079
FXUS65 KRIW 271833
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1233 PM MDT WED MAY 27 2026
KEY MESSAGES
- SHOWER AND THUNDERSTORM CHANCES (15 TO 40 PERCENT) TODAY ARE GREATEST
ACROSS JOHNSON AND NATRONA COUNTIES, AS WELL AS FOR THE WIND
RIVER AND ABSAROKA MOUNTAINS AND YELLOWSTONE.
- WARM TODAY, WITH GUSTY SOUTH TO SOUTHEAST WINDS THROUGH LATE
THIS EVENING ACROSS NORTHERN WYOMING.
- SLIGHTLY WARMER THURSDAY, WITH LESS RAIN CHANCES. MOST AREAS REMAIN
DRY, WITH CHANCES CONFINED NEAR MOUNTAINS.
- A WEATHER SYSTEM APPROACHES THE AREA FRIDAY NIGHT AND
SATURDAY, BRINGING BETTER CHANCES FOR RAIN. THE GREATEST
CHANCES ARE ACROSS WESTERN WYOMING.
UPDATE
ISSUED AT 1232 PM MDT WED MAY 27 2026
HAVE UPDATED PRECIPITATION CHANCES GIVEN THE LATEST HI-RES MODELS.
THE OVERALL LOOK TO TODAY REMAINS THE SAME, WITH 15 TO 40 PERCENT
RAIN SHOWER/THUNDERSTORM CHANCES OVER JOHNSON AND NATRONA COUNTIES,
AS WELL AS OVER THE NORTHERN WIND RIVER MOUNTAINS AND ACROSS THE
ABSAROKA RANGE INTO YELLOWSTONE. AN ISOLATED (15 PERCENT CHANCE OR
LESS) SHOWER OR STORM CAN'T BE RULED OUT ELSEWHERE, BUT THOSE
MENTIONED LOCATIONS ARE THE MOST LIKELY AREAS. LIKE HAS BEEN THE
TREND THE LAST FEW DAYS, ANY ACTIVITY WANES AFTER SUNSET AND SHOULD
BE COMPLETELY DONE BY 10PM. GUSTY OUTFLOW WINDS ARE THE MAIN HAZARD,
WITH GUSTS 30 TO 45 MPH THE MOST LIKELY HIGH END RANGE.
DISCUSSION
ISSUED AT 1254 AM MDT WED MAY 27 2026
I AM THINKING OF ANOTHER CHILDHOOD MEMORY HAS I WAS COMPOSING THE
FORECAST TONIGHT. ONE OF THE TRADITIONS OF BEING HOME SICK FROM
SCHOOL IN THE PRE-INTERNET AGE WAS WATCHING DAYTIME TV. AND ONE OF
THE MOST POPULAR SHOWS WAS (AND STILL IS), THE PRICE IS RIGHT. AND
OUR WEATHER PATTERN THIS MORNING REMAINS ME OF ONE OF THE GAMES ON
THAT VENERABLE GAME SHOW, SQUEEZE PLAY. IT RELATES TO THE WEATHER IS
WE ARE TRAPPED BETWEEN THE CUT OFF UPPER LEVEL LOW ROTATING NEAR THE
SIERRA NEVADA'S AND A STRONG RIDGE TO THE EAST.
FOR TODAY, IT IS SHOWING OFF WITH OUR PRECIPITABLE WATER VALUES.
THEY ARE PROJECTED TO BE ABOVE NORMAL AS MUCH AS 150 PERCENT IN SOME
LOCATIONS EAST OF THE DIVIDE. MEANWHILE, AREAS WEST OF THE DIVIDE
ARE BELOW NORMAL. THIS WOULD IMPLY THE GREATER CHANCE OF CONVECTION
SHIFTS HERE TODAY. BUT, THERE ARE A COUPLE MORE FACTORS. INSTABILITY
IS LESS, AS HEIGHTS HAVE RISEN BY AROUND 50 DECAMETERS. THERE IS
ALSO ONLY HALF AS MUCH PROJECTED CAPE AS YESTERDAY (350 J/KG TODAY
VERSUS 700 J/KG YESTERDAY, SO COVERAGE MAY BE LESS. THE LASTING
THING WE LOOK AT IS THE MEAN FLOW, AND THAT IS LARGELY SOUTH-
SOUTHEAST WITH THE SQUEEZE PLAY BETWEEN THE LOW AND THE RIDGE. THIS
LEADS ME TO THINK THAT THE BEST CHANCE OF CONVECTION WOULD BE
CLOSE TO AREAS WHERE THIS FLOW IS UPSLOPE. THIS MEANS LOCATIONS
LIKE ALONG AND EAST OF THE ABSAROKAS AND THE BIG HORNS, FOR
PLACES LIKE PARK. JOHNSON AND NATRONA COUNTY AS WELL AS PORTIONS
OF THE WIND RIVER BASIN AND YELLOWSTONE PARK. BUT GIVEN THE
MORE LIMITED INSTABILITY, COVERAGE LOOKS LESS, GENERALLY LESS
THAN 1 OUT OF 4 OR LESS. AN THE SQUEEZE PLAY WILL HAVE ONE MORE
IMPACT, THE WIND. THERE IS A DECENT PRESSURE GRADIENT IN THE
EASTERN PORTIONS OF THE AREA. THE NBM ENSEMBLE IS SHOWING A
GREATER THAN 2 IN 3 CHANCE OF WIND GUSTS PAST 30 MPH IN THE
BIGHORN BASIN AND JOHNSON COUNTY. THE STRONGEST WIND WOULD BE IN
JOHNSON COUNTY, WHERE THERE IS 1 IN 2 CHANCE OF GUSTS AROUND 40
MPH THIS AFTERNOON AS WE REACHING PEAK MIXING. TEMPERATURES
SHOULD BE SIMILAR TO YESTERDAY, ABOUT 5 TO 10 DEGREES ABOVE
NORMAL BUT NO EXTREMELY HOT CONDITIONS. MOST CONVECTION LOOKS
DIURNAL TODAY, WITH MOST SHOWERS AND STORMS ENDING AFTER SUNSET.
AT THIS TIME, CONVECTION LOOKS TO REACH A NADIR ON THURSDAY, AS
DRIER AIR SURGES FURTHER EASTWARD ACROSS THE STATE, WITH THE 0.50
INCH PRECIPITABLE WATER LINE ENVELOPING MOST OF WESTERN AND CENTRAL
WYOMING. ANY CONVECTION THIS DAY WOULD LIKELY REMAIN CLOSE TO THE
MOUNTAINS WITH HIGH LEVEL HEAT SOURCE AND UPSLOPE FLOW, MAINLY OF
THE SOUTH TO SOUTHEASTERN VARIETY AGAIN. THE VAST MAJORITY OF
LOCATIONS, ESPECIALLY IN THE LOWER ELEVATIONS, SHOULD REMAIN RAIN
FREE. WIND SHOULD ALSO BE LIGHTER EXCEPT FOR JOHNSON COUNTY, WHERE A
GUSTY WIND WILL CONTINUE. HIGH TEMPERATURES SHOULD RUN NEAR TO A
COUPLE OF DEGREES WARMER THAN WEDNESDAY.
CHANCES OF SHOWERS SHOULD BEGIN TO RISE SOMEWHAT ON FRIDAY AS THE
CUT OFF LOW BEGINS TO GET KICKED EASTWARD BY THE NEXT TROUGH
APPROACHING THE WEST COAST. THE ATMOSPHERE WILL BE VERY DRY TO START
THOUGH, SO THIS COULD END UP BEING A LATER SHOW. PLACEMENT IS ALSO
UNCERTAIN AS A LOT DEPENDS ON HOW QUICKLY DEEPER MOISTURE CAN BE
ADVECTED INTO THE AREA. THE CURRENT FORECAST LOOKS LIKE A REASONABLE
COMPROMISE, ALTHOUGH MOST OF THE DAY SHOULD BE RAIN FREE.
THERE IS NOW DECENT AGREEMENT IN THE LOW OPENING UP A BIT AND
LIFTING NORTHWARD FRIDAY NIGHT AND MOVING INTO WESTERN WYOMING ON
SATURDAY. THIS LOOKS LIKE THE WETTEST DAY AS A RESULT. THE EXACT
PATH OF THE LOW WILL BE CRITICAL THOUGH. IF IT TRACKS FURTHER WEST,
MANY AREAS EAST OF THE DIVIDE MAY HAVE A SOUTHWESTERLY DOWNSLOPING
FLOW WHICH WOULD KEEP SHOWERS AND THUNDERSTORMS TO A MINIMUM. THE
CURRENT FORECAST HAS THIS SHOWN FAIRLY WELL, WITH THE HIGHEST POPS
IN THE NORTHWEST THEN TAPERING THEM DOWN THE FURTHER SOUTH AND EAST
YOU GO.
THEN MORE UNCERTAINTY CREEPS INTO THE FORECAST FOR SUNDAY AND EARLY
NEXT WEEK. SOME MODELS AND ENSEMBLE MEMBERS SHOW THE LOW CUTTING OFF
AGAIN AND LINGERING NEAR THE AREA INTO EARLY NEXT WEEK, KEEPING THE
FORECAST COOLER AND UNSETTLED. OTHERS LIFT IT OUT AND BRING A
SOUTHWEST FLOW WHICH WOULD BRING WARMER WEATHER AND MAINLY CHANCES
OF DIURNAL CONVECTION. IT IS A COIN FLIP WHICH ONE WILL WIN OUT AT
THIS TIME THOUGH.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1100 AM MDT WED MAY 27 2026
VFR CONDITIONS EXPECTED THROUGHOUT THE ENTIRETY OF THE PERIOD.
INCREASED WINDS IN THE AFTERNOON BY 19-20Z, HIGHEST AT
BPI/CPR/RKS UP TO 25KT WITH PEAK HEATING AND STRONGEST MIXING TO
THE SURFACE. STORM ACTIVITY NEAR CPR/COD AFTER 20-21Z THROUGH
01-02Z COVERED WITH PROB30 GROUPS, ALTHOUGH ACTIVITY LOOKS TO
REMAIN EAST OF CPR OVER THE HIGHER TERRAIN. UPSLOPE FLOW FROM
THE SOUTHEAST WILL AID IN LOW CONFIDENCE OF STORMS ON STATION
(<10%) REMAINING MORE OUTSIDE EVEN THE VCTS CATEGORY. OTHERWISE,
WINDS DIMINISH AFTER 02-03Z WITH RADIATIONAL COOLING REMAINING
ELEVATED AT WRL UNTIL 09Z DUE TO DRAINAGE FLOW FROM THE
SOUTHEAST OFF THE WESTERN BIGHORNS. OVERALL STORM COVERAGE LESS
THAN TUESDAY AFTERNOON, EVEN WITH ITS LIMITED COVERAGE.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...WITTMANN
DISCUSSION...HATTINGS
AVIATION...LOWE
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