919
FXUS65 KRIW 170450
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
950 PM MST SUN FEB 16 2025
KEY MESSAGES
- MODERATE TO HEAVY SNOWFALL WILL CONTINUE ACROSS WESTERN
WYOMING THROUGH MONDAY NIGHT. TRAVEL IMPACTS ARE EXPECTED,
ESPECIALLY ACROSS MOUNTAIN PASSES.
- LIGHTER SNOWFALL IS EXPECTED ACROSS NORTHERN WYOMING TONIGHT THROUGH
TUESDAY, WITH THE BEST CHANCES FOR TRAVEL IMPACTS ACROSS THE
BIGHORN BASIN.
- REMAINING AREAS WILL SEE LIGHT SNOW CHANCES THROUGH TUESDAY.
- UNCERTAINTY INCREASES FOR A POSSIBLE MIDWEEK SYSTEM. WARMER
TEMPERATURES MAY BE ON THE WAY FOR NEXT WEEKEND.
DISCUSSION
ISSUED AT 359 PM MST SUN FEB 16 2025
THE LATEST WINTER STORM OF THE SEASON ARRIVED EARLY THIS MORNING TO
WESTERN WYOMING WITHIN THE NORTHWESTERLY FLOW. SNOWFALL RATES HAVE
INCREASED OVER THE LAST FEW HOURS OWING TO A PACIFIC MOISTURE SURGE
THROUGH THE SNAKE RIVER PLAIN. THE OVERALL SYNOPTIC SETUP REMAINING
LARGELY UNCHANGED OVER THE NEXT COUPLE OF DAYS WILL MAKE FOR A
FAIRLY STEADY PERIOD OF SNOWFALL ACROSS WESTERN WYOMING. TOTALS HAVE
TRENDED UP AS LATE FOR THE MOUNTAINS, WITH 2+ FEET POSSIBLE FOR THE
TETONS THROUGH MONDAY NIGHT. THE HEAVIEST SNOW IS EXPECTED AFTER
SUNSET THIS EVENING THROUGH MONDAY MORNING AS THE MOIST, UPSLOPING
SOUTHWESTERLY FLOW IS MAXIMIZED. RATES SHOULD THEN DECREASE SLIGHTLY
BY MONDAY NIGHT AS JET ENERGY AND MOISTURE TAPER A BIT. STILL,
MODERATE TO HEAVY SNOW WILL CONTINUE INTO TUESDAY, AND THE CURRENT
WINTER HIGHLIGHTS MAY END UP NEEDING EXTENDED. THE WESTERN VALLEYS
WILL CONTINUE TO SEE LIGHTER SNOW THROUGH THE EVENT, WITH AMOUNTS
GENERALLY IN THE 4 TO 8 INCH RANGE.
SNOW IS ALSO BEING OBSERVED ACROSS SWEETWATER COUNTY, OWING TO THE
INITIAL MOISTURE SURGE WITH THIS SYSTEM. THIS WILL CONTINUE THROUGH
THE EVENING, SUPPORTED IN PART BY THE ARRIVAL OF ADDITIONAL JET
ENERGY. ACCUMULATION WILL BE LIGHT, WITH ONLY A 50 PERCENT CHANCE TO
EXCEED 2 INCHES FOR MOST OF THE AREA. STILL, THIS IS USUALLY ENOUGH
TO CAUSE SOME TRAVEL IMPACTS, ESPECIALLY ALONG THE I-80 CORRIDOR.
AS USUAL WITH WEST OR NORTHWEST FLOW SETUPS WITH NO ACCOMPANYING
LOW, THE REMAINDER OF THE AREA WILL NOT BE AS FAVORED FOR SNOW.
THERE WILL BE PLENTY OF CHANCES FOR AT LEAST LIGHT ACCUMULATION,
THOUGH, ESPECIALLY ACROSS NORTHERN WYOMING. A NEARLY STATIONARY
FRONTAL BOUNDARY HAS SET UP FROM NORTHWEST TO SOUTHEAST ACROSS
SOUTHERN MONTANA TODAY. THIS FEATURE, COMBINED WITH A FAVORABLE
NORTHWESTERLY/WESTERLY UPSLOPING FLOW AND DECENT UPPER JET SUPPORT,
WILL SUPPORT PERIODS OF HEAVIER SNOWFALL FOR NORTHERN AND EASTERN
PORTIONS OF THE BIGHORN BASIN, ESPECIALLY TOWARD THE END OF THE
EVENT ON MONDAY EVENING AS THE FRONT FINALLY STARTS TO DROP SOUTH.
WITH 3 TO 6 INCHES NOW FORECAST FOR EASTERN PORTIONS OF THE BIGHORN
BASIN, WE HAVE ISSUED A WINTER WEATHER ADVISORY THERE VALID
TONIGHT THROUGH MONDAY NIGHT. NOTABLY, THERE IS SOME GUIDANCE
THAT IS EVEN MORE BULLISH THERE, WITH THE POTENTIAL FOR HIGHER
AMOUNTS IN THE GREYBULL TO LOVELL VICINITY (AROUND A 40% CHANCE
FOR AT LEAST 6 INCHES). OTHERWISE, THIS WILL NOT BE A
PARTICULARLY COLD SYSTEM, AND HIGHS ACROSS CENTRAL AND SOUTHERN
WYOMING WILL REACH THE MID 30S ON MONDAY. HOWEVER, AREAS NORTH
OF A SHOSHONI TO CASPER LINE WILL REMAIN UNDER A COLD POOL
MONDAY AND WILL NOT GET MUCH WARMER THAN THE LOW 20S (AND NEAR
THE MONTANA BORDER ON MONDAY - SINGLE DIGITS). THE SOUTHERN HALF
OF THE AREA WILL SEE A GUSTY WEST WIND ON MONDAY, THOUGH GUSTS
WILL NOT BE TOO IMPRESSIVE, GENERALLY REMAINING UNDER 35 MPH.
THE FRONT WILL DROP SOUTH ON TUESDAY, MAKING FOR A COLDER DAY EAST
OF THE DIVIDE WITH CONTINUED LIGHT SNOW ACROSS WESTERN AND NORTHERN
WYOMING. GUIDANCE IS HINTING AT THE NEXT SYSTEM ARRIVING SOMETIME IN
THE WEDNESDAY TO FRIDAY TIMEFRAME. HOWEVER, THERE IS STILL QUITE A
LOT OF SPREAD IN SOLUTIONS FOR THIS. IN FACT, ENSEMBLE GUIDANCE IS
NOW FAVORING A STRONG RIDGE BUILDING IN AS WE APPROACH THE WEEKEND.
THIS WOULD LEAD TO WIDESPREAD WARMER THAN NORMAL TEMPERATURES.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 949 PM MST SUN FEB 16 2025
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS.
MAIN SNOW IMPACTS WILL BE AT KJAC THROUGH THE PERIOD. CONFIDENCE IS
LOW AS GUIDANCE IS A BIT ALL OVER THE PLACE. SOME SHOW VISIBILITIES
UNDER A MILE, WHILE OTHERS KEEP IT LOW-END MVFR. HAVE OPTED FOR
PREVAILING MVFR AND IFR CONDITIONS THROUGH THE PERIOD. MODEL
REFLECTIVITY SHOWS HEAVIER SNOW AFTER 10Z. CEILINGS ARE ALSO
CHALLENGING, AGAIN WITH MODELS SHOWING VARIOUS SOLUTIONS; HAVE OPTED
FOR MIDDLE GROUND IN THE TAF.
THE OTHER PLACE OF NOTE IS KRKS, WHERE SOME AFTERNOON/EARLY EVENING
SNOW SHOWERS COULD IMPACT THE SITE, BRINGING BRIEF SNOW AND
VISIBILITY IMPACTS. LOW CONFIDENCE IN WHEN SNOW WILL END AT KPNA.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS.
SNOW CHANCES WILL MAINLY BE OVER NORTHERN WYOMING (KCOD/KWRL) FOR
MONDAY AFTERNOON. THERE IS A CHANCE A SNOW SHOWER COULD IMPACT ANY
SITE, BUT FOR KLND AND KRIW THOSE CHANCES ARE 15% OR LESS. WINDS
WILL MAINLY BE OUT OF THE NORTH/NORTHEAST THROUGH THE PERIOD.
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 5 AM MST TUESDAY FOR WYZ001-002-012-
024.
WINTER WEATHER ADVISORY UNTIL 5 AM MST TUESDAY FOR WYZ004.
WINTER WEATHER ADVISORY UNTIL 5 AM MST TUESDAY FOR WYZ008-013-
014-023-025.
DISCUSSION...MYERS
AVIATION...WITTMANN
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