423
FXUS65 KRIW 210350
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
950 PM MDT TUE OCT 20 2026
KEY MESSAGES
- ANY ISOLATED SHOWERS WILL BE CONFINED TO FAR WEST WYOMING AND
YELLOWSTONE NATIONAL PARK OVERNIGHT AND WEDNESDAY MORNING.
OTHERWISE, DRY CONDITIONS PREVAIL.
- DAYTIME HIGH TEMPERATURES REMAIN AROUND 8F TO 16F ABOVE
SEASONAL AVERAGES WEDNESDAY AND THURSDAY.
- A WEATHER SYSTEM BEGINS TO TRACK INTO THE REGION THURSDAY, AS
PRECIPITATION INCREASES THURSDAY NIGHT ACROSS AREAS WEST OF
THE CONTINENTAL DIVIDE. RAIN AND MOUNTAIN SNOW PERSISTS
THROUGH FRIDAY NIGHT, WITH RAIN CHANCES EVENTUALLY SPREADING
EAST OF THE DIVIDE FRIDAY EVENING.
- STRONG SOUTHWEST WIND GUSTING 40 TO 60 MPH IS EXPECTED ON
FRIDAY WITHIN THE WIND CORRIDOR FROM SWEETWATER COUNTY THROUGH
NATRONA COUNTY AND INTO JOHNSON COUNTY. THE WIND THEN SHIFTS
TO THE NORTH FRIDAY NIGHT AND SATURDAY BEHIND A COLD FRONT.
UPDATE
ISSUED AT 221 PM MDT TUE OCT 20 2026
ISOLATED SHOWERS WILL CONTINUE ACROSS WESTERN WYOMING THIS
AFTERNOON, MOSTLY OVER THE MOUNTAINS. NOT MUCH CHANGE IN THE SHORT
TERM, WITH WEDNESDAY AND THURSDAY A LITTLE WARMER AND BREEZIER AS
SOUTHWEST FLOW INCREASES AHEAD OF THE SYSTEM MENTIONED BELOW. THIS
IS STILL EXPECTED TO BRING RAIN AND MOUNTAIN SNOW TO THE AREA
BEGINNING THURSDAY AFTERNOON. LATEST GUIDANCE HAS DECREASED
ACCUMULATIONS SLIGHTLY; REGARDLESS, IMPACTS ARE STILL MOSTLY
EXPECTED TO BE LIMITED TO THE WESTERN PASSES. THIS SYSTEM WILL ALSO
LEAD TO STRONG WIND EAST OF THE DIVIDE ON FRIDAY AS A SURFACE LOW
DEEPENS TO THE NORTH.
DISCUSSION
ISSUED AT 130 AM MDT TUE OCT 20 2026
IR CURRENTLY SHOWS SOME INCREASING CLOUDS PUSHING IN FROM THE
SOUTHWEST OUT OF NORTHERN UTAH AND EASTERN IDAHO WEST OF THE
DIVIDE. SOME LIGHT SHOWER ACTIVITY WILL PUSH IN AS WELL BY
SUNRISE TUESDAY MORNING <20 PERCENT IN COVERAGE THAT WILL
CONTINUE THROUGH MUCH OF THE DAY. MINIMAL QPF AND NO IMPACTS ARE
EXPECTED WITH THIS SUBTLE MID LEVEL SHORTWAVE PROPAGATING UP
THE L/W PATTERN. THE MAIN UPPER LEVEL LOW IS CURRENTLY OFF THE
NORTHERN CALIFORNIA COAST DEEPENING WITH INCREASING DIVERGENCE
ALOFT AND SOUTHWARD MOVEMENT. THIS WILL CONTINUE TO PUSH SOUTH
TUESDAY, BEGINNING ITS EASTWARD MIGRATION COME WEDNESDAY THAT
WILL BE THE NEXT SYSTEM TO AFFECT THE NORTHERN ROCKIES AND MUCH
OF THE CWA THURSDAY AND BEYOND. THE MAIN FINGER OF THE PFJ
CONTINUE TO BE WELL NORTH STRETCHING FROM THE PACIFIC NORTHWEST
AND INTO SOUTHERN CANADA, KEEPING THE AFOREMENTIONED LOW CUTOFF
FROM THE MERIDIONAL PATTERN FOR THE THE ENTIRE COUNTRY.
A SLIGHT WARMING TREND CONTINUES THROUGH THURSDAY AHEAD OF THIS
SYSTEM, REMAINING ABOUT 5 TO 10 DEGREES ABOVE AVERAGE FOR THIS
TIME OF OCTOBER BUT CHANGES ARE INCOMING FOR FRIDAY AND BEYOND
OVER THE WEEKEND AND INTO THE FOLLOWING WORK WEEK. THE LOW IS
TRENDING TO BECOME MORE OF AN OPEN AND MORE PROGRESSIVE WAVE AS
IT NEARS WESTERN WYOMING FOR THURSDAY. AHEAD OF THIS SYSTEM,
EXPECT A TIGHTENING GRADIENT ABOUT 5 TO 7 MB DIFFERENCE ACROSS
THE STATE. SOUTHWEST WINDS WILL UPTICK UP TO 40 TO 50 MPH
GUSTS, POSSIBLE HIGHER INSTANCES FOR THE WIND CORRIDOR OF
SWEETWATER TO NATRONA COUNTIES. HIGHER TERRAIN OF SOUTH PASS TO
CASPER MOUNTAIN COULD PUSH 60 MPH WITH STEERING FLOW WINDS
MIXING TO THE SURFACE UNDER DAYTIME HEATING OF THE AFTERNOON.
AS A COLD FRONT DROPS THROUGH LATE THURSDAY AND INTO FRIDAY,
EXPECT COOLING TEMPERATURES DROPPING FREEZING LEVELS DOWN TO
8-9KFT. THIS WILL ALLOW FOR MOUNTAIN SNOW TO DEVELOP LATE
THURSDAY STRETCHING INTO FRIDAY AND THE WEEKEND. MODEL TRENDS
CONTINUE TO BE FAIRLY CONSISTENT ON AT LEAST ADVISORY LEVEL SNOW
TOTALS ALONG AND WEST OF THE DIVIDE FOR THE HIGHER TERRAIN
AREAS. WITH THE LOWERING FREEZING LEVELS, EXPECT IMPACTS TO
MOUNTAIN PASSES TO INCLUDE TETON AND TOGWOTEE FOR AT LEAST A
COUPLE INCHES. AS THE SYSTEM PROGRESSES FURTHER NORTHEAST,
EXPECT THE BIGHORNS TO GET THE BRUNT OF THE SNOWFALL THAT WILL
LIKELY SEE IMPACTS TO THE GRANITE AND POWDER RIVER PASSES. STAY
TUNED FOR UPDATED FORECASTS AND UPDATES TO ANY NEEDED HEADLINES
IN THE COMING DAYS.
VALLEY RAIN WILL BE MORE PREVALENT WEST OF THE DIVIDE AND BASINS
TO THE EAST LATER FRIDAY. MUCH OF THE AREA SHOULD AT LEAST SEE A
CHANCE FOR A BIT OR A COLD RAIN, HIGHER QPF AMOUNTS TO THE WEST
DUE TO THE SOUTHWEST TO WESTERN FLOW OF THIS SYSTEM. MINIMAL
ACCUMULATIONS EXPECTED EAST OF THE BIGHORNS BEING ON THE
LEEWARD SIDE OF THIS SYSTEM. A SECOND WAVE OF THE DIPPING JET
STREAM COME LATE WEEKEND INTO EARLY NEXT WEEK WILL REINFORCE THE
COOLER, MORE FALL LIKE AIR WITH MORE MOUNTAIN SNOW AND VALLEY
RAIN TO BE EXPECTED IF THE LONGER TERM MODEL SOLUTIONS COME INTO
FRUITION. BEING A WEEK OUT, TIME WILL TELL BUT THE WEATHER
PATTERN LOOKS TO BE CHANGING AND MORE ACTIVE FOR THE LATTER PART
OF OCTOBER AS WE INCH CLOSER TO WINTER.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 950 PM MDT TUE OCT 20 2026
VFR CONDITIONS PREVAIL AT ALL TERMINALS THROUGH THE FORECAST PERIOD
WITHIN SOUTHWEST FLOW ALOFT. A MID-CLOUD DECK ACCOMPANIED BY A FEW
LIGHT SHOWERS TRAVERSES FAR WEST WYOMING, INCLUDING IN THE VICINITY
OF KJAC, BETWEEN 10Z AND 16Z/WEDNESDAY. LITTLE MORE THAN A FEW
SPRINKLES EXPECTED FROM THIS ACTIVITY. ANOTHER ROUND COULD RETURN TO
THE FAR WEST FOR A FEW HOURS LATE WEDNESDAY AFTERNOON. OTHERWISE,
GENERALLY SCATTERED CLOUD DECKS THROUGH WEDNESDAY AFTERNOON. A SURGE
OF MID/HIGH-LEVEL MOISTURE APPROACHES KRKS LATE IN THE PERIOD
LEADING TO LOWERING MID-CLOUD CEILINGS AFTER 00Z/THURSDAY. AT THE
MOMENT, IT APPEARS PRECIPITATION REMAINS SOUTH OF KRKS. A FEW TRICKY
SURFACE WIND FORECASTS FOR WEDNESDAY AFTERNOON. DIFFERING SOLUTIONS
OFFERED BY HI-RES MODELS ON WHEN SOUTHERLY WIND MIXES AT KCPR AND
KRIW. HAVE TRIED TO STRIKE A BALANCE ON TIMING AND DIRECTION,
ALTHOUGH THE LATEST HRRR TRIES TO HOLD THE SOUTHERLIES AT BAY A FEW
ADDITIONAL HOURS AT KCPR AND ALTOGETHER AT KRIW. ON THE OTHER HAND,
KRKS SEES A 12-22KT SOUTHERLY WIND DEVELOP BETWEEN 19Z-21Z/WEDNESDAY
AND PREVAIL UNTIL AROUND SUNSET.
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...MYERS
DISCUSSION...LOWE
AVIATION...CNJ
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