEN 20Z-23Z/WEDNESDAY, AS THE SHORTWAVE MOVES EASTBOUND.
CLOUD COVER DECREASES BEHIND THE SHORTWAVE AND ALL TERMINALS ARE
VFR THROUGH 18Z/THURSDAY. THE ALREADY GUSTY WESTERLY SURFACE
WIND RATCHETS UP TO 35-45KTS WEDNESDAY AFTERNOON BEHIND THE
SHORTWAVE AND ASSOCIATED COLD FRONT. SPEEDS WILL NOT BE AS HIGH
AT KJAC, BUT THE DIRECTION WILL BE FROM 240-270 DEGREES. WIND
SPEEDS TREND DOWNWARD FROM 06Z-12Z/THURSDAY AT ALL TERMINALS,
LEAVING KRKS 15-25KTS AS THE ONLY LOCATION WITH SPEEDS GREATER
THAN 10KTS. MOUNTAIN TOPS OBSCURED THROUGH 01Z/THURSDAY.
EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KLND/KWRL TERMINALS
GUSTY WESTERLY SURFACE WIND SPEEDS STEADILY INCREASE WEDNESDAY
AFTERNOON AS A SHORTWAVE TROUGH DRIVEN BY AN APPROACHING 130-150KT
JET BEGINS TO MOVE ACROSS THE REGION. WIDESPREAD 35-45KT WESTERLY
SURFACE WIND PERSISTS THROUGH WEDNESDAY EVENING. SPEEDS
DECREASE BETWEEN 06Z-12Z, BUT GUSTS 25-35KTS ARE STILL LIKELY.
SURFACE WIND 15-25KTS CONTINUES THURSDAY MORNING AT KCPR AND
KCOD, WHILE FINALLY SLOWING TO LESS THAN 10KTS AT OTHER
TERMINALS. THERE SHOULD BE A PERIOD OF ONE TO THREE HOURS OF
ENHANCED WIND SPEEDS, GUSTING 50-55KTS FROM KRIW/KLND TO KCPR,
MID-AFTERNOON WEDNESDAY AS THE COLD FRONT SWEEPS EAST. ISOLATED
CONVECTIVE SHOWERS ARE POSSIBLE WITH FRONTAL PASSAGE. TERMINALS
REMAIN VFR THROUGH THE PERIOD. MOUNTAIN TOPS OCCASIONALLY
OBSCURED THROUGH 02Z/THURSDAY.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZLC AND ZDV FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL 11 PM MST THIS EVENING FOR WYZ001-
002-012-014-015-024.
HIGH WIND WARNING UNTIL 5 AM MST THURSDAY FOR WYZ003-008>010.
HIGH WIND WARNING UNTIL 5 PM MST THIS AFTERNOON FOR WYZ004>007-
011-013-017-018-023-025>029.
HIGH WIND WARNING UNTIL 11 PM MST THIS EVENING FOR WYZ016-019-
020-022-030.
UPDATE...WITTMANN
DISCUSSION...DZIEWALTOWSKI
AVIATION...CNJ
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