894
FXUS65 KRIW 152324
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
424 PM MST SAT FEB 15 2025
KEY MESSAGES
- THE NEXT SYSTEM ARRIVES TONIGHT, BRINGING MODERATE TO HEAVY SNOWFALL
ACROSS WESTERN WYOMING AND THE BIGHORN MOUNTAINS THROUGH THE
BEGINNING OF THE WEEK. TRAVEL IMPACTS EXPECTED, ESPECIALLY
ACROSS WESTERN MOUNTAIN PASSES.
- LIGHTER SNOW CHANCES WILL RETURN TO OTHER AREAS THROUGH
TUESDAY. THE BEST CHANCE FOR TRAVEL IMPACTS EAST OF THE
CONTINENTAL DIVIDE WILL BE ACROSS NORTHERN WYOMING.
DISCUSSION
ISSUED AT 421 PM MST SAT FEB 15 2025
LIGHT SNOW IS LINGERING ACROSS THE AREA TODAY AS THE PREVIOUS SYSTEM
DEPARTS. ANY ADDITIONAL ACCUMULATION THROUGH THE DAYLIGHT HOURS WILL
BE MINOR. OTHERWISE, TEMPERATURES ARE COLDER TODAY BEHIND
YESTERDAY'S FRONT, WITH HIGHS GENERALLY PEAKING IN THE 20S EAST OF
THE DIVIDE. THE GUSTY WIND ACROSS SOUTHERN WYOMING WILL CONTINUE
THROUGH THE AFTERNOON, SUBSIDING AFTER SUNSET.
THE NEXT SYSTEM IS QUICKLY APPROACHING WITHIN THE NORTHWESTERLY
FLOW. THIS WILL BRING A SURGE OF MOISTURE TO THE AREA WITH SNOW
BEGINNING TONIGHT ACROSS WESTERN WYOMING AFTER 06Z. WITH PERSISTENT
PACIFIC MOISTURE AND JET SUPPORT, THIS WILL BE A MUCH MORE PROLONGED
EVENT THAN THE LAST ONE. SNOW WILL BECOME HEAVIER AFTER SUNRISE
SUNDAY, REMAINING STEADY THROUGH SUNDAY NIGHT BEFORE DECREASING
SOMEWHAT ON MONDAY. WINTER HIGHLIGHTS HAVE NOW BEEN ISSUED FOR MUCH
OF WESTERN WYOMING THROUGH MONDAY NIGHT. THESE MAY NEED EXTENDED
THROUGH TUESDAY AS THERE WILL BE LITTLE CHANGE IN THE SETUP THROUGH
THEN. LASTLY, THE WESTERN BIGHORN MOUNTAINS WILL ALSO BE
PARTICIPATING IN THIS EVENT, THOUGH TOTALS THERE WILL BE LOWER - IN
THE ADVISORY RANGE FOR THE MOST PART.
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 WILL SET UP FROM NORTHWEST TO SOUTHEAST ACROSS
SOUTHERN MONTANA BY SUNDAY. 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.
THESE AREAS WILL LIKELY NEED A WINTER WEATHER ADVISORY, BUT
GIVEN THAT THE BEST CHANCE OF HIGHER RATES MAY NOT COME UNTIL
SUNDAY NIGHT OR MONDAY, WE WILL WAIT ON THIS FOR NOW. NORTHERN
JOHNSON COUNTY MAY ALSO JOIN IN ON THIS PARTICULAR FEATURE WITH
THIS EVENT, THOUGH UNCERTAINTY ON AMOUNTS IS HIGHER THERE.
ELSEWHERE, SOUTHERN AREAS (INCLUDING SWEETWATER COUNTY) WILL SEE
THEIR BEST CHANCES ON SUNDAY WITH THE INITIAL PACIFIC MOISTURE
SURGE. FORECAST ACCUMULATIONS HERE FOR SUNDAY ARE CURRENTLY
AROUND AN INCH, BUT THIS MAY NEED TO BE WATCHED FOR THE
POTENTIAL FOR A LITTLE MORE (THE GREATER ROCK SPRINGS AREA
CURRENTLY HAS AROUND A 55% CHANCE TO SEE AT LEAST TWO INCHES).
THIS WILL NOT BE A PARTICULARLY COLD SYSTEM, AND HIGHS ACROSS
CENTRAL AND SOUTHERN WYOMING WILL REACH THE 30S BOTH SUNDAY AND
MONDAY.
THE FRONT WILL DROP SOUTH ON TUESDAY, MAKING FOR A COLDER DAY EAST
OF THE DIVIDE WITH CONTINUED LIGHTER SNOW. AFTER MILDER TEMPERATURES
RETURN MIDWEEK, GUIDANCE IS HINTING AT THE NEXT SYSTEM ARRIVING
SOMETIME IN THE WEDNESDAY TO FRIDAY TIMEFRAME. HOWEVER, THERE IS
QUITE A LOT OF SPREAD IN SOLUTIONS FOR THIS AT THE MOMENT, AND ANY
POTENTIAL IMPACTS ARE UNCLEAR.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 400 PM MST SAT FEB 15 2025
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS.
VFR FLIGHT CONDITIONS CONTINUE AT ALL WEST OF THE DIVIDE TERMINALS
THE FIRST PART OF THE TAF PERIOD. GUSTY WINDS ARE EXPECTED TO
DIMINISH SHORTLY (AROUND 00Z THIS EVENING) AT KJAC, KBPI AND KPNA.
GUSTY WINDS CONTINUE THROUGH MUCH OF THE PERIOD AT KRKS. THE NEXT
WEATHER SYSTEM IS STILL ON TRACK TO MOVE INTO THE REGION AROUND 09Z,
BRINGING SNOW CHANCES AND MVFR/IFR FLIGHT CONDITIONS. KJAC WILL BE
THE FIRST TERMINAL TO SEE SNOW AND REDUCED FLIGHT CONDITIONS
FOLLOWED BY KPNA, KBPI, THEN KRKS. KRKS COULD SEE IFR FLIGHT
CONDITIONS WITH GUSTY WINDS AND SNOW CAUSING BLOWING SNOW SUNDAY
AFTERNOON BUT CONFIDENCE IS TOO LOW AT THIS TIME TO INCLUDE IN TAF.
THERE IS UNCERTAINTY AS TO HOW QUICKLY SNOW AND REDUCED FLIGHT
CONDITIONS MOVE INTO KPNA, KBPI, AND KRKS AND THIS IS REFLECTED
IN THE PROB30 GROUP. ANTICIPATE MOUNTAIN OBSCURATION WITH SNOW
AND LOW CEILINGS AND VISIBILITIES SUNDAY.
ADDITIONALLY AT KBPI AND KPNA, A LOW CLOUD DECK IS FORECAST TO
DEVELOP OVERNIGHT WITH THE INCREASED MOISTURE AHEAD OF THE SYSTEM,
LIGHT WINDS, AND SNOW ALREADY ON THE GROUND. HOWEVER, CONFIDENCE IS
TOO LOW AT THIS TIME ADD IFR CEILINGS.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS.
23Z SATELLITE IMAGERY SHOWS AN MVFR STRATUS CLOUD DECK IN THE AREA
OF KRIW. KRIW IS ON THE EDGE OF THIS CLOUD DECK BUT REMAINS
IMPACTED. BRIEF PERIODS OF JUMPS TO VFR THROUGH 02Z CANNOT BE RULED
OUT. THIS STRATUS SHOULD BEGIN TO DISSIPATE SHORTLY AFTER
SUNSET.
A WINTER WEATHER SYSTEM MOVES INTO THE REGION LATE TONIGHT AND WILL
BRING SNOW CHANCES AND MVFR/IFR FLIGHT CONDITIONS TO KCOD AND KCPR
THIS TAF PERIOD. BECAUSE THE SNOW CHANCES ARE LATER IN THE TAF
PERIOD, CONFIDENCE IS LOW (30%) IN EXACT TIMING AND DIRECT IMPACTS
TO BOTH TERMINALS SUNDAY. OTHERWISE, GENERALLY LIGHT WINDS (10KTS)
CONTINUE ALL ALL EAST OF THE DIVIDE TERMINALS EXCEPT AT KCPR WHERE
GUSTS AROUND 25KTS ARE FORECAST AFTER SUNRISE.
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 FROM 2 AM SUNDAY TO 5 AM MST TUESDAY FOR
WYZ001-002-012-024.
WINTER WEATHER ADVISORY FROM 5 AM SUNDAY TO 5 AM MST TUESDAY
FOR WYZ008-014.
WINTER WEATHER ADVISORY FROM 2 AM SUNDAY TO 5 AM MST TUESDAY
FOR WYZ013-023-025.
DISCUSSION...MYERS
AVIATION...GERHARDT
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