565
FXUS65 KRIW 190503
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1003 PM MST TUE FEB 18 2025
KEY MESSAGES
- BANDED CONVECTIVE SNOW SHOWERS WILL PERSIST ACROSS MUCH OF WESTERN
AND CENTRAL WY THROUGH THE AFTERNOON. LOCALLY HIGHER AMOUNTS ARE
POSSIBLE IN SNOWBANDS, BUT EXACT LOCATION OF THESE REMAINS UNCERTAIN.
- COLD TEMPERATURES ACROSS NORTHERN WY TONIGHT. THERE IS A 70%
CHANCE THAT LOW TEMPERATURES WILL REACH -15 OR LOWER FOR MUCH OF THE
BIGHORN BASIN AND NORTHERN JOHNSON COUNTY.
- ANOTHER, WEAKER SYSTEM BRINGS A CHANCE OF LIGHT TO MODERATE SNOW
TO WESTERN WYOMING WEDNESDAY NIGHT INTO THURSDAY.
- DRIER AND WARMER FROM FRIDAY INTO THE WEEKEND.
UPDATE
ISSUED AT 629 PM MST TUE FEB 18 2025
SNOW BANDS HAVE INCREASED IN COVERAGE THIS EVENING, WITH
MODERATE SNOW NOTED ACROSS THE SOUTHERN HALF OF THE BIGHORN
BASIN, TOGWOTEE PASS, AND THE WIND RIVER BASIN EASTWARD INTO
NATRONA COUNTY. RADAR RETURNS SHOW WIDESPREAD SNOW CONTINUING TO
PUSH THROUGH CENTRAL WYOMING, WHICH IS WOEFULLY UNDERDONE BY
CURRENT MODEL GUIDANCE. IF TRAVELING IN CENTRAL WYOMING THIS
EVENING BE AWARE OF MODERATE SNOW, WITH REDUCED VISIBILITY AND
SLICK ROADS. THE SNOW SHOULD SHIFT SOUTH AND TAPER OFF OVER THE
NEXT FEW HOURS, BUT IT APPEARS TO BE LINGERING A LITTLE LONGER
THAN EXPECTED FROM CODY TO GREYBULL. IF CLOUDS HANG ON A LITTLE
LONGER TONIGHT THE RESULT WILL BE SLIGHTLY WARMER LOW
TEMPERATURES ACROSS NORTHERN WYOMING WHERE THE CURRENT FORECAST
IS FOR LOWS IN THE 10 TO 20 BELOW ZERO RANGE. COULD SEE THAT
BEING MORE IN THE 5 TO 15 BELOW ZERO RANGE IF CLOUDS HANG ON FOR
MOST OF THE NIGHT.
DISCUSSION
ISSUED AT 158 PM MST TUE FEB 18 2025
SNOW BANDS IS THE WORD OF THE DAY TODAY AS A COLD FRONT PUSHES
THROUGH THE REGION. THE PARENT TROUGH WILL SLIDE THROUGH THE REGION
TODAY, DRAGGING A COLD FRONT WITH IT. THE COLD FRONT WILL CONTINUE
TO BRING CONVECTIVE SNOW BANDS ACROSS THE REGION. THESE BANDS
GENERALLY HAVE BEEN NW-SE ORIENTED, WITH LIMITED IMPACTS. THE
CONVECTIVE NATURE OF THESE BANDS MEANS THAT IT IS INCREDIBLY
DIFFICULT TO PIN POINT EXACTLY WHERE THEY WILL SET UP. NAMNEST AND
HRRR SOLUTIONS HAVE, HOWEVER, BEEN FAIRLY CONSISTENT WITH KEYING IN
ON A MORE PROMINENT AREA OF BANDING FROM DUBOIS THROUGH SHOSHONI AND
TOWARDS CASPER. THIS WOULD BE THE MOST LIKELY AREA FOR SNOWFALL
ACCUMULATIONS OVER 1 INCH WITH A 10% CHANCE OF ACCUMULATIONS OVER 3
INCHES. SOUTHERN PORTIONS OF THE BIGHORN BASIN ALONG A LINE GENERALLY
FROM MEETEETSE TO THERMOPOLIS AND PERHAPS AS FAR EAST AS TENSLEEP IS
THE OTHER LINE WHERE HI-RES MODELS HAVE BEEN FAIRLY CONSISTENTLY
KEYING IN ON A PROLONGED PERIOD OF SNOWBANDING THROUGH THE
AFTERNOON, AND COULD SEE AMOUNTS OF 2-3 INCHES UNDER THOSE BANDS
(20% CHANCE).
THE CONCERN WITH ANY OF THESE BANDS WILL BE LOCALIZED HIGHER
SNOWFALL AMOUNTS (UP TO 5 OR 6 INCHES IF THINGS SET UP RIGHT (<5%
CHANCE), AND BRIEF WHITEOUT CONDITIONS. NOTABLY, THE SNOW SQUALL
PARAMETER HAS BEEN CONSISTENTLY MODELED BY SPC AROUND 4-5 OR "HIGH
THREAT", AND THUS, WE CONTINUE TO MONITOR FOR LOCALIZED SNOW SQUALL
CONDITIONS. GREATEST CONCERN WILL BE ALONG SOUTH PASS AND EASTERN
SWEETWATER COUNTY LATER THIS AFTERNOON AND EARLY EVENING.
SNOW WILL TAPER OFF AND END OVERNIGHT AS THE PARENT TROUGH SLIDES
EASTWARD INTO THE PLAINS BY WEDNESDAY MORNING. WITH CLEARING SKIES
BEHIND THE FRONT AND WITH FRESH SNOW COVER, TEMPERATURES WILL
PLUMMET OVERNIGHT. THERE WAS CONSIDERATION FOR COLD WEATHER
ADVISORIES, HOWEVER, TEMPERATURES WILL GENERALLY REMAIN JUST WARMER
THAN CRITERIA AND IT WILL BE A SHORT-LIVED EVENT, WITH TEMPERATURES
EXPECTED TO WARM UP QUICKLY DURING THE DAY WEDNESDAY. HOWEVER,
ACROSS NORTHERN PORTIONS OF THE BIGHORN BASIN AND ACROSS NORTHERN
JOHNSON COUNTY, TEMPERATURES ARE EXPECTED TO DROP INTO THE DOUBLE
DIGITS BELOW ZERO, WITH A 60% OF TEMPERATURES BELOW -15F. WINDS WILL
BE LIGHT, AND OTHER THAN LOCALIZED COLDER LOCATIONS SUCH AS POWELL,
APPARENT TEMPERATURES WILL GENERALLY STAY AROUND -20F THROUGH THE
NIGHT.
WEDNESDAY AFTERNOON, THE NEXT SHORTWAVE PUSHES THROUGH. THE LOW WILL
TRACK ACROSS NORTHERN CO, WHICH WOULD TYPICALLY BE A PRIME TRACK FOR
SIGNIFICANT SNOWFALL ACROSS CENTRAL WY BASINS. HOWEVER, THE LOW IS
FAIRLY WEAK AND IS NOT TRACKING MUCH MOISTURE WITH IT. MUCH OF THE
MOISTURE IT DOES HAVE WITH IT WILL BE FOCUSED NEAR THE LOW CENTER,
AND THUS WILL HAVE LIMITED IMPACT FOR WY. THOUGH THERE IS A 10%
CHANCE OF SNOW ACROSS AREAS EAST OF THE DIVIDE, THE MAIN FOCUS FOR
SNOWFALL IN WY LOOKS TO BE ACROSS WESTERN AND SOUTHERN WY. WESTERN
MOUNTAINS COULD SEE 4 TO 6 INCHES WITH LOCALLY HIGHER AMOUNTS IN THE
TETONS THROUGH THURSDAY WITH THIS EVENT. THOUGH IT IS HARDLY
ANYTHING COMPARED TO THE 3 TO 4 FEET THEY RECEIVED OVER THE WEEKEND,
IT IS WORTH NOTING, NONETHELESS. ACROSS SOUTHWEST WY ALONG THE I-80
CORRIDOR, SNOWFALL AMOUNTS WILL GENERALLY BE LIGHT, LESS THAN AN
INCH WEDNESDAY NIGHT INTO THURSDAY.
AFTER THURSDAY, THE PATTERN QUIETS AS A RIDGE BUILDS. THIS WILL MEAN
A BREAK FROM THE ACTIVE SNOWY WEATHER AND ALSO A SIGNIFICANT WARM-
UP. TEMPERATURES BY THE LATER HALF OF THE WEEKEND WILL BE WELL ABOVE
NORMAL, WITH HIGH CONFIDENCE (80%) IN TEMPERATURES EXCEEDING 50F BY
MONDAY AFTERNOON FOR MOST EAST OF THE DIVIDE BASINS. THE EXCEPTION
WOULD BE THE BIGHORN BASIN, WHERE SIGNIFICANT SNOWPACK WILL LIKELY
ENHANCE THE COLD POOL, AND THUS, COULD PREVENT THE SAME DEGREE OF
WARMING THERE COMPARED TO THE REST OF THE REGION. STILL,
TEMPERATURES OVER 40F ARE STILL LOOKING LIKELY (70% CHANCE). WEST OF
THE DIVIDE BASINS AND VALLEYS ALSO HAVE A 60% CHANCE OF SEEING
TEMPERATURES EXCEEDING 40F BY MONDAY.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1002 PM MST TUE FEB 18 2025
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS
ANY LINGERING SNOW SHOULD END RIGHT AROUND THE START OF THE TAF
PERIOD, WITH CONDITIONS REMAINING OR IMPROVING TO VFR. THERE IS A
CHANCE OF FOG AT KBPI/KPNA WEDNESDAY MORNING, BUT CONFIDENCE REMAINS
LOW (20-30%), SO ONLY HAVE VCFG FEW002 FOR THOSE TERMINALS. NOT MUCH
IN THE WAY OF WEATHER IMPACTS THROUGH WEDNESDAY AFTERNOON FOR ALL
TERMINALS, BUT THE NEXT WEATHER SYSTEM WILL BRING MORE SNOW INTO THE
AREA WEDNESDAY EVENING NEAR THE END OF THE TAF PERIOD. MOUNTAIN
OBSCURATION WILL OCCUR AT TIMES THROUGH WEDNESDAY MORNING, IMPROVING
WEDNESDAY AFTERNOON.
WIND WILL BE LIGHT AT MOST TERMINALS THROUGH THE TAF PERIOD. AT KRKS
ELEVATED WIND (15-20 KNOTS) WILL CONTINUE UNTIL ABOUT 10Z/WED BEFORE
DROPPING TO 10 KNOTS, BUT WILL INCREASE BY LATE MORNING THROUGH THE
AFTERNOON HOURS, ONCE AGAIN.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS
LIGHT SNOW LINGERS AT KCPR/KRIW/KLND FOR A FEW HOURS TO START THE
TAF PERIOD. THIS WILL RESULT IN PREVAILING MVFR (BRIEFLY DROPPING
DOWN TO IFR) CONDITIONS BEFORE SNOW FINALLY TAPERS OFF EARLY
WEDNESDAY MORNING. CIGS ARE EXPECTED TO REMAIN MVFR/IFR AT KCPR
UNTIL 12Z/WED. FOG IS POSSIBLE (30-40%) AT KCOD WEDNESDAY MORNING,
BUT THIS WILL DEPEND GREATLY ON HOW QUICKLY SKIES CLEAR OVERNIGHT.
CLOUDS AND SNOW HAS BEEN LINGERING LONGER THAN ORIGINALLY EXPECTED,
SO THIS MAY LIMIT FOG DEVELOPMENT WEDNESDAY MORNING. AFTER SUNRISE
CONDITIONS SHOULD IMPROVE TO VFR AT ALL TERMINALS AND REMAIN SO
THROUGH THE REST OF THE TAF PERIOD. MOUNTAIN OBSCURATION WILL
CONTINUE OVERNIGHT, IMPROVING WEDNESDAY MORNING. WIND WILL REMAIN
LIGHT AT TERMINALS FOR THE NEXT 24 HOURS.
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 STORM WARNING UNTIL 11 PM MST THIS EVENING FOR WYZ001-
002-012-024.
UPDATE...ROWE
DISCUSSION...HENSLEY
AVIATION...ROWE
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