285
FXUS65 KRIW 200418
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
918 PM MST WED FEB 19 2025
KEY MESSAGES
- FAST MOVING WINTER STORM SWEEPS ACROSS SOUTHWESTERN WY TONIGHT
AND TOMORROW. STEADIEST SNOW WILL OCCUR ACROSS HIGHER
ELEVATIONS AND SWEETWATER COUNTY.
- CONFIDENCE IN LOCALLY HIGHER SNOWFALL AMOUNTS OF 4 TO 6 INCHES
ACROSS PORTIONS OF SOUTHWEST WY, INCLUDING THE I-80 CORRIDOR
HAS INCREASED. THERE IS A 70% CHANCE OF WINTER TRAVEL IMPACTS
BEGINNING BY 6 AM THURSDAY.
- A DRIER AND WARMER PATTERN IS LOOKING LIKELY STARTING FRIDAY
AND CONTINUING INTO THE WEEKEND. ACROSS LOWER ELEVATIONS EAST
OF THE DIVIDE, THERE IS A 50% CHANCE OF TEMPERATURES REACHING
60F MONDAY AFTERNOON.
UPDATE
ISSUED AT 108 PM MST WED FEB 19 2025
THE NEXT WEATHER SYSTEM IS ON TRACK TO SWEEP ACROSS MAINLY
SOUTHERN AND WESTERN WY DURING THE NEXT 24 HOURS. NO CHANGE
IN THE OVERALL TIMING FOR THE WESTERN MOUNTAINS, WITH SNOW
STARTING BY MID-EVENING TONIGHT AND CONTINUING THROUGH AROUND
SUNSET THURSDAY. PLACEMENT OF THE PASSING LOW IS NUDGED
SOUTHWARD JUST A BIT, WHICH IN TURN NUDGES OVERALL SNOW
ACCUMULATIONS FOR THE MOUNTAINS DOWNWARD SLIGHTLY. MAIN
ACCUMULATIONS WILL REMAIN ABOVE 7500 FEET, WITH GENERALLY 3 TO 6
INCHES POSSIBLE.
WITH THE SLIGHT SOUTHWARD NUDGE, THIS BRINGS SWEETWATER COUNTY
MORE IN LINE WITH SOME BETTER WRAPAROUND SNOWFALL. MODELS HAVE
INCREASED PRECIP MAINLY THURSDAY MORNING ACROSS SOUTHERN LINCOLN
INTO SWEETWATER COUNTY. MODELS KEEP JUMPING AROUND ON WHERE THE
WRAPAROUND OCCURS, BUT ALL ARE FOCUSING ON A BAND SOMEWHERE
ACROSS FAR SOUTHERN WY MAINLY BETWEEN SUNRISE AND NOON
THURSDAY. IF NEXT FEW RUNS CONTINUE THIS TREND, MAY NEED TO POST
AN ADVISORY FOR THE LOWER ELEVATIONS OF LINCOLN AND SWEETWATER
COUNTY, AS THERE WOULD BE ACCUMULATIONS ABOVE 3 INCHES, ALONG
WITH SOME GUSTY NORTH WINDS AS THE DAY PROGRESSES.
AS THE SYSTEM SWEEPS SOUTHEAST, SNOW SHOULD BE ENDING QUICKLY,
BY AROUND SUNSET FOR THE WESTERN MOUNTAINS AND BY MIDNIGHT ALONG
THE I-80 CORRIDOR.
DISCUSSION
ISSUED AT 217 AM MST WED FEB 19 2025
WE ARE FINALLY ENTERING A SOMEWHAT QUIETER PATTERN. WE
STILL HAVE A COUPLE OF CONCERNS THOUGH, WE STILL HAVE A FEW
SNOWBANDS OUT THERE THIS MORNING BUT THESE ARE SLOWLY WEAKENING AND
SHOULD BE GONE BY SUNRISE. TRANSITORY RIDGING WILL MOVE ACROSS THE
AREA TODAY AND BRING MAINLY DRY CONDITIONS. THERE WILL STILL BE A
FEW MOUNTAIN SNOW SHOWERS BUT NOTHING OF CONSEQUENCE. WE ALSO HAVE
SOME VERY COLD TEMPERATURES ACROSS NORTHERN PORTIONS OF OUR AREA.
HOWEVER, WIND REMAINS LIGHT AND LINGERING CLOUD COVER HAS KEPT
THINGS A BIT WARMER. THIS SHOULD BE THE COLDEST NIGHT AS WELL.
TEMPERATURES TODAY WILL BE BELOW NORMAL FOR MOST LOCATIONS BUT MORE
SUNSHINE SHOULD BRING A WARMER DAY THAN ON TUESDAY.
THIS QUIET WEATHER WILL NOT LAST LONG THOUGH AS THE NEXT PACIFIC
SYSTEM APPROACHES FROM THE WEST. THIS ONE IS FORTUNATELY NOT AS
INTENSE AS THE PREVIOUS ONE AND IS A FASTER MOVER, IN AND OUT OF THE
AREA IN AROUND 24 HOURS. WE DID GIVE THOUGHT TO SOME WINTER WEATHER
ADVISORIES BUT DECIDED AGAINST IT FOR NOW. THE NEXT QUESTIONS,
OBVIOUSLY, IS WHY? REASON NUMBER 1 WAS THE STORM WE JUST HAD, WHEN
SOME LOCATIONS PICKED UP OVER 3 FEET OF SNOW. AMOUNTS ARE MUCH LESS
WITH THIS. PROBABILISTIC GUIDANCE GIVES AT MOST A 1 OUT OF 2 CHANCE
OF OVER 6 INCHES OF NEW SNOW ACROSS THE TETONS AND SALT AND WYOMING
RANGE AND THIS IS MAINLY ABOVE PASS LEVEL. THE ONLY LOCATION FOR
OVER 4 INCHES IN THE LOWER ELEVATIONS IS ALPINE AND EVEN HERE IT IS
ONLY 1 OUT OF 7. SO, IMPACTS WOULD BE MUCH LESS. IN ADDITION, THE
BEST JET SUPPORT REMAINS SOUTH OF WYOMING, SO FORCING WILL NOT BE
THAT GREAT. ONE AREA I AM A BIT MORE CONCERNED ABOUT IS SWEETWATER
COUNTY. THIS AREA WILL BE CLOSER TO THE LEFT FRONT QUADRANT OF THE
AFOREMENTIONED JET. THERE IS A DECENT CHANCE OF SOME ACCUMULATING
SNOW. HOWEVER, THE HEAVIEST AMOUNT WOULD FALL SOUTH OF INTERSTATE 80
WHERE IMPACTS WOULD BE LITTLE. FOR EXAMPLE, ROCK SPRINGS ONLY HAS A
1 OUT OF 5 CHANCE OF 2 INCHES OR MORE. MOST OF THIS SNOW WOULD
OCCUR ON THURSDAY, SO THERE IS STILL SOME TIME TO EVALUATE THIS. AS
FOR EAST OF THE DIVIDE, THERE COULD BE SOME LIGHT SNOW AS THE
MOISTURE CROSSES THE MOUNTAINS BUT THE CHANCE OF ANY ACCUMULATION OF
AN INCH OR MORE IS LESS THAN 1 OUT OF 10.
MOST OF THIS SNOW SHOULD END THURSDAY NIGHT. FOLLOWING THIS, WE
SHOULD SEE A PATTERN CHANGE AS RIDGING BUILDS INTO THE AREA STARTING
ON FRIDAY. THIS SHOULD MEAN A WARNING TREND, WITH HIGHS IN THE 50S
POSSIBLE FOR SOME LOCATIONS STARTING ON SUNDAY, ALTHOUGH MONDAY
LOOKS LIKE THE BEST CHANCE. THE BEST CHANCE WOULD BE ACROSS CENTRAL
WYOMING, ESPECIALLY IN PLACES THAT HAVE LITTLE SNOW COVER. EVEN IF
THIS DOESN'T HAPPEN, THERE IS A VERY HIGH LIKELIHOOD THAT LOW
ELEVATION SNOW COVER WOULD BE SUBSTANTIALLY REDUCED OVER THE WEEKEND
AND EARLY NEXT WEEK. THE MAIN FLY IN THE OINTMENT HERE ARE A COUPLE
OF PACIFIC SYSTEMS THAT MAY APPROACH LATER IN THE WEEKEND AND EARLY
NEXT WEEK. AT THIS TIME, IT LOOKS LIKE THE BEST FORCING WOULD REMAIN
OVER MONTANA WITH JUST GLANCING BLOWS TO NORTHWESTERN WYOMING. THIS
IS FAR FROM CERTAIN THOUGH. HOWEVER, WE HAVE FAIRLY HIGH CONFIDENCE
WE WILL BE ENTERING INTO A SOMEWHAT DRIER AND WARMER PATTERN FOR THE
LATTER PART OF FEBRUARY.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 917 PM MST WED FEB 19 2025
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS.
AS THE NEXT WINTER STORM SYSTEM MOVES INTO THE REGION, MODELS HAVE
SLOWED THE ONSET OF THE PRECIPITATION ACROSS WESTERN WY (ESPECIALLY
AT KJAC) AND HAVE TRENDED THE HEAVIEST PRECIPITATION FARTHER SOUTH.
IMPACTS AT KJAC WILL BE FAIRLY LIMITED, WITH PREVAILING MARGINAL MVFR
CONDITIONS OVERNIGHT, AND ONLY OCCASIONAL IFR. THERE IS A 30% CHANCE
THAT KJAC COULD REMAIN MOSTLY VFR THROUGH THE PERIOD, WITH ONLY
OCCASIONAL MVFR CONDITIONS. STEADIEST SNOWFALL WILL OCCUR AT KRKS,
WITH LIKELY PREVAILING IFR (80% CHANCE) TO LIFR (40% CHANCE)
CONDITIONS AFTER 13Z.
THERE REMAINS LOW CONFIDENCE IN CLOUD CEILINGS AND TIMING OF
SNOWFALL AT KBPI, KPNA, THOUGH IT IS LOOKING INCREASINGLY LIKELY
THAT SNOW SHOWERS GENERALLY STAY TO THE SOUTH OF THOSE TERMINALS
THROUGH MUCH OF THE DAY.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS.
A WINTER SYSTEM MOVING THROUGH BRINGS SNOW MAINLY ALONG AND WEST OF
THE DIVIDE. THIS WILL MAINLY IMPACT SITES EAST OF THE DIVIDE WITH AN
OVERCAST MID-LEVEL CLOUD DECK. HOWEVER, SNOW CANNOT BE ENTIRELY
RULED OUT, THOUGH CHANCES ARE VERY LOW (10% OR LESS). BEST CHANCES
ARE AT KLND, WITH ABOUT A 20% CHANCE.
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
WINTER WEATHER ADVISORY FROM 2 AM TO 11 PM MST THURSDAY FOR
WYZ027>030.
UPDATE...STRAUB
DISCUSSION...HATTINGS
AVIATION...HENSLEY
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