361
FXUS65 KRIW 261836
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1236 PM MDT TUE MAY 26 2026
KEY MESSAGES
- SCATTERED SHOWERS AND THUNDERSTORMS TODAY. BEST CHANCES WILL
BE OVER WESTERN WYOMING (30 TO 60 PERCENT CHANCES) AND OVER
JOHNSON/NATRONA COUNTIES (15 TO 40 PERCENT CHANCES). GUSTY
WINDS 40 TO 50 MPH MAY OCCUR WITH ANY STORM, THOUGH AN
ISOLATED STRONGER GUST IS POSSIBLE.
- WARM TEMPERATURES THROUGH FRIDAY. SHOWER AND THUNDERSTORM
CHANCES OCCUR EACH DAY, BUT ARE LIMITED AND MAINLY ACROSS
NORTHERN AND CENTRAL WYOMING.
- INCREASING RAIN CHANCES INTO THE WEEKEND, WITH SLIGHTLY COOLER
TEMPERATURES.
UPDATE
ISSUED AT 1236 PM MDT TUE MAY 26 2026
THE FORECAST REMAINS ON TRACK TODAY. INCREASING MOISTURE BRINGS RAIN
SHOWERS AND THUNDERSTORMS TO THE AREA. A COMBINATION OF WHERE THE
BEST MOISTURE OCCURS AND CLOUD COVER LIMITING POSSIBLE CONVECTION,
KEEPS THE BEST CHANCES ACROSS FAR WESTERN WYOMING AND FOR JOHNSON
AND NATRONA COUNTIES. WHILE MOST OF THIS ACTIVITY ENDS BETWEEN
SUNSET AND ABOUT MIDNIGHT, SOME LINGERING SHOWERS ARE POSSIBLE
AROUND JOHNSON AND NATRONA COUNTIES THROUGH THE NIGHT. GUSTY OUTFLOW
WINDS ARE THE MAIN HAZARD WITH THIS CONVECTION, WHICH COULD BE 40 TO
60 MPH. SOME SMALL HAIL IS ALSO POSSIBLE, MAINLY FOR WESTERN
WYOMING.
DISCUSSION
ISSUED AT 111 AM MDT TUE MAY 26 2026
BACK WHEN I WAS A LITTLE KID AND DINOSAURS ROAMED THE EARTH (IT WAS
THE 1970S) I HAD A FAVORITE TOY, LIKE MANY LITTLE GIRLS AND BOYS
DID. AND MAY FAVORITE TOY WHEN I WAS 3 AND 4 YEARS OLD RELATES TO
THE ONE OF THE MAIN DRIVING FACTORS WITH THE WEATHER THE NEXT
SEVERAL DAYS. THE WEATHER FEATURE I AM SPEAKING OF IS AN UPPER LEVEL
LOW THAT IS MOVING ONSHORE IN THE PACIFIC NORTHWEST. AND THAT TOY I
AM SPEAKING OF IS THE SIT AND SPIN. MODELS HAVE FINALLY STARTED TO
COME INTO BETTER AGREEMENT THAT THE UPPER LEVEL LOW WILL, MOVE CLOSE
TO THE GREAT BASIN AND, SIT AND SPIN FOR A FEW DAYS.
AND THE MAIN IMPACT FROM THIS, IN CONJUNCTION WITH A STRONG,
BLOCKING RIDGE OVER THE PLAINS STATES, WILL KEEP SOUTHERLY FLOW OVER
THE AREA FOR THE NEXT SEVERAL DAYS. THIS WILL KEEP TEMPERATURES
ABOVE NORMAL FOR SEVERAL DAYS, GENERALLY BETWEEN 5 TO 15 DEGREES
ABOVE NORMAL. IT WILL ALSO KEEP ROTATING A FEW SHORTWAVES OVER
THE AREA, KEEPING VARYING CHANCES AND PLACEMENTS OF LARGELY
DIURNAL SHOWERS AND THUNDERSTORMS.
AND TODAY MAY BE ONE OF THE MORE ACTIVE DAYS ACROSS THE AREA. RADAR
SHOWS AN AREA OF RAIN AND EMBEDDED THUNDER ACROSS UTAH AND NORTHERN
COLORADO SLOWLY MOVING NORTHWARD AS THE SHORTWAVE MOVES NORTH. THIS
WILL BRING THE CHANCE OF SHOWERS AND STORMS TODAY. MODEL GUIDANCE IS
ZEROING IN ON TWO LOCATIONS. ONE IS WESTERN WYOMING, WHERE
UPPER LEVEL FORCING WILL BE GREATER WITH A WEAK JET STREAK
MOVING THROUGH, THIS IS WHERE THE MOST NUMEROUS SHOWERS AND STORMS
WILL BE. ONE QUESTION IS WILL THERE BE ANY STRONGER STORMS? THE
STORM PREDICTION CENTER HAS A MARGINAL RISK OF SEVERE
THUNDERSTORMS ACROSS NORTHERN YELLOWSTONE. SOUNDINGS ARE SHOWING
A DECENT AMOUNT OF SHEAR AS WELL. THE LIMITING FACTOR MAY BE
CLOUD COVER, ESPECIALLY FURTHER SOUTH WHERE SURFACE INSTABILITY
COULD BE LIMITED. THE HIGHEST VALUES (CAPE UP TO 700 J/KG AND
LIFTED INDICES OF MINUS 2) ARE ACROSS NORTHWESTERN WYOMING. SO,
IF ANY STRONGER STORMS DEVELOP IT WOULD LIKELY BE HERE. CHANCES
HERE RANGE FROM A 1 IN 3 CHANCE TO A 4 IN 5 CHANCE WITH THE
HIGHEST CHANCE IN THE NORTHERN MOUNTAINS. THE MAIN THREAT WOULD
BE STRONG WIND GUSTS GIVEN THE VERY STEEP LAPSE RATES, BUT SOME
SMALL HAIL MAY ALSO BE POSSIBLE. THE OTHER AREAS OF CONCERN IS
EAST OF THE BIG HORN RANGE IN JOHNSON AND NATRONA COUNTIES. LOW
LEVEL SOUTH-SOUTHEAST FLOW WILL LIKELY BRING SOME UPSLOPE FLOW
TO INITIATE SHOWERS AND STORMS. AND IN THIS AREA, THE HIGHEST
INSTABILITY PARAMETERS ARE FURTHER NORTH, ALTHOUGH SHEAR IS
LESS. CHANCES HERE RANGE FROM 1 IN 4 TO 1 OUT OF 2, WITH THE
HIGHEST POPS CLOSE TO THE BIGHORN RANGE. WITH SOME CLOUD COVER
TO START, THIS COULD BE A LATER SHOW AS WELL, WITH STORMS
EXTENDING INTO THE EVENING. ELSEWHERE, WE CAN'T RULE OUT A
SHOWER OR STORM, BUT WITH LESS INSTABILITY AND MORE CLOUD COVER,
THE CHANCE IS ONLY 1 OUT OF 5 OR LESS. THE SHORTWAVE WILL ALSO
BRING A GUSTY BREEZE IN SOME LOCATIONS, ALTHOUGH HIGH WIND IS
NOT EXPECTED.
LESS ACTIVITY IS NOW EXPECTED FOR WEDNESDAY AND THURSDAY, MOST
GUIDANCE IS SHOWING MUCH DRIER AIR MOVING IN FROM THE SOUTH, WITH
PRECIPITABLE WATER VALUES FALLING BELOW CLIMATOLOGICAL NORMALS
FOR MUCH OF THE SOUTHERN HALF OF THE STATE. ON WEDNESDAY, MOST
CONVECTION WOULD OCCUR EITHER IN OR NEAR THE NORTHERN MOUNTAINS
WHERE SOME WEAK UPSLOPE AND HIGH LEVEL HEAT SOURCE CONVECTION IS
POSSIBLE. A FEW SHOWERS AND STORMS (ABOUT A 1 OUT OF 3
COVERAGE) ARE ALSO POSSIBLE ACROSS JOHNSON AND NATRONA COUNTY,
WITH THE WESTERN BOUNDARY CLOSE TO THE 0.5 INCH PRECIPITABLE
WATER LINE. THURSDAY LOOKS EVEN DRIER AS THE ATMOSPHERE DRIES
OUT EVEN MORE. AND STORMS ON THESE DAYS WOULD BE IN THE SAME
LOCATIONS, BUT ONLY AROUND A 1 OUT OF 5 CHANCE.
IT CONTINUES TO LOOK LIKE FRIDAY OR SATURDAY WHEN WE GET THE PLUNGER
OUT TO BREAK UP THE BLOCKAGE AS ANOTHER TROUGH FINALLY KICKS THE
LOW TO THE EAST AND IT OPENS UP INTO A WAVE. THERE ARE STILL
DIFFERING SOLUTIONS ON HOW FAR EAST IT CAN GET. A CLOSER PASS
WOULD OBVIOUSLY BRING A BETTER CHANCE OF SHOWERS AND STORMS, BUT
THERE IS STILL A FAIR AMOUNT OF UNCERTAINTY RIGHT NOW. STAY
TUNED.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1138 AM MDT TUE MAY 26 2026
A LEADING SHORTWAVE WITHIN SOUTHERLY FLOW ALOFT IS ALONG THE
WESTERN WYOMING BORDER AND MOVING TO THE NORTH-NORTHWEST LATE
TUESDAY MORNING. SOUTHERLY WIND 15-30KTS HAS SURFACED AT A FEW
TERMINALS DURING THE LATE MORNING, AND OTHER TERMINALS WILL SEE
THIS WIND MIX TO THE SURFACE BY 20Z/TUESDAY. SPEEDS GENERALLY
DECREASE TO 7-12KTS BETWEEN 02Z-05Z/WEDNESDAY. BREAKING THE
FORECAST AREA INTO THIRDS FROM WEST-TO-EAST, DRIER AIR IS
WORKING NORTHWARD ACROSS THE CENTRAL THIRD, A TREND THAT
CONTINUES INTO THE EVENING. SHOWERS WILL BE HARDER TO COME BY
WITHIN THIS SECTOR. THOSE THAT DO FORM WOULD BE MORE LIKELY TO
PRODUCE GUSTY OUTFLOW WIND 30- 40KTS. THE WESTERN-THIRD HAS
MOISTURE AND WRAP-AROUND DYNAMICS TO GENERATE SCATTERED SHOWERS
AND THUNDERSTORMS FROM 19Z-03Z. KJAC AND KBPI HAVE THE BETTER
CHANCE OF SEEING A BRIEF SHOWER AND OUTFLOW WIND AROUND 30KTS.
THE EASTERN-THIRD, INCLUDING KCPR, CAN EXPECT AN UPTICK IN
CONVECTIVE COVERAGE AFTER 21Z/TUESDAY OWING TO INCREASED SOLAR
HEATING AND A PASSING JET STREAK. OUTFLOW WIND GUSTS TO 35KTS
AND A POSSIBLE BRIEF MVFR PERIOD (LESS THAN 30 MINUTES) WOULD BE
THE PRIMARY HAZARDS. CONVECTION WANES BETWEEN 02Z-04Z/WEDNESDAY,
LEAVING DRIER CONDITIONS AND DEPARTING CLOUD COVER OVERNIGHT.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page