675
FXUS65 KRIW 171512
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
912 AM MDT WED JUN 17 2026
KEY MESSAGES
- WIDESPREAD ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS ARE
ANTICIPATED TODAY DUE TO WIND GUSTS OF 30 TO 40 MPH AND
HUMIDITY AS LOW AS 10 PERCENT.
- SEASONAL TEMPERATURES THURSDAY WARM SEVERAL DEGREES ON FRIDAY
AHEAD OF AN INCOMING PACIFIC WEATHER SYSTEM. DRY CONDITIONS
PREVAIL BOTH DAYS ALONG WITH A BREEZY WEST WIND OVER THE
HIGH DESERTS OF SOUTHWESTERN WYOMING.
- PRECIPITATION CHANCES RETURN FOR THE WEEKEND, WITH AREAS OF
NORTHERN WYOMING THE MOST LIKELY TO SEE SCATTERED SHOWERS AND
THUNDERSTORMS.
DISCUSSION
ISSUED AT 315 AM MDT WED JUN 17 2026
A COLD FRONT IS CURRENTLY PROGRESSING SOUTHWARD OVER AREAS EAST OF
THE DIVIDE, HAVING ALREADY REACHED WORLAND AND THE NORTHERN HALF OF
JOHNSON COUNTY. VERY WEAK SHOWERS ALSO CONTINUE OVER NORTHERN
JOHNSON COUNTY AND ARE EXPECTED TO END IN THE NEXT HOUR OR SO. THE
FRONT WILL CONTINUE SOUTHWARD, REACHING CASPER AND RIVERTON AROUND
09Z/10Z THIS MORNING, AND REACH THE DIVIDE BY SUNRISE. THE
SURFACE PRESSURE GRADIENT WILL TIGHTEN, ESPECIALLY WEST OF THE
DIVIDE, IN RESPONSE TO THE FRONT. GUSTY NORTH TO NORTHWEST
WINDS, WITH GUSTS OF 30 TO 45 MPH, WILL CONTINUE OVER NORTHERN
PORTIONS IN THE WAKE OF THE FRONT. THESE AREAS ARE PRONE TO
THESE POST- FRONTAL CONDITIONS OF HIGHER WINDS. ADDITIONALLY,
NORTHWEST WINDS WILL INCREASE OVER SOUTHERN PORTIONS, INCLUDING
THE UPPER GREEN RIVER BASIN, WITH GUSTS OF 25 TO 35 MPH AFTER
15Z. WINDS WILL CONTINUE TO INCREASE ACROSS THE CWA, WITH GUSTS
OF 30 TO 40 MPH RETURNING FOR MOST AREAS AFTER 18Z. SHOWERS AND
ISOLATED THUNDERSTORMS WILL BE POSSIBLE OVER NORTHERN PORTIONS
BETWEEN 21Z AND 06Z, AS AN AREA OF CHANNELED VORTICITY MOVES
OVER THE AREA FROM THE NORTHWEST. ELEVATED TO CRITICAL FIRE
WEATHER CONDITIONS WILL BE IN PLACE AGAIN THIS AFTERNOON DUE TO
THE WINDS AND GENERALLY DRY CONDITIONS. HOWEVER, TEMPERATURES
WILL BE COOLER ACROSS THE CWA WITH AREAS EAST OF THE DIVIDE 5 TO
15 DEGREES COOLER DUE TO THE COLD FRONT. SOUTHERN PORTIONS WILL
BE AT THE MOST RISK, WITH THE WIDESPREAD NORTHWEST WINDS
GUSTING UP TO 40 MPH AND CRITICAL RH VALUES AS LOW AS 10%.
CONDITIONS WILL REMAIN MORE SEASONAL THURSDAY, WITH WINDS NOT BEING
SO STRONG. GUSTS UP TO 30 MPH LOOK TO BE CONFINED OVER AREAS WEST OF
THE DIVIDE IN THE AFTERNOON. A RIDGE LOOKS TO BUILD OVER THE REGION
FROM THE WEST FRIDAY, MARKING A RETURN FOR TEMPERATURES IN THE UPPER
80S AND LOWER 90S. FIRE WEATHER CONDITIONS WILL CONTINUE TO BE
ELEVATED TO CRITICAL ON THESE DAYS, WITH CRITICAL RH VALUES (<15%)
OCCURRING ACROSS MUCH OF THE CWA BY FRIDAY. CHANCES FOR
PRECIPITATION RETURN FOR THE WEEKEND, AS THE REMNANTS OF A PACIFIC
LOW MOVE OVER THE REGION. FOR NOW, THE NORTHERN HALF OF THE CWA
LOOKS TO HAVE THE BEST CHANCES TO RECEIVE ANY PRECIPITATION WITH
RAINFALL AMOUNTS OF 0.30" TO 0.60" CURRENTLY IN THE FORECAST OVER
THESE 2 DAYS. LOCALLY HEAVY RAIN COULD OCCUR FROM THESE STORMS, AS
PRECIPITABLE WATER VALUES OF 0.60" TO 1" ARE FORECASTED.
PRECIPITATION CHANCES COULD LINGER INTO MONDAY, AS THE SYSTEM IS
SLOW TO MAKE IT OVER THE CENTRAL PLAINS. A SLOWER SYSTEM LIKE THIS
COULD INCREASE THE CHANCES FOR PRECIPITATION AND PROVIDE SOME MUCH
NEEDED RAINFALL ACROSS THE AREA.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 448 AM MDT WED JUN 17 2026
SKC SKIES THIS MORNING ACROSS THE AREA TO START THE FORECAST, AS
A COLD FRONT REACHES THE DIVIDE AND BECOMES STATIONARY.
TERMINALS EAST OF THE CONTINENTAL DIVIDE SEE A POST- FRONTAL
NORTHERLY WIND STEADILY INCREASE BETWEEN 15Z AND 19Z AND LINGER
THROUGH MUCH OF WEDNESDAY EVENING. SHORTWAVE ENERGY, COMBINED
WITH FAVORABLE 700/500MB LAYER MOISTURE, GENERATES SOME LIGHT
SHOWERS AND INCREASED CLOUD COVER ACROSS NORTHERN WYOMING LATE
IN THE AFTERNOON AND INTO THE EVENING. CONFIDENCE REMAINS TOO
LOW TO INCLUDE A PROB30 GROUP FOR KCOD/KWRL. MOUNTAIN TOP
OBSCURATIONS WILL BE COMMON OVER THE BIGHORNS AS A RESULT OF
THESE INCREASED CLOUDS. WEST OF THE DIVIDE TERMINALS SEE WIND
GUSTS 25-35KT DEVELOP BETWEEN 14Z AND 18Z. THESE TERMINALS SEE
WIND DIMINISH WITH THE SETTING SUN AROUND 03Z.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON SMOKE, ICING, AND TURBULENCE FORECASTS.
FIRE WEATHER
ISSUED AT 315 AM MDT TUE JUN 16 2026
A DRY COLD FRONT IS MOVING OVER AREAS EAST OF THE DIVIDE EARLY
THIS MORNING AND WILL REACH THE DIVIDE BY SUNRISE. POST-FRONTAL
WINDS OVER NORTHERN ZONES WILL BRIEFLY DECREASE AFTER SUNRISE,
INCREASING AGAIN AFTER 0900. AT THE SAME TIME, NORTHWEST WINDS
OVER ZONES 277/278/279 WILL BEGIN TO INCREASE. GUSTS OF 30 TO
40 MPH WILL BE WIDESPREAD ACROSS THE FORECAST AREA AFTER 1200.
RH VALUES WILL BE CRITICAL ACROSS THE SOUTH, AND PORTIONS OF THE
WIND RIVER BASIN, AS THE FRONT IS EXPECTED TO BE STATIONARY
ALONG THE DIVIDE THROUGH THE DAY TODAY.
ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS CONTINUE THURSDAY,
WITH CRITICAL RH VALUES ACROSS SOUTHERN ZONES, AS WELL AS ZONES
280 AND 283. WEST-NORTHWEST WINDS, WITH GUSTS UP TO 30 MPH WILL
BE CONFINED TO AREAS WEST OF THE DIVIDE IN THE AFTERNOON. THERE
IS A 10 TO 20% CHANCE FOR WIND GUSTS OVER 25 MPH TO OCCUR OVER
PORTIONS OF ZONE 280.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...LAVOIE
AVIATION...CNJ/LAVOIE
FIRE WEATHER...LAVOIE
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