830
FXUS65 KRIW 272145
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
345 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 AS 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. OUR WEATHER PATTERN THIS MORNING REMAINS ME OF ONE OF
THE GAMES ON THAT VENERABLE GAME SHOW, SQUEEZE PLAY. IT RELATES
TO THE CURRENT WEATHER PATTERN AS WE ARE TRAPPED BETWEEN THE
CUT OFF UPPER LEVEL LOW ROTATING NEAR THE SIERRA NEVADAS 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 LAST 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 BIGHORNS, FOR PLACES LIKE PARK, JOHNSON AND
NATRONA COUNTIES AS WELL AS PORTIONS OF THE WIND RIVER BASIN
AND YELLOWSTONE NATIONAL PARK. BUT GIVEN THE MORE LIMITED
INSTABILITY, COVERAGE LOOKS LESS, GENERALLY LESS THAN 1 OUT OF 4
OR LESS. 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 REACH 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 /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 345 PM MDT WED MAY 27 2026
VFR CONDITIONS EXPECTED THROUGHOUT THE ENTIRETY OF THE PERIOD
WITH BREEZY WINDS AND MID LEVEL CLOUDS TO START THE PERIOD
OVERNIGHT. LINGERING SHOWERS NEAR COD/CPR HAVE STARTED
DIMINISHING AND OUT OF THE VCTS RADIUS AT THIS POINT IN TIME BUT
KEEPING PROB 30 GROUPS GOING. WINDS DIMINISH AFTER 02-03Z WITH
RADIATIONAL COOLING EXPECTED TO INCREASE ONCE AGAIN BY 18-20Z
THURSDAY AFTERNOON WITH PEAK HEATING AND MIXING TO THE SURFACE.
STORM ACTIVITY POSSIBLE ONCE AGAIN NEAR COD/CPR SIMILAR TO
TODAY, CARRYING PROB30 GROUPS AFTER 20Z, ALTHOUGH NOT EXPECTED
ON STATION AND ONLY CLOSE TO THE VCTS RADIUS (<10% CONFIDENCE).
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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