457
FXUS65 KRIW 261731
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1131 AM MDT TUE AUG 26 2025
KEY MESSAGES
- ONGOING SCATTERED RAIN SHOWERS AND ISOLATED THUNDERSTORMS
ACROSS FAR WEST WYOMING BECOME MORE WIDESPREAD AND PUSH
FARTHER NORTHEAST OVERNIGHT INTO WEDNESDAY MORNING.
- ABOVE NORMAL ATMOSPHERIC MOISTURE WILL LEAD TO THE POSSIBILITY
OF HEAVY RAINFALL. TOTAL RAINFALL OF 0.50 TO 1.50 INCHES WILL
BE COMMON FOR WEST-CENTRAL WYOMING BY SUNRISE FRIDAY, WITH
MANY OTHER AREAS SEEING 0.25 TO 0.75 INCHES OF RAIN.
- PRECIPITATION AND ASSOCIATED CLOUD COVER WILL LIMIT DAYTIME
HEATING, WHICH KEEPS DAYTIME HIGHS BELOW NORMAL THROUGH
SATURDAY.
DISCUSSION
ISSUED AT 130 AM MDT TUE AUG 26 2025
WV IMAGERY SHOWS THE CONTINUED NORTHWEST FLOW ALOFT ACROSS THE
CWA AS THE UPPER LEVEL RIDGE WEAKENS WITH ITS SOUTHWARD RETREAT
DUE TO DECREASING CONVERGENCE. IR SHOWS THE AMPLE CLOUD COVER
ACROSS MUCH OF THE STATE WITH THE FIRST OF MANY SHORTWAVES TO
PUSH IN FROM NORTHERN UTAH LATER THIS TUESDAY MORNING. RADAR IS
QUIET FOR NOW BUT WILL SOON PICK UP AROUND SUNRISE PUSHING INTO
FAR WESTERN AREAS SPREADING TO THE DIVIDE THROUGH THE MORNING
AND AFTERNOON.
CURRENTLY, HI-RES MODEL AGREEMENT IS FAR AND FEW BETWEEN ON
COVERAGE AND TIMING BUT THE NAMNEST HAS BEST HANDLED RECENT
RAINFALL, SO WILL RELY MORE HEAVILY ON IT IN THE NEXT COUPLE OF
DAYS UNTIL PROVEN OTHERWISE. TUESDAY'S RAINFALL AMOUNTS LOOK TO
BE MORE MINIMAL COMPARED TO THE UPCOMING EVENTS FOR WEDNESDAY
AND THURSDAY, BUT STILL LOOKS TO BE DECENT FOR THE FIRES WEST OF
THE DIVIDE TODAY. ENSEMBLE DATA GIVES A 30-40% CHANCES FOR OVER
A QUARTER INCH FOR SOME OF THE WESTERN HIGHER TERRAIN WITH
10-20% POSSIBLE THROUGH STAR VALLEY CLOSER TO HALF AN INCH.
REGARDLESS, DECENT RAINFALL WILL BE HAD FOR MANY WEST OF THE
DIVIDE AND TOWARDS THE SOUTHERN BORDER FOR SWEETWATER COUNTY
WHILE TO THE EAST REMAINS DRY. THIS ACTIVITY WILL NOT SPREAD
OVER THE DIVIDE UNTIL AFTER SUNSET AND OVERNIGHT INTO WEDNESDAY
MORNING. THE GOOD THING ABOUT THE UPCOMING RAINFALL IS THE
INSTABILITY LOOKS TO BE ON THE WEAKER SIDE IN THE PEAK HEATING
OF THE AFTERNOON DUE TO COOLER HIGH TEMPERATURES THAN RECENT
DAYS. AS SUCH, EXPECT ONLY SOME ISOLATED THUNDERSTORMS,
ESPECIALLY THAT FOR SWEETWATER COUNTY TUESDAY.
AS THE MAIN PACIFIC NORTHWEST LOW DEEPENS AND PUSHES FURTHER
EAST INTO WEDNESDAY, AN INCREASE OF DIVERGENCE WILL PUSH IN FOR
THE UPPER ROCKIES. IT IS HARD TO DECIPHER WITH THE MULTITUDE OF
WAVES WITH VARYING MODEL OUTPUTS WEDNESDAY AND THURSDAY WITH
SOME SHOWING A STEADY PUSH OF MONSOONAL MOISTURE AIDING IN THE
AFOREMENTIONED UPPER LEVEL LOWS AND ITS SHORTWAVES. RAINFALL
AMOUNTS ARE TRENDING A BIT UPWARD WITH THE LATEST MODEL RUNS,
WITH THE LIKELIHOOD OF OVER AN INCH WEST OF THE DIVIDE BECOMING
MORE 70-80% TO OCCUR. AREAS TO THE EAST ARE LOWER IN
PROBABILITIES OF 40-50% FOR HALF AN INCH OF MORE, WITH THE OPEN
TERRAIN WITH THE SOUTHWEST MOISTURE PLUME ACROSS THE WIND
CORRIDOR FROM RKS TO CPR SEEING THE HIGHEST QPF AMOUNTS
POSSIBLE. WITH THE AMPLE INCONSISTENCY WITH MANY MODELS AND
BETWEEN RUNS, THE FORECAST IS HIGHER IN SUBJECTIVITY TO CHANGE
THROUGHOUT THE DAY AND INTO THE EVENT ITSELF.
REGARDLESS, MUCH NEEDED RAINFALL WILL OCCUR FOR THE ENTIRE AREA
AND HOPE TO RENDER AID TO THE MANY FIRES ONGOING. ALL GOOD
THINGS DO COME TO AN END OR AT LEAST TAPER OFF. FRIDAY AND INTO
THE WEEKEND WILL SEE LESS CHANCES FOR RAINFALL AS INDUCED
RIDGING BUILDS IN FROM THE SOUTHWEST THAT WILL DRY SLOT MUCH OF
THE SOUTHERN HALF OF THE CWA AND WEST OF THE DIVIDE. NORTHWEST
FLOW ALOFT WILL CONTINUE FOR THE AREAS EAST OF THE DIVIDE AND
NORTHERN HALF OF THE CWA TO INCLUDE YELLOWSTONE THAT WILL KEEP
POPS IN THROUGH SATURDAY NIGHT BUT MORE ISOLATED IN NATURE AT
THAT POINT. THE EC INDICATES LONG TERM THE AFOREMENTIONED UPPER
LEVEL TO FILL WITH DECREASED DIVERGENCE ALOFT AS IT RETREATS
BACK OFF THE NORTHWEST COAST AND POSSIBLE EMBEDDING BACK INTO
ANOTHER LOW THAT EVENTUALLY PUSHES SOUTH. THIS WILL ALLOW UPPER
LEVEL RIDGING TO BUILD BACK IN OVER THE UPPER ROCKIES BY
WEEKEND'S END AND INTO NEXT WEEK. SEASONABLE TO JUST BELOW
AVERAGE TEMPERATURES WILL SEE A SLIGHT WARMING TREND AT THAT
TIME WITH MAINLY DRY CONDITIONS TO BE EXPECTED HEADING INTO THE
LONGER TERM FORECAST.
IN ALL, CONFIDENCE STILL WAVERS IN THE SHORT TERM IN REGARDS TO
PRECIPITATION TIMING AND COVERAGE. HOWEVER, RAINFALL IS
EXPECTED, IT JUST MIGHT VARY IN OUTPUT BASED ON HOW THIS SHAPES
OUT.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1120 AM MDT TUE AUG 26 2025
ISOLATED TO SCATTERED RAIN SHOWERS WITH VERY ISOLATED
THUNDERSTORMS HAVE ALREADY MOVED INTO WESTERN WY THIS MORNING,
AND WILL CONTINUE TO PUSH NORTHEAST THROUGH THE AFTERNOON,
INCREASING IN COVERAGE AS WELL AS INTENSITY. SMOKE FROM THE
DOLLAR LAKE FIRE CONTINUES TO INFLUENCE KJAC/KBPI/KPNA WITH
VSBYS DOWN TO 3SM AT TIMES, THOUGH INCREASING SHOWERS ACTIVITY
AS SSW WIND SHOULD IMPROVE CONDITIONS. VFR/MVFR CONDITIONS ARE
EXPECTED AT TERMINALS WEST OF THE DIVIDE, BECOMING MVFR THIS
EVENING AND OVERNIGHT AS PRECIPITATION INTENSIFIES. THE HEAVIEST
BAND OF PRECIPITATION SHIFTS NORTHEASTWARD WEDNESDAY MORNING,
BRINGING MORE VCSH TO SW WY AS WELL AS INCREASING SW WINDS.
SMOKE COULD INFLUENCE KJAC/KPNA AGAIN WED MORNING, SO HAVE
INCLUDED A BRIEF MENTION IN THOSE TAFS WHEN THE WINDS SHIFT TO
BRING SMOKE FROM THE DOLLAR LAKE FIRE. ISOLATED TO SCATTERED
THUNDERSTORMS ARE MOST LIKELY WEST OF THE DIVIDE THIS AFTERNOON
AND EARLY EVENING, AND COULD BRING GUSTS OF 20-25 KTS TO THOSE
TERMINALS.
EAST OF THE DIVIDE WILL SEE VFR CONDITIONS THROUGH THE DAY, WITH
PRECIPITATION FIRST MOVING INTO KLND/KRIW AFTER 27/06Z, THUS THE
CHANCE OF MVFR CONDITIONS INCREASES BY WEDNESDAY SUNRISE FROM
THE WIND RIVER BASIN TOWARD KCPR. SCATTERED SHOWERS THEN OCCUR
THROUGH THE DAY AND MOVE NORTHWARD TO BRING MVFR CONDITIONS TO
KCOD/KWRL WEDNESDAY AFTERNOON.
WHILE MVFR CONDITIONS ARE GENERALLY EXPECTED UNDER AND AROUND
AREAS OF SHOWERS AND STRONGER STORMS, CANNOT RULE OUT IFR
CONDITIONS WEDNESDAY MORNING DUE TO PATCHY FOG FROM THE SUDDEN
INCREASE IN LOW-LEVEL MOISTURE. THE MOUNTAINS WILL BE MOSTLY
OBSCURED ACROSS WESTERN WY THROUGHOUT THE FORECAST PERIOD.
OBSCURATIONS OF MOUNTAINS EAST OF THE DIVIDE WILL INCREASE
OVERNIGHT AND THROUGH WEDNESDAY.
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
AIR QUALITY ALERT UNTIL 1 PM MDT THIS AFTERNOON FOR WYZ012>016-
025-026.
DISCUSSION...LOWE
AVIATION...MCDONALD
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