303
FXUS65 KRIW 281518
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
918 AM MDT MON SEP 28 2026
KEY MESSAGES
- A WEATHER SYSTEM MOVING ACROSS THE AREA WILL BRING AREAS OF
SHOWERS AND ISOLATED THUNDERSTORMS TODAY INTO THIS EVENING.
- LOCALLY HEAVY RAIN WILL BE POSSIBLE WITH ANY SHOWER OR
THUNDERSTORM, BUT CONFIDENCE IS LOW FOR ANY ADVERSE IMPACTS.
- WEATHER CONDITIONS STAY QUIET THE REMAINDER OF THE WEEK, WITH
ONLY A COUPLE OF CHANCES OF LIGHT SHOWERS. TEMPERATURES WILL
STAY SEASONAL, EXCEPT ON FRIDAY. HIGHS WILL BE ABOUT 5 DEGREES
ABOVE NORMAL.
UPDATE
ISSUED AT 915 AM MDT MON SEP 28 2026
SHOWERS WILL BE ONGOING OVER CENTRAL AND SOUTHERN PORTIONS OF
THE CWA BY MIDDAY, GRADUALLY PUSHING INTO JOHNSON COUNTY AND
OVER THE BIGHORNS. SHOWERS WILL BECOME MORE SCATTERED IN
COVERAGE LATE IN THE AFTERNOON, AS ADDITIONAL SHOWERS AND
THUNDERSTORMS MOVE OVER FAR WESTERN PORTIONS. ALTHOUGH LOCALLY
HEAVY RAIN WILL BE THE MAIN THREAT THIS AFTERNOON, CONFIDENCE
REMAINS LOW DUE TO A LACK OF INSTABILITY AND STRONG DYNAMICS.
PRECIPITATION WILL THEN WANE ACROSS THE AREA THROUGH THE EVENING
AND END BEFORE MIDNIGHT. TEMPERATURES WILL BE SLIGHTLY COOLER
TONIGHT, WITH NEAR-FREEZING TEMPERATURES POSSIBLE OVER IN THE
WESTERN VALLEYS.
DISCUSSION
ISSUED AT 129 AM MDT MON SEP 28 2026
WE ARE CURRENTLY GETTING SOME MUCH NEEDED MOISTURE ACROSS THE AREA
WITH SOME AREAS OF SHOWERS AND ISOLATED THUNDERSTORMS. THIS IS
COURTESY OF A SHORTWAVE MOVING TOWARD THE AREA. IT IS GETTING AN A
ASSIST FROM A 95 KNOT JET STREAK THAT IS APPROACHING SOUTHWESTERN
WYOMING AND WILL CROSS SOUTHERN WYOMING THIS AFTERNOON AND EVENING,
PUTTING MUCH OF THE AREA IN THE LEFT FRONT QUADRANT OF IT TO ENHANCE
LIFT SOMEWHAT. AS A RESULT, ALMOST ALL AREAS WILL HAVE A CHANCE OF
SHOWERS TODAY. THERE WILL ALSO BE SOME EMBEDDED THUNDERSTORMS.
HOWEVER, WITH CLOUD COVER AROUND THE AREA, SURFACE INSTABILITY MAY
BE LIMITED. THE MAIN THREAT FROM ANY STORM WOULD BE LOCALLY HEAVY
RAIN, WITH PRECIPITABLE WATER VALUES GENERALLY RUNNING ANYWHERE
FROM 125 TO 150 PERCENT OF NORMAL. A MITIGATING FACTOR WILL BE
THAT THERE WILL BE STEERING FLOW, SO ANY STORMS WILL HAVE DECENT
MOTION AND NOT BE ABLE TO ANCHOR. WITH MORE CLOUD COVER,
TEMPERATURES WILL ALSO RUN AROUND 5 TO 10 DEGREES COOLER THAN
SUNDAY. COVERAGE OF SHOWERS AND THUNDERSTORMS SHOULD DECREASE
AFTER SUNSET, ENDING GENERALLY FROM NORTHWEST TO SOUTHEAST,
ALTHOUGH WITH THE JET STILL IN THE AREA OVERNIGHT, ISOLATED
SHOWERS AND THUNDERSTORMS MAY LINGER SOUTH OF A CASPER TO ROCK
SPRINGS LINE THROUGH THE NIGHT.
AND, WE COULD SEE SOME HIGHER ELEVATION SNOW FROM THIS. ANY
ACCUMULATION WOULD LIKELY BE RESTRICTED TO ABOVE 11000 FEET
THOUGH. THE HIGHEST ELEVATIONS OF THE WIND RIVER RANGE, LIKE THE
GANNETT PEAK, HAVE A 1 IN 2 CHANCE OF SEEING 3 INCHES OF NEW
SNOW. THERE SHOULD BE LITTLE OR NO IMPACT TO TRAVEL THOUGH.
WE SHOULD THEN ENTER A QUIETER PERIOD OF WEATHER AS RIDGING BUILDS
INTO THE AREA FROM THE WEST, PUSHING DRIER AIR INTO WESTERN AND
CENTRAL WYOMING. THERE MAY BE JUST ENOUGH LEFTOVER MOISTURE FOR SOME
ISOLATED SHOWERS IN SOUTHERN WYOMING, BUT THIS LOOKS LIKE THE
EXCEPTION RATHER THAN THE RULE. FOLLOWING THAT, THINGS LOOK MAINLY
DRY THROUGH THE WEEK AND EVEN INTO THE WEEKEND. A LARGE MAJORITY OF
THE GUIDANCE KEEPS THE MOISTURE ASSOCIATED WITH AN UPPER LEVEL
LOW AND THE REMNANTS OF HURRICANE POLO TO THE SOUTH OF THE AREA
THROUGH THE FORECAST PERIOD. A WEAK COLD FRONT WILL MOVE INTO
NORTHERN AND CENTRAL WYOMING WEDNESDAY NIGHT. THIS FRONT IS
MOISTURE STARVED THOUGH, SO IT WILL LIKELY ONLY BRING SOME
CLOUDS AND SOMEWHAT COOLER TEMPERATURES AND A GUSTY BREEZE,
ESPECIALLY TO NORTHERN WYOMING. ANOTHER FRONT MAY MOVE THROUGH
FRIDAY NIGHT OR SATURDAY, BUT AGAIN IT HAS LITTLE MOISTURE TO
WORK WITH SO ANY SHOWERS WOULD BE ISOLATED WITH THE ONLY IMPACTS
BEING SOMEWHAT COOLER TEMPERATURES AND SOME GUSTY BREEZES.
TEMPERATURES WILL GENERALLY AVERAGE ABOVE NORMAL, WITH THURSDAY
AND SUNDAY LOOKING LIKE THE COOLEST DAYS BEHIND THE FRONT. BUT
EVEN HERE, TEMPERATURES WILL ONLY FALL BACK TO NEAR NORMAL
LEVELS. SO, ONCE WE GET PAST THE NEXT 24 TO 36 HOURS, THINGS
LOOK FAIRLY UNEVENTFUL AS WE HEAD INTO OCTOBER.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 434 AM MDT MON SEP 28 2026
A WEATHER SYSTEM WILL BRING AREAS OF SHOWERS AND ISOLATED
THUNDERSTORMS THROUGH MUCH OF THE TAF PERIOD, BEFORE ENDING FROM
NORTHWEST TO SOUTHEAST AFTER SUNSET TONIGHT, ALTHOUGH A FEW
SHOWERS MAY LINGER IN VICINITY OF KRKS AND KCPR MUCH OF THE
NIGHT. LARGELY VFR CONDITIONS ARE EXPECTED A MAJORITY OF THE
TIME, BUT BRIEF MVFR OR EVEN IFR CONDITIONS MAY OCCUR IN THE
HEAVIER SHOWERS AND THUNDERSTORMS. CONFIDENCE IN TIMING OF THE
ROUNDS OF SHOWERS AND THUNDERSTORMS, ESPECIALLY AFTER 18Z TODAY,
REMAINS LOW AS MODEL AGREEMENT REMAINS LOW. WIND SHOULD REMAIN
UNDER 11 KNOTS FOR THE MOST PART, ALTHOUGH GUSTS TO 30 TO 35
KNOTS WILL BE POSSIBLE IN VICINITY OF ANY SHOWER OR
THUNDERSTORM. OCCASIONAL MOUNTAIN OBSCURATIONS WILL BE AROUND
THROUGH THE DAY AND INTO THE NIGHT. PATCHY FOG MAY DEVELOP AFTER
07Z TONIGHT, ALTHOUGH NOT ENOUGH CONFIDENCE TO INCLUDE IN THE
FORECAST AT THIS TIME.
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
NONE.
UPDATE...LAVOIE
DISCUSSION...HATTINGS
AVIATION...HATTINGS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page