326
FXUS65 KRIW 010503
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1103 PM MDT SAT MAY 31 2025
KEY MESSAGES
- WARM THROUGH THE WEEKEND WITH SOME AREAS PEAKING AROUND 90 DEGREES
ON SUNDAY.
- SHOWERS AND THUNDERSTORMS RETURN SUNDAY AFTERNOON, ESPECIALLY ACROSS
NORTHWESTERN WYOMING. STRONG WIND GUSTS AND HAIL WILL BE A
CONCERN WITH THE STRONGEST STORMS.
- RIVER AND STREAM FLOODING POTENTIAL WILL CONTINUE TO INCREASE
THROUGH THE WEEKEND AS SNOWMELT IS EXACERBATED BY WARM
TEMPERATURES.
- COOLER AND WETTER CONDITIONS EXPECTED MONDAY THROUGH THE
MIDDLE OF NEXT WEEK, THOUGH PRECIPITATION AMOUNTS REMAIN
UNCERTAIN.
UPDATE
ISSUED AT 150 PM MDT SAT MAY 31 2025
WITH HIGH PRESSURE NOW OVER THE AREA, SKIES ARE MOSTLY CLEAR TODAY
SAVE FOR SOME SHALLOW CUMULUS OVER THE MOUNTAINS AND SOUTHERN
WYOMING. A ROGUE SHOWER IS POSSIBLE OVER THE SOUTHERN WIND RIVER
RANGE THIS AFTERNOON, BUT EVEN HERE CHANCES ARE LESS THAN 10
PERCENT. AS NOTED BELOW, TEMPERATURES WILL CONTINUE TO RISE THROUGH
SUNDAY, WITH SOME LOCATIONS SEEING THEIR FIRST 90 DEGREE DAY.
ISOLATED SHOWERS AND THUNDERSTORMS WILL RETURN SUNDAY AFTERNOON AS
THE NEXT SYSTEM APPROACHES, MOST WIDESPREAD ACROSS NORTHWESTERN
WYOMING. COOLER AND WETTER CONDITIONS ARE THEN EXPECTED THROUGH
EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 211 AM MDT SAT MAY 31 2025
IT IS NOW THE LAST DAY OF METEOROLOGICAL SPRING (IT RUNS FROM MARCH
THROUGH MAY) AND WE WILL BE TRANSITIONING INTO SUMMER AND IT
WILL CERTAINLY FEEL LIKE IT THIS WEEKEND. RIDGING WILL BUILD
OVER THE COWBOY STATE AND BRING THE WARMEST WEATHER SO FAR THIS
YEAR. TEMPERATURES WERE A BIT WARMER THAN FORECAST YESTERDAY.
SO, WITH SIMILAR CONDITIONS WE RAISED THEM A FEW DEGREES,
ESPECIALLY EAST OF THE DIVIDE. THIS COULD BE THE DAY WE SEE OUR
FIRST 90 DEGREE READING AT OUR MAJOR CLIMATE STATIONS, MOST
LIKELY GREYBULL AND/OR WORLAND. AS FOR PRECIPITATION, I CAN'T
COMPLETELY RULE OUT A STRAY SHOWER OVER THE WIND RIVER RANGE.
HOWEVER, WITH THE CHANCE LESS THAN 1 OF 10, WE HAVE ELECTED TO
LEAVE THE FORECAST DRY.
THE HEAT WILL PEAK ON SUNDAY, AS SOUTHWEST FLOW INCREASES AHEAD
OF THE NEXT WEATHER MAKERS, A TROUGH AND COLD FRONT MOVING IN
FROM THE PACIFIC NORTHWEST AND AN UPPER LEVEL LOW TO THE
SOUTHWEST. CHANCES ARE INCREASING A GOOD COVERAGE OF 90 DEGREE
HIGHS ACROSS THE LOWER ELEVATIONS EAST OF THE DIVIDE ON THIS
DAY. AND WITH THE FEW DAYS OF WARM TEMPERATURES, CONCERNS ABOUT
RISING CREEKS AND RIVERS ARE INCREASING. THERE ARE A FEW
CONCERNS RIGHT NOW, BUT WE WILL HAVE TO KEEP WATCHING IT. AND
THERE IS ANOTHER CONCERN. WITH THE COLD FRONT APPROACHING,
THUNDERSTORMS WILL BECOME MORE LIKELY, ESPECIALLY IN
NORTHWESTERN PORTIONS WHERE THE EFFECTS WILL ARRIVE DURING THE
TIME OF PEAK HEATING. MODELS ARE SHOWING CAPE VALUES CLIMBING
OVER 1000 J/KG AND LIFTED INDICES AS LOW AS MINUS 4. THE RESULT
COULD BE SOME STRONG TO POSSIBLY SEVERE THUNDERSTORMS, WITH
HIGH WIND AND MARGINALLY SEVERE HAIL THE MAIN THREATS. THE
CHANCE OF SHOWERS AND STORMS WILL EXTEND ACROSS GENERALLY THE
NORTHWESTERN HALF OF THE AREA, WITH THE HIGHEST CHANCES OF
SHOWERS ACROSS THE NORTHWEST WITH A 3 OUT OF 5 CHANCE, TAPERING
TO 1 IN 5 CHANCE FURTHER SOUTH AND WEST.
THINGS HAVE TRENDED A BIT DRIER FOR LATER SUNDAY NIGHT WITH THE MAIN
PLAYERS AND AREAS OF ENERGY REMAINING SPLIT, KEEPING THE BEST CHANCE
ACROSS MONTANA AND TO THE SOUTHWEST. THE BEST CHANCE FOR MEANINGFUL
PRECIPITATION STILL LOOKS TO BE MONDAY NIGHT INTO TUESDAY. THERE ARE
STILL SOME DIFFERENCES, ALTHOUGH THERE IS AT LEAST SOME BETTER
AGREEMENT IN THE DETERMINISTIC GUIDANCE IN HAVING THE MOST IMPACTS
TO THE SOUTH AND EAST OF THE AREA WITH THE MOST PRECIPITATION IN
SOUTHERN WYOMING. AS FOR THE ENSEMBLE GUIDANCE, THE CHANCE OF A HALF
INCH OF PRECIPITATION FROM MONDAY THROUGH TUESDAY NIGHT HAS
DROPPED, ESPECIALLY ACROSS NORTHERN WYOMING. YESTERDAY, IT WAS
ANYWHERE FROM 1 IN 2 TO 3 OUT OF 4; NOW IT IS 1 OUT OF 4 TO 2
OUT OF 5. CENTRAL WYOMING HAS DECREASED FROM A 3 OUT OF 5 CHANCE
TO A 2 OUT OF 5 CHANCE. HOWEVER, STILL HAVE LOW CONFIDENCE IN
THIS SOLUTION BECAUSE OF THE LARGE AMOUNT OF PLAYERS WITH THIS
SYSTEM. A LOT OF THE PRECIPITATION ACROSS NORTHERN WYOMING MAY
COME ON TUESDAY WITH ANOTHER TRAILING SHORTWAVE MOVING INTO THE
AREA.
IN ADDITION, EVEN THOUGH IT WILL BE JUNE, WE HAVE TO MENTION
THE DREADED "S" WORD, SNOW. IT WILL TURN MUCH COOLER BEHIND THE
FRONT, WITH HIGH TEMPERATURES AVERAGING 20 DEGREES BELOW NORMAL
FOR MANY ON TUESDAY. THE 700 MILLIBAR TEMPERATURES WILL LOWER
MONDAY NIGHT, POSSIBLY AS LOW AS MINUS 2C, WHICH WOULD DROP
SNOW LEVELS AS LOW AS 7500 FEET. PROBABILISTIC GUIDANCE IS
SHOWING A GREATER THAN 1 IN 2 CHANCE OF 3 INCHES OR MORE ACROSS
THE HIGHER ELEVATIONS OF THE BIGHORNS, WIND RIVERS AND
ABSAROKAS. THE HIGHEST ELEVATIONS OF THE BIGHORN RANGE HAVE A
GREATER THAN 1 IN 2 CHANCE OF 6 INCHES OR MORE OF SNOW FROM
MONDAY THROUGH TUESDAY NIGHT. IMPACTS TO PASSES WOULD LIKELY BE
MINIMAL GIVEN THE VERY WARM TEMPERATURES THIS WEEKEND, BUT
COULD IMPACT OUTDOOR RECREATION EARLY IN THE WEEK.
CYCLONIC CURVATURE REMAINS OVER WYOMING ON WEDNESDAY KEEPING A
COOL AND UNSETTLED PATTERN, ESPECIALLY EAST OF THE DIVIDE, BUT
SHOWERS SHOULD BE LESS NUMEROUS. FLOW THEN BECOMES MORE ZONAL
FOR THE REST OF THE WEEK. THERE WILL BE A FEW CHANCES FOR
CONVECTION THROUGH THE LATTER PORTION OF NEXT WEEK, BUT TIMING
AND PLACEMENT OF THE SHOWERS IS HIGHLY UNCERTAIN THIS FAR OUT.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1103 PM MDT SAT MAY 31 2025
VFR CONDITIONS ALONG WITH MOSTLY SKC SKIES WILL PREVAIL ACROSS ALL
TERMINALS THROUGH MUCH OF THE TAF PERIOD. WINDS ARE EXPECTED TO
REMAIN LIGHT THROUGH THE PERIOD AS WELL WITH ONLY A FEW SLIGHT WIND
DIRECTION SHIFTS. A COLD FRONT WILL BEGIN TO NEAR THE AREA BY THE
LATE SUNDAY MORNING. THE NEARING FRONT WILL BEGIN TO PRODUCE
SCATTERED SHOWERS AND THUNDERSTORMS. NEARLY ALL TERMINALS WILL HAVE
CHANCES TO SEE SHOWERS AND THUNDERSTORMS WITH THE BEST LIKELIHOOD
BEING EAST OF THE DIVIDE OVER NORTHERN AND CENTRAL WY. THE MAIN
CONCERN WITH ANY SHOWERS OR THUNDERSTORMS THAT DEVELOP NEARBY
TERMINALS WILL BE STRONG GUSTY OUTFLOW WINDS POSSIBLY OF 40 OR MORE
KNOTS. THIS IS ESPECIALLY THE CASE FOR TERMINALS SUCH AS KCOD, KWRL,
KLND, KRIW, AND KCPR. IF ANY SHOWERS TO TRACK OVER TERMINALS THERE
COULD BE A BRIEF PERIOD OF MODERATE TO HEAVY RAINFALL WITH
CONDITIONS DROPPING TO MVFR. THE TIMEFRAME FOR THESE SHOWERS AND
THUNDERSTORMS LOOKS TO BE FROM 20Z SUNDAY THROUGH 06Z MONDAY. THE
FRONT WILL ALSO BRING IN MIDLEVEL SCT TO BKN CLOUD DECKS THROUGH THE
END OF THE TAF PERIOD.
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...MYERS
DISCUSSION...HATTINGS
AVIATION...DZIEWALTOWSKI
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