922
FXUS65 KRIW 291103
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
503 AM MDT THU MAY 29 2025
KEY MESSAGES
- WARMER AND DRIER TODAY AND FRIDAY WITH AN ISOLATED SHOWERS AND
THUNDERSTORMS.
- THE WARMEST WEATHER OF THE YEAR IS EXPECTED THIS WEEKEND, WITH
THE FIRST 90 DEGREE HIGH TEMPERATURES POSSIBLE SUNDAY.
- A TRANSITION TO A COOLER AND WETTER PATTERN IS LIKELY EARLY
NEXT WEEK (3 OUT OF 5 CHANCE).
DISCUSSION
ISSUED AT 156 AM MDT THU MAY 29 2025
THERE ARE STILL A FEW LEFTOVER SHOWERS OUT THERE EARLY THIS MORNING.
HOWEVER, RADAR TRENDS ARE DOWN AND WITH CLOUD TOPS CONTINUING TO
WARM, THESE SHOULD BE GONE BY SUNSET. CONVECTION SHOULD BE LESS
TODAY AS RIDGING BUILDS INTO THE AREA TODAY. ANY CONDITIONS WOULD BE
LIMITED TO IN AND NEAR THE MOUNTAINS, WITH AN EMPHASIS ON AREAS
ALONG AND WEST OF THE CONTINENTAL DIVIDE. THE CHANCE IS AT MOST 1 IN
3 IN MOST MOUNTAIN LOCATIONS, DROPPING TO AROUND 1 IN 4 TO 1 OUT OF
5 IN THE ADJACENT LOWER ELEVATIONS. WITH MORE SUNSHINE EXPECTED,
TEMPERATURES WILL BE WARMER, RISING TO NEAR TO SLIGHTLY ABOVE NORMAL
LEVELS FOR MOST LOCATIONS. LIKE TONIGHT, A VAST MAJORITY OF THESE
SHOWERS SHOULD BE OVER BY MIDNIGHT.
THERE IS MORE UNCERTAINTY FOR TOMORROW, MAINLY IN EASTERN PORTIONS
OF THE AREA. AND THE CULPRIT THAT IS CAUSING THE FIRST CONUNDRUM IN
THE IS A TROUGH / WEAK UPPER LEVEL LOW THAT WILL BE MOVING SOUTHWARD
OUT OF THE PRAIRIE PROVINCES IN CANADA. GUIDANCE IS SPLIT ON THE
POSITION OF THIS FEATURE, WITH THE GFS HAVING THE SYSTEM FURTHER
WEST, FAR ENOUGH TO WEST TO BRING SOME CONVECTION TO AREAS EAST OF
THE DIVIDE. OTHER GUIDANCE KEEPS THE LOW FURTHER EAST AND THE AREA
LARGELY DRY. FOR NOW, WE COMPROMISED AND WENT WITH LOW END POPS
(ABOUT 1 OUT OF 5) FOR MUCH OF THE AREA EAST OF THE DIVIDE. THE
OTHER CONCERN IS THE SYSTEM MAY TIGHTEN THE PRESSURE GRADIENT A BIT
AND BRING SOME GUSTY WIND, MAINLY IN AREAS FAVORED BY NORTHWEST FLOW
(JOHNSON COUNTY, NORTHERN BIG HORN BASIN) BUT HIGH WIND IS NOT
EXPECTED. THIS SYSTEM COULD ALSO KEEP TEMPERATURES COOLER IN JOHNSON
AND NATRONA COUNTY IF IT IS FURTHER WEST. WITH THE UNCERTAINTY WE
LEFT CONTINUITY ALONE. BUT EVEN IF THE WESTERN SOLUTION VERIFIES,
MOST AREAS WILL BE RAIN FREE MOST OF THE TIME.
RIDGING THEN REALLY AMPLIFIES FOR THE WEEKEND. SATURDAY LOOKS LIKE A
DRY DAY WITH TEMPERATURES AVERAGING 5 TO 10 DEGREES ABOVE NORMAL.
THE HEAT WILL PEAK ON SUNDAY AS SOUTHWEST FLOW INCREASES AHEAD OF A
PAIR OF UPPER LEVEL LOWS, ONE APPROACHING FROM THE SOUTHWEST AND ONE
FROM THE NORTHWEST. THIS COULD BE THE DAY WE SEE OUR FIRST 90 DEGREE
HIGHS OF THE YEAR, ESPECIALLY IN THE WARMER LOCATIONS LIKE GREYBULL
AND WORLAND. AND, WITH THE FEW DAYS OF WARMER WEATHER, WE HAVE SOME
FLOODING CONCERNS. WE STILL HAVE A DECENT AMOUNT OF SNOW ABOVE 9500
FEET AND THE WARM TEMPERATURES THIS WEEKEND COULD MELT THIS OUT AND
RAISE LEVELS ON CREEKS AND STREAMS. THE CHANCE OF CONVECTION WILL
ALSO RETURN, WITH SHOWERS AND THUNDERSTORMS POSSIBLE ACROSS THE
NORTHERN PORTIONS OF THE AREA.
AS WE HEAD INTO THE NEXT WEEK, WE HAVE SOME THINGS WE ARE FAIRLY
CONFIDENT IN A COOLER AND WETTER PATTERN AS WE COME UNDER THE
INFLUENCE OF THE TWO UPPER LEVEL LOWS. WE STILL HAVE VERY LOW
CONFIDENCE IN DETAILS OF THE PLACEMENT AND AMOUNTS OF POTENTIAL
PRECIPITATION. UPPER LEVEL LOWS ARE VERY FICKLE IN MOVEMENT AND THE
FACT WE HAVE TWO OF THEM MAKES IT EXPONENTIALLY HARDER TO PREDICT.
THIS COULD BE A RATHER WET PERIOD THOUGH. NBM ENSEMBLE GUIDANCE
SHOWS AT LEAST A 1 IN 2 CHANCE OF ALL LOCATIONS FOR A HALF AN INCH
OF RAIN FROM MONDAY MORNING THROUGH WEDNESDAY NIGHT WITH THE
NORTHERN HALF OF THE AREA HAVING A 1 OUT OF 2 CHANCE OF AN INCH OR
MORE THROUGH THE SAME TIME PERIOD. IN ADDITION, THE MOUNTAINS MAY
HAVE THE CHANCE FOR SOME SNOW. THE 700 MILLIBAR TEMPERATURES MAY
FALL AS LOW AS MINUS 1 ON MONDAY NIGHT OVER THE BIGHORNS WHICH COULD
LOWER SNOW LEVELS AS LOW AS 8000 TO 8500 FEET.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 459 AM MDT THU MAY 29 2025
FOG CONTINUES TO FLUCTUATE AROUND KCPR THIS MORNING, WITH VIS
REMAINING BELOW 1SM THROUGH 14Z. THIS FOG SHOULD BE BURNING OFF
QUICKLY BEYOND THAT. ALL SITES THEN REMAIN MOSTLY SUNNY THROUGH
THE DAY, WITH LIGHT WINDS EXPECTED. SOME SHOWER AND
THUNDERSTORM ACTIVITY MAY BUILD ALONG THE HIGHER ELEVATIONS,
WHICH MAY PRODUCE SOME LOCALLY GUSTY WINDS AT NEARBY TAF SITES
(KCOD/KLND/KBPI/KPNA). KCOD REMAINS THE BEST POSSIBILITY FOR
GUSTS, SO HAVE KEPT BRIEF WIND SHIFT THERE AROUND 00Z. SIGNAL
FOR AND FOG FORMATION REMAINS VERY LOW OVERNIGHT TONIGHT, SO ALL
SITES WILL BE NEARLY CLEAR WITH LIGHT WINDS.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HATTINGS
AVIATION...STRAUB
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