876
FXUS65 KRIW 270440
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1040 PM MDT TUE AUG 26 2025
KEY MESSAGES
- ONGOING SCATTERED RAIN SHOWERS AND ISOLATED THUNDERSTORMS
ACROSS WESTERN AND CENTRAL 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 LOW 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 /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1039 PM MDT TUE AUG 26 2025
WEST OF THE DIVIDE...
SHOWERS AND THUNDERSTORMS WILL BE WIDESPREAD THROUGH MUCH OF THE
FORECAST WITH PERIODS OF PREVAILING LIGHT TO MODERATE RAIN SHOWERS.
VFR CONDITIONS ARE EXPECTED TO PERSIST AS SHOWERS AND THUNDERSTORMS
DEVELOP BUT OCCASIONAL DROPS TO MVFR OR POSSIBLY IFR CANNOT BE RULED
OUT. KJAC IS THE ONLY EXCEPTION TO THIS AS PERIODS OF MVFR DUE TO
LOWERED CEILINGS WILL BE POSSIBLE DURING THE MORNING ON WEDNESDAY.
PRECIPITATION SHOULD BEGIN BUILDING ACROSS WESTERN TERMINALS SUCH AS
KJAC, KBPI, KPNA, AND KRKS NEAR THE START OF THE PERIOD. SHOWERS
WILL BE ON/OFF AT KJAC THROUGH MUCH OF THE PERIOD WITH A PROB30 BY
THE AFTERNOON DUE TO ISOLATED THUNDERSTORMS. A SHORT BREAK IN
PREVAILING PRECIPITATION LOOKS TO OCCUR AT KPNA AND KBPI AROUND 10Z
BEFORE PERIODIC SHOWERS AND THUNDERSTORMS RETURN BY THE LATE
MORNING. SHOWERS AND STORMS LINGER THROUGH THE AFTERNOON GRADUALLY
DISSIPATING BY THE EVENING. LOW CLOUDS ARE LIKELY TO CREATE MOUNTAIN
OBSCURATION ACROSS MUCH OF THE AREA THROUGH THE TAF PERIOD.
EAST OF THE DIVIDE...
SHOWERS AND THUNDERSTORMS WILL BE NEARBY KLND AND KRIW TO START THE
TAF PERIOD. A PREVAILING PERIOD OF SHOWERS DEVELOPS SHORTLY BEFORE
12Z WEDNESDAY. SHOWERS PERSIST THROUGH MUCH OF THE DAY WITH AN
ISOLATED THUNDERSTORM POSSIBLE DURING WEDNESDAY AFTERNOON.
PRECIPITATION LOOKS TO DISSIPATE BY WEDNESDAY EVENING WITH A FEW
LINGERING SHOWERS POSSIBLE INTO THE END OF THE PERIOD. KCPR
LOOKS TO HAVE A SIMILAR TIME FRAME TO KLND AND KRIW BUT SHOWERS
OCCURRING JUST A FEW HOURS LATER. KCOD AND KWRL LOOK TO BE ON
THE FRINGE OF THE MOISTURE LEADING TO A LATER START TIME FOR
PRECIPITATION. SHOWERS MAY START DEVELOPING NEARBY KCOD BY THE
LATE MORNING WEDNESDAY WITH GREATER CONFIDENCE BY THE EARLY
AFTERNOON. KWRL IS EXPECTED TO SEE SHOWERS HOLD OFF UNTIL AROUND
21Z WHERE THEY PERIODIC CONTINUE THROUGH THE REMAINDER OF THE
TAF PERIOD. LOW CLOUDS ARE LIKELY TO CREATE MOUNTAIN OBSCURATION
ACROSS MUCH OF THE AREA THROUGH THE TAF PERIOD.
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/LAVOIE
DISCUSSION...LOWE
AVIATION...DZIEWALTOWSKI
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