623
FXUS65 KRIW 262245
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
345 PM MST FRI DEC 26 2025
KEY MESSAGES
- PERIODS OF MODERATE TO HEAVY SNOWFALL WILL CONTINUE ACROSS WESTERN
WY THROUGH SATURDAY AFTERNOON.
- WARM TEMPERATURES WILL SUBSIDE FOR A SHORT PERIOD AS A COLD
FRONT BRINGS MORE SEASONABLE TEMPERATURES TO THE STATE FOR THE
WEEKEND.
- SNOW SHOWERS ARE POSSIBLE EAST OF THE DIVIDE BEHIND THE
FRONTAL PASSAGE SATURDAY EVENING INTO SUNDAY MORNING.
- THE END OF DECEMBER AND 2025 IS LOOKING MILD WITH MOSTLY QUIET
WEATHER EXPECTED AT THIS TIME.
UPDATE
ISSUED AT 1245 PM MST FRI DEC 26 2025
SNOW WILL CONTINUE TO MOVE INTO PORTIONS OF WESTERN WY THIS
AFTERNOON. TEMPERATURES ACROSS WESTERN VALLEYS HAVE BEEN
FLUCTUATING WITH JACKSON SEEING SOME PERIODS OF RAIN OR WET
SNOW THIS MORNING. TEMPERATURES WILL CONTINUE TO DROP WITH
PRECIPITATION TURNING OVER TO ALL SNOW BY SUNSET. MODERATE TO
HEAVY PERIODS OF SNOWFALL WILL BE POSSIBLE THROUGH THE EVENING
WITH A BRIEF DECREASE IN INTENSITY EXPECTED LATE FRIDAY EVENING.
SNOWFALL INTENSIFIES ONCE AGAIN BY THE MORNING SATURDAY AND
CONTINUING INTO THE AFTERNOON. MOST OF THE FORECAST REMAINS
UNCHANGED WITH THE ONE EXCEPTION BEING THE EXTENSION OF WINTER
WEATHER ADVISORIES ACROSS THE MOUNTAINS OF WESTERN WY. THIS IS
DUE TO A SECOND ROUND OF MODERATE SNOWFALL THAT ARRIVES DURING
THE MORNING AND AFTERNOON HOURS SATURDAY. THE SECOND ROUND OF
SNOW IS FORECAST TO BRING ANOTHER 2 TO 6 INCHES FOR LOW TO MID
ELEVATIONS WITH THE HIGHER ELEVATIONS SEEING 6 TO 10 INCHES.
OTHERWISE, THINGS REMAIN ON TRACK WITH THE FRONTAL PASSAGE
EXPECTED TO OCCUR DURING THE MORNING HOURS SATURDAY. SNOW
SHOWERS WILL BE POSSIBLE EAST OF THE DIVIDE POST FRONTAL PASSAGE
WHICH WOULD BE DURING THE EVENING SATURDAY INTO THE EARLY
MORNING HOURS SUNDAY. THE FORECAST FOR THE START OF NEXT WEEK
INTO THE END OF DECEMBER HAS NOT CHANGED. WARMER TEMPERATURES
RETURN WITH MOSTLY QUIET CONDITIONS PREVAILING AS WELL.
DISCUSSION
ISSUED AT 303 AM MST FRI DEC 26 2025
IT WAS MORE OF THE SAME YESTERDAY. SEVEN MORE RECORD HIGH
TEMPERATURES FELL. I WAS A LITTLE WARM WITH MY TEMPERATURES, BUT
MANY AREAS HAD A NICE CHRISTMAS AFTERNOON. TODAY WE WILL BEGIN THE
TRANSITION BACK INTO REALITY AS TEMPERATURES WILL TREND DOWN SOME
EACH DAY, REACHING A NADIR ON SUNDAY AND MONDAY BEFORE REBOUNDING
SOMEWHAT BEFORE THE NEW YEAR.
RADAR IS CURRENTLY SHOWING SOME SHOWERS ACROSS NORTHWESTERN WYOMING.
THE NEXT PACIFIC TROUGH AND COLD FRONT WILL BE APPROACHING THE AREA
TODAY AND BRINGING SOME SNOW TO WESTERN PORTIONS OF THE AREA. THIS
WILL INCREASE THROUGH THE DAY, WITH THE HEAVIEST EXPECTED THIS
AFTERNOON AND EVENING AS THE TROUGH AXIS PASSES THROUGH THE AREA.
ONE DIFFERENCE WITH THIS SYSTEM IS THAT THERE WILL BE COOLER AIR IN
PLACE, SO SNOW LEVELS SHOULD DROP TO THE VALLEY FLOORS BY THIS
AFTERNOON AND BRING SOME SNOW TO THE WESTERN VALLEYS. AS FOR
AMOUNTS, THE CURRENT FORECAST LOOKS TO BE LARGELY ON TARGET. MOST OF
THE AREAS WITH THE ADVISORIES HAVE AT LEAST A 4 OUT 5 CHANCE OF 6
INCHES OF NEW SNOW OR MORE, THE CHANCE OF 12 INCHES OR MORE STILL
LOOKS FAIRLY SMALL, GENERALLY LESS THAN 1 OUT OF 4. THE EXCEPTIONS
ARE THE HIGHEST ELEVATIONS BUT IMPACTS HERE WOULD BE LIMITED. I DO
HAVE A COUPLE OF CONCERNS THOUGH...
ONE IS THAT DECENT SNOW MAY CONTINUE PAST THE 11 PM ENDING OF THE
ADVISORY. HOWEVER, MOST GUIDANCE DOES SHOW THE HEAVIEST SNOW ENDING
BY 11 PM, ALTHOUGH LIGHTER SNOW WILL CONTINUE THROUGH THE REMAINDER
OF THE NIGHT. THE IMPACTED AREAS WOULD BE IN AREAS WITH FEW PEOPLE
THOUGH. THE OTHER IS WHAT HAPPENS TONIGHT, ESPECIALLY LATER TONIGHT
AS THE SYSTEM MOVES INTO SOUTHERN WYOMING. THIS INCLUDES ALONG
INTERSTATE 80. THE GROUND IS RATHER WARM GIVEN THE RECENT RECORD
HIGH TEMPERATURES. COLDER AIR COULD SPREAD IN QUICKLY AND ANY SNOW
THAT FALLS COULD MELT AND THEN REFREEZE ON ROADS, POSSIBLY BRINGING
A FLASH FREEZE. AMOUNTS WILL NOT BE THE PROBLEM. PROBABILISTIC
GUIDANCE ONLY GIVES AT MOST A 1 IN 3 CHANCE OF OVER 2 INCHES OF SNOW
AND THIS IS OVER FAR SOUTHEASTERN PORTIONS OF THE COUNTY WHERE
POPULATION AND IMPACTS ARE SLIM TO NONE. THIS MAY BE BETTER HANDLED
WITH SHORT FUSE SPECIAL WEATHER STATEMENTS THOUGH. A FEW SHOWERS ARE
ALSO POSSIBLE EAST OF THE DIVIDE, BUT AMOUNTS HERE WOULD BE VERY
LIGHT.
IN ADDITION, WE HAVE THE CONCERN FOR WIND. LIKE WAS STATED IN THE
UPDATE YESTERDAY AFTERNOON, THINGS CONTINUE TO LOOK BORDERLINE. WE
DO HAVE A FEW 50 KNOT WIND BARBS AT 700 MILLIBARS, BUT NOTHING
WIDESPREAD. THE NBM ENSEMBLE ALSO KEEPS THE CHANCE OF WIND GUSTS
PAST 60 MPH GENERALLY LESS THAN 1 OUT OF 2. THE EXCEPTIONS ARE THE
HIGHER ELEVATIONS OF THE GREEN MOUNTAINS AND THE SOUTH SIDE OF
CASPER. HOWEVER, HIGH WIND CRITERIA IS HIGHER IN THIS VICINITY. FOR
NOW, WE WILL OPT FOR A SPECIAL WEATHER STATEMENT SINCE WE FEEL ANY
HIGH WIND GUSTS WOULD BE ISOLATED. WIND SHOULD DECREASE LATER
TONIGHT AFTER THE FRONT PASSES. AS FOR TEMPERATURES, THEY WILL BE
ABOVE NORMAL ONCE AGAIN, WITH A FEW RECORDS POSSIBLE AGAIN.
THE THING THAT WILL PUT AN END TO THE WARM TEMPERATURES WILL THEN
MOVE IN FOR SATURDAY AND SATURDAY NIGHT IN THE FORM OF A CANADIAN
COLD FRONT. IT WILL SWEEP INTO NORTHERN WYOMING IN THE AFTERNOON AND
DROP SOUTHWARD THROUGH THE NIGHTTIME HOURS. WE HAVE THE USUAL
CONCERNS WITH THESE SYSTEMS. THE FIRST IS FOR WIND. THERE IS A
DECENT PRESSURE GRADIENT WITH IT AS WELL AS GOOD COLD ADVECTION AND
NORTHWEST FLOW. THIS IS THE CLASSIC FORMULA FOR STRONG WIND GUSTS IN
PLACES LIKE THE NORTHERN BIG HORN BASIN AND JOHNSON COUNTY. THE NBM
ENSEMBLES GIVE AROUND A 1 IN 3 CHANCE OF WIND GUSTS PAST 55 MPH IN
THE AFTERNOON AND EVENING AS THE FRONT PASSES. IT WOULD BE BRIEF BUT
THERE IS A DEFINITE POSSIBILITY. THE OTHER CONCERN IS SNOW. THE
SYSTEM IS CONTINENTAL IN ORIGIN, SO IT DOES NOT HAVE A LOT OF
MOISTURE TO WORK WITH. IT IS ALSO A FAST MOVER SO PRECIPITATION
WOULD NOT LAST A LONG TIME. THE ONLY LOCATION THAT HAS ANY CHANCE OF
OVER 6 INCHES OF SNOW IS THE TETONS BUT EVEN HERE IT IS ONLY 1 OUT
OF 3. AS FOR EAST OF THE DIVIDE, SOME LOCATIONS HAVE A 1 IN 4 CHANCE
OF AN INCH OF SNOW. THIS IS LARGELY IN AREAS LIKE RIVERTON, LANDER
AND CASPER WHERE A BRIEF PERIOD OF NORTHERLY UPSLOPE MAY DEVELOP
LATER SATURDAY NIGHT BEHIND THE FRONT, AND AROUND BUFFALO. THIS IS
FAR FROM CERTAIN THOUGH SINCE THESE ANAFRONTAL SNOW EVENTS
TEND TO BE BANDED AND HARD TO PINPOINT. THE MAIN CONCERN WOULD BE A
POSSIBLE FLASH FREEZE WITH INITIAL SNOW FALLING ON WARM GROUND AND
MELTING BEFORE TEMPERATURES FALL INTO THE TEENS AND EVEN THE SINGLE
DIGITS. TRAVEL COULD GET DIFFICULT IN SOME AREAS LATER SATURDAY
NIGHT. AND IT WILL FEEL MUCH COLDER SATURDAY NIGHT, AS PLACES
LIKE BUFFALO COULD BE 60 DEGREES COOLER SUNDAY MORNING COMPARED
TO CHRISTMAS AFTERNOON.
A PERIOD OF QUIETER WEATHER SHOULD THEN MOVE IN FOR THE REST OF THE
CALENDAR YEAR AS RIDGING BUILDS OVER THE AREA. SUNDAY AND MONDAY
LOOK COLDER BUT LIKELY ONLY SEASONABLY COLD, AND A LOT DEPENDS ON
SNOW COVER. AREAS THAT DON'T SEE MUCH SNOW FROM THE COLD FRONT MAY
END UP WARMER. FLOW THEN GRADUALLY TURNS MORE ZONAL TOWARD THE
MIDDLE OF NEXT WEEK, BRINGING A RETURN OF ABOVE NORMAL TEMPERATURES,
BUT NOT RECORD BREAKING ONES LIKE WE HAD MUCH OF THIS WEEK.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 345 PM MST FRI DEC 26 2025
WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI TERMINALS
A FETCH OF MOISTURE ARRIVING FROM THE SOUTHWEST WILL CONTINUE TO
FEED INTO KJAC THROUGH THE EVENING HOURS. IFR/MVFR CONDITIONS
PREVAIL THROUGH ABOUT 03Z/SATURDAY. MVFR AND LIGHT SNOW PERSISTS
OVERNIGHT BEFORE ANOTHER ROUND OF HEAVIER SNOW REACHES KJAC AROUND
12Z/SATURDAY. AN ADDITIONAL AREA OF LIGHT SNOW SPREADS ACROSS KPNA
AND KBPI EARLY SATURDAY EVENING BEFORE EVENTUALLY SHIFTING TO KRKS.
FREQUENT MVFR CONDITIONS, ALONG WITH INTERMITTENT IFR CONDITIONS,
ARE ANTICIPATED FRIDAY EVENING AND OVERNIGHT AT THESE TERMINALS.
SATURDAY FINDS IFR/MVFR SNOW THROUGH MOST OF THE DAY AT KJAC, WHILE
INCREASING WEST-NORTHWEST FLOW BEGINS TO DRY THINGS OUT FOR THE
REMAINING TERMINALS. GUSTY SOUTHWEST SURFACE WIND SLOWS THIS FRIDAY
EVENING, BUT 12-25KT WEST TO NORTHWEST SURFACE WIND BLOWS SATURDAY
AFTERNOON AT KRKS, KPNA, AND KBPI. MOUNTAINS OBSCURED.
EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KLND/KWRL TERMINALS
THE MOIST, SOUTHWEST FLOW ALOFT CONTINUES OVERNIGHT. A FEW LIGHT
RAIN SHOWERS MAY STILL SNEAK OFF THE EAST SLOPES OF THE ABSAROKA AND
WIND RIVER MOUNTAINS AND AFFECT KCOD AND KLND, BUT EXPECTED IMPACTS
WOULD BE BRIEF. KCPR COULD SEE A BRIEF SPRINKLE OVERNIGHT, BUT AGAIN
NO IMPACTS. ALL TERMINALS TO REMAIN VFR WITH GUSTY SOUTHWEST SURFACE
WIND PERSISTING THROUGH MIDDAY SATURDAY. THE WIND SHOULD DIMINISH
OVERNIGHT AT KRIW AND KWRL BEFORE INCREASING 18Z-19Z/SATURDAY. A
COLD FRONT PUSHES THROUGH KCOD AND KWRL 18Z-20Z/SATURDAY BEFORE
CONTINUING TOWARD A KCPR-KLND LINE BY 00Z/SUNDAY. SURFACE WIND
SWITCHES TO THE NORTH TO NORTHWEST BEHIND THE COLD FRONT. CONDITIONS
MAY (20-30 PERCENT CHANCE) DETERIORATE TO MVFR IN LIGHT SNOW AT KCOD
LATE IN THE PERIOD DUE TO FAVORABLE UPSLOPE FLOW. MOUNTAIN TOPS
OBSCURED.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZLC AND ZDV FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
CLIMATE
ISSUED AT 303 AM MST FRI DEC 26 2025
ON CHRISTMAS DAY, THERE WERE 7 MORE RECORD HIGH TEMPERATURES AT
OFFICIAL CLIMATE SITES, BRING THE MONTHLY TOTAL TO 66. ALL BUT
ONE OF THESE RECORD HIGH TEMPERATURES OCCURRED IN THE PAST 2
WEEKS. ALL 9 OFFICIAL CLIMATE SITES HAVE HAD THE WARMEST FIRST
25 DAYS OF DECEMBER IN STATION HISTORY. THE RIVERTON AIRPORT IS
5 DEGREES WARMER THAN THE SECOND WARMEST PERIOD (IN 2021) AND
THE ROCK SPRINGS AIRPORT IS 4.8 DEGREES WARMER THAN THE SECOND
WARMEST PERIOD (IN 1958).
RIW WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 5 PM MST SATURDAY FOR WYZ001-002-
012-014-024.
UPDATE...DZIEWALTOWSKI
DISCUSSION...HATTINGS
AVIATION...CNJ
CLIMATE...HATTINGS
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