355
FXUS65 KRIW 152301
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
401 PM MST SAT FEB 15 2025
KEY MESSAGES
- SNOW ENDING ACROSS THE WEST THIS MORNING, WHILE LIGHT SNOW
OCCURS EAST OF THE DIVIDE AND ENDS THIS AFTERNOON.
- THE NEXT WEATHER SYSTEM BRINGS MODERATE TO HEAVY SNOW TO
WESTERN WYOMING FROM SUNDAY THROUGH AT LEAST MONDAY NIGHT.
- A GOOD CHANCE OF ADDITIONAL SNOW IN NORTHERN WYOMING, BUT
AMOUNTS AND SOUTHERN EXTENT REMAIN SOMEWHAT UNCERTAIN.
DISCUSSION
ISSUED AT 121 AM MST SAT FEB 15 2025
WE ARE NOW HEADING INTO WHAT I CALL THE MATTRESS SALE WEEKEND, SINCE
THAT SEEMS TO BE THE THING MANY PEOPLE IDENTIFY THIS HOLIDAY WEEKEND
AS. WE CONTINUE TO HAVE CONTRASTING WEATHER ACROSS THE AREA, SO
WE WILL SPLIT THE DISCUSSION INTO WEST AND EAST OF THE DIVIDE.
WEST OF THE DIVIDE...SOME SNOW CONTINUES TO FALL OVER THE WEST, BUT
THE HEAVIEST LOOKS LIKE IT IS COMING TO AN END AS THE COLD FRONT
PASSES AND THE JET ENERGY MOVES AWAY TO THE EAST. THERE IS STILL A
GREATER THAN 3 OUT OF 5 CHANCE OF 3 INCHES OR MORE BETWEEN NOW AND
11 AM, SO WE WILL LET THE WARNINGS RIDE FOR NOW. HOWEVER, THE
STEADIEST SNOW WILL BE OVER BEFORE SUNRISE. A FEW SNOW SHOWERS
WILL ALSO BE POSSIBLE FOR SWEETWATER COUNTY, BUT ACCUMULATIONS
HERE WOULD BE LIGHT, GENERALLY LESS THAN 1 INCH OR LESS. THE
MAIN CONCERN HERE WILL BE SOME GUSTY NORTHWEST WIND DEVELOPING
AS THE FRONT PASSES. HIGH WIND IS NOT LIKELY, BUT IS A GREATER
THAN 1 IN 2 CHANCE OF GUSTS PAST 35 MPH, ESPECIALLY SOUTH OF
INTERSTATE 80. THERE WILL THEN BE A LULL IN THE PRECIPITATION
THIS AFTERNOON THROUGH MOST OF TONIGHT BEFORE THE NEXT SYSTEM
APPROACHES FROM THE WEST. MORE ON THAT BELOW.
THE NEXT PACIFIC SYSTEM WILL APPROACH THE AREA LATER TONIGHT, BUT
THE BULK OF THE IMPACTS SHOULD HOLD OFF UNTIL AFTER AROUND 5 AM ON
SUNDAY. THIS LOOKS LIKE MORE OF A LONG LIVED EVENT THOUGH. A
CONTINUOUS FEED OF PACIFIC MOISTURE WILL BE COMING INTO THE AREA
THROUGH AT LEAST MONDAY NIGHT. THERE WILL BE SOME DECENT UPPER LEVEL
SUPPORT AS WELL. FIRST ON SUNDAY WITH THE AREA UNDER THE INFLUENCE
OF THE RIGHT REAR QUADRANT OF A JET STREAK MOVING ACROSS SOUTHERN
MONTANA, AND THEN THE LEFT FRONT QUADRANT OF A JET STREAK MOVING
ACROSS SOUTHERN WYOMING SUNDAY NIGHT. SNOW AMOUNTS LOOK FAIRLY
IMPRESSIVE AS WELL, WITH PROBABILISTIC GUIDANCE GIVING AT LEAST
AN 8 IN 10 CHANCE OF OVER A FOOT OF NEW SNOW IN THE HIGHER
ELEVATIONS FROM SOUTHWESTERN YELLOWSTONE THROUGH THE SALT AND
WYOMING RANGES THROUGH MONDAY NIGHT. MOST OF THE WESTERN
VALLEYS HAVE AT LEAST A 3 IN 5 CHANCE OF 8 INCHES OR MORE OF
SNOW. WITH THAT, WE WILL HOIST NEW WINTER STORM WATCHES FOR THE
WESTERN MOUNTAINS AND VALLEYS STARTING AT 5 AM SUNDAY AND
CONTINUING THROUGH 5 AM TUESDAY. THESE MAY HAVE TO BE EXTENDED,
BUT GUIDANCE DIVERGES MORE THIS FAR OUT.
THERE IS ONE MORE CONCERN. WITH THE JET STREAK OVER SWEETWATER
COUNTY AND SOME INSTABILITY ON SUNDAY, THERE WILL BE THE
POTENTIAL FOR CONVECTIVE SNOW SHOWERS AND POSSIBLY SNOW SQUALLS
IN THAT AREA THAT COULD IMPACT INTERSTATE 80. WINDS ALOFT ARE
RATHER STRONG, APPROACHING 40 TO 45 KNOTS AT 700 MILLIBARS,
WHICH COULD MIX TO THE SURFACE. THIS WOULD BE MAINLY IN THE
AFTERNOON. THIS IS FAR FROM CERTAIN THOUGH, SO WE WILL CONTINUE
TO WATCH IT.
FOLLOWING THIS, THERE IS FAIRLY GOOD AGREEMENT OF RIDGING BRINGING
DRIER WEATHER FOR WEDNESDAY. ANOTHER PACIFIC TROUGH MAY APPROACH THE
AREA THURSDAY WITH THE NEXT CHANCE OF SNOW, BUT DETAILS ON TIMING
AND AMOUNTS OBVIOUSLY GET MORE DIFFICULT THIS FAR OUT.
EAST OF THE DIVIDE...THE COLD FRONT IS DROPPING SOUTHWARD NOW AND
BRINGING SOME MAINLY LIGHT SNOW TO NORTHERN WYOMING. THE FORECAST IS
WORKING OUT FAIRLY WELL HERE, WITH MOST OF THE SNOW FALLING IN BIG
HORN AND JOHNSON COUNTIES NOW, AND THIS WILL SPREAD SOUTHWARD
THROUGH THE MORNING. MANY AREAS EAST OF A POWELL-TO-SHOSHONI
LINE HAVE AT LEAST A 1 IN 2 CHANCE OF AN INCH OF NEW SNOW OR
MORE. HOWEVER, WHEN YOU BUMP THIS UP TO 2 INCHES, THE CHANCE
DROPS TO LESS THAN 1 OUT OF 5 FOR ALL LOCATIONS EXCEPT THE
MOUNTAINS AND A SMALL AREA ROUGHLY FROM POWELL TO BASIN. THIS
WILL BE A QUICK HITTER AS WELL, WITH NORTHERN AREAS HAVING MOST
SNOW STOP BY NOON AND ALL AREAS OVER BY 5 PM THIS EVENING. THIS
WILL BE A COLDER DAY AS WELL, ESPECIALLY ACROSS CENTRAL
WYOMING, DUE TO THE COLD FRONT. HIGHS WILL REMAIN IN THE TEENS
ACROSS MOST OF THE AREA, WITH THE EXCEPTIONS OF PLACES LIKE THE
WIND RIVER BASIN, WHERE THE LACK OF SNOW COVER WILL ALLOW
TEMPERATURES TO RISE INTO THE 20S. MAINLY DRY WEATHER IS THEN
EXPECTED THROUGH TONIGHT.
WE THEN MOVE TO SUNDAY, AND THIS IS WHERE UNCERTAINTY INCREASES
AND I END UP PULLING OUT MORE OF MY THINNING HAIR. THERE ARE
SOME INDICATIONS THAT WE COULD BE LOOKING AT A DECENT SNOW EVENT
FOR FAR NORTHERN WYOMING. WE WILL HAVE A BOUNDARY NEAR THE
MONTANA BORDER, ALTHOUGH THIS ONE IS NOT NEARLY AS SHARP AS THE
ONE LAST WEEK THAT BROUGHT THE HEAVY SNOW TO CODY. WE WILL ALSO
HAVE SOME JET ENERGY IN PLACE, BUT THE JET IS NOT AS STRONG,
TOPPING OUT AT 100 KNOTS AS OPPOSED TO THE 150 KNOT JET FROM THE
PREVIOUS SYSTEM. DETERMINISTIC MODELS ARE SPLIT; THE GFS, FOR
EXAMPLE, KEEPS MOST OF THE ENERGY AND DEEPEST MOISTURE OVER
MONTANA THROUGH MONDAY WITH ONLY A GLANCING BLOW FOR THE FAR
NORTH AND SOME UPSLOPE SNOW FOR THE WESTERN SLOPES OF THE
BIGHORNS. MEANWHILE, THE ECMWF IS A LITTLE FURTHER SOUTH AND
KEEPS PERIODS OF SNOW OVER THE NORTH THROUGH MONDAY AND EVEN
TUESDAY, ALTHOUGH MOST ACCUMULATIONS ARE LIGHT. AS FOR
POTENTIAL HIGHLIGHTS, PROBABILISTIC GUIDANCE KEEPS THE 1 IN 2
CHANCE OF A 3 INCHES OR MORE OF SNOW THROUGH THE PERIOD LARGELY
NORTH OF A BUFFALO-GREYBULL-CODY LINE. THIS WOULD FAVOR
ADVISORIES, BUT WITH THE UNCERTAINTY WE WILL PUNT TO THE DAY
SHIFT TO MAKE THE CALL ON THIS. THE WESTERN BIGHORNS COULD ALSO
DO FAIRLY WELL FROM THIS, WITH A NEAR 100 PERCENT CHANCE OF 6
INCHES OF NEW SNOW. ADVISORIES MAY BE NEEDED HERE AS WELL.
CENTRAL WYOMING SHOULD REMAIN LARGELY DRY THROUGH MOST OF MONDAY.
MOST MODELS KEY IN HERE FOR TUESDAY FOR THE CHANCE OF ANY SNOW AS
THE FRONTAL BOUNDARY MOVES SOUTH. THERE WILL CONTINUE TO BE THE
CONTRAST IN TEMPERATURES AS WELL, WITH WELL BELOW NORMAL CONTINUING
ACROSS NORTHERN WYOMING WITH WARMER TEMPERATURES FURTHER SOUTH.
THINGS TURN COLDER ON WEDNESDAY, BUT AREAS SHOULD BE DRY BEHIND
THE FRONT. THINGS LOOK MAINLY DRY FOLLOWING THAT FROM THURSDAY
INTO THE WEEKEND.
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...HATTINGS
AVIATION...GERHARDT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page