141
FXUS65 KRIW 051018
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
418 AM MDT SUN JUL 5 2026
KEY MESSAGES
- A HOT DAY TODAY WITH ISOLATED AFTERNOON AND EVENING
THUNDERSTORMS IN NORTHWESTERN WYOMING (A 1 IN 5 CHANCE). ANY
SHOWER OR STORM COULD HAVE STRONG WIND GUSTS.
- AN INCREASED CHANCE OF SHOWERS AND THUNDERSTORM MONDAY THROUGH
WEDNESDAY, WITH THE MOST NUMEROUS STORMS EXPECTED ON TUESDAY.
- THE HOTTEST TEMPERATURES OF THE YEAR ARE LIKELY FRIDAY AND
ESPECIALLY NEXT WEEKEND WITH SOME RECORD HIGH TEMPERATURES
POSSIBLE.
DISCUSSION
ISSUED AT 136 AM MDT SUN JUL 5 2026
WE HAVE NOW REACHED THE END OF THE HOLIDAY WEEKEND. ALL IN ALL, THE
FOURTH OF JULY WAS PRETTY NICE, WITH WARM TEMPERATURES, NO
CONVECTION AND LOTS OF SUNSHINE. ALL THAT EXCEPT FOR A NEW FIRE
START SOUTHEAST OF LANDER. BUT, WE DON'T WANT TO TALK ABOUT THE
PAST, LET'S TALK ABOUT THE FUTURE, THIS IS A FORECAST AFTER ALL.
THERE WILL BE TWO CHANGES. THE FIRST WILL BE WARMER TEMPERATURES AS
FLOW TURNS SOUTHWEST AHEAD OF A WEAK COLD FRONT. TEMPERATURES SHOULD
AVERAGE AROUND 5 DEGREES WARMER THAN YESTERDAY, MAKING THIS THE
HOTTEST DAY FOR QUITE A WHILE, POSSIBLY THE HOTTEST SO FAR THIS
YEAR. THIS IS LOOKING LIKE THE DAY WHEN WE WILL SEE THE FIRST 100
DEGREE HIGH TEMPERATURES OF THE YEAR, WITH MUCH OF THE EASTERN AND
SOUTHERN BIGHORN BASIN HAVING AROUND A 1 IN 2 CHANCE OF SEEING HIGHS
AT OR OVER THE CENTURY MARK. JUST ABOUT ALL LOCATIONS EAST OF THE
DIVIDE IN THE LOWER ELEVATIONS WILL SEE HIGHS IN THE 90S, WITH SOME
80S TO LOW 90S WEST OF THE DIVIDE. THE SECOND CHANGE IS THE CHANCE
FOR CONVECTION RETURNS. THE ATMOSPHERE REMAINS RATHER DRY
(PRECIPITABLE WATER VALUES ARE BELOW NORMAL). HOWEVER, THERE IS
ENOUGH MID LEVEL MOISTURE FOR SOME ISOLATED SHOWERS AND
THUNDERSTORMS ACROSS NORTHWESTERN WYOMING, LARGELY WEST AND NORTH OF
A FRANNIE TO ALPINE LINE. THE ONLY HAZARD WOULD BE STRONG WIND
GUSTS. THERE ARE VERY STEEP LOW LEVEL LAPSE RATES (GREATER THAN
9C/KM) ALONG WITH VERY LARGE DEW POINT DEPRESSIONS (UP TO 60
DEGREES). ALL THIS ADDS UP TO THE THREAT OF MICROBURSTS, EVEN FROM
SMALL SHOWERS (THE INFAMOUS "LITTLE GREEN BLOBS)." COVERAGE WILL BE
SMALL, GENERALLY LESS THAN 1 OUT OF 5 IN THE IMPACTED AREA THOUGH.
MOST OF THESE SHOWERS SHOULD END SHORTLY AFTER SUNSET WITH DRY
CONDITIONS THROUGH MONDAY MORNING. ELSEWHERE, ELEVATED FIRE WEATHER
IS LIKELY WITH HUMIDITY FALLING INTO THE SINGLE DIGITS AT TIMES.
LARGELY LIGHT WIND THOUGH SHOULD KEEP CONDITIONS FROM BECOMING
CRITICAL.
A COLD FRONT (OR A REASONABLE FACSIMILE OF ONE) THEN SLIPS INTO
NORTHERN WYOMING, GETTING CLOSE TO CONTINENTAL DIVIDE BY MONDAY
MORNING. THIS SHOULD KNOCK HIGH TEMPERATURES DOWN AROUND 5 TO 10
DEGREES COMPARED TO TODAY. THE OTHER DIFFERENCE WILL BE AN INCREASE
IN MOISTURE AS LOW PRESSURE PASSES TO THE SOUTHEAST OF WYOMING AND
TURNS LOW LEVEL FLOW TO THE SOUTH AND SOUTHEAST. PRECIPITABLE WATER
VALUES RISE TO AROUND 125 TO 150 PERCENT OF NORMAL BY 00Z TUESDAY.
THIS MEANS AN INCREASE IN CONVECTION ACROSS THE AREA, AND MAYBE SOME
NEEDED RAIN. MOST GUIDANCE FAVORS NORTHERN WYOMING, WHERE GREATEST
INSTABILITY WILL BE FOUND (UP TO AROUND 500 J/KG OF CAPE). MOST
SOUNDINGS SHOW A DECENT CAP INITIALLY THOUGH, SO THIS FAVORED TO BE
A LATER SHOW, MAINLY IN THE EVENING WITH SOME CONVECTION LINGERING
INTO THE OVERNIGHT HOURS. GUIDANCE IS FAIRLY CONSISTENT IN HAVING
THE HIGHEST CHANCE (UP TO A 1 OUT OF 2 CHANCE) ACROSS NORTHERN
WYOMING, WITH DECREASING POPS FURTHER SOUTH, WITH LITTLE CHANCE IN
SOUTHEASTERN SWEETWATER COUNTY. MOST STORMS SHOULD NOT REACH SEVERE
LIMITS, BUT THERE COULD BE A FEW.
STORM COVERAGE SHOULD PEAK ON TUESDAY. A MORE DEFINED SHORTWAVE
WILL BE MOVING THROUGH THE AREA. PRECIPITABLE WATER VALUES ALSO
REACH A MAXIMUM ON THIS DAY, WITH MANY LOCATIONS SEEING GREATER THAN
150 PERCENT OF NORMAL AND SOME LOCATIONS REACHING VALUES OVER AN
INCH. THE ATMOSPHERE IS ALSO THE MOST UNSTABLE ON THIS DAY, WITH
NEGATIVE LIFTED INDICES ACROSS THE ENTIRE AREA. AS FOR STRONGER
STORMS, AGAIN THE MOST FAVORED LOCATION WOULD BE ACROSS THE NORTH
WHERE THE GREATEST CAPE (>1000 J/KG) AND LIFTED INDICES (DOWN TO
MINUS 4 WILL BE FOUND). LOCALLY HEAVY RAIN IS ALSO POSSIBLE WITH
MOIST ATMOSPHERE. THERE WILL BE SOME MOVEMENT WITH THE STORMS AND
WITH THE RECENT DRY WEATHER THERE IS ROOM IN THE SOIL SO THIS SHOULD
MITIGATE THE FLOODING THREAT SOMEWHAT. MORE CLOUD COVER SHOULD ALSO
KEEP TEMPERATURES COOLER ON THIS DAY. THE CURRENT HIGHS ARE PROBABLY
THE WARMEST IT WOULD BE, IT MAY TURN UP BEING COOLER. MOST OF THESE
STORMS SHOULD END AFTER SUNSET.
STARTING ON WEDNESDAY, WE WILL HAVE WHAT IS CALLED AN INVERSE
RELATIONSHIP. A VERY STRONG RIDGE WILL BEGIN BUILDING ACROSS THE
SOUTHWEST AND WILL BE EXPANDING NORTHWARD INTO THE LATE NEXT WEEK
AND ESPECIALLY INTO NEXT WEEKEND. THE INVERSE RELATIONSHIP WILL BE
TEMPERATURES GOING UP, AND CHANCES OF CONVECTION GOING DOWN. ON
WEDNESDAY, THERE WILL STILL BE ENOUGH LINGERING MOISTURE FOR A
DECENT COVERAGE OF STORMS, BUT MORE SCATTERED. DRIER AIR REALLY
SURGES INTO THE AREA STARTING THURSDAY, ANY STORMS WOULD BE
RESTRICTED TO EASTERN PORTIONS OF THE AREA ON THIS DAY. TEMPERATURES
REALLY BEGIN CLIMBING ON FRIDAY AND ESPECIALLY INTO THE WEEKEND.
MANY RUNS OF THE ENSEMBLES CENTER THE RIDGE ON OR VERY CLOSE TO
WYOMING, WITH 500 MILLIBAR HEIGHTS AS HIGH AS 6000 METERS. THIS IS
THE CLASSIC DEFINITION OF A DEATH RIDGE, BRINGING VERY HOT
TEMPERATURES AND LITTLE TO NO CHANCE OF RAIN. ENSEMBLE FORECASTS
START GIVING AT LEAST A 2 OUT OF 5 CHANCE OF HIGHS OVER 100 ONCE
AGAIN IN THE TYPICALLY WARM LOCATIONS BY FRIDAY. BUT THE WEEKEND IS
WHERE THE HEAT MAY REALLY HIT. ON BOTH SATURDAY AND SUNDAY, THE NBM
ENSEMBLE GIVES A GREATER THAN 3 OUT OF 5 CHANCE OF TRIPLE DIGIT
HIGHS BOTH DAYS BELOW 5500 FEET. SOME OF THE TYPICALLY WARMER SPOTS,
LIKE GREYBULL AND WORLAND HAVE A 2 OUT OF 5 CHANCE OF HIGHS OVER
105. A WORD OF CAUTION, THIS IS STILL A WEEK OUT AND THINGS CAN
CHANGE. HOWEVER, WE DO HAVE THE CHANCE OF ONE OF THE MORE NOTABLE
HEATWAVES WE HAVE SEEN IN A WHILE.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 417 AM MDT SUN JUL 5 2026
VFR CONDITIONS WILL PREVAIL THROUGH 12Z MONDAY. THE DAY WILL START
DRY BUT A WEAK WEATHER SYSTEM WILL APPROACH THE AREA THIS AFTERNOON
WITH ISOLATED SHOWERS AND THUNDERSTORMS AFTER 20Z TODAY (AROUND A 20
PERCENT CHANCE) IN VICINITY OF KCOD AND KJAC WHERE THE PROB30 GROUP
WAS CONTINUED. WE CAN'T RULE ON OUT AROUND KWRL BUT WITH LESS THAN A
10 PERCENT CHANCE WE LEFT IT OUT FOR NOW. ANY SHOWER OR THUNDERSTORM
WOULD BE MAINLY VIRGA. THE MAIN HAZARD WOULD BE VERY STRONG WIND
GUSTS, POSSIBLY AS STRONG AS 50 KNOTS. A WEAK COLD FRONT WILL DROP
INTO NORTHERN WYOMING SUNDAY NIGHT, SWITCHING WIND DIRECTION TO THE
NORTH. OUTSIDE OF ANY SHOWER OR THUNDERSTORM, WIND SHOULD REMAIN 12
KNOTS OR LESS FOR THE MOST PART.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HATTINGS
AVIATION...HATTINGS
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