544
FXUS65 KRIW 091730
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1130 AM MDT SAT MAY 9 2026
KEY MESSAGES
- SCATTERED SHOWERS AND THUNDERSTORMS (40% TO 80%) ARE EXPECTED
THROUGH THE DAY TODAY, WITH A FEW STRONG THE SEVERE
THUNDERSTORMS OVER NATRONA COUNTY FROM NOON TO 6PM/7PM. GUSTY
WINDS AND HAIL ARE POSSIBLE IN ANY STRONG TO SEVERE
THUNDERSTORM.
- WARMER TEMPERATURES AND DRY WEATHER SUNDAY THROUGH AT LEAST
MID NEXT WEEK. THE WARMEST DAYS WILL LIKELY BE MONDAY THROUGH
WEDNESDAY WITH WIDESPREAD HIGHS IN THE 80S, AND POTENTIALLY
INTO THE LOW 90S.
- ELEVATED TO NEAR CRITICAL FIRE WEATHER IS LIKELY FOR THE NEXT
SEVERAL DAYS, WITH MONDAY AND THURSDAY LOOKING LIKE THE MOST
CONCERNING DAYS AT THIS TIME.
DISCUSSION
ISSUED AT 229 AM MDT SAT MAY 9 2026
IN SOME OF MY DISCUSSIONS I TALK ABOUT THE SIGNS OF SEASONS
CHANGING. AND TODAY, I SAW ONE OF THE SIGNS THAT SUMMER IS
APPROACHING. AS I WAS DRIVING UP FOR MY USUAL GRAVEYARD SHIFT AROUND
9:45 PM, IT WAS THE FIRST DAY WHEN THERE WAS STILL SOME LIGHT IN THE
WESTERN SKY. IT WILL CONTINUE TO GET SLOWLY BRIGHTER AS WE MOVE
TOWARD THE SUMMER SOLSTICE ON JUNE 20TH, WHEN TIME OF TOTAL
DARKNESS SHRINKS TO ONLY AROUND 5 HOURS.
AND AS FOR THE WEATHER TODAY, TWO OF THE MAIN WEATHER IMPACTS
THROUGH THE FORECAST PERIOD ARE MOST COMMON IN THE SUMMERTIME,
THUNDERSTORMS AND FIRE WEATHER CONCERNS. AS FOR TODAY, THE MAIN
CONCERN WILL BE THUNDERSTORMS. THE TRIGGER FOR THIS WILL BE A
SHORTWAVE DROPPING SOUTHEASTWARD OUT OF MONTANA. THE MAIN IMPACTS
FROM THIS SHOULD REMAIN EAST OF THE CONTINENTAL DIVIDE, MOST MODEL
GUIDANCE AND THE GENERAL THUNDERSTORM OUTLOOK SHOWS THIS. THE NEXT
QUESTION IS, WILL ANY OF THE THUNDERSTORMS BE OF THE STRONGER
VARIETY? THERE ARE SOME DECENT PARAMETERS FOR STRONGER STORMS, WITH
AROUND 35 KNOTS OF BULK SHEAR TO LEAD TO LONGER LASTING STORMS. WE
ALSO HAVE DECENT CAPE WITH UP TO 500 J/KG ACROSS SOUTHERN NATRONA
COUNTY. THIS LINES UP WELL WITH THE MARGINAL RISK OF SEVERE
THUNDERSTORMS ISSUED BY THE STORM PREDICTION CENTER THIS MORNING.
MODEL SOUNDINGS ARE SHOWING INVERTED V SIGNATURES INITIALLY,
INDICATING THAT STORMS WOULD BE MORE OF THE HIGH BASED VARIETY.
WET BULB ZERO LEVELS ARE ALSO FAIRLY LOW, MEANING THAT
SMALL HAIL WILL BE POSSIBLE OF ANY STORM THAT DEVELOPS. A STRONG
WIND GUST WILL ALSO BE POSSIBLE. THIS MAY ALSO BE AN EARLIER
SHOW, WITH MOST GUIDANCE SHOWING STORMS DEVELOPING BY NOON AND
ENDING BY AROUND SUNSET THIS EVENING. COVERAGE LOOKS SCATTERED
SO IT IS STILL DIFFICULT TO PINPOINT THEM, BUT THE BEST CHANCE
WILL BE ACROSS JOHNSON AND NATRONA COUNTIES WITH AROUND A 1 IN 2
CHANCE AT ANY LOCATION, WITH DECREASING CHANCES FURTHER WEST
WHERE MOISTURE IS NOT AS DEEP. TEMPERATURES LOOK TO REMAIN BELOW
NORMAL EAST OF THE DIVIDE, AROUND 5 DEGREES ON AVERAGE. WEST OF
THE DIVIDE, EXPECT TEMPERATURES CLOSE TO SEASONAL NORMALS.
IT WILL BEGIN TO MORE SUMMER LIKE FOR THE SUNDAY AND MUCH OF NEXT
WEEK. SUNDAY LOOKS NICE A NICE SPRING DAY WITH HIGHS IN THE 60S AND
70S, LIGHT TO MODERATE WIND AND A GOOD DEAL OF SUNSHINE. WE THEN
TURN TO THE OTHER CONCERN, FIRE WEATHER, FOR MONDAY. THE RIDGE WILL
GET FLATTENED BY AN APPROACHING SHORTWAVE. THIS WAVE HAS LITTLE
MOISTURE TO WORK WITH, BUT WILL BRING SOME GUSTY WIND, WITH A
GREATER THAN 2 OUT OF 3 CHANCE OF WIND GUSTS PAST 30 MPH FOR MUCH OF
THE AREA. COMBINED WITH TEMPERATURES 15 TO 20 DEGREES ABOVE NORMAL
AND RELATIVE HUMIDITY FALLING UNDER 15 PERCENT ACROSS MUCH OF THE
AREA, ELEVATED TO CRITICAL FIRE WEATHER LOOKS FAIRLY LIKELY FOR MUCH
OF THE AREA MONDAY AFTERNOON. RIDGING THEN BUILDS BACK OVER THE AREA
AND BRINGS LIGHTER WIND FOR TUESDAY BEFORE ANOTHER WAVE APPROACHES
FOR WEDNESDAY AND MAY BRING A FEW SHOWERS AND STORMS WEST OF
THE DIVIDE. SOUTHWEST, DOWNSLOPING FLOW WILL BRING EVEN WARMER
TEMPERATURES. AND WITH THE THEME OF SUMMER, WE MAY SEE THE FIRST
APPEARANCE OF A SUMMER PHENOMENON, HIGHS IN THE 90S. ENSEMBLE
GUIDANCE IS SHOWING LOCATIONS MAINLY BELOW 4200 FEET IN THE BIG HORN
BASIN WITH ANYWHERE FROM A 1 IN 3 TO A 1 OUT OF 2 CHANCE OF THE
FIRST 90 DEGREE HIGH ON WEDNESDAY, LARGELY IN ANY AREA FOLLOWING THE
BIG HORN RIVER FROM THERMOPOLIS THOUGH WORLAND, GREYBULL AND UP
TOWARD LOVELL. MANY OTHER AREAS WILL SEE HIGHS WELL INTO THE 80S. A
GUSTY BREEZE WILL ALSO BRING ELEVATED FIRE WEATHER, ALTHOUGH WIND
DOES NOT LOOK AS STRONG ON WEDNESDAY AS ON MONDAY. CONDITIONS LOOK
SIMILAR ON THURSDAY AS WELL, ALTHOUGH MAYBE A COUPLE OF DEGREES
COOLER. THE NEXT MORE POTENT SYSTEM IN THE FORM OF AN UPPER LEVEL
LOW MAY APPROACH FOR THE END OF THE NEXT WEEK. HOWEVER, THERE IS LOW
MODEL AGREEMENT IN TIMING AND PLACEMENT FOR ANY PRECIPITATION, SO
DETAILS ARE NOT POSSIBLE TO HASH OUT THIS FAR OUT.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1130 AM MDT SAT MAY 9 2026
WEST OF THE DIVIDE...KJAC/KRKS/KPNA/KBPI TERMINALS
SHORTWAVE ENERGY ALONG THE NORTHWEST WYOMING BORDER TRACKS SOUTHEAST
SATURDAY AFTERNOON AND EARLY EVENING. A FEW SHOWERS COULD POP OVER
THE MOUNTAINS TO THE EAST, AND POTENTIALLY WEST, OF KJAC EARLY
SATURDAY AFTERNOON. THESE WOULD BE SHORT-LIVED WITH NO IMPACTS. ALL
OTHER TERMINALS TO SEE LITTLE MORE THAN CUMULUS CLOUDS THROUGH
SUNSET SATURDAY. GUSTY WEST-NORTHWEST WIND 15-30KTS PREVAILS
UNTIL 01Z-03Z/SUNDAY. WIND SPEEDS DIMINISH AT SUNSET, ALTHOUGH
KRKS WILL SEE A SURGE OF EAST-NORTHEAST WIND 10-15KTS FOR THE
LATE EVENING.
EAST OF THE DIVIDE...KCPR/KCOD/KRIW/KLND/KWRL TERMINALS
SHORTWAVE ENERGY ALONG THE NORTHWEST WYOMING BORDER TRACKS SOUTHEAST
SATURDAY AFTERNOON AND EARLY EVENING. CONVECTION HAS ALREADY BEGUN
AND COVERAGE INCREASES FROM 19Z-23Z/SATURDAY. EXPECT THE PRIMARY
IMPACTS TO BE EMBEDDED THUNDERSTORMS, SMALL HAIL, AND WIND GUSTS
AROUND 30KTS. SCATTERED SHOWERS LINGER AROUND KCPR UNTIL AROUND
SUNSET SATURDAY, WHILE MOST OF THE CONVECTION QUICKLY TAPERS OF
BY 01Z/SUNDAY AS THE SHORTWAVE GRADUALLY CLEARS THE AREA. VFR
AND DRY CONDITIONS PREVAIL AT ALL TERMINALS THE REST OF THE
NIGHT AND SUNDAY MORNING.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZLC AND ZDV FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
FIRE WEATHER
ISSUED AT 229 AM MDT SAT MAY 9 2026
LOCALLY ELEVATED FIRE WEATHER IS POSSIBLE ACROSS SOUTHERN
WYOMING TODAY. AFTER A LULL ON SUNDAY, AND APPROACHING WEATHER
SYSTEM ON MONDAY WILL BRING A GUSTY WIND. COMBINED WITH LOW
HUMIDITY AND ABOVE NORMAL TEMPERATURES, ELEVATED TO NEAR
CRITICAL FIRE WEATHER LOOKS LIKELY FOR MONDAY. THE MIDDLE OF
NEXT WEEK COULD ALSO SEE ELEVATED FIRE WEATHER.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HATTINGS
AVIATION...CNJ
FIRE WEATHER...HATTINGS
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