965
FXUS65 KRIW 261105
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
505 AM MDT TUE AUG 26 2025
KEY MESSAGES
- SCATTERED RAIN SHOWERS AND ISOLATED THUNDERSTORMS THIS TUESDAY
MORNING AND AFTERNOON BECOMING MORE WIDESPREAD OVERNIGHT INTO
WEDNESDAY.
- AMPLY RAINFALL WILL CONTINUE WEDNESDAY AND THURSDAY.
- MORE SEASONABLE TEMPERATURES AND ISOLATED RAIN SHOWERS FRIDAY
AND INTO THE WEEKEND.
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 /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 504 AM MDT TUE AUG 26 2025
SHOWER AND ISOLATED THUNDERSTORMS WILL SLOWLY SPREAD FROM WEST OF
THE DIVIDE TO EAST OF THE DIVIDE THIS TAF PERIOD. CHANCES INCREASE
AT KJAC AFTER 13Z THEN ALL OTHER WEST OF THE DIVIDE TERMINALS AFTER
20-22Z. CONFIDENCE OF SHOWER ONSET IS AROUND 30% AT KBPI AND KPNA SO
MAINTAINED A PROB30 GROUP AT THIS TIME. KBPI AND KPNA HAVE THE
GREATEST CHANCE OF SEEING MVFR FLIGHT CONDITIONS WITH HEAVIER
SHOWERS AFTER 05Z WEDNESDAY. KRKS HAS THE HIGHEST CHANCE (30%) AT
SEEING A THUNDERSTORM AROUND 23Z SO A PROB30 IS MAINTAINED. SHOWER
CHANCES THAN PERSIST MOST OF THE REMAINDER OF THE TAF PERIOD AT ALL
WEST OF THE DIVIDE TERMINALS. EAST OF THE DIVIDE, VICINITY SHOWERS
BEGIN AT KRIW AND KLND AROUND 01Z WEDNESDAY WITH CONFIDENCE
REMAINING LOW TO MEDIUM (AROUND 50%) IN DIRECT SHOWERS SO KEPT VCSH
AT THIS TIME. DIRECT IMPACTS FROM SHOWERS BEGINS AFTER 09Z WEDNESDAY
AT ALL EAST OF THE DIVIDE TERMINALS, HOWEVER, CONFIDENCE IS AROUND
30% SO A PROB30 IS MAINTAINED AT THIS TIME. ANY HEAVIER SHOWERS
COULD PRODUCE BRIEF PERIODS OF MVFR FLIGHT CONDITIONS. THUNDERSTORM
CHANCES REMAIN LOW (AROUND 20%) WITH THE MOST LIKELY SCENARIO
BEING EMBEDDED LIGHTNING IN RAIN SHOWERS DURING THE AFTERNOON
HOURS.
OTHERWISE, WINDS REMAIN GENERALLY LIGHT (AROUND 10KTS OR LESS) MOST
TERMINALS THIS TAF PERIOD. KCPR AND KRKS ARE THE EXCEPTION WITH
GUSTS AROUND 20-25 KTS POSSIBLE. EXPECT MID-LEVEL BKN TO OVC CLOUDS
MOST OF THE TAF PERIOD. A LOWER VFR CLOUD DECK IS FORECAST TO
DEVELOP KRKS AFTER 22Z AND AT ALL OTHER WEST OF THE DIVIDE
TERMINALS AFTER 01Z/02Z. WILDFIRE SMOKE MAY CAUSE SOME
OBSCURATION MAINLY ALONG THE WIND RIVER RANGE THROUGH THIS 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 THIS AFTERNOON FOR WYZ012>016-
025-026.
DISCUSSION...LOWE
AVIATION...GERHARDT
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