021
FXUS65 KRIW 170921
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
321 AM MDT WED JUN 17 2026
KEY MESSAGES
- A DRY COLD FRONT CONTINUES TO MOVE SOUTHWARD THIS MORNING,
LEADING TO COOLER HIGHS TODAY. AREAS EAST OF THE CONTINENTAL
DIVIDE WILL BE 5 TO 15 DEGREES COOLER.
- SEASONAL TEMPERATURES THURSDAY WARM SEVERAL DEGREES 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 SFC
PRESSURE GRADIENT WILL TIGHTEN, ESPECIALLY WEST OF THE DIVIDE, IRT
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 /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 959 PM MDT TUE JUN 16 2026
TERMINALS ACROSS WESTERN AND CENTRAL WYOMING REMAIN VFR THROUGH THE
FORECAST PERIOD, WITH THE PRIMARY HAZARD REMAINING GUSTY WIND. EVEN
WITH WIND DECREASING SLIGHTLY LATE TUESDAY EVENING, THE APPROACH OF
A COLD FRONT PASSING THROUGH NORTHERN WYOMING OVERNIGHT WILL KEEP
WINDS GUSTY OVERNIGHT. TERMINALS EAST OF THE CONTINENTAL DIVIDE SEE
A POST-FRONTAL NORTHERLY WIND STEADILY INCREASE DURING THE DAY 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 WEDNESDAY AFTERNOON AND EVENING. WEST OF THE DIVIDE
TERMINALS SEE WIND GUSTS 25-35KTS DEVELOP 14Z-17Z/WEDNESDAY,
EXCEPT KJAC WHERE WINDS MIX CLOSER TO 18Z. THESE TERMINALS SEE
WIND DIMINISH WITH THE SETTING SUN AROUND 03Z/THURSDAY.
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
FIRE WEATHER...LAVOIE
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