594
FXUS65 KRIW 260000
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
600 PM MDT MON MAY 25 2026
KEY MESSAGES
- ISOLATED TO SCATTERED RAIN SHOWERS AND THUNDERSTORMS CONTINUE
THIS EVENING ENDING BY MIDNIGHT. GUSTY OUTFLOW WINDS 30 TO 50
MPH ARE THE MAIN HAZARD WITH ANY SHOWER OR STORM.
- RAIN SHOWERS RETURN EARLY TUESDAY MORNING, MAINLY WEST OF THE
CONTINENTAL DIVIDE.
- INCREASED MOISTURE BRINGS BETTER CHANCES OF SHOWERS AND
THUNDERSTORMS TUESDAY AFTERNOON INTO TUESDAY EVENING. STRONG
WINDS ARE THE MAIN HAZARD WITH THESE STORMS.
- A FAIRLY STAGNANT WEATHER PATTERN KEEPS ABOVE NORMAL
TEMPERATURES MUCH OF THE WEEK, WITH DAILY CHANCES OF AFTERNOON
SHOWERS AND THUNDERSTORMS.
UPDATE
ISSUED AT 1234 PM MDT MON MAY 25 2026
A WARM MEMORIAL DAY, WITH HIGHS IN THE MID-TO-UPPER 70S WEST OF THE
DIVIDE AND 80S EAST OF THE DIVIDE. A FEW SPOTS IN THE BIGHORN BASIN
COULD ALSO HIT THE 90 DEGREE MARK. FOR REFERENCE, NORMAL HIGHS
ARE IN THE UPPER 60S TO LOW 70S FOR THE END OF MAY. SIMILAR TO
YESTERDAY, SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE THIS
AFTERNOON, DIMINISHING BETWEEN SUNSET AND ABOUT 10PM. MOST
CONVECTION TODAY WILL BE ALONG AND WEST OF THE DIVIDE, THOUGH
SOME ACTIVITY MAKES IT EAST, MOST LIKELY FOR THE BIGHORN AND
WIND RIVER BASINS. ALSO LIKE YESTERDAY, OUTFLOW WINDS 30 TO 50
MPH ARE THE BIGGEST CONCERN WITH ANY SHOWER OR STORM. THOSE
RECREATING OUTSIDE THIS HOLIDAY WEEKEND SHOULD BE AWARE OF THESE
POSSIBLE SUDDEN WINDS.
DISCUSSION
ISSUED AT 114 AM MDT MON MAY 25 2026
THE OVERALL THEME OF THE FORECAST REMAINS LARGELY THE SAME AS THIS
TIME YESTERDAY. THINGS ARE LARGELY QUIET AT THIS TIME AROUND WESTERN
AND CENTRAL WYOMING. AND THE MAIN PLAYERS IN THE FORECAST REMAIN THE
SAME, AN APPROACHING UPPER LEVEL LOW THAT WILL MOVE ONSHORE IN
THE PACIFIC NORTHWEST TODAY AND A RIDGE THAT WILL BUILD ACROSS
THE PLAINS STATES FOR MUCH OF THE WEEK. AND THEIR POSITIONS WILL
HAVE THE MAIN INFLUENCE ON OUR WEATHER EACH DAY, AS WE WILL
LIKELY BE BETWEEN THE TWO OF THEM.
AS FOR TODAY, THE AXIS OF THE MOST SHOWERS AND STORMS SHOULD SHIFT
TO WESTERN WYOMING. DEW POINTS SHOULD RUN AROUND 5 TO 10 DEGREES
ABOVE YESTERDAY AND CAPE IS MAXIMIZED IN THIS LOCATION, WITH UP TO
1000 J/KG. WE DID INCREASE POPS HERE SOMEWHAT, BUT THE CHANCE OF ANY
LOCATION SEEING A SHOWER OR THUNDERSTORM GENERALLY RANGES FROM 1 OUT
OF 5 IN THE LOWER ELEVATIONS TO UP TO 2 OUT OF 5 IN THE MOUNTAINS.
MOST THUNDERSTORMS SHOULD BE OF THE RUN OF MILL VARIETY, ALTHOUGH A
STRONGER STORM OR TWO CAN'T BE RULED OUT. THERE IS MORE OF A
QUESTION EAST OF THE DIVIDE, WHERE THE LOWER ATMOSPHERE WILL BE
DRIER, AND SOUTHWEST FLOW SHOULD BRING SOME DOWNSLOPING FLOW. WE DID
BUMP POPS UP A BIT, WITH THE BEST CHANCE ACROSS NORTHERN WYOMING,
WHERE THE ATMOSPHERE IS A BIT MORE UNSTABLE, ESPECIALLY THE CODY
FOOTHILLS. MOST OF ANY ACTIVITY IN THIS AREA WOULD LIKELY BE NEAR
THE MOUNTAINS, AND THE CHANCE IS GENERALLY LOWER THAN 1 OUT OF 3. WE
CAN'T RULE A SHOWER OUT ANYWHERE, BUT ELSEWHERE THE CHANCE IS LESS
THAN 1 OUT OF 10. SOUTHWEST FLOW WILL BRING A WARM DAY AS WELL, WITH
TEMPERATURES RUNNING AROUND 10 DEGREES ABOVE NORMAL, AND MAYBE A FEW
90S IN THE BIGHORN BASIN. LIKE PREVIOUS DAYS, ACTIVITY WILL BE
LARGELY DIURNAL AND MOST WILL END SHORTLY AFTER SUNSET.
THINGS MAY GET A BIT MORE ACTIVE TOMORROW. THE UPPER LEVEL LOW WILL
BE ONSHORE BY THIS TIME AND THE FIRST SHORTWAVE WILL BE MOVING
ACROSS THE AREA FROM SOUTH TO NORTH. LOW LEVEL FLOW WILL ALSO BE
TURNING MORE TO THE SOUTH AND EAST, BRINGING IN MORE LOW LEVEL
MOISTURE. PRECIPITABLE WATER RISE SOMEWHAT AS WELL, TO AS HIGH AS AN
INCH IN EASTERN PORTIONS OF THE AREA, WHICH IS GREATER THAN 175
PERCENT OF NORMAL AND ABOVE THE 90TH PERCENTILE WITH CLIMATOLOGY.
ONE LIMITING FACTOR MAY BE CLOUD COVER THOUGH, AS THIS MAY LIMIT
INSTABILITY. THE TWO MOST LIKELY ZONES LOOK TO AGAIN BE THE WESTERN
MOUNTAINS, WHERE CAPE VALUES CLIMB TO HIGHER THAN 1000 J/KG AND
LIFTED INDICES FALL TO MINUS 3. THE OTHER IS ACROSS JOHNSON AND
NATRONA COUNTIES, WHERE UPSLOPE MAY BRINGING CONVECTIVE INITIATION
AGAINST THE BIGHORNS. AS FOR STRONGER STORMS, THE BEST CHANCE OF
THAT WOULD BE IN WESTERN WYOMING WHERE THERE IS MORE DIRECTIONAL
SHEAR PRESENT. LOCALLY HEAVY RAIN IS POSSIBLE WITH ANY STORM PUT
THERE WILL BE AROUND 20 KNOTS OF STORM MOTION, SO THIS SHOULD LIMIT
ANY FLOODING POTENTIAL. STORM CHANCES RANGE FROM AROUND 1 OUT OF 2
IN THE WESTERN MOUNTAINS TO LESS THAN 1 OUT 6 IN PORTIONS OF THE
BIGHORN AND WIND RIVER BASINS WHERE THE LEAST ACTIVITY WILL BE
FOUND. AGAIN, MOST ACTIVITY SHOULD END AFTER SUNSET, BUT A FEW
SHOWERS MAY LINGER THROUGH THE NIGHT.
UNCERTAINTY INCREASES AFTER THIS, AS THE GUIDANCE CONTINUES TO
STRUGGLE WITH THE EVOLUTION OF THE MOVEMENT OF THE UPPER LEVEL LOW.
HOWEVER, THERE HAS BEEN A TREND IN THE RIDGE BEING A BIT STRONGER
AND KEEPING THE LOW FURTHER TO THE WEST. THIS WOULD MEAN A SOMEWHAT
DRIER AND WARMER FORECAST. THE FORECAST FOR WEDNESDAY IS LIKELY THE
WETTEST IT COULD BE. THE MOST ACTIVE DAYS MAY END UP BRING FRIDAY OR
SATURDAY, BUT AGAIN A LOT DEPENDS ON THE TRACK OF THE LOW AND HOW
THE TROUGH AXIS MOVES AS THE LOW EVENTUALLY OPENS UP. THE TREND FOR
NOW IS FOR CONTINUED ABOVE NORMAL TEMPERATURES AND SOME CHANCES OF
CONVECTION EACH DAY, WITH THE BEST CHANCE IN WESTERN WYOMING.
DETERMINING WHICH DAY WILL BE THE MOST ACTIVE AND WHERE THE HEAVIER
RAIN FALLS REMAINS UNCERTAIN. WE MAY ALSO HAVE TO DEAL WITH SOME
RISING CREEKS, STREAMS AND RIVERS AS THE WARM SPELL MAY BE ABLE TO
MELT OUT SOME OF THE HIGHER LEVEL SNOWPACK.
AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 453 PM MDT MON MAY 25 2026
VFR CONDITIONS PREVAIL THROUGH 00Z/WEDNESDAY AS SOUTHERLY FLOW ALOFT
BRINGS INCREASED MOISTURE TO THE REGION. ONGOING SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS BEGIN TO DIMINISH IN COVERAGE AND
STRENGTH AROUND 01Z/TUESDAY, BUT ISOLATED CONVECTION LINGERS THROUGH
05Z/TUESDAY. THE CHANCE OF BRIEF MVFR WITH HEAVIER SHOWERS IS WANING
LATE MONDAY AFTERNOON, AND GUSTY OUTFLOW WIND 30-40KTS REMAINS THE
MAIN HAZARD. THE SOUTHERLY UPPER-LEVEL FLOW KEEPS CLOUD COVER AND
ISOLATED LIGHT SHOWERS OVER SOUTHWEST AND FAR WESTERN WYOMING
OVERNIGHT AND TUESDAY MORNING. THIS CLOUD COVER SHOULD SLOW THE
ONSET OF DEEPER CONVECTION TUESDAY, WHICH BECOMES MORE COMMON AFTER
21Z/TUESDAY. THERE IS A BETTER CHANCE OF BRIEF MVFR CONDITIONS IN
HEAVIER RAIN TUESDAY AFTERNOON AS PRECIPITABLE WATER VALUES AND
SURFACE DEW POINTS INCREASE. STRONGER STORMS MAY OCCUR AROUND KCPR
LATE IN THE DAY GIVEN BETTER SURFACE HEATING AND FAVORABLE DYNAMICS,
INCLUDING A 50-60KT NORTHWARD-MOVING JET MAX. ALL TERMINALS TO SEE
GUSTY SOUTHERLY SURFACE WIND DEVELOP BETWEEN 16Z-20Z/TUESDAY.
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...CNJ
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