070
FXUS65 KRIW 190140
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
640 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 /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 326 PM MST TUE FEB 18 2025
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS:
BANDS OF SNOW CONTINUE TO SPREAD ACROSS KJAC THIS AFTERNOON.
RADAR NOTES SHOWERS REMAIN LINED UP UPSTREAM OF KJAC, SO
EXTENDED TEMPO GROUPING INTO THE EVENING. A COUPLE OF THESE SNOW
SHOWERS MAY CLIP KBPI/KPNA, BUT ONLY INTO EARLY THIS EVENING AS
ALL SHOWERS BEGIN TO WEAKEN. MIDLEVEL BKN CLOUD DECKS REMAIN IN
PLACE AT KRKS, AND THICKEN BACK UP AT KBPI/KPNA/KJAC OVERNIGHT
AFTER SNOW CHANCES HAVE ENDED. SKIES REMAIN PARTLY TO MOSTLY
CLOUDY OVERNIGHT, BUT WILL BE MAINLY MID TO HIGH LEVEL CLOUD
DECKS THROUGH THE DAY WEDNESDAY.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS:
SNOW BANDS CONTINUE TO SWEEP SOUTHEAST TODAY AT OR NEAR ALL
SITES. SNOW WILL VARY AT ALL SITES THROUGH AROUND 06Z, WHEN THE
SYSTEM PROGRESSES TO THE SOUTHEAST. SKIES WILL GRADUALLY CLEAR
BETWEEN 06Z AND 12Z, WITH MOST SITES ONLY SEEING SCT HIGH LEVEL
LAYERS AFTER 12Z. WINDS REMAIN LIGHT FROM THE NORTH DURING THE
DAY, GENERALLY UNDER 10KTS.
RIW WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL 11 PM MST THIS EVENING FOR WYZ001-
002-012-024.
UPDATE...ROWE
DISCUSSION...HENSLEY
AVIATION...STRAUB
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