461
FXUS65 KRIW 091043
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
443 AM MDT WED SEP 9 2026
KEY MESSAGES
- ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS PERSIST FOR
PORTIONS OF MAINLY CENTRAL AND SOUTHWEST WYOMING THIS WEEK DUE
TO GUSTY AFTERNOON WEST TO NORTHWEST WIND 25 TO 40 MPH AND
MINIMUM RELATIVE HUMIDITY IN THE TEENS.
- FREEZING TEMPERATURES OCCUR ACROSS THE WESTERN VALLEYS AND
BASINS EARLY WEDNESDAY MORNING, WITH THE COLDEST LOCATIONS
SEEING LOWS BETWEEN 24 AND 28. SENSITIVE OUTDOOR PLANTS ARE
LIKELY TO BE IMPACTED BY TEMPERATURES BELOW 28 DEGREES.
- DAYTIME HIGH TEMPERATURES REMAIN NEAR SEASONAL NORMALS
THROUGH THE WEEK, WITH MINIMAL CHANCES FOR RAIN.
- CONFIDENCE CONTINUES TO INCREASE FOR A STORM SYSTEM TO ARRIVE
THIS WEEKEND. AN INITIAL COLD FRONT PUSHES ACROSS THE REGION
FRIDAY AFTERNOON AND EVENING, SETTING THE STAGE FOR COOLER AND
WETTER WEATHER SATURDAY AND SUNDAY.
DISCUSSION
ISSUED AT 223 AM MDT WED SEP 9 2026
A FREEZE WARNING REMAINS IN EFFECT FOR THE WESTERN VALLEYS, THE
UPPER GREEN RIVER BASIN AND SOUTHERN LINCOLN COUNTY THIS MORNING.
TEMPERATURES OF 26 TO 32 DEGREES ARE EXPECTED AGAIN IN THESE AREAS,
WITH MORE COLD PRONE LOCATIONS POSSIBLY DROPPING AS LOW AS 22
DEGREES.
OTHERWISE, DRY CONDITIONS, CLEAR SKIES AND SEASONAL TEMPERATURES
WILL BE IN THE FORECAST AGAIN TODAY. THE MAIN HAZARD WILL ONCE AGAIN
BE FIRE WEATHER. THE LIGHTEST WINDS OF THE WEEK ARE EXPECTED TODAY,
HOWEVER ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS WILL BE IN PLACE
DUE TO CRITICALLY LOW RH VALUES AND WIND GUSTS UP TO 25 MPH. THESE
WINDS WILL BE PRIMARILY LOCATED FROM SOUTHERN LINCOLN COUNTY TO
NATRONA COUNTY THROUGH THE AFTERNOON. THE FIRE WEATHER WATCH THAT
WAS ISSUED FOR THESE AREAS HAS BEEN UPGRADED TO RED FLAG WARNINGS AS
A RESULT. HAVE ALSO EXTENDED THESE NEW WARNINGS INTO THURSDAY.
BURNING OF ANY KIND IS HIGHLY DISCOURAGED DUE TO THE VERY DRY
CONDITIONS, REGARDLESS OF HOW LIGHT THE WINDS MIGHT BE.
CRITICAL FIRE WEATHER CONDITIONS WILL BECOME MORE WIDESPREAD ACROSS
THE CWA AGAIN THURSDAY, AS WINDS INCREASE. WIND GUSTS OF 25 TO 35
MPH WILL RETURN FOR MOST AREAS IN THE AFTERNOON. EXCEPTIONS WILL BE
FOR LOCATIONS LIKE EASTERN PORTIONS OF THE BIGHORN BASIN AND
NORTHERN PORTIONS OF JOHNSON COUNTY. THESE WINDS WILL RETURN FOR
FRIDAY AFTERNOON AS WELL. THE MAIN DIFFERENCE WILL BE ANOTHER DRY
COLD FRONT WILL MOVE ACROSS NORTHERN AREAS EAST OF THE DIVIDE.
INITIAL INDICATIONS ARE THIS FRONT WILL BECOME STATIONARY ALONG
SOUTHERN PORTIONS OF THE BIGHORN BASIN AND JOHNSON COUNTY BY MIDDAY
FRIDAY. MODELS REMAIN SPLIT WHETHER THE FRONT WILL PUSH FURTHER
SOUTHWARD THROUGH THE OVERNIGHT HOURS FRIDAY AND ALLOW FOR THE
ASSOCIATED COLD POOL TO INFILTRATE INTO THE BIGHORN BASIN AND
JOHNSON COUNTY.
MOISTURE WILL BEGIN TO INCREASE SATURDAY AHEAD OF THE INCOMING STORM
SYSTEM, WITH THE WESTERN MOUNTAINS AND CENTRAL PORTIONS OF THE CWA
HAVING THE BEST CHANCES FOR PRECIPITATION SATURDAY AFTERNOON INTO
SATURDAY NIGHT. SNOW LEVELS WILL STAY AROUND 10KFT THROUGH THE
NIGHT, SO HUNTERS/BACKCOUNTRY ENTHUSIASTS SHOULD PREPARE FOR SNOW.
THE STORM ITSELF WILL MOVE OVER THE COWBOY STATE DURING THE DAY
SUNDAY, WITH THE COLDEST AIR STAYING OVER NORTHWESTERN PORTIONS.
SNOW LEVELS WILL RANGE BETWEEN 7000 AND 8500FT IN THIS AREA AND MOST
OF THE PRECIPITATION WILL STAY OVER NORTHERN PORTIONS OF THE STATE.
FREEZING TEMPERATURES WILL RETURN TO WESTERN PORTIONS MONDAY AND
TUESDAY MORNINGS IN THE WAKE OF THIS SYSTEM, WITH READINGS IN THE
MIDDLE 30S TO LOWER 40S ELSEWHERE. MONDAY WILL BE A CRISP AUTUMN
DAY, WITH HIGHS IN THE 60S TO NEAR 70S DEGREES UNDER MOSTLY CLEAR
SKIES.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 440 AM MDT WED SEP 9 2026
ALL TERMINALS TO BE VFR/SKC THROUGH THE ENTIRE FORECAST PERIOD
WITHIN DRY WEST-NORTHWEST ALOFT. LITTLE MORE THAN LATE DAY
FEW MID- CLOUD OVER THE FAR NORTH. WIND SPEEDS ARE LESS THAN
10KT BEFORE DAYTIME MIXING ALLOWS FOR WESTERLY SURFACE 11-22KT
TO INCREASE BETWEEN 19Z-21Z AT KCPR AND TERMINALS WEST OF THE
CONTINENTAL DIVIDE. KRKS WILL LIKELY SEE AFTERNOON GUSTS
25-30KT. SOME LATE DAY 9-13KT WEST- NORTHWEST WINDS SURFACE FOR
A FEW HOURS AT KRIW AND KLND. ALL WINDS DECREASE BETWEEN
01Z-03Z/THURSDAY AS THE ATMOSPHERE DECOUPLES.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZLC AND ZDV FOR
THE LATEST INFORMATION ON SMOKE, ICING, AND TURBULENCE FORECASTS.
FIRE WEATHER
ISSUED AT 230 AM MDT MON SEP 7 2026
FIRE WEATHER WATCHES IN ZONES 277/278/279 HAVE BEEN UPGRADED TO
RED FLAG WARNINGS AND HAVE BEEN EXTENDED INTO THURSDAY. WINDS
WILL BE THE LIGHTEST ACROSS THE AREA TODAY, WITH GUSTS OF 25 MPH
OCCURRING FROM ZONE 277 TO 280/300 AND THE MOUNTAIN ZONES 285,
286 AND 288. RH RECOVERY WILL BE FAIR TO POOR FOR MOST ZONES
TONIGHT. THE ONLY AREAS WILL GOOD RECOVERY WILL BE ZONES 140/278
AND THE JACKSON/STAR VALLEYS.
WINDS WILL INCREASE ACROSS THE AREA THURSDAY, WITH GUSTS OF 25
TO 35 MPH OCCURRING ACROSS MOST ZONES. THE EXCEPTIONS WILL BE
ZONES 275, 282 AND THE NORTHERN HALF OF 281. RH RECOVERY WILL BE
FAIR TO POOR AGAIN FOR MOST AREAS AGAIN THURSDAY NIGHT. ANOTHER
COLD FRONT WILL MOVE OVER NORTHERN WY FRIDAY MORNING AND LOOKS
TO BECOME STATIONARY ALONG SOUTHERN PORTIONS OF THE BIGHORN
BASIN AND ZONE 281 BY MIDDAY. WIND GUSTS OF 25 TO 35 MPH WILL
ONCE AGAIN BE WIDESPREAD, HOWEVER RHS ARE FORECASTED TO BE JUST
ABOVE THE CRITICAL THRESHOLD.
RIW WATCHES/WARNINGS/ADVISORIES
FREEZE WARNING UNTIL 9 AM MDT THIS MORNING FOR WYZ013-023-
025>027.
RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT THURSDAY FOR
WYZ277>279.
RED FLAG WARNING UNTIL 9 PM MDT THURSDAY FOR WYZ280-289-300.
DISCUSSION...LAVOIE
AVIATION...CNJ/LAVOIE
FIRE WEATHER...LAVOIE
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