415
FXUS65 KRIW 251839
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1239 PM MDT SUN OCT 25 2026
KEY MESSAGES
- COOL TODAY. ISOLATED SHOWERS (15-30% CHANCES) OCCUR ACROSS SOUTHERN
WYOMING. CHANCES (25-40%) LINGER OVERNIGHT ACROSS FAR EASTERN
SWEETWATER COUNTY TO AROUND CASPER.
- A QUICK-MOVING WEATHER SYSTEM BRINGS STRONG WINDS TO THE AREA
LATE MONDAY NIGHT THROUGH TUESDAY. THE STRONGEST WINDS OCCUR
OVER THE MOUNTAINS AND FROM SOUTH PASS TO CASPER, WHICH WILL
BE GUSTING IN EXCESS OF 50 MPH.
- WESTERN MOUNTAIN SNOW OCCURS MONDAY NIGHT INTO EARLY TUESDAY MORNING.
A FEW INCHES OF SNOW IS POSSIBLE OVER TETON AND TOGWOTEE
PASSES, WHICH COULD BRING MINOR IMPACTS TO TRAVEL THROUGH
TUESDAY MORNING.
UPDATE
ISSUED AT 1237 PM MDT SUN OCT 25 2026
A QUICK SYSTEM BRINGS LIGHT SHOWERS TO PORTIONS OF SOUTHERN WYOMING
TODAY AND POSSIBLY UP TO AROUND NATRONA AND JOHNSON COUNTIES
OVERNIGHT. OVERALL CHANCES ARE ABOUT 15 TO 30 PERCENT, WITH SLIGHTLY
BETTER ODDS AROUND CASPER. ANY ACCUMULATIONS WOULD BE LIGHT, UNDER
0.1 INCHES.
THE FOCUS REMAINS ON THE LARGER SYSTEM MONDAY NIGHT THROUGH TUESDAY.
LATEST GUIDANCE LEAVES CONFIDENCE HIGH ENOUGH THAT A HIGH WIND WATCH
HAS BEEN HOISTED FOR THE THE WIND CORRIDOR, FROM ABOUT SOUTH PASS TO
CASPER. WIND GUSTS SHOULD START INCREASING JUST AHEAD OF THE FRONT,
AROUND 4AM TUESDAY, WITH THE STRONGEST WINDS EXPECTED THROUGH ABOUT
11AM AS THE FRONT TRACKS EASTWARDS. THOUGH IT REMAINS WINDY, THE
TREND WILL BE DECREASING WINDS TUESDAY AFTERNOON. OUTSIDE THE WATCH
ZONE, IT WILL STILL BE WINDY, MAINLY AROUND THE MOUNTAINS. GUSTS
OVER 30 MPH WILL BE COMMON AND COULD BE STRONGER AS THE FRONT
PASSES. FOR SNOW, AMOUNTS HAVE NOT CHANGED MUCH FROM THE FULL
DISCUSSION BELOW. MAIN IMPACTS WOULD BE FOR ANY EARLY TUESDAY
MORNING COMMUTES ALONG TETON AND TOGWOTEE PASSES. THIS SYSTEM IS
QUICK-MOVING, SO THE DURATION OF SNOWFALL IS LIMITED, MAYBE TO ABOUT
A 6 HOUR PERIOD BETWEEN ABOUT 11PM MONDAY NIGHT AND 5AM TUESDAY.
DISCUSSION
ISSUED AT 135 AM MDT SUN OCT 25 2026
IT WAS QUITE BRIGHT THIS EVENING WHEN DRIVING TO WORK FROM MY HOUSE
TO THE HUMBLE RIVERTON WEATHER ABODE TO THE WEST OF TOWN. THIS IS
COURTESY OF THE ALMOST FULL HUNTERS MOON, WHICH PEAKS TOMORROW NIGHT
AROUND MIDNIGHT OR SO. MOST AREAS WOULD HAVE A BETTER CHANCE OF
SEEING IT TONIGHT THOUGH, AS THERE WILL BE A COUPLE OF SYSTEMS
IMPACTING THE AREA OVER THE NEXT COUPLE OF DAYS.
THE FIRST SYSTEM IS AN UPPER LEVEL LOW OVER ARIZONA THAT WILL LIFT
NORTHEAST OVER THE NEXT COUPLE OF DAYS. THIS SYSTEM LOOKS MUCH MORE
LIKE A GLANCING BLOW AS IT WILL BE WEAKENING AND THE BEST FORCING
WILL REMAIN TO THE SOUTH AND EAST OF THE AREA. THE BEST CHANCE OF
SHOWERS WILL BE FROM LATER THIS AFTERNOON INTO TONIGHT AND
ESPECIALLY FROM SOUTH OF A ROCK SPRINGS TO CASPER LINE. THIS LOOKS
MORE LIKE A MINOR NUISANCE SYSTEM. ALL AREAS WITH THE EXCEPTION
OF THE HIGHEST ELEVATIONS OF CASPER MOUNTAIN AND THE WIND RIVER
RANGE HAVE LESS THAN A 1 IN 2 CHANCE OF A TENTH OF AN INCH OF
PRECIPITATION. MANY LOCATIONS WILL SEE NOTHING. THE BEST CHANCE
OF SHOWERS WILL BE IN SOUTHERN WYOMING TODAY, SHIFTING TOWARD
NATRONA COUNTY AS WELL AS EASTERN PORTIONS OF FREMONT AND
SWEETWATER COUNTIES TONIGHT. ALL SHOWERS SHOULD END BY OR
SHORTLY AFTER SUNRISE MONDAY. IT WILL BE ANOTHER COOL DAY AS
WELL, WITH HIGH TEMPERATURES SIMILAR TO HIGHS ON SATURDAY.
THE SECOND, AND MORE SIGNIFICANT SYSTEM, IMPACTS THE AREA FROM
MONDAY NIGHT THROUGH TUESDAY. THIS WILL BE A QUICK LOW MOVING
INTO THE PACIFIC NORTHWEST TONIGHT AND ACROSS THE NORTHERN
ROCKIES MONDAY NIGHT INTO TUESDAY. THIS WILL SET UP THE TYPICAL
FALL / WINTER WESTERLY FLOW SITUATION ACROSS THE AREA, WITH MOST
PRECIPITATION FALLING IN WESTERN WYOMING WITH FAVORABLE
OROGRAPHICS AND WIND BEING THE MAIN IMPACT EAST OF THE DIVIDE.
WITH THIS BEING THE HEART OF FOOTBALL SEASON, WE WILL TACKLE
EACH OF THESE THREATS INDIVIDUALLY, BUT HOPEFULLY NOT BE
PENALIZED FOR BEING WRONG.
WE WILL START WITH THE PRECIPITATION, WHICH INCLUDES SOME
ACCUMULATING SNOW, MAYBE EVEN FOR THE LOWER ELEVATIONS. MOST OF THE
WESTERN MOUNTAINS HAVE A NEARLY 100 PERCENT CHANCE OF A TENTH OF AN
INCH OF QPF OR MORE FROM MONDAY NIGHT THROUGH TUESDAY. THE AREA WITH
A GREATER THAN 1 IN 2 CHANCE OF A THIRD OF AN INCH OF QPF OR GREATER
IS WHERE YOU WOULD EXPECT IT WITH A WEST TO SOUTHWEST FLOW, MAINLY
FROM THE NORTHERN SALT AND WYOMING RANGES THROUGH THE TETONS
AND SOUTHWESTERN YELLOWSTONE PARK. AMOUNTS HAVE INCREASED
SOMEWHAT FROM YESTERDAY, WITH A DECENT AMOUNT OF THE
AFOREMENTIONED AREA HAVING A GREATER THAN 1 IN 2 CHANCE OF A
HALF INCH OR MORE. THERE WILL BE SOME DECENT UPPER LEVEL
FORCING WITH THIS SYSTEM, WITH AN 100 TO 110 KNOT JET STREAK
MOVING OVER THE AREA, ENHANCING PRECIPITATION RATES. THE
LIMITING FACTOR WILL BE THE SPEED OF THE SYSTEM, WITH MOST OF
THE PRECIPITATION FALLING IN A PERIOD FROM LATER MONDAY EVENING
THROUGH SUNRISE ON TUESDAY.
BUT THE MAIN QUESTION EVERYONE IS WONDERING ABOUT IS THE
POTENTIAL FOR SNOW. ONE FACTOR WILL BE HOW FAST A COLD FRONT CAN
MOVE THROUGH AND LOWER SNOW LEVELS. THROUGH MOST OF MONDAY
EVENING, 700 MILLIBAR TEMPERATURES WOULD LIKELY REMAIN AT 0
CELSIUS OR HIGHER, KEEPING SNOW LEVELS AT 8500 FEET OR HIGHER.
THE MAIN TIME OF SNOW ACCUMULATION WOULD BE FROM MIDNIGHT MONDAY
NIGHT THROUGH SUNRISE TUESDAY, WHEN 700 MILLIBAR TEMPERATURES
FALL AS LOW AS MINUS 5C TO MINUS 6C, WHICH WOULD LOWER SNOW
LEVELS TO VALLEY FLOORS. MOST LOCATIONS, INCLUDING PORTIONS OF
THE JACKSON AND STAR VALLEYS, HAVE AT LEAST A 1 IN 2 CHANCE OF
AN INCH OF SNOW OR MORE. AS FOR THE CHANCE OF 3 INCHES, THE 1 IN
2 PROBABILITY IS GENERALLY AROUND 7500 FEET OR HIGHER, WHICH
INCLUDES PLACES LIKE TETON AND TOGWOTEE PASSES. THE MOUNTAIN
ADVISORY AMOUNT IS 6 INCHES, AND THE CHANCE OF THIS IS MAINLY
ABOVE 10000 FEET WHERE IMPACTS ARE MINIMAL. HOWEVER, WITH THE
JET OVERHEAD, THERE WILL BE A FAIR AMOUNT OF WIND THAT COULD
BRING SOME BLOWING SNOW. AS FOR POTENTIAL HIGHLIGHTS, THE CHANCE
IS AROUND 2 OUT OF 5 FOR ADVISORIES, PROBABLY FROM MONDAY NIGHT
INTO MIDDAY TUESDAY. WE WON'T ISSUE ANY YET BUT FUTURE SHIFTS
WILL HAVE TO TAKE A CLOSER LOOK. MOST LOWER ELEVATION AREAS
WOULD HAVE FEW IMPACTS, BUT THERE COULD BE A SMALL ACCUMULATION
OF SNOW IN PLACES LIKE BIG PINEY, PINEDALE OR DUBOIS LATER
MONDAY NIGHT OR TUESDAY MORNING.
IN AREAS EAST OF THE DIVIDE, THE MAIN CONCERN SHIFTS TO STRONG
TO POTENTIALLY HIGH WIND. THE PRESSURE GRADIENT WILL TIGHTEN
AHEAD OF THE COLD FRONT AND WITH A COMBINATION OF THE JET
OVERHEAD AND 700 MILLIBAR WINDS CLIMBING AS HIGH AS 55 KNOTS,
THINGS WILL GET QUITE BLUSTERY. A LARGE PORTION OF AREAS EAST
OF THE DIVIDE HAVE AT LEAST A 1 IN 2 CHANCE OF WIND GUSTS OVER
40 MPH. THE CORE OF THE HIGHEST WIND IS WHERE YOU WOULD EXPECT
IT IN THIS PATTERN, FROM MUDDY GAP THROUGH CASPER, WHERE THERE
IS A GREATER THAN 1 IN 2 CHANCE OF WIND GUSTS PAST 55 MPH. THE
CURRENT FORECAST HAS BORDERLINE HIGH WIND, AND THE NATIONAL
BLEND OF MODELS TENDS TO NOT CAPTURE WIND WELL IN THIS AREA. WE
MAY NEED SOME HIGH WIND HIGHLIGHTS, WITH THE CHANCE AROUND 1 OUT
OF 2 AT THIS TIME. WITH THE MAIN THREAT NOT UNTIL TUESDAY, WE
WILL NOT ISSUE RIGHT NOW, BUT WILL CONSIDER FOR FUTURE SHIFTS.
RIDGING SHOULD THEN BUILD OVER THE AREA THROUGH MOST OF THE
REMAINDER OF THE WORK WEEK, BRINGING LOCALLY BREEZY CONDITIONS
AND NEAR TO ABOVE NORMAL TEMPERATURES. A COUPLE OF WEAK
DISTURBANCES MAY BRING A FEW SHOWERS TO THE WEST, BUT AMOUNTS
LOOK SMALL. THE NEXT MORE WIDESPREAD PRECIPITATION CHANCE MAY
MOVE IN NEXT WEEKEND AS A SYSTEM APPROACHES FROM THE SOUTHWEST,
BUT DETAILS ARE DIFFICULT TO HASH OUT THIS FAR OUT.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1050 AM MDT SUN OCT 25 2026
LOW CLOUDS/FOG IN THE JACKSON/STAR VALLEYS IS STARTING TO
DISSIPATE AND EXPECTED TO CLEAR OUT BY 19Z.
AN AREA OF CLOUDS EXTENDS FROM THE SOUTHWESTERN CORNER OF THE
STATE TO THE BIGHORNS AS PART OF AN AREA OF LOW PRESSURE OVER
THE UINTAS. THESE CLOUDS, SCT-OVC FL050-100, WILL SHIFT TO THE
NORTH-NORTHWEST THROUGH THE AFTERNOON AS THE CENTER OF THE LOW
MOVES TOWARD THE NORTHEAST. THERE REMAINS A 30% CHANCE FOR LIGHT
SHOWERS TO OCCUR OVER KRKS FROM 21Z TO 01Z AS A RESULT. MVFR
CEILINGS WILL DEVELOP AT KCPR BY 06Z, QUICKLY DROPPING TO
IFR/LIFR BY 08Z. LIGHT SHOWERS WILL BE POSSIBLE BY THIS TIME
WITH THE ALREADY LOWERING CEILINGS BEING THE BIGGER THREAT.
MOUNTAIN OBSCURATIONS WILL BECOME MORE WIDESPREAD ACROSS THE
AREA AFTER 06Z AS WELL.
CLOUDS WILL SCATTER OUT ACROSS THE AREA WITH SKC SKIES OVER THE
CENTRAL BASINS TOWARD THE END OF THE TAF PERIOD, AS THE MAIN
STORM SYSTEM BEGINS TO MOVE OVER THE NE PANHANDLE. WINDS WILL
CONTINUE TO BE LIGHT (11KT OR LESS) THROUGH THE TAF PERIOD.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC
FOR THE LATEST INFORMATION ON SMOKE, ICING, AND TURBULENCE
FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
HIGH WIND WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY
AFTERNOON FOR WYZ019-020.
UPDATE...WITTMANN
DISCUSSION...HATTINGS
AVIATION...LAVOIE
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