341
FXUS65 KRIW 101800
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1200 PM MDT FRI JUL 10 2026
KEY MESSAGES
- WARMING TREND STARTS THIS AFTERNOON WITH A FEW ISOLATED
THUNDERSTORMS FOR WESTERN MOUNTAINS OF TETONS/NORTHERN
WINDS/SOUTHERN ABSAROKAS.
- VERY HOT AND RECORD BREAKING TEMPERATURES ARRIVE ON SATURDAY
AND CONTINUE INTO MONDAY AND POSSIBLY TUESDAY. THE HOTTEST
TEMPERATURES ARE EXPECTED ON SUNDAY.
- A COMBINATION OF VERY HOT TEMPERATURES, VERY LOW HUMIDITY AND
BREEZY CONDITIONS MAY BRING CRITICAL FIRE WEATHER SUNDAY AND
MONDAY AFTERNOONS.
UPDATE
ISSUED AT 1200 PM MDT FRI JUL 10 2026
FORECAST STILL ON TRACK FOR THE WELL ABOVE AVERAGE AND HOT
TEMPERATURES OVER THE WEEKEND AND INTO EARLY NEXT WEEK. IR
STARTING TO SHOW SOME BUILDING CLOUD TOPS ACROSS THE
TETONS/NORTHERN WINDS/SOUTHERN ABSAROKAS THAT WILL SEE SOME
ISOLATED STORMS THROUGH THE AFTERNOON HOURS AFTER AROUND 3PM
FOR THESE AREAS. MORE SCATTERED AFTER 6PM BUT DIMINISH QUICKLY
TOWARDS SUNSET LOSING DAYTIME HEATING. MAIN THREAT WILL BE SOME
GUSTY OUTFLOW WINDS, BUT NOT LOOKING STRONG AS IT HAS BEEN BEING
ON THE OTHER SIDE OF THE DIVIDE AS WELL.
DISCUSSION
ISSUED AT 245 AM MDT FRI JUL 10 2026
WE ARE NOW TRANSITIONING FROM THUNDERSTORMS BEING THE EMPHASIS TO
HEAT BEING TO EMPHASIS. THE RADAR IS QUIET RIGHT NOW, AND SHOULD BE
THROUGH MOST OF THE MORNING. HOWEVER, THERE IS JUST ENOUGH
INSTABILITY AND MID LEVEL MOISTURE FOR SOME ISOLATED CONVECTION THIS
AFTERNOON, MAINLY IN AND NEAR THE WESTERN MOUNTAINS. THESE WOULD BE
VERY ISOLATED, WITH CHANCES GENERALLY LESS THAN 1 OUT OF 5 AT ANY
GIVEN LOCATION. AND GIVEN THE DRY LOW LEVELS, THE MAIN THREAT FROM
ANY SHOWER OR STORM WOULD BE THOSE STRONG WIND GUSTS THAT ARE
UBIQUITOUS WITH JULY CONVECTION IN WYOMING. ANY STORMS WOULD END
FAIRLY QUICKLY THIS EVENING. TEMPERATURES WILL ALSO BE WARMING
TODAY. IT WILL BE HOT, BUT THE TYPE OF HOT WE SEE EVERY JULY IN
WESTERN AND CENTRAL WYOMING.
THE HEAT WILL REALLY RAMP UP ON SATURDAY AS THE DEATH RIDGE OVER THE
DESERT SOUTHWEST MOVES NORTHWARD TOWARD THE NORTHERN ROCKIES. THE
500 MILLIBAR HEIGHTS WILL CLIMB AS HIGH AS 5970 METERS ON SATURDAY
AFTERNOON, BRINGING A VERY HOT TODAY. MOST LOCATIONS BELOW 5500 FEET
HAVE AT LEAST A 1 IN 2 CHANCE OF HIGH TEMPERATURES OF 100 DEGREES OR
HIGHER, WITH ELEVATIONS BELOW 7000 FEET HAVING A NEARLY 100 PERCENT
CHANCE OF HIGHS OVER 90 DEGREES. HUMIDITY WILL BE LOW ON THIS DAY AS
WELL, WITH WIDESPREAD RELATIVE HUMIDITY FALLING INTO THE SINGLE
DIGITS IN THE LOWER ELEVATIONS. HOWEVER, THE PEAK OF THE HEAT IS
STILL LOOKING TO BE ON SUNDAY. THE CENTER OF THE HEAT DOME SHOULD BE
CENTERED OVER WYOMING ON THIS DAY, WITH 500 MILLIBAR HEIGHTS RISING
AS HIGH AS 6000 METERS. AT THE SAME TIME, 700 MILLIBAR TEMPERATURES
CLIMB AS HIGH AS 23 DEGREES CELSIUS. AT THIS IS A RECIPE FOR VERY
HOT TEMPERATURES, WITH SOME MONTHLY AND ALL TIME HIGH TEMPERATURES
POSSIBLY BEING SET DURING THIS AFTERNOON. LOCATIONS BELOW 6000 FEET
HAVE AT LEAST A 9 OUT OF 10 CHANCE OF HIGH TEMPERATURES OVER 100 ON
SUNDAY AFTERNOON. EVEN PLACES LIKE ROCK SPRINGS, FARSON AND EVEN
JACKSON HAVE A 1 IN 2 CHANCE OF BREAKING 100 DEGREES. THE CENTER OF
THE HEAT CONTINUES TO LOOK TO BE BIG HORN BASIN WHERE LOCATIONS FROM
THERMOPOLIS TO LOVELL HAVE AT LEAST A 9 OF 10 CHANCE OF HIGH
TEMPERATURES AT LEAST 105, AND THE HOTTEST LOCATIONS LIKE BASIN AND
GREYBULL HAVE A 3 OUT OF 5 CHANCE OF HIGH TEMPERATURES OF 110. THE
HEAT CONTINUES INTO MONDAY, ALTHOUGH WITH CENTER OF THE RIDGE MOVING
INTO THE NORTHERN PLAINS, IT MAY BE A FEW DEGREES COOLER. HOWEVER,
IT WILL STILL BE SIMILAR TO SATURDAY, WITH WIDESPREAD 100 DEGREE
TEMPERATURES BELOW 5500 FEET AND 90S BELOW 7000 FEET. TEMPERATURES
REMAIN VERY HOT INTO TUESDAY AS WELL, ALTHOUGH A FEW DEGREES COOLER
THAN ON MONDAY.
NOW ABOUT THE EXTREME HEAT WARNING. WE REALIZE THAT THE HEAT INDEX
WILL BE LOWER THAN THE TEMPERATURES, DUE TO THE HUMIDITY BEING VERY
LOW (BELOW 5 PERCENT AT TIMES). HOWEVER, DUE TO POSSIBLY HISTORIC
NATURE OF THE HIGH TEMPERATURES, WE DECIDED NOT TO SPLIT HAIRS AND
JUST UPGRADE EVERYTHING. IT WILL BE UNHEALTHY FOR A LOT OF PEOPLE
AND IMPACTS ARE MORE IMPORTANT THE RAW CRITERIA.
AS FOR OTHER THINGS, WE ALSO HAVE TO TALK ABOUT FIRE WEATHER.
HUMIDITY WILL BE VERY LOW THROUGH MONDAY, WITH MANY LOCATIONS SEEING
VALUES BELOW 10 PERCENT. HOWEVER, WIND IS EXPECTED TO REMAIN BELOW
CRITICAL LEVELS BOTH TODAY AND TOMORROW. THE MAIN DAY OF CONCERN
WOULD BE SUNDAY, WHEN A DECENT SOUTHWESTERLY BREEZE WILL DEVELOP.
THE STRONGEST WIND WOULD BE IN NORTHERN PORTIONS OF THE AREA,
ESPECIALLY THE BIGHORN BASIN WHERE SOME AREAS HAVE AT LEAST A 4 OUT
OF 5 CHANCE OF WIND GUSTS OVER 25 MPH. THIS COULD BRING CRITICAL
FIRE WEATHER TO THESE LOCATIONS WITH THE EXTREMELY LOW HUMIDITY AND
DRY FUELS. GUIDANCE IS STILL A LITTLE SPLIT ON THIS THOUGH. WE WE
HOLD OFF ON ANY FIRE WEATHER HIGHLIGHTS FOR NOW BUT WILL WATCH IT
CLOSELY. CONCERNS COULD LINGER INTO MONDAY AND POSSIBLY EVEN TUESDAY.
AS FOR CONVECTION, THE WARM TEMPERATURES ALOFT CAPPING THE
ATMOSPHERE AND LACK OF MOISTURE SHOULD KEEP THE AREA DRY THROUGH THE
WEEKEND. THE CHANCE RISES A BIT ON MONDAY AS GUIDANCE DOES SHOW SOME
WEAK EASTERLY FLOW AS THE CORE OF THE RIDGE MOVING EASTWARD
PROVIDING SOME UPSLOPE. MOISTURE IS STILL LACKING THOUGH. THE MAIN
CHANCE WOULD BE IN THE NORTHWESTERN MOUNTAINS BUT THE CHANCE IS LESS
THAN 1 OUT OF 10 AT THIS POINT. THE CHANCE DOES INCREASE A BIT ON
TUESDAY AS MOISTURE INCREASES A BIT BUT EVEN HERE THE CURRENT
FORECAST IS PROBABLY TOO WET GIVEN THE STILL WARM TEMPERATURES ALOFT
CAPPING THE ATMOSPHERE. CHANCES SHOULD INCREASE FOR THE MIDDLE OF
THE WEEK AS THE RIDGE SLOWLY WEAKENS AND INCREASING MOISTURE BRINGS
A BETTER CHANCE OF MAINLY DIURNAL CONVECTION INTO THE END OF THE
WEEK. TEMPERATURES SHOULD COOL OFF SOME FOR THE MIDDLE OF THE WEEK
BUT WILL REMAIN ABOVE NORMAL FOR MUCH OF NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1110 AM MDT FRI JUL 10 2026
VFR CONDITIONS PREVAIL THROUGH THE PERIOD, WITH WARM HIGH
TEMPERATURES TODAY OF ABOUT 90 DEGREES OR MORE. SOME ISOLATED
SHOWERS AND THUNDERSTORMS OCCUR ACROSS WESTERN WYOMING THIS
AFTERNOON. PROB30 GROUPS COVER THE 15 TO 30 PERCENT CHANCES, WITH
GUSTY OUTFLOW WINDS BEING THE MAIN HAZARD WITH ANY CONVECTION.
LIGHTER WINDS OCCUR OVERNIGHT, WITH A CLEAR TO MOSTLY CLEAR SKY.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
FIRE WEATHER
ISSUED AT 1200 PM MDT FRI JUL 10 2026
ELEVATED FIRE WEATHER FOR THIS AFTERNOON PUSHING TO NEAR
CRITICAL SATURDAY WITH WARMER TEMPERATURES AND LOWER RELATIVE
HUMIDITY VALUES. WINDS WILL REMAIN RELATIVELY LIGHT FOR BOTH
DAYS AROUND 10 TO 20 MPH. SUNDAY WILL SEE AN INCREASE IN WINDS,
WITH GUSTS OUT OF THE SOUTH TO SOUTHEAST UP TO 25 TO 35 MPH. AS
SUCH, A FIRE WEATHER WATCH HAS BEEN ISSUED FOR LATE SUNDAY
MORNING THROUGH LATE SUNDAY EVENING COUPLED WITH BEING THE
HOTTEST DAY OF THE NEXT FEW DAYS WITH WIDESPREAD TRIPLE DIGITS AND
LOWEST OF THE HUMIDITY VALUES NEARING THE 5 PERCENT MARK.
RIW WATCHES/WARNINGS/ADVISORIES
EXTREME HEAT WARNING FROM NOON SATURDAY TO 9 PM MDT MONDAY FOR
WYZ003>006-010-011-013-016>020-023-025>030.
FIRE WEATHER WATCH FROM SUNDAY MORNING THROUGH SUNDAY EVENING
FOR WYZ275-276-280>283.
UPDATE...LOWE
DISCUSSION...HATTINGS
AVIATION...WITTMANN
FIRE WEATHER...LOWE
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