037
FXUS65 KRIW 271757
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1157 AM MDT TUE MAY 27 2025
KEY MESSAGES
- AFTER NOON TODAY, SCATTERED SHOWERS AND THUNDERSTORMS WILL
DEVELOP OVER THE MOUNTAINS, AND DRIFT SOUTHEASTWARD OVER THE
BASINS LATE THIS AFTERNOON AND EVENING.
- SEVERAL HIGH-RESOLUTION FORECAST MODELS SHOW TRAINING
THUNDERSTORMS OVER THE EASTERN FOOTHILLS OF THE BIGHORNS THIS
AFTERNOON, LEADING TO AN ISOLATED FLASH FLOODING CONCERN.
- NORTHERN AND CENTRAL WYOMING WILL SEE DRIZZLE AND RAIN SHOWERS
CONTINUE OVERNIGHT INTO WEDNESDAY MORNING. THE POWDER RIVER
BASIN LOOKS TO RECEIVE THE MOST RAIN WITH THIS QUICK-MOVING
WEATHER SYSTEM.
- WARMING TEMPERATURES CONTINUE TO LOOK LIKELY FOR THE END OF
THE WEEK, PUSHING 15 TO 20 DEGREES ABOVE AVERAGE BY THIS
WEEKEND.
UPDATE
ISSUED AT 1157 AM MDT TUE MAY 27 2025
THE FORECAST DISCUSSION BELOW REMAINS ON TRACK. THUNDERSTORMS
HAVE ALREADY STARTED FORMING OVER THE HIGH TERRAIN, AND WILL
CONTINUE TO INCREASE IN COVERAGE THROUGHOUT THE AFTERNOON.
STORMS DRIFT SOUTHEASTWARD DURING THE LATE AFTERNOON AND
EVENING, IMPACTING MOST BASINS BY THE EVENING HOURS.
ONE ITEM OF NOTE IS SEVERAL NEARLY STATIONARY BOUNDARIES THAT
ARE WELL-DEPICTED IN CAMS THIS AFTERNOON AND EVENING,
ESPECIALLY ON THE EASTERN FOOTHILLS OF THE BIGHORN MOUNTAINS.
WITH PRECIPITABLE WATER VALUES IN THE 0.7 TO 0.8 INCH RANGE
(WELL ABOVE NORMAL), IT'S WORTH WATCHING THIS AREA FOR TRAINING
STORMS AND ISOLATED FLASH FLOODING. LOW CHANCE (<10%) FOR ANY
GIVEN LOCATION, BUT THE LOW-END POTENTIAL IS THERE TODAY GIVEN
THE INGREDIENTS PRESENT.
DISCUSSION
ISSUED AT 251 AM MDT TUE MAY 27 2025
AFTER A BIT OF LULL IN THE CONVECTION YESTERDAY, THINGS WILL BECOME
MORE ACTIVE TODAY. THE MAIN PLAYERS IN THE WEATHER ARE AN UPPER
LEVEL LOW ROTATING ACROSS THE UPPER PLAINS STATES AND A SHORTWAVE
THAT WILL BE DROPPING SOUTHWARD INTO WYOMING TODAY. RADAR ALREADY
SHOWS A FEW SHOWERS OVER MONTANA THAT MAY DROP INTO NORTHERN WYOMING
EARLY THIS MORNING, BUT MOST OF THE ACTIVITY SHOULD HOLD OFF UNTIL
THE AFTERNOON AS THE WAVE DROPS ACROSS THE AREA. JUST ABOUT ALL
LOCATIONS WILL HAVE AT LEAST A 1 IN 5 CHANCE OF A SHOWER OR
THUNDERSTORM THIS AFTERNOON OR EVENING. THE BEST CHANCE WILL BE
FOUND ACROSS AREAS EAST OF THE DIVIDE. THIS EVENT MAY HAVE SOME
STAYING POWER, WITH THE HIGHEST CHANCES IN THE EVENING HOURS ACROSS
MANY AREAS AS THE WAVE AXIS PASSES THROUGH. THERE COULD BE A DECENT
AMOUNT OF RAIN WITH THESE, WITH SOME LOCATIONS, MAINLY EAST OF THE
DIVIDE, HAVING PRECIPITABLE WATERS 125 TO 150 PERCENT HIGHER THAN
NORMAL, FAR NORTHERN AREAS HAVE AROUND A 1 IN 3 CHANCE OF A QUARTER
INCH OF QPF OR MORE. AS FOR STRONGER STORMS, THERE COULD BE A COUPLE
BUT THE CHANCE HAS DECREASED. THE MAIN THREATS WOULD BE THE USUAL
GUSTY WIND AND SMALL HAIL. THIS EVENT WILL CONTINUE INTO THE NIGHT
AS WELL, ALTHOUGH THE CHANCE OF THUNDER WILL DECREASE.
ANOTHER TROUGH AXIS ROTATING AROUND THE UPPER LEVEL LOW WILL CROSS
THE AREA ON WEDNESDAY AND BRING ANOTHER CHANCE OF SHOWERS. THE
CHANCE OF THUNDER DECREASES ON THIS DAY, WITH COOLER TEMPERATURES
AND CLOUD COVER LIMITING INSTABILITY. THE BEST CHANCE OF THUNDER MAY
SHIFT FURTHER WEST, WHERE THERE COULD BE MORE SUNSHINE. THE CHANCES
OF OVER A QUARTER INCH OF PRECIPITATION REMAIN SIMILAR, GENERALLY
AROUND 1 IN 4 TO 1 IN 3 WITH HIGHER CHANCES IN THE MOUNTAINS.
THE PATTERN WILL BEGIN TO TRANSITION ON THURSDAY AS THE UPPER LEVEL
LOW FINALLY GETS KICKED EASTWARD AND RIDGING BUILDS OVER THE
ROCKIES. THE RESULT WILL BE AN UPWARD TREND IN TEMPERATURES AND A
DOWNWARD TREND IN PRECIPITATION CHANCES. A COUPLE OF SHORTWAVES
MOVING BY TO THE NORTH MAY BRING A CHANCE OF A FEW DIURNAL SHOWERS
AND STORMS EACH DAY ON THURSDAY AND FRIDAY, MAINLY IN THE NORTH.
HOWEVER, MOST AREAS WILL NOT SEE ONE. TEMPERATURES SHOULD PEAK ON
SUNDAY, WHEN SOME OF THE LOWER ELEVATIONS EAST OF THE DIVIDE COULD
SEE THE FIRST 90 DEGREE HIGH TEMPERATURES OF THE YEAR. AND WITH THE
TEMPERATURES INCREASING, THIS WILL ENHANCE THE HIGHER ELEVATION
SNOWMELT AND LIKELY LEAD TO RISING CREEKS AND RIVERS AND POSSIBLE
SOME FLOODING CONCERNS, ESPECIALLY OVER THE WEEKEND. TO EARLY TO
PINPOINT PROBLEM AREAS, BUT WE WILL BE WATCHING IT CAREFULLY.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1123 AM MDT TUE MAY 27 2025
VFR CONDITIONS PREVAIL THROUGH 06Z/WEDNESDAY WITH THE POSSIBLE
EXCEPTION OF LOCALIZED MVFR WITH HEAVIER RAIN-PRODUCING
THUNDERSTORMS. CONVECTION WILL AGAIN BE CENTERED ON THE ABSAROKA
AND WIND RIVER RANGES ALONG WITH THE SOUTHERN BIGHORN RANGE.
KJAC REMAINS FREE FROM THUNDERSTORMS TUESDAY AFTERNOON, WHILE
ALL OTHER TERMINALS HAVE PROB30 GROUPS TO ACCOUNT FOR THE
THUNDERSTORM POTENTIAL, GENERALLY FOR SOME DURATION BETWEEN
21Z/TUESDAY AND 02Z/WEDNESDAY. THE PRIMARY HAZARD WILL BE GUSTY
OUTFLOW WIND 30-40KTS, AND KRKS IS THE BEST CANDIDATE FOR GUSTS
AT THE HIGHER END OF THAT RANGE. A SECONDARY SHORTWAVE DROPS
SOUTH ACROSS THE FORECAST AREA LATE TONIGHT AND WEDNESDAY
MORNING. LIGHT RAIN SHOWERS AND LOWERED MID-CLOUD CEILINGS
OCCUR AS THIS DISTURBANCE SWEEPS SOUTH BETWEEN ABOUT
09Z-18Z/WEDNESDAY. KCPR COULD SEE LOCALIZED MVFR DURING THIS
TIME FRAME. MOUNTAIN TOPS OCCASIONALLY OBSCURED ALONG AND EAST
OF THE CONTINENTAL DIVIDE AFTER 10Z/WEDNESDAY.
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...VANDENBOOGART
DISCUSSION...HATTINGS
AVIATION...CNJ
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