046
FXUS65 KRIW 082301
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
501 PM MDT FRI MAY 8 2026
KEY MESSAGES
- ISOLATED (10%-15%) VIRGA AND LIGHT SHOWER POTENTIAL ACROSS
YELLOWSTONE NATIONAL PARK, THE ABSAROKAS, AND THE BIGHORN
BASIN AFTER 5PM/6PM MDT.
- EXPECT HIGHS IN THE 60S ON SATURDAY WITH BREEZY 20 TO 35 MPH
WINDS. SHOWER AND THUNDERSTORM CHANCES (40% TO 80%) ALONG AND
EAST OF THE DIVIDE, ESPECIALLY ACROSS JOHNSON AND NATRONA
COUNTIES, MUCH OF SATURDAY.
- DRY AND WARM SUNDAY THROUGH MOST OF NEXT WEEK, WITH WIDESPREAD
HIGHS IN THE 80S BY MONDAY. BREEZY WINDS AND MINIMUM RELATIVE
HUMIDITY VALUES BELOW 15% WILL CONTRIBUTE TO ELEVATED TO NEAR
CRITICAL FIRE WEATHER CONDITIONS MUCH OF NEXT WEEK.
UPDATE
ISSUED AT 1231 PM MDT FRI MAY 8 2026
NORTHWEST FLOW ALOFT CONTINUES WITH RIDGING WEST OF WYOMING. EXPECT
A WARM AFTERNOON WITH HIGH TEMPERATURES IN THE UPPER 60S AND LOW
70S. THERE IS CONSENSUS AMONG MULTIPLE DETERMINISTIC GUIDANCES THAT A
VORTICITY MAXIMUM WILL TRAVERSE WYOMING BEGINNING AROUND 5PM/6PM MDT
THIS EVENING AHEAD SATURDAY'S SHORTWAVE. A SLIGHT UPTICK OF MID-
LEVEL MOISTURE WILL ACCOMPANY THIS EVENING'S VORTICITY MAXIMUM,
ESPECIALLY ACROSS YELLOWSTONE NATIONAL PARK, THE ABSAROKAS, AND THE
BIGHORN BASIN. MODEL SOUNDINGS INDICATE DRY LOW LEVELS ACROSS THESE
AREAS AND HIGH CLOUD BASES ABOVE 10,000 FEET AGL. THIS MEANS THAT
THERE IS A LOW CHANCE (10% TO 15%) FOR ISOLATED INSTANCES OF LIGHT
RAIN ACROSS AND AROUND THE AFOREMENTIONED LOCATIONS. HOWEVER, THE
MOST LIKELY SCENARIO IS THAT LITTLE LIQUID WILL MAKE IT TO THE
GROUND AND THAT IT WILL LARGELY BE VIRGA FROM ROUGHLY 5PM/6PM TODAY
UNTIL AFTER MIDNIGHT TONIGHT.
THE FORECAST REMAINS ON TRACK FOR A SHORTWAVE EMBEDDED WITHIN THE
NORTHWEST FLOW TO TRAVERSE ACROSS WYOMING ON SATURDAY. THERE IS A
SLIGHT UPTICK IN MOISTURE WITH THIS SHORTWAVE GIVEN THE PACIFIC
ORIGIN. AN ASSOCIATED COLD FRONT WILL PUSH DOWN FROM THE NORTH AND
SUPPORT SHOWERS AND THUNDERSTORMS ALONG AND EAST OF THE DIVIDE
BEGINNING SATURDAY MORNING. THE GREATEST COVERAGE OF THUNDERSTORMS
IS STILL EXPECTED TO OCCUR ACROSS JOHNSON AND NATRONA COUNTIES (60%
TO 80%) FROM SATURDAY MORNING THROUGH 6PM SATURDAY. RAINFALL AMOUNTS
ARE FORECAST TO RANGE FROM A TRACE TO 0.10 INCH ACROSS MOST
AREAS EAST OF THE DIVIDE. THE BIGHORNS, JOHNSON COUNTY, AND
NORTHEASTERN NATRONA COUNTY HAVE A 40% TO 70% CHANCE OF SEEING
0.25 INCHES OF RAIN BY SATURDAY NIGHT.
MOISTURE IS EXPECTED TO STAY EAST OF THE DIVIDE, WHICH WILL LEAVE
AREAS WEST OF THE DIVIDE DRY WITH RELATIVE HUMIDITY VALUES BELOW
20%. THERE IS A 60% TO 80% CHANCE THAT MINIMUM RELATIVE HUMIDITY
WILL BE 15 PERCENT OR LOWER ACROSS SWEETWATER COUNTY ON SATURDAY
AFTERNOON. THIS LOW HUMIDITY, COMBINED WITH GUSTY 25 MPH TO 35 MPH
WINDS (THANKS TO THE TIGHTENING PRESSURE GRADIENT), WILL SUPPORT
ELEVATED TO NEAR CRITICAL FIRE WEATHER CONDITIONS ACROSS SOUTHERN
WYOMING ON SATURDAY AFTERNOON. TEMPERATURES HAVE REMAINED CONSISTENT
IN A WARM UP TO AROUND 20 DEGREES ABOVE NORMAL (80S!) MOST OF NEXT
WEEK. THESE ABNORMALLY WARM TEMPERATURES ALONG WITH DRY AND BREEZY
CONDITIONS SUGGEST THAT A WEEK OF ELEVATED TO NEAR CRITICAL FIRE
WEATHER CONDITIONS IS UPON US.
DISCUSSION
ISSUED AT 100 AM MDT FRI MAY 8 2026
NORTHWEST FLOW ALOFT CONTINUES ACROSS THE CWA AS DEPICTED ON WV
IMAGERY WITH THE PFJ NOW RETREATED TO THE NORTHEAST COMING OUT
OF CANADA THROUGH EASTERN MONTANA TO NORTHEASTERN WY TO THE
GREAT PLAINS. IR SHOWS SUBSIDENCE PUSHING IN FROM THE WEST AS
THE AMPLE CLOUD COVER IS PUSHING EAST OUT OF THE AREA BY SUNRISE
FRIDAY MORNING. A FEW SCATTERED SHOWERS LINGER ACROSS EASTERN
FREMONT AND INTO NATRONA COUNTY THAT WILL DIMINISH AND EXIT THE
CWA BEFORE SUNRISE AS WELL.
CONVERGENCE AND DRY SLOTTING EXPECTED FOR FRIDAY WITH WARMER
TEMPERATURES (~5 DEGREES WARMER THAN THURSDAY) WITH DRY
CONDITIONS EXPECTED. SOME BREEZY WINDS WEST OF THE DIVIDE AND
ACROSS THE WIND CORRIDOR, BUT NOTHING EXCEPTIONAL WITH AN
OVERALL WEAK TO MODERATE PRESSURE GRADIENT ACROSS THE CWA. THE
NEXT SUBTLE SHORTWAVE WILL PROPAGATE DOWN THE NORTHWEST FLOW
DROPPING A WEAK FRONTAL BOUNDARY IN FROM THE NORTH COME SATURDAY
MORNING. THIS WILL BRING SOME SCATTERED RAIN SHOWERS AND
ISOLATED THUNDERSTORMS BY SATURDAY AFTERNOON AND EVENING WITH
40-50% COVERAGE AND CONFIDENCE A BIT MORE NORTHEAST THAN IT WAS
THURSDAY. THE STRONGEST STORMS LOOK TO BE EAST OF THE BIGHORNS
FOR JOHNSON/NATRONA COUNTIES WHERE CAPE VALUES LOOK TO BE MORE
INTRIGUING FOR WYOMING STANDARDS ~250-350 J/KG. GUSTY OUTFLOWS
LOOK TO BE THE HAZARD OUTSIDE OF ANY LIGHTNING TO OCCUR AND
SOMETHING TO KEEP AN EYE ON. NOTHING OF HIGH SIGNIFICANCE BUT
ANY RAINFALL WILL HELP IN THESE AREAS. REGARDLESS, ONCE THE SUN
SETS, ANY LINGERING SHOWER ACTIVITY WILL WEAKEN AND EXIT TO THE
EAST BEFORE MIDNIGHT AND DRY OUT COME SUNDAY MORNING.
SUNDAY AND INTO NEXT WEEK WILL SEE A STRONGER UPPER LEVEL RIDGE
TO BUILD IN TO BE MORE ORIENTED ACROSS THE ROCKIES. THIS WILL
BRING MUCH WARMER TEMPERATURES AND DRY CONDITIONS FOR SEVERAL
DAYS. AFTERNOON HIGH TEMPERATURES EAST OF THE DIVIDE LOOK TO
PUSH WELL INTO THE 80S WITH 70S TO THE WEST. BREEZY CONDITIONS
WILL LEAD TO ELEVATED FIRE WEATHER CONDITIONS DUE TO THE LOW RH
VALUES AND WARMER TEMPERATURES, EVEN WITH GREENUP NOW ONGOING
FOR ALL ZONES. THE NEXT WEATHER SYSTEM OF NOTE LOOKS TO BE BY
WEEK'S END LATE THURSDAY INTO FRIDAY THAT SHOULD BRING A
REPRIEVE FROM THE WARMER TEMPERATURES AND INCREASING
PRECIPITATION CHANCES ONCE AGAIN.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 459 PM MDT FRI MAY 8 2026
VFR CONDITIONS ARE EXPECTED ACROSS THE REGION OVER THE NEXT 24
HOURS. MID LEVEL CLOUD COVER INCREASES THIS EVENING, ESPECIALLY
ACROSS THE NORTHERN HALF OF WYOMING AS THE NEXT WEATHER SYSTEM
BEGINS MOVING INTO THE REGION.
ISOLATED RAIN SHOWERS DEVELOP OVERNIGHT FOR THE NORTHERN HALF OF THE
STATE. THERE IS A 60% CHANCE OF BRIEF HIT-OR-MISS SHOWERS AFFECTING
KWRL AND KCPR AFTER MIDNIGHT AND INTO SATURDAY MORNING, BUT HEAVY
RAIN IS NOT EXPECTED. SCATTERED RAIN SHOWERS AND THUNDERSTORMS WILL
DEVELOP SATURDAY AFTERNOON. BRIEF MVFR CONDITIONS ARE POSSIBLE (30%)
WITH SHOWERS AND STORMS AT KRIW, KLND, AND KCPR SATURDAY AFTERNOON.
WINDS SHIFT TO BECOME NORTHERLY SATURDAY MORNING AS A SUBTLE COLD
FRONT PUSHES SOUTHWARD INTO THE REGION FROM MONTANA, MAINLY
AFFECTING LOCATIONS EAST OF THE CONTINENTAL DIVIDE. GUSTS RANGE FROM
15 TO 25 KT WITH THIS WEAK COLD FRONT. WINDS WILL DECREASE AFTER
SUNSET SATURDAY EVENING, WITH CLEARING SKIES BEHIND THE QUICK-MOVING
WEATHER SYSTEM.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...GERHARDT
DISCUSSION...LOWE
AVIATION...VANDENBOOGART/ROWE
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