782
FXUS65 KRIW 290413
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1013 PM MDT THU MAY 28 2026
KEY MESSAGES
- ISOLATED TO SCATTERED SHOWERS AND STORMS CONTINUE FOR A FEW
HOURS THIS EVENING, MAINLY ACROSS NORTHWEST WYOMING. BRIEF
HEAVY RAIN AND GUSTY WIND ARE THE MAIN CONCERNS.
- SIMILAR CONDITIONS WITH VERY WARM TEMPS AND BREEZY SOUTH WINDS
ARE EXPECTED AGAIN ON FRIDAY, THOUGH SOUTHWEST WY WILL SEE
INCREASING CLOUDS AND COOLER TEMPERATURES LATE IN THE
AFTERNOON AND EVENING.
- A WEATHER SYSTEM APPROACHES FRIDAY NIGHT INTO SATURDAY MORNING
WITH A GOOD CHANCE FOR SHOWERS AND ISOLATED THUNDERSTORMS
ACROSS ALL OF WESTERN AND CENTRAL WY ON SATURDAY. THE HEAVIEST
PRECIPITATION LOOKS TO FALL IN WESTERN WYOMING AND OVER THE
MOUNTAINS, BUT EXACT AMOUNTS ARE STILL UNCERTAIN.
- TEMPERATURES SHOULD COOL TO THE UPPER 50S ACROSS SOUTHWEST WY
AND 70S ACROSS NORTH-CENTRAL WY ON SATURDAY, WITH BELOW
NORMAL TEMPERATURES REMAINING THROUGH MONDAY.
- ELEVATIONS ABOVE 9000 FEET MAY SEE ACCUMULATING SNOW OVER THE
WEEKEND, WITH THE HIGHEST AMOUNTS IN THE TETONS, CENTRAL TO
NORTHERN WIND RIVERS, AND SOUTHERN ABSAROKAS. YNP COULD SEE
AROUND AN INCH OF PRECIPITATION OVER THE WEEKEND AS WELL.
UPDATE
ISSUED AT 150 PM MDT THU MAY 28 2026
THE STRONG UPPER-LEVEL LOW CONTINUES TO SPIN OVER NORTHERN
CALIFORNIA AND NORTHWEST NEVADA TODAY. THIS PATTERN IS BRINGING
SOUTH-SOUTHEAST MID-LEVEL FLOW TO WYOMING, WITH INCREASED
MOISTURE EAST OF THE CONTINENTAL DIVIDE. AS EXPECTED, SHOWERS
AND THUNDERSTORMS HAVE ALREADY DEVELOPED EARLY THIS AFTERNOON
OVER THE NORTHERN ABSAROKAS NEAR CODY, AS WELL AS OVER AND
AROUND THE BIGHORN MOUNTAINS. ADDITIONAL ISOLATED STORMS ARE
LIKELY AROUND YELLOWSTONE (NORTHWEST WYOMING) AND FROM THE
CASPER MOUNTAIN AREA NORTHWARD INTO JOHNSON COUNTY. THESE STORMS
WILL SLOWLY MOVE NORTH-NORTHEAST WITH BRIEF HEAVY RAIN, SMALL
HAIL, AND GUSTY OUTFLOW AROUND 40-45 MPH THE PRIMARY THREATS.
VERY DRY AIR HAS MOVED INTO SOUTHWEST WYOMING EARLY THIS
AFTERNOON TOO WITH THE SOUTHERLY SURFACE FLOW AND BOUNDARY LAYER
MIXING, AND WILL PUSH SLOWLY NORTHWARD THROUGH THE AFTERNOON AS
SOMEWHAT OF A DRYLINE DEVELOPS FROM SE TO NW ACROSS THE AREA.
THE 19Z SPC MESOANALYSIS INDICATES A POTENTIAL OF 500-1000 J/KG
CAPE FOR THESE AREAS. AROUND SUNSET AS THE BOUNDARY LAYER
FORCING RELAXES AND BREEZY/GUSTY WINDS DIMINISH, CAMS ARE
SHOWING EASTERLY FLOW MOVING INTO CENTRAL WYOMING FROM THE
HIGH- BASED CONVECTION TO THE EAST.
ON FRIDAY, THE UPPER-LEVEL LOW IS FORECAST TO MOVE INTO NEVADA
AND BECOME SOMEWHAT NEGATIVELY-TILTED. DRY, WARM SOUTHERLY FLOW
WILL AGAIN OCCUR OVER WESTERN AND CENTRAL WYOMING WITH
HUMIDITIES DROPPING TO AROUND 10 PERCENT FOR MUCH OF THE LOWER
ELEVATIONS WITH WIND GUSTS OF 20-25 MPH. THIS WILL BRING
ELEVATED FIRE WEATHER CONDITIONS TO WESTERN AND CENTRAL WYOMING.
MODEL GUIDANCE IS AGAIN SHOWING ISOLATED SHOWERS OVER THE NW
WYOMING MOUNTAINS, BIGHORNS, AND THE CASPER MOUNTAIN AREA. BOTH
THE HRRR AND RRFS ARE SHOWING "DECENT" CONVECTIVE OVER THE
CASPER AREA LATE IN THE AFTERNOON FOR SOME POTENTIAL OUTFLOW
WIND GUSTS OF 40-55 MPH. WILL STOP THIS UPDATE AT MIDNIGHT
FRIDAY NIGHT AS THE UPPER- LEVEL LOW THEN SWINGS INTO NORTHERN
UTAH AND STARTS AN INTERESTING 48-HOUR PERIOD OF WEATHER FOR THE
WEEKEND.
DISCUSSION
ISSUED AT 1238 AM MDT THU MAY 28 2026
WE CONTINUE TO HAVE THE TWO MAIN PLAYERS IN OUR WEATHER THIS
MORNING. IN THE RIGHT (EAST) CORNER, WE HAVE A RIDGE OVER THE
PLAINS STATES. AND IN THE LEFT (WEST) CORNER WE HAVE A BOWLING
BALL, AKA A CLOSED LOW THAT HAS BEEN CUTOFF FOR A FEW DAYS OVER
CALIFORNIA AND NEVADA, JUST MEANDERING A BIT FROM TIME TO TIME.
THE TREND FOR DAILY CONVECTION HAS BEEN DOWNWARD. WITH HEIGHTS
CONTINUING TO BUILD, IT WILL LIKELY REACH A MINIMUM TODAY. MUCH
DRIER AIR WILL CONTINUE TO MOVE EASTWARD, WITH BELOW A HALF AN
INCH OF PRECIPITABLE WATER COVERING MOST OF WESTERN AND CENTRAL
WYOMING BY LATER THIS AFTERNOON. ANY THUNDERSTORMS WOULD BE
LIMITED TO FAR NORTHERN AND NORTHEASTERN AREAS. THERE COULD BE A
COUPLE NEAR THE ABSAROKAS AND BIGHORNS, WHERE SOME WEAK UPSLOPE
OR HIGH LEVEL HEAT SOURCE MAY BRING SOMETHING BUT EVEN HERE THE
CHANCE IS LESS THAN 1 OUT OF 5. THE MAIN STORY TODAY WILL BE
THE WARM TEMPERATURES, WITH SOME OF THE WARMER AREAS, LIKE THE
BIGHORN BASIN, HAVING SOME AREAS THAT ECLIPSE THE 90 DEGREE MARK
THIS AFTERNOON. THERE WILL ALSO STILL BE A BIT OF A BREEZE
TODAY, BUT SOMEWHAT LIGHTER THAN YESTERDAY. AREAS IN NORTHERN
JOHNSON COUNTY STILL HAVE AROUND A 1 IN 2 CHANCE OF GUSTS OVER
35 MPH AT TIMES THIS AFTERNOON THOUGH. ANY CONVECTION SHOULD END
FAIRLY QUICKLY THIS EVENING, WITH DRY WEATHER AFTER MIDNIGHT.
THINGS SHOULD FINALLY START MOVING ON FRIDAY AS THE RIDGE WEAKENS
AND SHIFTS A BIT EAST AND THE LOW BEGINS TO MOVE. FLOW WILL TURN
MORE TO THE SOUTHEAST THROUGH THE DAY AND INCREASE MOISTURE INTO THE
AREA. IT WILL TAKE A WHILE FOR THE ATMOSPHERE TO MOISTEN THOUGH. AS
A RESULT, MOST OF THE DAY SHOULD BE WARM AND DRY WITH ANY CONVECTION
HOLDING OFF UNTIL MID TO LATE AFTERNOON. TEMPERATURES SHOULD RUN
FAIRLY SIMILAR TO TODAY'S HIGHS.
IT IS LOOKING MORE AND MORE LIKELY THAT AT LEAST PORTIONS OF THE
AREA WILL SEE A DECENT AMOUNT OF PRECIPITATION OVER THE WEEKEND.
WHERE IT FALLS DEPENDS UPON WHERE THE LOW EVENTUALLY TRACKS AND BOTH
THE ENSEMBLES AND DETERMINISTIC MODELS CONTINUE TO HAVE DIFFERENT
SOLUTIONS. A FURTHER WEST TRACK, LIKE SOME ENSEMBLE MEMBERS AS WELL
AS THE GFS HAVE, WOULD KEEP THE HEAVIER PRECIPITATION OVER WESTERN
WYOMING. AREAS FURTHER EAST WOULD HAVE A DOWNSLOPING FLOW AND
THEREFORE LESS PRECIPITATION. IF THE LOW IS FURTHER EAST, DECENT
PRECIPITATION WOULD BE SPREAD MORE THROUGHOUT THE AREA. THE WEATHER
PREDICTION CENTER DOES HAVE NORTHERN PORTIONS OF THE AREA IN A
MARGINAL RISK OF EXCESSIVE RAINFALL AS WELL FOR BOTH SATURDAY AND
POSSIBLY SUNDAY AS THE LOW MAY SLOW DOWN AND LINGER CLOSE TO THE
AREA, BUT AGAIN THERE ARE SOLUTIONS ON BOTH SIDES OF THIS EQUATION.
AS FOR PRECIPITATION AMOUNTS, WE WILL TURN TO THE REALM OF THE
ENSEMBLES TO TRY TO ANSWER THIS QUESTION. THE NATIONAL BLEND OF
MODELS GIVES A GREATER THAN 1 IN 2 CHANCE OF A QUARTER OF AN INCH OF
QPF THROUGH MONDAY MORNING ROUGHLY NORTH AND WEST OF A ROCK SPRINGS
TO RIVERTON TO BUFFALO LINE. MUCH NORTHWESTERN WYOMING,
INCLUDING YELLOWSTONE PARK, THE ABSAROKAS AND TETONS HAVE A
GREATER THAN 1 IN 2 CHANCE OF AN INCH OF QPF OR MORE. STILL
SOME UNCERTAINTY FOR EXACT PLACEMENT, BUT THE CHANCE IS
DEFINITELY THERE.
AND THEN WE HAVE TO TAKE A LOOK AT THE POSSIBILITY OF THE "S" WORD,
SNOW. YES, THERE COULD BE SOME SNOW WITH THIS SYSTEM. IT WILL NOT
OCCUR IN THE VALLEYS. HOWEVER, WE ARE GETTING INTO THE TIME OF YEAR
WHEN MOUNTAIN RECREATION INCREASES SUBSTANTIALLY AND WE HAVE TO
LOOK AT IT. THE GFS GIVES 700 MILLIBAR TEMPERATURES FALLING AS
LOW AS MINUS 1C, WHICH WOULD PUT SNOW LEVELS AROUND 8000 FEET.
THIS MAY BE A BIT LOW, IT LOOKS LIKELY CLOSER TO 8500 OR 9000
FEET. HOWEVER, THERE COULD BE SOME ACCUMULATION. THE NATIONAL
BLEND OF MODELS GIVES A GREATER THAN 1 IN 2 CHANCE OF 3 INCHES
OF SNOW ABOVE 10000 FEET THROUGH MONDAY MORNING. SOME OF HIGHEST
PEAKS IN THE WIND RIVER RANGE AND TETONS COULD SEE 6 INCHES OR
MORE OF SNOW FROM THIS. IT DOESN'T LOOK TO IMPACT TRAVEL TOO
SUBSTANTIALLY SINCE ROADS ARE VERY WARM RIGHT NOW. HOWEVER, IF
YOU ARE TRAVELING OVER MOUNTAIN PASSES, DON'T BE SURPRISED IF
YOU SEE SOME SNOW THIS WEEKEND, ESPECIALLY OVER THE HIGHER ONES
LIKE TOGWOTEE PASS WHICH IS CLOSE TO 10000 FEET IN ELEVATION.
FOLLOWING THIS, DRIER WEATHER LOOKS TO RETURN TO THE AREA AND FLOW
BECOMES MORE ZONAL WITH FLAT RIDGING BRINGING DRIER WEATHER AND
TEMPERATURES RETURNING TO NORMAL FOR MUCH OF THE AREA FOR THE
START OF NEXT WEEK.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1008 PM MDT THU MAY 28 2026
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. SHOWERS HAVE
ENDED ACROSS THE AREA AND WINDS WILL REMAIN LIGHT THROUGH
16Z-18Z. WINDS WILL BEGIN TO INCREASE ACROSS THE SOUTH BY THIS
TIME, NAMELY KRKS, AND SPREAD NORTHWARD WITH INCREASING WINDS AT
THE REMAINING TERMINALS THROUGH 21Z. STORM ACTIVITY WILL
INCREASE BETWEEN 19Z AND 21Z, MAINLY OVER AREAS EAST OF THE
DIVIDE. KCOD AND KCPR CONTINUE TO HAVE THE BEST CHANCES TO BE
DIRECTLY IMPACTED. CONFIDENCE IS AROUND 10 TO 20% FOR KWRL TO BE
IMPACTED FROM ANY PASSING SHOWER/STORM AT THIS TIME. EXPECTED
ONCE AGAIN AROUND KCOD/KCPR AFTER 20Z WITH CONFIDENCE ON STATION
BETWEEN 10-15%. SHOWER AND STORM CHANCES BEGIN TO INCREASE
ACROSS THE AREA, ESPECIALLY OVER SWEETWATER COUNTY AND THE GREEN
RIVER BASIN AFTER SUNSET. VCSH IS LIKELY FOR MOST TERMINALS BY
04Z.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...MCDONALD
DISCUSSION...HATTINGS
AVIATION...LAVOIE
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