380
FXUS65 KRIW 160446
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
946 PM MST SAT NOV 15 2025
KEY MESSAGES
- HIGH CLOUDS WILL CONTINUE TO INCREASE FROM THE SOUTH THROUGH
THE OVERNIGHT HOURS ACROSS THE FORECAST AREA, RESULTING IN
MOSTLY CLOUDY TO OVERCAST SKIES.
- HIGH CONFIDENCE IN HIGH TEMPERATURES 15 TO 20 DEGREES ABOVE
NORMAL SUNDAY WITH BREEZY WINDS.
- RAIN AND SNOW BEGINNING SUNDAY AFTERNOON ACROSS THE WEST AND
SPREADING EAST OF THE CONTINENTAL DIVIDE EARLY MONDAY. THE
GREATEST SNOW AMOUNTS ARE EXPECTED (80% CHANCE) ACROSS THE
WESTERN MOUNTAINS; HOWEVER, THE GREEN RIVER BASIN AND WESTERN
VALLEYS COULD SEE A LIGHT DUSTING TO 1 INCH BY MONDAY MORNING.
- SEASONAL TEMPERATURES LOOK FAVORABLE MUCH OF NEXT WEEK WITH
MULTIPLE OPPORTUNITIES FOR PRECIPITATION.
UPDATE
ISSUED AT 107 PM MST SAT NOV 15 2025
20Z WATER VAPOR IMAGERY SHOWS THE TRANSITORY RIDGE AXIS APPROACHING
THE SOUTHWEST CORNER OF WYOMING WITH STRONG NORTHWESTERLY FLOW
ALOFT OVER MONTANA AND THE EASTERN HALF OF WYOMING. GUSTY 20 MPH
TO 25 MPH WINDS ARE BEING OBSERVED ACROSS MANY LOCATIONS EAST
OF THE CONTINENTAL DIVIDE, THANKS TO THE STRONG FLOW ALOFT. AS
THE RIDGE AXIS TRAVERSES THE STATE OVER THE NEXT 24 HOURS,
EXPECT WINDS TO DECREASE AND CLOUD COVER TO INCREASE. ON THE
WEST SIDE OF THE AXIS, SOUTHWESTERLY FLOW ALOFT WILL USHER RICH
PACIFIC MOISTURE INTO THE STATE AHEAD OF THE FORECASTED UPPER
LOW EJECTING INTO THE REGION.
PRECIPITATION CHANCES HAVE REMAINED CONSISTENT IN SPREADING
SOUTHWEST TO NORTHEAST AS AN ASSOCIATED 700MB LOW TREKS ACROSS
THE STATE LATE SUNDAY INTO MONDAY. MEAN 700MB TEMPERATURES
BEHIND THE LOW ONLY DROP TO -2C TO -4C BY MONDAY MORNING. THIS
REFLECTS SNOW LEVELS GENERALLY AROUND 6500 FT TO 7500 FT, WITH
THE 6500 FT SNOW LEVELS WEST OF THE DIVIDE. THIS FAVORS A LIGHT
DUSTING TO AN INCH OF SNOW (50-80%) FOR LOCATIONS ACROSS THE
GREEN RIVER BASIN EARLY MONDAY MORNING. THE HIGHER ELEVATION
WESTERN MOUNTAINS HAVE AN 80-90% CHANCE OF SNOW AMOUNTS OF AT
LEAST 6 INCHES BY MONDAY MORNING, BUT DROP TO ONLY AROUND 50%
FOR 10 INCHES ACROSS THE HIGHEST PEAKS. NO HIGHLIGHTS ARE
EXPECTED AT THIS TIME GIVEN THE WESTERN MOUNTAIN PASSES HAVE
LESS THAN A 40% CHANCE OF AT LEAST 6 INCHES OF SNOW BY MONDAY
MORNING. AS FOR THOSE EAST OF THE DIVIDE, PRECIPITATION IS STILL
FORECAST TO FALL AS RAIN WITH SNOW LEVELS ONLY DROPPING TO 7500
FT WHEN PRECIPITATION IS EXPECTED. MONDAY IS FORECAST TO BE A
WET ONE FOR MOST. COOLER AND MORE SEASONABLE TEMPERATURES ARE
STILL EXPECTED THROUGH THE REST OF THE WORK WEEK WITH VARIOUS
CHANCES FOR PRECIPITATION, PARTICULARLY WEDNESDAY INTO
THURSDAY.
DISCUSSION
ISSUED AT 104 AM MST SAT NOV 15 2025
WE STILL HAVE SOME GUSTY WIND OUT THERE EARLY THIS MORNING. THESE
SHOULD CONTINUE TO DECREASE THROUGH THE NIGHT THOUGH AS THE JET
STREAK MOVES AWAY AND RIDGING, ALTHOUGH OF THE TRANSITORY KIND,
BUILDS BACK OVER WYOMING. THIS SHOULD RESULT IN A FAIRLY NICE START
TO THE WEEKEND, WITH A MIX OF CLOUDS AND SUN AND ANOTHER DAY OF MILD
TEMPERATURES, ANYWHERE FROM 10 TO 20 DEGREES ABOVE NORMAL. WITH THE
RADAR LARGELY QUIET, WE HAVE REMOVED THE POPS FOR THIS MORNING.
THERE WILL STILL BE SOME BREEZY CONDITIONS AROUND CASPER TODAY,
BUT WITH 700 MILLIBAR WINDS FALLING THROUGH THE DAY, NO REALLY
STRONG WIND GUSTS ARE EXPECTED. AND WE COULD SEE A FEW MORE
RECORD HIGH TEMPERATURES TODAY AS WELL.
THE WEATHER WILL TURN MORE ACTIVE SUNDAY AND ESPECIALLY SUNDAY
NIGHT AND MONDAY AS THE NEXT WAVE MOVES IN FROM THE SOUTH. WE
DID MAKE A FEW TWEAKS THIS MORNING. FOR ONE, MOST GUIDANCE HAS A
SLOWER ARRIVAL OF THE SYSTEM. SO WE REMOVED THE POPS FOR LATE
TONIGHT. AND EVEN ON SUNDAY, THE LATEST GUIDANCE IS SHOWING ONLY
HALF OF QPF FOR SUNDAY WHEN COMPARED TO YESTERDAY. THE POPS WE
HAVE IN THE FORECAST MIGHT BE THE WETTEST IT COULD BE, AND THESE
MAY NEED TO BE CUT SOME MORE IF TRENDS CONTINUE. AND WITH THE
SLOWER PROGRESSION OF THE SYSTEM, SUNDAY LOOKS DRY ACROSS
CENTRAL WYOMING. AND IT LOOKS LIKE ONE MORE MILD DAY, WITH MANY
LOCATIONS SEEING HIGH TEMPERATURES IN THE 60S ONCE AGAIN. A
GUSTY WIND WILL DEVELOP IN THE SOUTHWEST FLOW LOCATIONS FROM
MUDDY GAP THROUGH CASPER, BUT WITH 700 MILLIBAR WINDS ONLY
AROUND 35 KNOTS, HIGH WIND IS NOT EXPECTED.
THE MAIN PART OF THE PRECIPITATION MOVES IN SUNDAY NIGHT INTO
MONDAY, AS THE UPPER LEVEL LOW LIFTS NORTHWARD INTO WYOMING AND
WE GET THE BEST UPPER LEVEL DIVERGENCE AND JET DYNAMICS. THERE
CONTINUE TO BE SOME DIFFERENCES IN PLACEMENT OF THE SHOWERS
THOUGH. IN THE DETERMINISTIC MODEL WORLD, THE EUROPEAN MODEL HAD
AROUND TWICE THE QPF OF THE GFS. IT ALSO SPREADS SHOWERS TO
MOST AREAS EAST OF THE DIVIDE WHILE THE GFS IS LARGELY DRY,
KEEPING MOST OF THE PRECIPITATION TO THE WESTERN MOUNTAINS. SO,
WE TURN TO THE WORLD OF PROBABILISTIC FORECASTING, MAINLY THE
ENSEMBLES. STARTING WITH SNOWFALL AMOUNTS, WE FIRST LOOK AT
ADVISORY LEVEL CRITERIA, WHICH IS 6 INCHES IN THE MOUNTAINS. THE
ONLY LOCATIONS SHOWING AT LEAST A 1 IN 2 CHANCE OF 6 INCHES OR
MORE ARE THE HIGHER ELEVATIONS OF THE TETONS, SALT/WYOMING
RANGES AND SOUTHWESTERN YELLOWSTONE. THE CHANCE OF 12 INCHES IS
BASICALLY ZERO. THERE COULD BE SOME ADVISORIES ISSUED, BUT IT
IS BORDERLINE RIGHT NOW. WE STILL HAVE TIME SINCE IMPACTS
WOULDN'T BEGIN UNTIL AFTER SUNSET SUNDAY AFTERNOON. WITH 700
MILLIBAR TEMPERATURES REMAINING ABOVE 0 CELSIUS THROUGH THE DAY
ON SUNDAY, SNOW WOULD BE CONFINED TO THE HIGHER ELEVATIONS.
COOLER AIR DOES WRAP AROUND SUNDAY NIGHT, WITH SNOW LEVELS
FALLING TO AROUND 6500 FEET BY MONDAY MORNING. THE WESTERN
VALLEYS COULD SEE SOME LIGHT ACCUMULATIONS, BUT IMPACTS AT THIS
TIME LOOK NEGLIGIBLE. EAST OF THE DIVIDE, SNOW LEVELS SHOULD
REMAIN ABOVE 7000 FEET, KEEPING THE POPULATED AREAS LIKELY
ALMOST ALL RAIN. QPF EAST OF THE DIVIDE ALSO LOOKS LIGHT, WITH
AT MOST A 1 IN 4 CHANCE OF A QUARTER INCH OR MORE EXCEPT IN THE
MOUNTAINS.
THIS WILL BE THE TRANSITION INTO MORE TYPICAL NOVEMBER WEATHER, AS
THE PATTERN LOOKS MORE ACTIVE AS A TROUGH MOVES INTO THE WESTERN
UNITED STATES. FLOW IS MORE WESTERLY TO EVEN SOUTHWESTERLY FOR THE
MOST PART, SO AIR WILL BE PACIFIC, AND THIS SHOULD KEEP TEMPERATURES
MAINLY ONLY FALLING TO NEAR NORMAL. A FEW SYSTEMS WILL BE MOVING
AROUND WYOMING, BUT MODELS ARE ALL OVER THE PLACE IN REGARDS TO
TIMING AND PLACEMENT. SO THE REASONING REMAINS THE SAME AS
YESTERDAY. WE HAVE FAIRLY HIGH CONFIDENCE OF A COOLER AND MORE
ACTIVE PATTERN, BUT THE DETAILS OF TIMING AND AMOUNTS OF
PRECIPITATION REMAIN IN FLUX.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 940 PM MST SAT NOV 15 2025
SCT-BKN CLOUDS, FL150-220, CONTINUE TO PUSH NORTHWARD ACROSS
THE FORECAST AREA AS ALL TERMINALS REMAIN VFR. AN UPPER LEVEL
LOW ALONG THE SOUTHERN CALIFORNIA COAST TRACKS INLAND OVERNIGHT
AND SUNDAY MORNING, NEARING WYOMING BY MIDDAY SUNDAY. SOUTHERLY
SURFACE FLOW AHEAD OF THIS FEATURE LEADS TO AN INCREASE IN
SOUTHERLY WIND AT KCPR AND KRKS BY 18Z. ISOLATED LIGHT SHOWERS
APPROACH FROM THE SOUTH OVER FAR WESTERN PORTIONS, IMPACTING
KJAC BETWEEN 14Z AND 16Z AND AGAIN BETWEEN 19Z AND 21Z.
CONDITIONS ARE EXPECTED TO REMAIN VFR WITH THESE SHOWERS. SNOW
LEVELS WILL BE AROUND 9000 FT OVER THE WESTERN MOUNTAINS THROUGH
THE DAY. MORE WIDESPREAD PRECIPITATION WILL DEVELOP AND MOVE
OVER FAR SOUTHERN PORTIONS OF THE STATE BY 00Z, MOVING NORTHWARD
THROUGH 06Z MONDAY. CLOUD HEIGHTS WILL LOWER TO FL050-080
ACROSS AREAS WEST OF THE DIVIDE BY 00Z AND CONTINUE TO LOWER TO
MVFR WITH THE RAIN. KRKS AND KBPI/KPNA WILL BE IMPACTED BETWEEN
00Z AND 06Z, WITH SNOW LEVELS RANGING BETWEEN 7000 AND 8500 FT.
THIS AREA OF RAIN WILL CROSS THE DIVIDE AND IMPACT KCPR,
KRIW/KLND BY 05Z/06Z. THERE IS A 30% CHANCE FOR LIFR
CEILINGS/IFR VISIBILITIES OCCURRING WITH THE PRECIPITATION ACROSS
MOST AREAS WEST OF THE DIVIDE BY THE END OF THE TAF PERIOD.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZLC AND ZDV FOR
THE LATEST INFORMATION ON SMOKE, ICING, AND TURBULENCE FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...GERHARDT
DISCUSSION...HATTINGS
AVIATION...LAVOIE
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