530
FXUS65 KRIW 160451
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
951 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 /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 950 PM MST SAT FEB 15 2025
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS.
THE NEXT WINTER STORM BEGINS TO MOVE IN TO START THE TAF PERIOD. AT
JAC, HI-RES MODELS START TO PUSH IN IMPACTFUL (LOWERING FLIGHT
CATEGORIES CHANCES) AROUND 07Z, WITH THE MAIN PUSH OF SNOW COMING IN
BETWEEN 09Z AND 11Z. VISIBILITIES WILL LARGELY BE HALF A MILE TO A
MILE THROUGH MUCH OF THE PERIOD STARTING BETWEEN 12Z AND 14Z; HAVE
OPTED FOR 1 MILE IN THE TAF, WITH ABOUT A 60% CHANCE OF PREVAILING
CONDITIONS AROUND HALF A MILE. CONDITIONS MAY BEGIN TO IMPROVE AFTER
01Z/MON, BUT CONFIDENCE IS LOW AT THIS RANGE.
AT RKS, THE BEST SNOW CHANCES HOLD OFF UNTIL ABOUT 17Z. THERE ARE
INDICATIONS THAT SOME SNOW SHOWERS MAY BRING RAPID DECREASES IN
VISIBILITIES ALONG WITH GUSTY WINDS. THESE CHANCES ARE THROUGH THE
ENTIRE AFTERNOON. HAVE INCLUDED A PREVAILING SNOW GROUP, BUT THERE
COULD BE PERIODS WHERE SNOW IS NOT FALLING.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS.
EXPECTING DRY, AND VFR, CONDITIONS TO PREVAIL THROUGH THE PERIOD.
THERE COULD BE A COUPLE EXCEPTIONS, THOUGH. AT COD, SNOW WILL BE
OCCURRING OVER THE NEARBY MOUNTAINS, AND AN OCCASIONAL SHOWER MAY
IMPACT THE SITE THROUGH THE AFTERNOON. BETTER SNOW CHANCES COME FROM
THE NORTH AT THE VERY END OF THE PERIOD, BUT MAY NEED TO BE PUSHED
BACK INTO THE NEXT PERIOD. CPR MAY ALSO SEE AN OCCASIONAL SNOW
SHOWER THIS AFTERNOON, INDICATED WITH A PROB30 GROUP.
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...WITTMANN
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