200
FXUS65 KRIW 250914
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
214 AM MST THU DEC 25 2025
KEY MESSAGES
- SNOW CONTINUING IN THE WESTERN MOUNTAINS AND STRONG WIND FROM
SOUTH PASS THROUGH CASPER TODAY, BOTH DECREASING IN THE
AFTERNOON.
- ANOTHER DAY OF RECORD BREAKING HIGH TEMPERATURES IS LIKELY
THIS AFTERNOON.
- ANOTHER WEATHER SYSTEM WILL BRING THE NEXT CHANCE OF SNOW AND
WIND FROM FRIDAY INTO FRIDAY NIGHT.
- A CANADIAN COLD FRONT MOVES THROUGH THE AREA SATURDAY AND
SATURDAY NIGHT AND BRINGS MORE SEASONABLE TEMPERATURES FOR
SUNDAY INTO MONDAY.
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. AND THIS BEING
CHRISTMAS DAY, IT REMAINS ME OF MY CHILDHOOD IN THE LATE 70S AND 80S
WHEN THE CHRISTMAS SPECIALS PLAYED ON NETWORK TV, USUALLY CBS.
I CAN STILL HEAR THE OLD 5 SECOND BUMPER OF "A CBS SPECIAL
PRESENTATION" WITH THE HORNS AND DRUMS. IT ALWAYS MEANT
SOMETHING COOL WAS COMING ON. AND THE SPECIAL I AM REFERRING TO
THE 1974 RANKIN-BASS STOP MOTION ANIMATION "A YEAR WITHOUT A
SANTA CLAUS." IT FEATURED THE TWO CHARACTERS OF THE HEAT MISER
AND THE SNOW MISER, REPRESENTING THE WARM AND COLD WEATHER.
THIS YEAR, IT SEEMS LIKE THE SNOW MISER HAS BEEN ON A TWO MONTH LONG
LEAVE OF ABSENCE WITH ONLY CAMEO APPEARANCES. AND HAS 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 DIVIDE.
ONE OF THINGS BRINGING THIS THOUGH ARE 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 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 FORM OF SNOW. CHANCES OF
OVER 3 INCHES IN THE VALLEYS REMAIN SMALL, GENERALLY 1 OUT OF 3
OR LESS THOUGH. BUT, 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 FORM OF A CANADIAN COLD FRONT THAT WILL BRING A COLDER AIR
MASS 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 COLDEST THEY
COULD GET THOUGH. IF THERE IS LITTLE OR NO SNOW ON THE GROUND,
ALBEDO WOULD BE LIMITED. IT WILL BE 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 FRIDAY/
ISSUED AT 930 PM MST WED DEC 24 2025
WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI TERMINALS
LIGHT RAIN BUT VFR CONDITIONS TO START THE PERIOD AT JAC/BPI/PNA
WITH LOW CEILINGS AND LITTLE RESTRICTION TO VISIBILITY. PERIODS
OF A MORE STEADY RAIN AFTER 08-13Z THAT WILL BRING MVFR
CONDITIONS AT THESE LOCATIONS PUSHING TO RKS BETWEEN 13-17Z. ANY
RAIN AND RESTRICTED CONDITIONS LAST THROUGH 18-19Z BEFORE
DISSIPATED AND LIFTING TO VFR THE REMAINDER OF THE PERIOD.
OTHERWISE, WINDS 10KTS OR LESS BUT WITH WIND SHEAR ALOFT THAT
WILL MIX DOWN AFTER 18-19Z WITH DAYTIME HEATING THROUGH ABOUT
00-01Z. LIGHT WINDS AND MID LEVEL CEILINGS THERE ON OUT INTO THE
OVERNIGHT HOURS THROUGH FRIDAY MORNING.
EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KLND/KWRL TERMINALS
VFR CONDITIONS AND DRY WEATHER EXPECTED TO THE EAST BUT WITH
STRONGER WINDS REMAINING ELEVATED OVERNIGHT GUSTING UP TO
20-25KTS. STRONGEST WINDS BETWEEN 19-01Z WITH DAYTIME HEATING
AND MIXING WITH MID LEVEL CEILINGS THROUGHOUT THE PERIOD, UP TO
30KTS AT CPR/LND. WINDS DIMINISH WITH RADIATIONAL COOLING THERE
AFTER WITH LINGERING HIGH CLOUDS REMAINING.
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 DECEMBER WARMEST 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 61.
RIW WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR
WYZ012-014.
HIGH WIND WARNING UNTIL 11 AM MST THIS MORNING FOR WYZ015-019-
020-022.
DISCUSSION...HATTINGS
AVIATION...LOWE
CLIMATE...
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