708
FXUS65 KRIW 260430
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
930 PM MST THU DEC 25 2025
KEY MESSAGES
- RAIN/SNOW FALLING WEST OF THE DIVIDE OVERNIGHT BUT LIGHT IN
NATURE BECOMING MORE STEADY FRIDAY WITH THE WARM TEMPERATURES
CONTINUING FOR TOMORROW.
- A WEATHER SYSTEM FRIDAY BRINGS WESTERN SNOW AND WIDESPREAD
GUSTY WINDS OVER 30 MPH, WITH MANY AREAS OVER 40 MPH. THIS
SYSTEM ALSO BRINGS A COLD FRONT SATURDAY, WHICH BRINGS MUCH
COOLER (BUT SEASONABLE) TEMPERATURES FOR THE WEEKEND.
UPDATE
ISSUED AT 1232 PM MST THU DEC 25 2025
THE ISOLATED LIGHT RAIN AND SNOW SHOWERS DECREASE THROUGH THE
AFTERNOON, ALONG WITH THE STRONGEST WINDS FROM LAST NIGHT AND THIS
MORNING. GUSTY WINDS ARE STILL EXPECTED OVER THE MOUNTAINS AND THE
USUAL LOCATIONS, LIKE FROM SOUTH PASS TO CASPER. WIDESPREAD WINDS
INCREASE EARLY FRIDAY MORNING. EVIDENCE IS NOT QUITE HIGH ENOUGH FOR
ANY WIND HIGHLIGHTS FRIDAY, WITH 700MB WINDS ONLY PEAKING ABOUT 45
KNOTS. THAT SAID, WIDESPREAD GUSTS 40 TO 50 MPH ARE STILL FORECASTED
ACROSS PORTIONS OF THE AREA, AND LOCALIZED WIND PRONE LOCATIONS,
LIKE OUTER DRIVE IN CASPER, COULD SEE GUSTS MORE IN THE 50 TO 60
MPH RANGE.
FOR SNOW WITH FRIDAY'S SYSTEM, GUIDANCE WOULD SUGGEST AT LEAST
ADVISORY AMOUNTS OVER THE WESTERN MOUNTAINS. WITH RELATIVELY COLDER
TEMPERATURES IN PLACE FRIDAY, (SNOW LEVELS 6000 TO 6500 FEET) WOULD
ACTUALLY HAVE BETTER CONFIDENCE IN SNOW AMOUNTS COMPARED TO THE
RECENT WARMER SYSTEMS WHERE SNOW AMOUNTS GENERALLY UNDERPERFORMED
COMPARED TO WHAT WAS FORECASTED. WINTER WEATHER ADVISORIES HAVE BEEN
ISSUED TO COVER THIS SNOW. MAIN WEATHER IMPACT CONCERNS WOULD BE FOR
ANY TRAVEL OVER MOUNTAIN PASSES, (TETON, TOGWOTEE, SOUTH, ETC.)
WHERE SNOW AND WIND COULD BRING SOME WINTER TRAVEL CONDITIONS.
DISCUSSION
ISSUED AT 152 AM MST THU DEC 25 2025
THE WEATHER HAS BEEN EXCEPTIONALLY ABNORMAL ACROSS WESTERN AND
ESPECIALLY CENTRAL WYOMING FOR MUCH OF THIS MONTH. THIS YEAR,
IT SEEMS LIKE THE SNOW MISER HAS BEEN ON A TWO MONTH LONG LEAVE
OF ABSENCE WITH ONLY CAMEO APPEARANCES AND IS STILL NOWHERE TO
BE FOUND. AT THE OFFICE AS I WRITE THIS, OUR OFFICE IS SITTING
AT 53 DEGREES, WHICH IS THE AVERAGE HIGH TEMPERATURE FOR
RALEIGH, NORTH CAROLINA, WHERE I WENT TO COLLEGE BACK IN THE
DARK AGES CALLED THE 90S. AND IT LOOKS LIKE WE WILL HAVE ANOTHER
DAY OF RECORD WARM TEMPERATURES, MAINLY EAST OF THE CONTINENTAL
DIVIDE. ONE OF THINGS BRINGING THIS THOUGH IS STRONG TO HIGH
WIND, COURTESY OF AN APPROACHING TROUGH AND AN 120 KNOT JET OVER
THE AREA. WE HAVE HIGH WIND WARNINGS OUT ROUGHLY FROM SOUTH
PASS THROUGH CASPER THROUGH 11 AM THIS MORNING. MOST GUIDANCE
SHOWS 700 MILLIBAR WIND REMAINING 50 KNOTS OR MORE THROUGH THIS
PERIOD BEFORE DECREASING, AND BRINGING LIGHTER WIND AS A RESULT.
THE AREA STILL LOOKS GOOD WITH MOST AREAS HAVING AT LEAST A 3
OUT OF 5 CHANCE OF WIND GUSTS PAST 55 MPH. THERE COULD BE A FEW
HIGH GUSTS AROUND LANDER AS WELL, BUT THESE WOULD BE ISOLATED.
WE WILL ISSUE A SPECIAL WEATHER STATEMENT TO COVER FOR THIS.
AND WE HAVE A SNOWY PART OF THE SYSTEM AS WELL. SNOW HAS BEEN
FALLING LARGELY ABOVE 8000 FEET TODAY, BRINGING SLICK CONDITIONS TO
THE MOUNTAIN PASSES, MAINLY TETON AND TOGWOTEE PASSES. THE CURRENT
ADVISORY LOOKS TO BE IN GOOD SHAPE RIGHT NOW, ALTHOUGH A BULK
OF THE SNOW SHOULD FALL BEFORE NOON AS THE BEST FORCING MOVES
EAST OF THE AREA BY THAT TIME. WE WILL CONTINUE AS IS FOR NOW.
SNOW LEVELS MAY FALL TO AROUND 7000 FEET THIS AFTERNOON, SO
THERE COULD BE SOME LIGHT ACCUMULATION IN THE VALLEYS, BUT
NOTHING TO WRITE HOME ABOUT.
THERE SHOULD BE A LULL IN THE SNOW AND WIND LATER THIS AFTERNOON AND
THROUGH TONIGHT. THEN, ANOTHER PACIFIC TROUGH WILL APPROACH THE
AREA. THERE IS A BIT MORE UNCERTAINTY WITH THIS ONE, AS THE
MODELS HAVE DIFFERENT PLACEMENT OF THE HEAVIEST QPF. ENSEMBLE
GUIDANCE GIVES A GREATER THAN 4 OUT OF 5 CHANCE OF OVER 6 INCHES
OF SNOW IN THE WESTERN MOUNTAINS THROUGH SATURDAY. CHANCES OF
12 INCHES ARE MORE LIMITED THOUGH, GENERALLY LESS THAN 1 OUT OF
2. AND AREAS THAT HAVE THE GREATEST CHANCE ARE THE WIND RIVER
RANGE AND SOUTHWESTERN YELLOWSTONE, AREAS WHERE IMPACTS ARE
FAIRLY LIMITED. I COULD SEE SOME MORE HIGHLIGHTS HERE, BUT WILL
HOLD OFF FOR NOW WITH THE CURRENT ADVISORIES SO AS NOT TO
CONFUSE PEOPLE. ONE DIFFERENCE HERE IS THAT COLDER AIR WILL BE
IN PLACE, WITH 700 MILLIBAR TEMPERATURES FALLING TO MINUS 9
CELSIUS BY FRIDAY EVENING ACROSS THE WESTERN VALLEYS, MAKING
MOST OF THE PRECIPITATION IN THE FORM OF SNOW. CHANCES OF OVER
3 INCHES IN THE VALLEYS REMAIN SMALL, GENERALLY 1 OUT OF 3 OR
LESS THOUGH. ALTHOUGH THERE WILL NOT BE A WHITE CHRISTMAS, IT
COULD BE A WHITE BOXING DAY, AT LEAST LATE IN THE DAY. SOME SNOW
COULD EVEN MAKE IT IN SOUTHERN WYOMING IN THE AFTERNOON OR
EVENING, BUT ACCUMULATIONS HERE SHOULD REMAIN ON THE LIGHT SIDE.
AS FOR EAST OF THE DIVIDE, THERE WILL BE ONE MORE MILD DAY.
HOWEVER, THE PEAK OF THE HEAT WILL BE TODAY WITH TEMPERATURES
ABOUT 10 DEGREES COOLER ON FRIDAY THAN CHRISTMAS DAY AS 700
MILLIBAR TEMPERATURES FALL ABOUT 5 DEGREES CELSIUS. IT WILL
STILL BE WELL ABOVE NORMAL THOUGH. THERE COULD BE ANOTHER PERIOD
OF HIGH WIND AS WELL, AS THE PRESSURE GRADIENT TIGHTENS AHEAD
OF THE TROUGH AND SOUTHWEST FLOW INCREASES WITH 700 MILLIBAR
WIND AGAIN REACHING 50 TO 55 KNOTS. ENSEMBLES ARE GIVING A
GREATER THAN 1 OUT OF 2 CHANCE OF WIND GUSTS PAST 55 MPH FROM
SOUTH PASS THROUGH CASPER AND ALSO IN THE LEE OF THE ABSAROKAS.
WE WILL HOLD OFF ON ANY HIGHLIGHTS FOR THIS, GIVEN THE CURRENT
ONES IN EFFECT. IF CONDITIONS LOOK LIKELY, WE CAN ISSUE ON THE
DAY SHIFT TODAY OR EARLY FRIDAY MORNING. AS FOR PRECIPITATION,
CHANCES LOOK SMALL AGAIN WITH THE DOWNSLOPING FLOW.
THERE WILL BE ONE MORE SYSTEM FOR SATURDAY, AND THAT WILL REALLY PUT
AN END TO THE MILD WEATHER, AT LEAST TEMPORARILY. THIS WILL BE
IN THE FORM OF A CANADIAN COLD FRONT THAT WILL BRING A COLDER
AIRMASS FROM, YOU GUESSED IT, CANADA. AS FOR PRECIPITATION,
GIVEN THE CONTINENTAL ORIGIN, MOISTURE IS LIMITED AND WITH THE
FRONT'S FAST MOVEMENT, AMOUNTS WOULD BE LIGHT. MANY AREAS EAST
OF THE DIVIDE COULD SEE SOME SNOWFLAKES FOR THE FIRST TIME IN A
WHILE THOUGH ON SATURDAY INTO SATURDAY NIGHT.
TEMPERATURES THEN RETURN TO LEVELS MORE NORMAL FOR LATE DECEMBER ON
SUNDAY. THE NUMBERS WE HAVE IN THE FORECAST MAY BE THE COLDEST
THEY COULD GET THOUGH. IF THERE IS LITTLE OR NO SNOW ON THE
GROUND, ALBEDO WOULD BE LIMITED. IT WILL FEEL RATHER COLD
THOUGH, GIVEN THE RECENT BALMY WEATHER. THE COLD WEATHER WON'T
LAST LONG THOUGH, AS RIDGING BUILDS BACK OVER THE AREA AND FLOW
TURNS WESTERLY AGAIN FOR MUCH OF NEXT WEEK. THIS WILL BRING A
RETURN TO ABOVE NORMAL TEMPERATURES, ALTHOUGH NOT AS WARM AS
THIS PAST WEEK. IT WILL ALSO LIKELY BE RATHER WINDY AT TIMES
GIVEN THE FAST ZONAL FLOW.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 930 PM MST THU DEC 25 2025
WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI TERMINALS
VFR CONDITIONS TO START THE PERIOD WITH LIGHT RAIN AT JAC, AND
SHOWERS IN THE VICINITY OF BPI/PNA THAT WILL CONTINUE THROUGH
THE PERIOD. CONDITIONS DETERIORATE THROUGHOUT THE DAY FRIDAY
WITH LOWERING CEILINGS AND VISIBILITY BECOMING MVFR AT JAC AS IT
SWITCHES OVER TO SNOW. IFR EXPECTED AFTER 00Z WITH THE FRONTAL
BOUNDARY PUSHING THROUGH THE END OF THE PERIOD. BPI/PNA WILL
SEE MVFR CONDITIONS AFTER THE 00Z TIME PERIOD WITH FROPA AS THE
GUSTY WINDS DIMINISH TO AROUND 10KTS IN ITS WAKE. RKS WILL
REMAIN VFR WITH DRY CONDITIONS BUT STRONGER WINDS UP TO 30KTS
WITH DAYTIME HEATING AHEAD OF THE FRONT REMAINING ELEVATED
THROUGH THE END OF THE PERIOD UP TO 18-20KTS AFTER 00Z. MOUNTAIN
OBSCURATIONS WILL REMAIN THROUGHOUT WITH THE MID LEVEL CEILINGS
THE BEST CONDITIONS EXPECTED.
EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KLND/KWRL TERMINALS
VFR CONDITIONS THROUGHOUT THE PERIOD WITH GUSTY WINDS EXPECTED
TO MIX DOWN AFTER 16-17Z, STRONGEST AT CPR UP TO 35KTS AND 25KTS
ELSEWHERE. THESE WINDS WILL REMAIN ELEVATED AFTER 00Z BUT
WEAKER. COD WILL SEE THE BEST CHANCE FOR RAIN SHOWERS AFTER 00Z
AS WELL AS IT PUSHES OVER THE ABSAROKAS, AND LND AFTER 03Z
COMING OFF THE WINDS BUT LESS CONFIDENCE (10-20%) CARRYING ONLY
VCSH. OTHERWISE, EXPECT MOUNTAIN OBSCURATIONS AS WELL THROUGHOUT
THE PERIOD WITH MID LEVEL CEILINGS DURING THE DAY LOWERING TO
AROUND TO 5KFT AFTER THE 00Z TIMEFRAME. FROPA WILL OCCUR INTO
THE NEXT TAF CYCLE BUT IMPROVING CONDITIONS THERE AFTER.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZLC AND ZDV FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
CLIMATE
ISSUED AT 152 AM MST THU DEC 25 2025
ANOTHER DAY OF RECORD HIGH TEMPERATURES ARE LIKELY TODAY ACROSS
MUCH OF THE AREA. THERE WERE EIGHT RECORD HIGH TEMPERATURES AT
OUR NINE OFFICIAL CLIMATE SITES YESTERDAY, WITH ONLY BIG PINEY
NOT HAVING A RECORD HIGH. TWO LOCATIONS, THE RIVERTON AIRPORT
AND GREYBULL HAD THEIR ALL-TIME WARMEST DECEMBER TEMPERATURE ON
THE AFTERNOON OF THE 24TH. THIS BRINGS THE TOTAL OF RECORD HIGH
TEMPERATURES THIS MONTH SO FAR AT OUR NINE OFFICIAL CLIMATE
SITES TO 59.
RIW WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 5 AM TO 11 PM MST FRIDAY FOR
WYZ001-002-012-014-024.
UPDATE...WITTMANN
DISCUSSION...HATTINGS
AVIATION...LOWE
CLIMATE...
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