163
FXUS65 KRIW 291921
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1221 PM MST MON DEC 29 2025
KEY MESSAGES
- CHILLY TEMPERATURES AND LINGER ACROSS MUCH OF THE COWBOY
STATE TODAY ESPECIALLY FOR WESTERN VALLEYS.
- TEMPERATURES WILL GRADUALLY WARM THROUGH THE WEEK WITH HIGHS
RETURNING TO ABOVE NORMAL VALUES BY NEW YEARS EVE.
- DRY CONDITIONS PREVAIL FOR MUCH OF THE WEEK WITH THE NEXT
CHANCE FOR PRECIPITATION POSSIBLY ARRIVING BY THURSDAY WITH
THE BEST CHANCES BEING OVER WESTERN WY.
UPDATE
ISSUED AT 1212 PM MST MON DEC 29 2025
NOTHING TO UPDATE REGARDING THE PREVIOUS DISCUSSION AS THE
OVERALL PATTERN REMAINS QUIET AND MILD THROUGH THE NEXT FEW
DAYS. CHILLY TEMPERATURES ARE FORECAST ACROSS THE STATE TODAY
WITH HIGHS IN THE 30S EAST OF THE DIVIDE AND 20S TO LOW 30S WEST
OF THE DIVIDE. COLDER AIR IS PERSISTING IN SOME WESTERN VALLEYS
WHERE RECENT SNOWFALL OCCURRED SUCH AS STAR VALLEY, WHERE HIGHS
MAY STRUGGLE TO GET INTO THE 20S TODAY. OTHERWISE, NOT MUCH
MORE TO ADD IN TERMS OF THE SHORT TERM FORECAST. THE NEXT CHANCE
FOR PRECIPITATION LOOKS TO POSSIBLY ARRIVE BY THE SECOND HALF
OF THE WEEK WITH CHANCES FAVORING WESTERN WY. MODELS ARE NOT
SHOWING ALL THE IMPRESSIVE OF A SYSTEM SO IMPACTS AT THIS TIME
ARE LOOKING MINIMAL.
DISCUSSION
ISSUED AT 132 AM MST MON DEC 29 2025
HIGH PRESSURE WILL BE HOLDING CONTROL ALONG THE NORTHERN ROCKIES
DURING THE NEXT SEVERAL DAYS, DEFLECTING THE STORM TRACK BACK
INTO CANADA AND KEEPING MILD TEMPERATURES GOING FOR WYOMING.
LOWS THIS MORNING HAVE BEEN COLD, WITH TEMPS WELL BELOW ZERO FOR
THE WESTERN VALLEYS, AND IN THE SINGLE DIGITS ABOVE ZERO EAST OF
THE DIVIDE. SOUTHWEST FLOW RETURNS TODAY, HELPING TO CARVE OUT
SOME OF THE COLD POOL THAT HAS SETTLED IN THE REGION. WITH THE
COLD POOL NOT OVERLY STRONG AND NOT REINFORCED BY ANY SNOWPACK,
EXPECT A GOOD RECOVERY OF TEMPERATURES INTO THE 30S THIS
AFTERNOON. WESTERN VALLEYS THAT DO HAVE SNOWPACK AND ARE
STARTING A LOWER TEMPERATURES WILL HAVE MORE TROUBLE GETTING
OUT OF THE TEENS THIS AFTERNOON. THIS PATTERN WILL CONTINUE
THROUGH THE REMAINDER OF THE WEEK, AS THE RIDGE HOLDS IN PLACE,
PUSHING SYSTEMS OFF TO THE NORTH AND CONTINUING TO CARVE UP ANY
REMAINING COLD POOL. MOST AREAS WILL BE BACK IN THE 40S BY
WEDNESDAY, WITH JACKSON HOLE AND STAR VALLEY HOLDING BACK A BIT
DEPENDING ON HOW FAST SURFACE SNOW THINS OUT.
THE RIDGE TRIES TO SHIFT MORE EAST LATE IN THE WEEK, OPENING THE
DOOR FOR SOME MOISTURE TO GET BACK INTO THE WESTERN MOUNTAINS,
BUT A LACK OF SIGNIFICANT SUPPORTING STORM SYSTEMS WILL KEEP ANY
SNOWFALL ON THE LIGHTER SIDE FOR THE TIME BEING.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1032 AM MST MON DEC 29 2025
WITH UPPER-LEVEL HIGH PRESSURE OVER THE GREAT BASIN TODAY,
NORTH-NORTHWEST MID- AND UPPER-LEVEL FLOW IS RESULTING IN VFR
CONDITIONS AT ALL TAF SITES THROUGH THE DAY AND INTO TUESDAY,
THOUGH BRIEF MVFR CONDITIONS (10-20%) ARE POSSIBLE AT KJAC TUE
MORNING AS A WEAK MID-LEVEL DISTURBANCE MOVES FROM MT INTO
CENTRAL AND EASTERN WY. MOST OF NORTHWEST WY IS COVERED BY A
MID-LEVEL DECK OF CLOUDS THIS MORNING, AND THESE SHOULD
DISSIPATE DURING THE AFTERNOON AS HIGH CLOUDS STREAM OVER THE
STATE FROM THE NORTH. MOST TAF SITES WILL SEE RELATIVELY LIGHT
WINDS THROUGHOUT THE TAF PERIOD, THOUGH SEVERAL, INCLUDING KBPI,
KPNA, KRKS, & KCPR, WILL SEE GUSTY NW TO SW WINDS (20-30 KTS) DURING
THE AFTERNOON.
AS THE PREVIOUSLY MENTIONED DISTURBANCE DROPS SOUTHEAST TUESDAY
MORNING, MID- AND HIGH-LEVEL CLOUDS WILL INCREASE ACROSS THE
AREA FROM ABOUT 30/09Z TO 30/21Z BEFORE CLEARING LATE TUE
AFTERNOON. GUSTY WEST-SOUTHWEST WINDS WILL RETURN TO KRKS AND
KCPR TUE AFT AS WELL. THE NW WY MOUNTAINS ABOVE 10K FT WILL
LIKELY BE OBSCURED THIS AFTERNOON, AND AGAIN FROM 30/09-21Z.
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
NONE.
UPDATE...DZIEWALTOWSKI
DISCUSSION...STRAUB
AVIATION...MCDONALD
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