965
FXUS65 KRIW 240254
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
754 PM MST TUE DEC 23 2025
KEY MESSAGES
- MAINLY QUIET NIGHT AHEAD WITH ABOVE NORMAL TO RECORD HIGH
TEMPERATURES CHRISTMAS EVE DAY.
- SOUTHWEST WINDS, WITH GUSTS OF 30 TO 40 MPH, OCCUR CHRISTMAS
EVE DAY OVER THE WIND CORRIDOR (EASTERN SWEETWATER COUNTY TO
SOUTHERN JOHNSON COUNTY) AND THE EAST SLOPES OF THE WIND
RIVER, ABSAROKA AND BIGHORN MOUNTAINS. LOCALLY HIGHER GUSTS UP
TO 55 MPH POSSIBLE IN THE MORE WIND PRONE LOCATIONS.
- VALLEY RAIN/MOUNTAIN SNOW WILL DEVELOP BY THE AFTERNOON
CHRISTMAS EVE AND CONTINUE INTO THE DAY ON CHRISTMAS.
- HIGH WIND WITH GUSTS AROUND 60 MPH WILL BE POSSIBLE CHRISTMAS
EVE NIGHT INTO CHRISTMAS MORNING FROM SOUTH PASS TO PORTIONS
OF NATRONA COUNTY, INCLUDING THE CASPER AREA.
UPDATE
ISSUED AT 1140 AM MST TUE DEC 23 2025
NO MAJOR CHANGES WITH THE FORECAST THROUGH THE NEXT FEW DAYS, AS
WINDY AND WARM CONDITIONS REMAIN IN PLACE. HAVE ADDED A HIGH WIND
WATCH FOR THE WIND CORRIDOR FOR LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING. 700MB WINDS ARE FORECAST AROUND 50 OR 55 KNOTS, WITH A
FAVORED SOUTHWEST FLOW. GUSTS 50 TO 60 MPH ARE LIKELY DURING THIS
TIME, WITH WIND PRONE AREAS (LIKE OUTER DRIVE IN CASPER OR SOUTH
PASS) LIKELY SEEING THE HIGHEST VALUES. OUTSIDE THESE HIGHLIGHTED
AREAS, IT WILL BE AT LEAST BREEZY. MOISTURE INCOMING TO WESTERN
WYOMING BRINGS SNOW (SNOW LEVELS ABOVE 8000 FEET) AND LOWER
ELEVATION RAIN. HAVE HELD OFF ON ANY WINTER HIGHLIGHTS FOR THE
MOUNTAINS FOR NOW, AS CONFIDENCE IS NOT QUITE HIGH ENOUGH IN THE
AMOUNTS. FOR THURSDAY, HAVE REDUCED RAIN CHANCES A BIT EAST OF
THE DIVIDE, AS WITH THIS FLOW PATTERN PRECIPITATION HAS
DIFFICULTY GETTING OVER THE MOUNTAINS.
FOR THIS FORECASTER, A WHITE CHRISTMAS IS HAVING ENOUGH SNOW ON THE
GROUND TO COVER THE (DEAD) GRASS. BUT WHETHER YOU USE MY DEFINITION
OR THE ONE IN THE FULL DISCUSSION BELOW, LOWER ELEVATIONS WILL NOT
SEE A WHITE CHRISTMAS.
DISCUSSION
ISSUED AT 112 AM MST TUE DEC 23 2025
LIGHT SNOW WILL CONTINUE OVER FAR NORTHWESTERN PORTIONS THIS MORNING
AND END BEFORE SUNRISE. THIS WILL BE THE LAST OF THE SNOW THAT
OCCURRED ACROSS WESTERN PORTIONS ABOUT 48 HRS AGO DUE TO THE
ATMOSPHERIC RIVER. A BROAD RIDGE WILL BUILD OVER MUCH OF THE
INTERMOUNTAIN WEST TODAY, PUSHING THE PACIFIC MOISTURE OVER THE
PACNW. THIS WILL LEAD TO A SOUTHWEST FLOW PATTERN ALOFT AND
UNSEASONABLY WARM TEMPERATURES TODAY AND WEDNESDAY. GUSTY SOUTHWEST
WINDS WILL CONTINUE IN THE SAME AREAS FROM MONDAY AS WELL, NAMELY
THE WIND CORRIDOR (EASTERN SWEETWATER COUNTY TO SOUTHERN JOHNSON
COUNTY) AND THE EAST SLOPES OF THE WIND RIVER, ABSAROKA AND BIGHORN
MOUNTAINS. GUSTS OF 30 TO 40 MPH WILL BE COMMON IN THESE AREAS, WITH
LOCALLY HIGHER GUSTS UP TO 55 MPH POSSIBLE. THESE WINDS WILL BE
SLIGHTLY STRONGER CHRISTMAS EVE, WITH GUSTS OF 40 TO 50 MPH AND
LOCALLY HIGHER GUSTS UP TO 65 MPH. ABOVE NORMAL TO RECORD HIGH
TEMPERATURES WILL CONTINUE IN THESE AREAS WITH THE GUSTY WINDS, WITH
50 DEGREE READINGS COMMON ACROSS SWEETWATER AND SOUTHERN LINCOLN
COUNTIES AND EAST OF THE DIVIDE. RIVERTON, LANDER, NATRONA AND
SOUTHERN JOHNSON COUNTIES COULD REACH 60 DEGREES, WITH THE LATTER
LOCATIONS HAVING THE BEST CHANCES. EXPECT THESE TEMPERATURES TO
RETURN CHRISTMAS EVE, WITH MORE LOCATIONS EAST OF THE DIVIDE
HAVING BETTER CHANCES OF REACHING 60F. CONDITIONS WILL BE DRY
TODAY, WITH A SLIGHT CHANCE FOR VIRGA SHOWERS OVER SWEETWATER
COUNTY THIS EVENING AND FLURRIES OF SNOW OVER THE WIND RIVER AND
GROS VENTRE MOUNTAINS AND THE SALT RIVER/WYOMING RANGES LATE
TONIGHT. FOG WILL BE POSSIBLE TONIGHT IN THE WESTERN VALLEYS,
BUT IT LOOKS LIKE SKIES WILL BE MOSTLY CLOUDY TO OVERCAST.
A LONGWAVE TROUGH WILL BE IN PLACE OVER THE EPAC TONIGHT INTO
CHRISTMAS EVE WITH A CLOSED LOW EVENTUALLY DEVELOPING BY CHRISTMAS.
THE TROUGH WILL PROGRESS VERY LITTLE EASTWARD TODAY THROUGH
CHRISTMAS DUE THE RIDGE, RESULTING IN SHORTWAVES EJECTING OVER THE
WEST COAST, THE GREAT BASIN AND NORTHERN ROCKIES. THE FIRST OF THESE
SHORTWAVES WILL REACH WESTERN PORTIONS OF THE COWBOY STATE BY THE
AFTERNOON CHRISTMAS EVE, BRINGING VALLEY RAIN AND MOUNTAIN SNOW.
SNOW LEVELS WILL RANGE BETWEEN 8000 AND 9000FT, DROPPING TO AROUND
7000FT LATE IN THE AFTERNOON ON CHRISTMAS. THIS LOOKS TO BE A
REPEAT OF LAST SUNDAY/MONDAY, WITH 0.50" OF RAIN AND 8 TO 16
INCHES OF SNOW IN THE MOUNTAINS. HIGH WIND WATCHES MAY BE
NEEDED CHRISTMAS EVE NIGHT FOR SOUTH PASS AND NATRONA COUNTY, AS
700MB SOUTHWEST WINDS INCREASE TO 50-60KT BY 06Z THURSDAY.
THESE WINDS WILL DECREASE THROUGH THE AFTERNOON CHRISTMAS DAY,
AS A COLD FRONT MOVES OVER THE AREA. THIS WILL MAKE IT A NOT-SO-
PLEASANT CHRISTMAS FOR THOSE IN THE CASPER AREA AND THE REST OF
THE NATRONA COUNTY. IN SUMMATION, RAIN EXPECTED FOR WESTERN
AREAS BELOW 8000FT BUT WILL BE A GOOD DAY FOR THE SKI SLOPES.
THE CAVEAT HERE WILL BE WIND GUSTS OF 30 TO 40 MPH CHRISTMAS
MORNING. WIND GUSTS OF 30 TO 50 MPH OVER THE WIND CORRIDOR
CHRISTMAS EVE INTO CHRISTMAS MORNING, WITH GUSTS AROUND 60 MPH
ACROSS PORTIONS OF NATRONA COUNTY. SO A WHITE CHRISTMAS IS NOT
EXPECTED THIS YEAR. A WHITE CHRISTMAS, IN THIS FORECASTER'S
OPINION, IS WHEN SNOW FALLS CHRISTMAS EVE NIGHT AND/OR CHRISTMAS
MORNING. SNOW ON THE GROUND THAT IS A COUPLE OF WEEKS OLD ISN'T
VERY SPECIAL AND BY THIS DEFINITION WE COULD HAVE A WHITE
CHRISTMAS FROM AS FAR BACK AS THANKSGIVING.
THE PACIFIC UPPER LOW LOOKS TO FINALLY MOVE ONSHORE OVER NORTHERN CA
BY FRIDAY, EJECTING MOST OF ITS ENERGY AND MOISTURE, AS WELL AS
WEAKENING THE RIDGE, IN THE PROCESS. A SEPARATE SYSTEM BEGINS TO
DROP SOUTHWARD FROM CANADA, MARKING AN END TO THE UNSEASONABLE "HOT"
STREAK. CHANCES FOR SNOW IN THE WESTERN VALLEYS INCREASE BY THIS
TIME, ALONG WITH CHANCES FOR PRECIPITATION ACROSS SOUTHERN PORTIONS.
THERE IS EVEN A CHANCE FOR SNOW OCCURRING OVER FAR NORTHERN PORTIONS
OF THE CWA FRIDAY NIGHT INTO SATURDAY WITH THE PASSAGE OF THE
CANADIAN COLD FRONT.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 345 PM MST TUE DEC 23 2025
VFR CONDITIONS CONTINUE THROUGH THE NEXT 24 HOURS FOR MOST AREAS,
WITH DENSE HIGH CIRRUS CONTINUING TO POUR ACROSS THE REGION. SOME
LOWER CLOUDS ARE POSSIBLE AT KBPI/KPNA OVERNIGHT, BUT WILL LIKELY
REMAIN SCT FOR LOWEST CLOUD DECK, WITH CIGS STILL ABOVE 5000FT.
NEXT ROUND OF SHOWERS MOVES INTO KJAC WEDNESDAY AFTERNOON, WITH
CURRENT TIMING OF RAIN SHOWERS STARTING AROUND 20Z. PRECIP WILL STAY
AS RAIN WELL INTO THE EVENING HOURS TOMORROW.
GUSTY WINDS BEGIN TO RAMP UP ACROSS CENTRAL WY TOMORROW, MAINLY
IMPACTING KCPR AND KRKS WITH GUSTS 25 TO 35KTS.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
HIGH WIND WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
MORNING FOR WYZ019.
HIGH WIND WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
MORNING FOR WYZ020.
UPDATE...WITTMANN
DISCUSSION...LAVOIE
AVIATION...STRAUB
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