512
FXUS65 KRIW 311717
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1117 AM MDT SAT MAY 31 2025
KEY MESSAGES
- VERY WARM THIS WEEKEND WITH THE FIRST 90 DEGREE HIGHS ON THE
YEAR LIKELY IN SOME LOCATIONS. RISING CREEKS AND STREAMS
REMAIN A CONCERN.
- AND APPROACHING WEATHER SYSTEM WILL BRING AFTERNOON
THUNDERSTORMS SUNDAY, SOME POSSIBLY STRONG TO SEVERE IN
NORTHWESTERN WYOMING.
- A WETTER AND MUCH COOLER PATTERN MOVES IN FOR EARLY NEXT WEEK.
ALTHOUGH EXACT TIMING AND AMOUNTS OF PRECIPITATION REMAIN
UNCERTAIN.
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 OUT FIRST 90
DEGREE AT OUR MAJOR CLIMATE STATIONS, MOST LIKELY GREYBULL 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 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 WERE 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 THREAT. 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
AND 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, IF 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 MENTIONED 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
MON DAY NIGHT, POSSIBLY AS LOW AS MINUS 2, 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 BIG HORNS, WIND RIVERS AND ABSAROKAS.
THE HIGHEST ELEVATIONS OF THE BIG HORN 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 BE 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 /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1114 AM MDT SAT MAY 31 2025
VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS ALL TERMINALS
THROUGHOUT THE TAF PERIOD. WINDS ARE EXPECTED TO REMAIN MOSTLY LIGHT
THROUGH THE PERIOD, ESPECIALLY OVERNIGHT, WHEN MOST TERMINALS WILL
SEE WIND SPEEDS LESS THAN 5KTS. CLEAR SKIES ALSO WILL PREVAIL WITH
SOME PATCHES OF LOW TO MID LEVEL FAIR WEATHER CLOUDS POSSIBLE THIS
AFTERNOON, AND MORE LIKELY BY THE END OF THE 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.
DISCUSSION...HATTINGS
AVIATION...HENSLEY
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