469
FXUS65 KRIW 201030
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
430 AM MDT TUE OCT 20 2026
KEY MESSAGES
- A WEAK DISTURBANCE PUSHES THROUGH THE CWA TUESDAY WITH
ISOLATED SHOWER ACTIVITY (<20%), MAINLY HIGHER TERRAIN WEST OF
THE DIVIDE.
- ABOVE AVERAGE TEMPERATURES CONTINUE THROUGH THURSDAY AHEAD OF
A COOL DOWN FRIDAY AND OVER THE WEEKEND.
- INCREASING WINDS THURSDAY AHEAD OF THE NEXT SYSTEM WITH VALLEY
RAIN AND MOUNTAIN SNOW LIKELY OVERNIGHT INTO FRIDAY AND OVER
THE WEEKEND. TOTALS OF LOW CONFIDENCE (~30%) BUT HIGHER FOR
IMPACTS TO MOUNTAIN PASSES (50-60%).
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 FOR 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 4O 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 /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 430 AM MDT TUE OCT 20 2026
VFR CONDITIONS EXPECTED THROUGHOUT THE ENTIRETY OF THE PERIOD AT
ALL TAF SITES. LIGHT WINDS 10KTS OR LESS, EXCEPT A SLIGHT 18KT
GUST AT CPR DURING PEAK HEATING OF THE AFTERNOON MIXING TO THE
SURFACE. WINDS BECOME LIGHT TOWARDS SUNSET AFTER 01-02Z WITH
RADIATIONAL COOLING. INCREASED MID LEVEL CLOUDS DURING THE
AFTERNOON, CEILINGS TO THE WEST OF THE DIVIDE. ISOLATED SHOWER
ACTIVITY (<20%) WEST OF THE DIVIDE AS WELL, DURING THE AFTERNOON
AT BPI/PNA BUT CONFIDENCE LOW ON STATION ONLY CARRYING VCSH.
OTHERWISE, DRY CONDITIONS FOR POINTS EAST AFTER AFTER SUNSET
THROUGH THE OVERNIGHT HOURS INTO WEDNESDAY MORNING.
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
NONE.
DISCUSSION...LOWE
AVIATION...LOWE
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