414
FXUS65 KRIW 121012
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
412 AM MDT SUN JUL 12 2026
KEY MESSAGES
- THE HEAT WAVE CONTINUES TODAY, WITH THE HOTTEST TEMPERATURES
TODAY. SOME ALL TIME RECORD HIGH TEMPERATURES ARE LIKELY TO
BROKEN THIS AFTERNOON.
- ELEVATED TO CRITICAL FIRE WEATHER IS LIKELY THIS AFTERNOON
ACROSS MOST OF THE AREA WITH HUMIDITY FALLING AS LOW AS 4
PERCENT AND A GUSTY SOUTHERLY BREEZE DEVELOPING.
- WELL ABOVE NORMAL TEMPERATURES CONTINUE THROUGH TUESDAY.
FOLLOWING THAT, IT WON'T BE AS HOT WITH AN INCREASING CHANCE
OF SHOWERS AND THUNDERSTORMS.
DISCUSSION
ISSUED AT 136 AM MDT SUN JUL 12 2026
A RIDGE OF 5990 METERS AT 700 MILLIBARS IS NOW CENTERED OVER
WYOMING. AND, NO SURPRISE, IT IS BROUGHT A VERY HOT DAY
YESTERDAY, WITH NUMEROUS RECORDS SET. IF WE WERE TO COMPARE THE
HEAT THIS TO AN INTERNAL COMBUSTION ENGINE IN A CAR, WE WOULD BE
RUNNING AT AROUND 4000 TO 5000 RPMS, WITH THE ENGINE WORKING
HARD BUT NOT REALLY HARD. TODAY WILL BE THE DAY WE PUSH THE
ENGINE UP TO THE RED LINE, AND COULD BE ONE OF THE HOTTEST DAYS
WE HAVE SEEN IN MANY YEARS, ESPECIALLY IN CERTAIN PORTIONS OF
THE AREA. IT IS EVEN WARM RIGHT NOW. AS I WRITE THIS, IT IS
STILL 80 DEGREES AT OUR OFFICE AT 1 AM THIS MORNING.
GUIDANCE SHOWS 700 MILLIBAR TEMPERATURES CLIMBING AN AVERAGE OF 2
DEGREES HIGHER THAN YESTERDAY, TOPPING OUT AT AROUND 23 DEGREES
CELSIUS. THIS TRANSLATES INTO TEMPERATURES AN AVERAGE OF 3 TO 5
DEGREES HIGHER THAN YESTERDAY. ENSEMBLE GUIDANCE IS GIVING A NEARLY
10 PERCENT CHANCE OF HIGH TEMPERATURES OVER 100 DEGREES BELOW 6000
FEET WITH LOCATIONS BELOW 7500 FEET HAVING A NEARLY 100 PERCENT
CHANCE OF OVER 90 DEGREES. MOST LOCATIONS BELOW AROUND 4800 FEET
HAVE AT LEAST A 4 OUT OF 5 CHANCE OF HIGH TEMPERATURES OF 105
DEGREES OR HIGHER, ESPECIALLY THE EASTERN HALF OF THE BIG HORN
BASIN, WHICH HAS A GREATER THAN 9 OUT OF 10 CHANCE. WHEN WE BUMP IT
UP TO 110, MOST OF THE STRETCH FROM THERMOPOLIS TO LOVELL HAS AT
LEAST A 1 IN 3 CHANCE, WITH THE HIGHEST CHANCE FROM BASIN TO EAST OF
LOVELL IN THE LOWER ELEVATIONS, AS HIGH AS 2 OUT 3 OF 110 DEGREES OF
HIGHER. I HAVE POSTED SOME FACTS ABOUT THE TEMPERATURES AND
POTENTIAL FOR ALL TIME RECORD HIGHS IN THE CLIMATE SECTION OF THE
DISCUSSION AS WELL AS ON SOCIAL MEDIA. THE OTHER THING TO TALK ABOUT
IS CRITICAL FIRE WEATHER, WE HAVE TWO SLAM DUNK INGREDIENTS THE
THIRD MAY BE MORE QUESTIONABLE IN SPOTS. DRY FUELS ARE ONE OF THE
SLAM DUNKS. THE OTHER IS LOW HUMIDITY, WHICH WILL FALL TO AS LOW AS
4 PERCENT IN SOME LOCATIONS. THE ONE QUESTION IS WIND. ALMOST ALL
GUIDANCE IS SHOWING THE STRONGEST WIND ACROSS NORTHERN PORTIONS OF
THE RED FLAG WARNING AREA, WITH GUSTS AS HIGH AS 35 MPH. THE
SOUTHERN ZONES, ESPECIALLY ZONE 283, ARE A BIT BORDERLINE ON THIS.
HOWEVER, GIVEN THE LOW HUMIDITY AND RECORD HEAT, WE WILL KEEP IT UP.
OTHERWISE, IT WILL BE ALMOST COMPLETELY DRY. SOME GUIDANCE DOES HOW
A BIT MORE MID LEVEL MOISTURE IN WESTERN WYOMING AND SOME POSSIBLE
CUMULUS BUILDUP IN THAT VICINITY. GIVEN THE VERY DRY LOW LEVELS,
ANYTHING THAT FALLS OUT OF THE CLOUDS WOULD ONLY BE VIRGA. WE DID
ADD SOME 10 PERCENT POPS THOUGH, MAINLY FOR SPOT PURPOSES.
THE CENTER OF THE RIDGE WILL MOVE EASTWARD SOMEWHAT ON MONDAY. AND
IT MAY BE JUST FAR ENOUGH TO ALLOW A BIT OF RETURN FLOW MOISTURE TO
MOVE UP THE BACKSIDE OF THE RIDGE FOR SOME ISOLATED CONVECTION IN
THE WESTERN MOUNTAINS. THIS IS ISOLATED WITH A CAPITAL I THOUGH,
WITH AT MOST A 1 OUT OF 6 CHANCE WITH MOST LOCATIONS SEEING
NOTHING. SLIGHT SMALLER THICKNESS AND 700 MILLIBAR TEMPERATURES
COOLING TO AROUND SATURDAY'S LEVELS WILL ALLOW FOR SLIGHTLY
COOLER TEMPERATURES, BUT STILL WELL ABOVE NORMAL WITH STILL A
GREATER THAN 4 OUT OF 5 CHANCE OF HIGH TEMPERATURES ABOVE 1000
DEGREES BELOW 5400 FEET. ALL TIME RECORD HIGHS ARE NOT EXPECTED
ON THIS DAY, BUT THE BIG HORN BASIN FROM WORLAND THROUGH EAST
OF LOVELL WILL AGAIN HAVE AT LEAST A 2 OUT OF 5 CHANCE OF HIGHS
OF 105 OR GREATER. THERE WILL BE LESS WIND ON THIS DAY, SO AT
LEAST FIRE WEATHER CONCERNS WILL BE DECREASED.
TUESDAY WILL BE ANOTHER VERY HOT DAY. A MAJORITY OF GUIDANCE IS
SHOWING THE RIDGE BUILDING BACK WEST THIS DAY, SO TEMPERATURES COULD
END UP BEING A DEGREE OR TWO WARMER, WITH AGAIN A GREATER THAN 1 IN
2 CHANCE OF HIGHS OVER 105 IN THE BIGHORN BASIN AND MOST LOCATIONS
BELOW 5500 FEET SEEING HIGHS OVER 100 DEGREES, MANY FOR A FOURTH
DAY IN A ROW. THERE WILL BE MORE MOISTURE IN THE AIR THOUGH, WITH
PRECIPITABLE WATERS CLIMBING BACK TOWARD NORMALS LEVELS. THIS COULD
LEAD TO AN INCREASED COVERAGE OF CONVECTION. HOWEVER, CONTINUED VERY
WARM AIR ALOFT MAY CAP MOST OF THE ACTIVITY. FOR NOW, WE HAVE
CONFINED IT TO THE NORTHERN MOUNTAINS BUT UNCERTAINTY IS HIGH HERE.
THE RIDGE WILL FINALLY BEGIN TO WEAKEN SOMEWHAT AS WE HEAD INTO
WEDNESDAY. IT WILL STILL BE RATHER HOT, BUT NOT LIKE THIS
WEEKEND. AND NEXT, TO QUOTE MONTY PYTHON, NOW FOR SOMETHING
COMPLETELY DIFFERENT. THAT IS THE POTENTIAL, EMPHASIS ON
POTENTIAL, FOR SOME HEAVY RAIN FROM THUNDERSTORMS. WE WILL HAVE
LOW LEVEL EAST TO SOUTHEASTERLY FLOW TO BRING UPSLOPE
CONDITIONS. PRECIPITABLE WATER VALUES WILL ALSO BE RATHER HIGHS,
CLIMBING TO OVER 150 PERCENT OF NORMAL IN SOME LOCATIONS BY
WEDNESDAY AFTERNOON. THERE COULD ALSO BE A SUBTLE SHORTWAVE
TOPPING THE RIDGE TO PROVIDE SOME LIFT, ALTHOUGH THESE ARE
DIFFICULT TO TIME THIS FAR OUT. THE WPC DOES HAVE THE AREA UNDER
A MARGINAL RISK OF EXCESSIVE RAINFALL AS WELL. THIS IS NOT A
CERTAINTY BUT WE WILL WATCH IT. FOLLOWING THIS IT LOOKS LIKE WE
WILL BE ON THE NORTHERN EDGE OF THE RIDGE WITH THE POTENTIAL OF
SHORTWAVES RUNNING OVER THE RIDGE, BRINGING CHANCES OF
CONVECTION EACH DAY. TEMPERATURES WILL REMAIN ABOVE NORMAL
THROUGH NEXT WEEKEND, THOUGH NOT AS HOT AS THIS WEEKEND.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 409 AM MDT SUN JUL 12 2026
VFR CONDITIONS ARE EXPECTED THROUGH 12Z. THERE WILL BE MORE
CUMULUS BUILDUP IN THE WESTERN MOUNTAINS. A COUPLE OF VIRGA
SHOWERS ARE POSSIBLE BUT THE CHANCE IS LESS THAN 15 PERCENT. THE
ONLY IMPACTED TERMINAL WOULD BE KJAC BUT HERE THE CHANCE IS ONLY
AROUND 10 PERCENT. WIND GUSTS OVER 15 KNOTS ARE POSSIBLE AT ALL
TERMINALS WITH GUSTS OVER 20 KNOTS POSSIBLE AT ALL THE TERMINALS
EAST OF THE CONTINENTAL DIVIDE AFTER 19Z AND BEFORE 06Z MONDAY.
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 136 AM MDT SUN JUL 12 2026
A COMBINATION OF RECORD HIGH TEMPERATURES, HUMIDITY FALLING AS
LOW AS 4 PERCENT AND A GUSTY SOUTHERLY BREEZE WILL BRING
ELEVATED FIRE WEATHER TO MUCH OF THE AREA. CRITICAL FIRE WEATHER
IS LIKELY THIS AFTERNOON WITH THE AREAS OF MOST CONCERN BRING
PARK, BIG HORN, WASHAKIE, HOT SPRINGS AND JOHNSON COUNTIES.
HUMIDITY WILL REMAIN BELOW 15 PERCENT ON MONDAY BUT WITH LIGHTER
WIND FIRE CONDITIONS SHOULD IMPROVE SOMEWHAT.
CLIMATE
ISSUED AT 136 AM MDT SUN JUL 12 2026
WE HAVE THE POTENTIAL FOR A RECORD SETTING DAY TODAY AS FAR AS
ALL TIME RECORD HIGH STATION HIGH TEMPERATURES. THIS IS
ESPECIALLY SO AT LOCATIONS WITH A SHORTER PERIOD OF RECORD, LIKE
THE GREYBULL AND RIVERTON AIRPORTS, WHERE THE STATIONS BETWEEN
A 70 AND 80 PERCENT CHANCE OF BREAKING THEIR ALL TIME RECORD
HIGHS (108 F AT GREYBULL AND 102 F AT RIVERTON). SOME LONGER
TERM STATIONS ALSO HAVE A GOOD CHANCE WITH THE WORLAND AIRPORT
(ALL TIME RECORD OF 107 F) HAVING A 70 PERCENT CHANCE. MOST
IMPRESSIVE, LANDER HAS A 60 PERCENT CHANCE OF BREAKING THE ALL
TIME RECORD HIGH TEMPERATURE OF 102 F, AND RECORDS HERE DATE
BACK TO 1891.
RIW WATCHES/WARNINGS/ADVISORIES
EXTREME HEAT WARNING UNTIL 9 PM MDT MONDAY FOR WYZ003>006-010-
011-013-016>020-023-025>030.
RED FLAG WARNING FROM 11 AM THIS MORNING TO 10 PM MDT THIS
EVENING FOR WYZ275-276-280>283.
DISCUSSION...HATTINGS
AVIATION...HATTINGS
FIRE WEATHER...HATTINGS
CLIMATE...HATTINGS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page