642
FXUS65 KRIW 251335
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
735 AM MDT SUN OCT 25 2026
KEY MESSAGES
- ANOTHER COOL DAY TODAY WITH ISOLATED (15-25%) SHOWERS, MAINLY
IN THE SOUTHERN HALF OF WYOMING.
- AN APPROACHING WEATHER SYSTEM BRINGS MOUNTAIN SNOW AND STRONG
WIND MONDAY NIGHT INTO TUESDAY.
- DRIER WEATHER RETURNS LATER IN THE WEEK WITH NEAR TO ABOVE
NORMAL TEMPERATURES.
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 AS WELL AS EASTERN PORTIONS OF FREMONT AND SWEETWATER
COUNTIES TONIGHT. ALL SHOWERS SHOULD END BY OR SHORTLY AFTER
SUNRISE MONDAY. IT WILL ANOTHER COOL DAY AS WELL, WITH HIGH
TEMPERATURES SIMILAR TO HIGHS ON SATURDAY.
THE SECOND, AND MORE IMPACTFUL SYSTEM IMPACTS THE AREA FROM MONDAY
NIGHT THROUGH TUESDAY. THIS WILL BE A FAST MOVING LOW MOVING INTO
THE PACIFIC NORTHWEST TONIGHT AND MOVING 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 RANGE 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 AN 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 SUNDAY EVENING
THROUGH SUNRISE ON MONDAY.
BUT THE MAIN QUESTION EVERYONE IS WONDERING ABOUT IT 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 SUNDAY NIGHT THROUGH SUNRISE
MONDAY, WHEN 700 MILLIBAR TEMPERATURES FALL AS LOW AS MINUS 5 TO
MINUS 6, 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 POTENTIAL 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 WORKWEEK, 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 /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 402 AM MDT SUN OCT 25 2026
A WEATHER SYSTEM WILL MOVE NORTHEASTWARD TOWARD THE AREA AND
SPREAD THICKENING CLOUDS ACROSS ROUGHLY THE SOUTHERN TWO THIRDS
OF THE AREA. MOST LOCATIONS WILL SEE VFR CONDITIONS THROUGH 12Z
MONDAY. DEEPER MOISTURE WILL BRING AROUND A 30 PERCENT CHANCE OF
A SHOWER IN VICINITY OF KBPI, KPNA AND KRKS THIS AFTERNOON AND
EVENING, SO PROB30 GROUPS HAVE BEEN ADDED TO THOSE SITES. IN
VICINITY OF KCPR, THERE IS A 50 PERCENT CHANCE OF MVFR
CONDITIONS AFTER 04Z TONIGHT WITH AROUND A 40 PERCENT CHANCE OF
SHOWERS AFTER 04Z TONIGHT. A SHOWER CAN'T BE RULED OUT LATER
THIS AFTERNOON IN VICINITY OF KRIW AND KLND, BUT WITH THE CHANCE
LESS THAN 20 PERCENT WE LEFT IT OUT OF THE TAFS FOR NOW.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HATTINGS
AVIATION...HATTINGS
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