338
FXUS65 KRIW 261015
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
315 AM MST FRI DEC 26 2025
KEY MESSAGES
- SNOW CONTINUING IN WESTERN WYOMING, WITH A GUSTY TO STRONG
WIND IN MANY LOCATIONS EAST OF THE DIVIDE TODAY.
- ABOVE NORMAL TEMPERATURES CONTINUE EAST OF THE DIVIDE,
ALTHOUGH NOT AS WARM AS RECENT DAYS.
- A COLD FRONT WILL BRING A CHANCE OF LIGHT SNOW SATURDAY AND
SATURDAY NIGHT, AS WELL AS A RETURN TO MORE TYPICAL LATE
DECEMBER TEMPERATURES.
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 /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 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 11 PM MST THIS EVENING FOR
WYZ001-002-012-014-024.
DISCUSSION...HATTINGS
AVIATION...LOWE
CLIMATE...HATTINGS
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