026
FXUS65 KRIW 202240
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
340 PM MST MON JAN 20 2025
KEY MESSAGES
- COLD TEMPERATURES WILL CONTINUE TODAY, BUT THE COLDEST TEMPERATURES
OCCURRED THIS MORNING.
- STRONG WINDS ARE EXPECTED TUESDAY, WITH MOST LIKELY CHANCES
FOR HIGH WINDS (30%) IN THE ABSAROKAS AND CODY FOOTHILLS AND
ALONG OUTER DRIVE ON THE SOUTH SIDE OF CASPER.
- A WEATHER SYSTEM PASSING TO OUR EAST WILL BRING SLIGHT
SNOWFALL CHANCES (30%) TUESDAY NIGHT THROUGH WEDNESDAY.
- WARMING TEMPERATURES THROUGH FRIDAY, HELPED BY THE WINDS, BUT
A WEATHER SYSTEM LOOKS TO BRING ADDITIONAL COLD AIR AND
WIDESPREAD LIGHT SNOW CHANCES FOR THE WEEKEND.
DISCUSSION
ISSUED AT 214 PM MST MON JAN 20 2025
LOW TEMPERATURES THIS MORNING WERE THE COLDEST WE'VE SEEN THIS
SEASON AND THE COLDEST WE WILL SEE AT LEAST IN THE NEXT WEEK. SOME
HIGH ELEVATION SITES IN YELLOWSTONE NATIONAL PARK AND THE TETONS SAW
TEMPERATURES REACH THE -30S AND EVEN -40S, AND THAT DOESN'T INCLUDE
WIND CHILL! TEMPERATURES REMAIN COLD TODAY. THOUGH MOST LOCATIONS
SHOULD SEE TEMPERATURES CLIMB ABOVE ZERO, IT WON'T BE BY MUCH, WITH
HIGHS GENERALLY NEAR ZERO TO THE SINGLE DIGITS ABOVE ZERO.
TEMPERATURES AGAIN DROP TO THE DOUBLE DIGITS BELOW ZERO TONIGHT, BUT
WON'T BE AS COLD AS LAST NIGHT, DESPITE CLEAR SKIES. THE WARMER
OVERNIGHT LOWS ARE IN PART DUE TO WINDS PREVENTING THE STRONG BASIN
INVERSIONS FROM SETTING UP AND OVERALL WAA. COLD WEATHER ADVISORIES
REMAIN IN EFFECT THROUGH TUESDAY MORNING FOR MUCH OF THE CWA.
A TROUGH WILL BRING REINFORCING COLD AIR TO LOCATIONS TO OUR EAST,
BUT FOR US, WILL ONLY ACT TO TIGHTEN THE PRESSURE GRADIENT AND THUS,
INCREASE WINDS ACROSS MUCH OF THE CWA. ALONG THE ABSAROKAS, 50 TO
60KTS AT 700MB LOOK LIKELY TUESDAY MORNING THROUGH THE AFTERNOON,
WITH 45 TO 50KTS ALONG THE WIND RIVER MOUNTAINS AND WIND CORRIDOR
FROM SOUTH PASS TO CASPER MOUNTAIN. STRONGEST WINDS WILL BE
DOWNSLOPING ALONG THE EAST SLOPES OF THE ABSAROKAS, WHICH COULD
BRING HIGH WINDS (70% CHANCE) TO THE CLARK AREA NORTHWEST OF CODY.
HREF ENSEMBLES ARE HINTING THAT THERE COULD BE UP TO 70 TO 80%
CHANCES FOR HIGH WIND FOR CODY, WITH BETTER CHANCES TOWARDS CLARK
AND CHIEF JOSEPH HIGHWAY. ONLY CERTAIN HI-RES MODELS ARE INDICATING
HIGH WIND FOR CODY, MOST NOTABLY THE HIRES-FV3. THUS,
CONFIDENCE IS MEDIUM (40 TO 50%) AND HAVE GONE WITH A HIGH WIND
WATCH FOR THE CODY FOOTHILLS. DUE TO THE HIGHER CONFIDENCE FOR
CHIEF JOSEPH HIGHWAY, HAVE GONE WITH A WARNING FOR THAT ZONE,
BOTH IN EFFECT THROUGH TUESDAY EVENING.
700MB FLOW WILL BE PRIMARILY NORTHWESTERLY WHILE SURFACE FLOW WILL
HAVE MORE OF A WESTERLY COMPONENT TO IT. EVEN STILL, THERE IS NOT A
SOUTHWEST COMPONENT THAT WOULD FAVOR HIGH WIND FOR SOUTH PASS OR
OTHER PORTIONS OF THE WIND CORRIDOR. THAT BEING SAID, DO STILL
EXPECT AT LEAST SEVERAL HOURS TUESDAY AFTERNOON WHERE GUSTS COULD BE
50 TO 60 MPH FOR OUTER DRIVE (SOUTH SIDE OF CASPER) AND 55 TO 65 MPH
FOR SOUTH PASS.
WINDS WILL DIMINISH TOWARDS SUNSET TUESDAY. THE WINDS WILL HELP TO
WARM US UP ACROSS MUCH OF THE CWA. DRY DOWNSLOPING WINDS IN THE
BIGHORN BASIN, NORTHERN WIND RIVER BASIN (NORTH OF CROWHEART) AND
PORTIONS OF THE WIND CORRIDOR, ALONG WITH THE EAST FOOTHILLS OF THE
BIGHORN MOUNTAINS AND JOHNSON COUNTY WILL ERODE OUT MUCH OF THE COLD
AIR AND TEMPERATURES TUESDAY WILL WARM UP TO NEAR SEASONAL NORMALS.
FOR AREAS WEST OF THE DIVIDE, COLD AIR IN THE BASINS WILL LINGER.
THE COLD POOL IN THE CENTRAL WIND RIVER BASIN COULD SEE SOME
EROSION, BUT THERE IS LOW CONFIDENCE IN LOCATIONS LIKE RIVERTON AND
SHOSHONI SEEING ENOUGH WIND TO ERODE AWAY THE DEEP COLD POOL. THAT
BEING SAID, THERE IS LOW CONFIDENCE IN TEMPERATURES BETWEEN
CROWHEART AND NORTH OF RIVERTON, AS THEY WILL BE FULLY DEPENDENT ON
HOW FAR THE NORTHWEST WIND MAKES IT DOWN THE BASIN.
CLOUD COVER WILL INCREASE TUESDAY AS WELL, AS THE TROUGH CAUSING THE
PRESSURE GRADIENT TO TIGHTEN BEGINS TO PUSH INTO WY. IMPACTS WILL BE
RELATIVELY LIMITED, WITH LIGHT SNOW BEING POSSIBLE ACROSS THE
NORTHERN WY MOUNTAINS AND YNP BY LATE TUESDAY NIGHT. AMOUNTS LOOK
MINIMAL, WITH MAYBE 1 TO 3 INCHES ACROSS YNP AND THE ABSAROKAS AND 2
TO 5 IN THE BIGHORNS, WITH HIGHEST AMOUNTS TOWARDS THE NORTHERN
PORTION OF THE RANGE. LOWER ELEVATIONS OF YNP, THE BIGHORN BASIN,
AND NORTHERN JOHNSON COUNTY COULD ALSO SEE A DUSTING OF SNOW TUESDAY
NIGHT INTO WEDNESDAY. BIGGER CONCERN WOULD BE BLOWING SNOW,
ESPECIALLY ACROSS JOHNSON COUNTY AND THE BIGHORNS WHERE GUSTY
NORTHWEST WINDS COULD PERSIST THROUGH MUCH OF TUESDAY NIGHT AND
WEDNESDAY.
BASIN TEMPERATURES WILL WARM UP FARTHER ON FRIDAY, WITH GUSTY WINDS
AHEAD OF THE NEXT WEATHER SYSTEM. THIS WEATHER SYSTEM HAS A LOT OF
UNCERTAINTY SURROUNDING IT, AS MODELS DISAGREE ON TRACK AND
INTENSITY OF THE PARENT LOW. GFS SOLUTIONS ARE MUCH MORE BULLISH
THAN THE ECMWF, AND IF GFS SOLUTIONS COME TRUE, A POTENT WINTER
STORM WITH SNOW AND COLD AIR COULD BE IN THE MAKING. BEING
BEYOND THE 5+ DAY RANGE AND GIVEN THE UNCERTAINTY IN THE MODELS,
WILL LEAVE DETAILS TO BE WORKED OUT, BUT CERTAINLY WILL BE
MONITORING THIS SYSTEM THIS WEEK.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 345 PM MST MON JAN 20 2025
VFR CONDITIONS EXPECTED FOR ALL TAF SITES FOR THE ENTIRETY OF
THE PERIOD. WITH INCREASING WIND AND MIXING OVERNIGHT, NO
FOG/STRATUS IS EXPECTED FOR LND/RIW AS IT HAS BEEN. WINDS WILL
INCREASE AT PNA/RKS/CPR/COD BY 04-06Z AS A QUICK MID LEVEL
TROUGH PUSHES THROUGH GIVING WAY TO GAP FLOW FROM THE WEST TO
NORTHWEST FOR THESE LOCATIONS. CPR WILL BE STRONGEST OVER 40KTS
BY 09Z FOLLOWED BY COD OVER 35KTS AFTER 16Z REMAINING ELEVATED
THROUGH THE END OF THE PERIOD. RKS/PNA WEST OF THE DIVIDE WILL
BE A BIT LESS OVER 30KTS EXPECTED FOR THIS SAME TIME PERIOD. PNA
SHOULD DIMINISH AFTER 12Z WHILE RKS REMAINS GUSTY DUE TO ITS
ELEVATED LOCATION. INCREASING CLOUDS ALOFT BUT NO SNOW IS
EXPECTED. NO IMPACTS EXPECT AT JAC WITH NO OBSCURATIONS AS WELL
WITH NO OTHER WEATHER ELEMENTS EXPECTED AT THIS TIME.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON SMOKE, ICING, AND TURBULENCE
FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY UNTIL 10 AM MST TUESDAY FOR WYZ001>007-
010>020-022-025-026-030.
HIGH WIND WARNING FROM 2 AM TO 5 PM MST TUESDAY FOR WYZ002.
HIGH WIND WATCH FROM LATE TONIGHT THROUGH TUESDAY AFTERNOON
FOR WYZ003.
COLD WEATHER ADVISORY UNTIL 5 AM MST TUESDAY FOR WYZ008-009.
DISCUSSION...HENSLEY
AVIATION...LOWE
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