676
FXUS65 KRIW 262226
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
426 PM 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.
UPDATE
ISSUED AT 115 PM MDT TUE AUG 26 2025
THERE IS PLENTIFUL MOISTURE STREAMING NORTH INTO THE STATE TUESDAY
AFTERNOON WITH MORE ARRIVING TONIGHT AND WEDNESDAY. 12Z TUESDAY
UPPER AIR SOUNDINGS INDICATED AROUND 0.75 INCHES OF PRECIPITABLE
WATER AT KRIW, WHILE KSLC REPORTED CLOSE TO 1.25 INCHES. THESE
TOTALS ARE RUNNING AROUND 140 PERCENT AND 190 PERCENT OF NORMAL,
RESPECTIVELY, FOR LATE AUGUST. EXTENSIVE CLOUD COVER HAS TEMPERED
CONVECTIVE DEVELOPMENT ACROSS WEST AND SOUTHWEST WYOMING THROUGH
MIDDAY TUESDAY. HOWEVER, SIMILAR TO MONDAY, AREAS THAT HAVE
SEEN SUNSHINE ON THE FRINGES OF THE CLOUD SHIELD ARE SEEING
CONVECTIVE DEVELOPMENT. THIS TREND CONTINUES THROUGH TUESDAY
AFTERNOON. MORE WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS
ERUPT OVERNIGHT AS SHORTWAVE ENERGY ARRIVES FROM CENTRAL UTAH
AND PROVIDES BETTER DYNAMICS. AS A RESULT, THE SHOWERS AND
STORMS SPREAD INTO CENTRAL WYOMING BY SUNRISE WEDNESDAY.
PRECIPITATION IS HEAVIEST ACROSS THE SOUTHWEST OVERNIGHT AND
EARLY WEDNESDAY, WHILE WESTERN AND CENTRAL WYOMING SEE THE
HEAVIER, WIDESPREAD SHOWERS BETWEEN 3 AM AND 3 PM WEDNESDAY.
WEST-CENTRAL WYOMING, INCLUDING LARGE PORTIONS OF TETON,
LINCOLN, AND SUBLETTE COUNTIES, ARE INCLUDED IN THE WEDNESDAY
WPC EXCESSIVE RAINFALL OUTLOOK. FAVORABLE EFI/SOT VALUES SUPPORT
A VERY UNUSUAL EVENT RELATIVE TO WHAT MIGHT TYPICALLY BE
EXPECTED AT THIS TIME OF YEAR. FOR THE BULK OF NORTHWEST
WYOMING, STORM TOTAL RAINFALL OF 0.50 TO 1.00 INCH WILL BE
COMMON, ALTHOUGH OROGRAPHICALLY-FAVORED MOUNTAIN LOCATIONS
COULD SEE TOTALS TO AROUND 1.30 INCHES. UPDATED 60-HOUR QPF
TOTALS POINT TO WIDESPREAD 0.25 TO 0.50 INCH RAINFALL AMOUNTS
ACROSS THE LOWER ELEVATIONS OF SOUTHWEST, CENTRAL, AND MUCH OF
NORTHERN WYOMING.
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 /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 352 PM MDT TUE AUG 26 2025
SHOWERS AND ISOLATED THUNDERSTORMS WILL BECOME MORE NUMEROUS THIS
EVENING ACROSS SOUTHWEST AND SOUTHERN WY AS A GENERAL AREA OF UPPER-
LEVEL LOW PRESSURE APPROACHES WY FROM THE SOUTHWEST. LINGERING MVFR
CONDITIONS DUE TO WILDFIRE SMOKE THIS AFTERNOON WILL CLEAR OUT WITH
THE PRECIPITATION AND INCREASING SOUTHWEST WIND EARLY THIS EVENING.
GENERAL VFR CEILINGS AND VSBYS SHOULD BECOME MORE MVFR THIS EVENING
AND OVERNIGHT THOUGH AT THE 4 TAF SITES WEST OF THE DIVIDE AS
PRECIPITATION INTENSIFIES. PRECIPITATION TOTALS SHOULD AMOUNT TO
AROUND HALF AN INCH FROM KBPI/KPNA TO KJAC. THERE IS A SMALL CHANCE
OF IFR IN THE EARLY MORNING HOURS WEDNESDAY WITH LOW CLOUDS AND/OR
FOG DUE TO THE INCREASE IN LOW-LEVEL MOISTURE OVERNIGHT, AND
POSSIBLY LINGERING SMOKE AT KPNA. LIGHT TO MODERATE RAIN SHOWERS ARE
EXPECTED AT THESE SITES DURING THE DAY WEDNESDAY, WITH KRKS HAVING
THE BEST (SLIGHT) CHANCE OF THUNDERSTORMS DURING THE AFTERNOON. KBPI
AND KRKS SHOULD SEE SOME GUSTY WEST WINDS UP TO 20 KTS DURING THE
AFTERNOON. SOMEWHAT OBSCURED MOUNTAINS ACROSS WESTERN WY WILL BE
MOSTLY OBSCURED OVERNIGHT AND INTO WEDNESDAY THROUGH EARLY THU
MORNING.
EAST OF THE DIVIDE WILL SEE INCREASING CLOUDS OVERNIGHT WITH LIGHT
SHOWERS POSSIBLE AROUND KLND STARTING AROUND MIDNIGHT, BUT THE BEST
CHANCES FOR THE WIND RIVER BASIN TO BE WEDNESDAY MORNING AFTER
12Z. A FEW SHOWERS AND THUNDERSTORMS HAVE BEGUN TO MOVE INTO THE
WESTERN HALF OF THE BIGHORN BASIN. AS A RESULT A TEMPO HAS BEEN
ADDED TO KCOD AS PRECIPITATION HAS BEGUN TO NEAR THE TERMINAL.
THE BULK OF THE PRECIPITATION WILL MOVE INTO KCPR AND KWRL MID
MORNING, AND FINALLY INTO KCOD EARLY IN THE AFTERNOON AS A
GENERAL WIDE BAND MOVE TO THE NNE DURING THE DAY. THUS, VFR
CONDITIONS SHOULD BECOME MVFR AT TIMES ON WEDNESDAY, WITH THE
MOUNTAINS BECOMING OBSCURED DURING THE DAY. WINDS COULD BECOME
GUSTY 20-25 KTS AT KCPR WITH NEARBY SHOWERS, BUT OVERALL WINDS
WOULD REMAIN 10-12 KTS OR LESS.
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 WEDNESDAY FOR WYZ014-015-025.
UPDATE...CNJ
DISCUSSION...LOWE
AVIATION...MCDONALD
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