327
FXUS65 KRIW 190755
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
155 AM MDT THU JUN 19 2025
KEY MESSAGES
- CRITICAL FIRE WEATHER CONDITIONS DEVELOP THURSDAY AND CONTINUE
THROUGH SATURDAY AS A RESULT OF HOT, DRY, AND WINDY CONDITIONS
ACROSS THE REGION. WIND GUSTS UP TO 45 MPH FRIDAY AND
SATURDAY.
- VERY POOR OVERNIGHT RH RECOVERIES, PARTICULARLY ACROSS
SOUTHWEST WY, WILL EXACERBATE CRITICAL FIRE WEATHER CONDITIONS
THROUGH SATURDAY.
- A COLD FRONT BRING SOME RELIEF TO THE HOT TEMPERATURES
SATURDAY TO THE WEST, AND BY SUNDAY TO OTHER PARTS OF THE
REGION. SOME PRECIPITATION IS POSSIBLE AS WELL, BUT THERE ARE
STILL A LOT OF UNCERTAINTIES WITH AMOUNTS AND TIMING.
- FREEZING TEMPERATURES EXPECTED OVER THE WESTERN MOUNTAINS,
WESTERN VALLEYS AND THE UPPER GREEN RIVER BASIN SATURDAY NIGHT
AND SUNDAY NIGHT.
DISCUSSION
ISSUED AT 130 AM MDT THU JUN 19 2025
THE AXIS OF A STRONG RIDGE WILL BE OVER THE COWBOY STATE TODAY,
LEADING TO 90 DEGREE TEMPERATURES FOR MANY LOCATIONS ACROSS THE CWA,
WITH A FEW LOCATIONS FLIRTING WITH TYING OR BREAKING RECORD HIGHS.
ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS WILL BE IN PLACE ACROSS
MUCH OF THE AREA AS WELL, WITH RH VALUES DROPPING AS LOW AS 9
PERCENT. SOUTHWEST WINDS, WITH GUSTS OF 25 TO 35 MPH, WILL BE FAIRLY
WIDESPREAD, WITH THE STRONGER WINDS OCCURRING OVER NORTHWESTERN
PORTIONS. THIS WILL BE DUE TO A SHORTWAVE MOVING OVER THE AREA. THE
HRRR CONTINUES TO BE THE MORE BULLISH SOLUTION, DEPICTING WIDE
SWATHS OF GUSTS AROUND 35 MPH PUSHING INTO THE WIND RIVER AND
BIGHORN BASINS. WILL LEAVE THIS SOLUTION OUT OF THE FORECAST FOR
NOW, BUT AN INTERESTING TREND TO WATCH. THERE IS AN INCREASED THREAT
FOR HIGH-BASED (MAINLY VIRGA) THUNDERSTORMS IN THE AFTERNOON ACROSS
AREAS EAST OF THE DIVIDE. THESE STORMS WILL BE FAIRLY ISOLATED, WITH
THE BIGHORN BASIN, BIGHORN MOUNTAINS AND JOHNSON COUNTY HAVING THE
BEST CHANCES (20-30%). THE MAIN IMPACT FROM THESE STORMS WILL BE
WIND GUSTS UP TO 60 MPH, DUE TO THE LARGE (50-60) DEWPOINT
DEPRESSIONS.
SIMILAR CONDITIONS RETURN FRIDAY, WITH THE STRONGER GUSTS OF 30 TO
40 MPH BEING MORE WIDESPREAD ACROSS THE SOUTH AND NATRONA COUNTY. BY
SATURDAY, THESE CONDITIONS SPREAD INTO THE BIGHORN BASIN AND
SOUTHERN JOHNSON COUNTY. WIND GUSTS OF 25 TO 45 MPH WILL BE
WIDESPREAD ACROSS THE FORECAST AREA, WITH THE EXCEPTION OF FAR
NORTHERN PORTIONS OF JOHNSON COUNTY AND THE BIGHORN BASIN. WINDS
LOOK TO STAY FAIRLY LIGHT HERE. THIS WILL BE DUE TO A DIGGING
LONGWAVE TROUGH WITH A CLOSED LOW OVER THE PACNW AND A DOMINANT HIGH
CENTER OVER THE LOWER MISSISSIPPI VALLEY (THIS HIGH WILL GRADUALLY
MOVE OVER THE TN/OH VALLEYS BY SATURDAY AND REMAIN IN PLACE INTO
EARLY NEXT WEEK). THIS WILL, IN TURN, STRENGTHEN THE PRESSURE
GRADIENT OVER THE COWBOY STATE AND LEAD TO THE HIGHER WINDS. BURNING
OF ANY KIND IS HIGHLY DISCOURAGED TODAY THROUGH SATURDAY! FAR
WESTERN PORTIONS WILL HAVE SOME RELIEF FROM THE HOT TEMPERATURES AS
A COLD FRONT ASSOCIATED WITH THE CLOSED LOW WILL MOVE OVER THE AREA
LATE FRIDAY NIGHT/EARLY SATURDAY MORNING, RESULTING IN HIGH
TEMPERATURES IN THE 70S. THE FRONT WILL BECOME STATIONARY OVER
WESTERN AND FAR NORTHERN PORTIONS, HOWEVER TEMPERATURES WILL STILL
BE 5 TO 10 DEGREES COOLER FOR MANY LOCATIONS AS THE RIDGE SHIFTS
EASTWARD AND THE LONGWAVE TROUGH HAVING A GREATER INFLUENCE OVER THE
REGION. CRITICAL FIRE WEATHER CONDITIONS WILL BE MAINLY CONFINED TO
THE WIND CORRIDOR (FROM THE EASTERN HALF OF SWEETWATER COUNTY TO
NATRONA COUNTY) SATURDAY AFTERNOON. PRECIPITATION CHANCES ARE STILL
PROGGED TO REMAIN OVER NORTHERN PORTIONS SATURDAY NIGHT LIKELY DUE
TO MOST OF THE AVAILABLE MOISTURE BEING AROUND THE CLOSED LOW.
FREEZING TEMPERATURES WILL RETURN SATURDAY NIGHT OVER THE WESTERN
MOUNTAINS, THE WESTERN VALLEYS AND UPPER GREEN RIVER BASIN,
IMPACTING LOCATIONS SUCH AS, JACKSON, AFTON, BIG PINEY, PINEDALE AND
HOBACK JUNCTION. THIS COULD RESULT IN SOME SNOW IN YELLOWSTONE.
THE FRONT WILL PROGRESS EASTWARD DURING THE DAY SUNDAY, POSSIBLY
REACHING CASPER AND RIVERTON BY 00Z MONDAY. TEMPERATURES WILL STILL
BE 10 TO 15 DEGREES COOLER AS THE FRONT MOVES THROUGH AND
PRECIPITATION CHANCES STAY OVER THE NORTH. NEEDLESS TO SAY, FIRE
WEATHER CONDITIONS WILL NOT BE AS EXTENSIVE AND WILL BE CONFINED
OVER SOUTHERN PORTIONS. THE BELOW NORMAL TEMPERATURES LOOK TO
CONTINUE INTO MONDAY AS THE LONGWAVE TROUGH REMAINS IN PLACE ACROSS
THE INTERMOUNTAIN WEST. THIS WILL BE A NICE REPRIEVE FOR THIS TIME
OF YEAR, WITH HIGHS IN THE 70S. THE NEXT CHANCE FOR WIDESPREAD
PRECIPITATION COULD ARRIVE ON TUESDAY, AS THE AFOREMENTIONED
DOMINANT HIGH PRESSURE KEEPS THE GULF OPEN AND A STRONG SOUTHERLY
FLOW OCCURS BETWEEN IT AND THE LONGWAVE TROUGH.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 945 PM MDT WED JUN 18 2025
VFR CONDITIONS EXPECTED THROUGHOUT THE ENTIRE PERIOD FOR ALL TAF
SITES. CLEAR SKIES AND LIGHT WINDS OVERNIGHT UNDER A WEAK
INVERSION. INCREASING WINDS AFTER 17-19Z WITH DAYTIME HEATING
AND STRONGER MIXING TO THE SURFACE. 25-30KT GUSTS WEST OF THE
DIVIDE TO GO ALONG WITH KRIW, WITH ALL OTHER SITES SLIGHTLY
LOWER GUSTS UP TO 18KTS AND HIGHEST AT KRKS UP TO 30KTS. WINDS
DECREASE AFTER AROUND 02Z TOWARDS SUNSET WITH RADIATIONAL
COOLING AS THE SCATTERED UPPER LEVEL CLOUDS CLEAR OUT INTO THE
OVERNIGHT HOURS INTO FRIDAY MORNING. OTHERWISE, POSSIBLE
THUNDERSTORM CHANCES FOR FURTHER NORTH AROUND KCOD BETWEEN
21-00Z. ALTHOUGH, CONFIDENCE IS NOT AS HIGH (20-30%), A PROB30
GROUP WILL BE CARRIED DURING THAT 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.
DISCUSSION...LAVOIE
AVIATION...LOWE
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