808
FXUS65 KRIW 291032
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
432 AM MDT FRI MAY 29 2026
KEY MESSAGES
- ONE MORE WARM DAY WITH LOCALLY BREEZY CONDITIONS. A FEW
SHOWERS AND THUNDERSTORMS WILL BE AROUND IN LOCATIONS SIMILAR
TO YESTERDAY.
- AND APPROACHING WEATHER SYSTEM WILL BRING A GOOD CHANCE OF
SHOWERS TO MUCH OF THE AREA FROM LATER TONIGHT INTO THE
WEEKEND, WITH MOST RAIN ACROSS NORTHERN AND WESTERN WYOMING.
- ACCUMULATING SNOW IS LIKELY THIS WEEKEND IN THE MOUNTAINS,
ESPECIALLY ABOVE 9500 FEET.
DISCUSSION
ISSUED AT 230 AM MDT FRI MAY 29 2026
METEOROLOGY IS ONE OF THE PHYSICAL AND MATHEMATICAL SCIENCES. AND
THE WEATHER IS BASICALLY GOVERNED BY COMPLEX MATHEMATICAL EQUATIONS
(SOME I WOULD LIKE TO FORGET, I STILL HAVE NIGHTMARES ABOUT DYNAMICS
CLASS 28 YEARS AFTER I FINALLY PASSED IT). ONE OF THE MOST COMMON IS
THE SINE WAVE, MOST OFTEN USED WITH ROSSBY WAVES. THE WEATHER OFTEN
RUNS LIKE A WAVE PATTERN WITH CRESTS AND TROUGHS OF DIFFERENT
PARAMETERS. AND WE ARE CURRENTLY IN A CREST AND TROUGH OF ONE RIGHT
NOW. ON THURSDAY, WE HAD THE CREST IN TEMPERATURES, WITH A TROUGH IN
COVERAGE OF PRECIPITATION. STARTING TODAY AND ESPECIALLY GOING INTO
THIS WEEKEND, THIS IS GOING TO BEGIN FLIPPING.
THE MAIN REASON IS THE CUT OFF LOW THAT HAS BEEN SPINNING ACROSS
CALIFORNIA AND NEVADA FOR THE PAST FEW DAYS. IT WILL FINALLY GET A
NUDGE AND WILL BEGIN HEADING NORTHEASTWARD TOWARD WYOMING TODAY.
MOISTURE WILL BEGIN TO HEAD BACK INTO THE AREA, ALTHOUGH IT WILL
TAKE A WHILE TO DEEPEN. THERE WILL BE A FEW MORE SHOWERS AND STORMS
AROUND TODAY. HOWEVER, MOST GUIDANCE SHOWS IT WILL BE LATER SHOW
WITH SOME STICKING AROUND INTO THE EVENING. WITH THE FLOW TURNING
SOUTHEAST, THE MOST IMPACTED AREAS WILL BE SIMILAR TO YESTERDAY, THE
FAVORED UPSLOPE AREAS LIKE AROUND THE EAST SLOES OF THE ABSAROKAS
AND THE BIGHORNS AS WELL AS NATRONA AND JOHNSON COUNTY WHERE
MOISTURE WILL BUILD THE FASTEST. EVEN HERE, THE CHANCE OF A SHOWER
OR STORM IS PROBABLY NO MORE THAN 1 OUT OF 3. IT WILL BE ANOTHER
VERY WARM DAY, BUT WITH INCREASING CLOUD COVER PROBABLY A FEW
DEGREES COOLER THAN YESTERDAY. AND THERE WILL AGAIN BE A BIT OF
A GUSTY BREEZE, ESPECIALLY IN SOUTHWEST WYOMING, WHERE, COMBINED
WITH STILL LOW HUMIDITY, MAY BRING ELEVATED FIRE WEATHER THIS
AFTERNOON.
PRECIPITATION WILL REALLY INCREASE LATER TONIGHT AND INTO SATURDAY
AS THE UPPER LEVEL LOW FINALLY MOVES INTO WYOMING. MOST GUIDANCE
SHOWS THE SAME GENERAL PATTERN AS YESTERDAY, WITH A NORTHWEST TO
SOUTHEAST GRADIENT OF QPF WITH THE HIGHEST AMOUNTS IN THE WEST AND
NORTH. AREAS FURTHER TO THE EAST WILL LIKELY HAVING MORE OF A
SOUTHWEST DOWNSLOPING FLOW THAT WILL KEEP THE PRECIPITATION MORE
SHOWERY. EVERY LOCATION WILL HAVE A CHANCE OF RAIN THOUGH. AS FOR
HOW MUCH, WE WILL TAKE A LOOK AT THE NBA ENSEMBLES FOR THIS. AT THIS
POINT, IT IS FAIRLY SIMILAR TO YESTERDAY, WITH A GREATER THAN 1 IN 2
CHANCE OF A QUARTER OF AN INCH OF QPF OR MORE MAINLY NORTH AND WEST
OF A EVANSTON TO RIVERTON TO KAYCEE LINE. THE HIGHEST AMOUNTS STILL
LOOK TO BE IN NORTHWESTERN WYOMING AND NEAR THE BIGHORNS THOUGH,
WITH A GREATER THAN 1 IN 2 CHANCE OF AN INCH OF QPF OR MORE. THE
WEATHER PREDICTION CENTER CONTINUES TO HAVE A MARGINAL RISK OF
EXCESSIVE RAINFALL ACROSS NORTHERN WYOMING ON BOTH SATURDAY AND
SUNDAY. IT HAS BEEN FAIRLY DRY, SO THERE IS ROOM IN THE SOIL. BUT IT
IS SOMETHING TO KEEP IN MIND. SATURDAY CONTINUES TO LOOK LIKE THE
WETTEST DAY. HOWEVER, THE LOW WILL LIKELY SLOW DOWN SOMEWHAT AND
STALL OVER MONTANA. THIS WILL KEEP UNSETTLED WEATHER OVER PARTS OF
THE AREA, WITH NORTHERN WYOMING THE MOST IMPACTED. HOW FAR SOUTH IT
CAN STAY THIS WAY IS IN QUESTION, SINCE THERE ARE DIFFERENCES IN
GUIDANCE AS TO WHEN THE LOW WILL LIFT OUT OF THE AREA.
NEEDLESS TO SAY, IT WILL BE MUCH COOLER WITH THE CLOUD COVER AND
SHOWERS. THIS IS ESPECIALLY SO ON THE WESTERN SIDE OF THE LOW WHERE
FLOW WILL BE NORTHERLY. A PLACE LIKE JACKSON MAY STAY BELOW 55 ALL
WEEKEND. AND THIS BRINGS US TO ANOTHER PART OF THE SYSTEM, THE
CHANCE OF SNOW. YES ANY VISITORS TO THE COWBOY STATE, IT CAN SNOW
HERE ANY MONTH OF THE YEAR. NOW, IT WILL NOT ACCUMULATE IN THE LOWER
ELEVATIONS, AND TRAVEL SHOULD NOT BE IMPACTED MUCH AS IT HAS BEEN
VERY WARM AND THE HIGH SUN ANGLE WOULD MELT SNOW ON ROADS. HOWEVER,
WE DO HAVE A DECENT CHANCE OF SOME ACCUMULATING SNOW IN THE
MOUNTAINS. SOME MODELS DROP THE 700 MILLIBAR TEMPERATURES AS LOW AS
MINUS 1, WHICH WOULD LOWER SNOW LEVELS TO 8000 FEET. WE STILL THINK
THIS IS TOO LOW, IT WOULD LIKELY BE CLOSER TO 9000 FEET. ARES ABOVE
9500 FEET IN THE WESTERN MOUNTAINS HAVE A GREATER THAN 1 IN 2 CHANCE
OF AN INCH OR SNOW, AND THIS INCLUDES TOGWOTEE PASS. SOME OF THE
HIGHER ELEVATIONS OF THE TETONS AND WIND RIVERS COULD SEE 6 INCHES
OR MORE OF SNOW THIS WEEKEND. SO IF YOU ARE RECREATING IN THE
MOUNTAINS, PREPARE FOR A COLD AND WET WEEKEND. YOU WILL ALSO LIKELY
SEE SOME SNOW IF YOU ARE DRIVING OVER TOGWOTEE PASS.
EARLY NEXT WEEK IS IN QUESTIONS AS WELL. SOME GUIDANCE LINGERS THE
LOW CLOSE ENOUGH FOR SOME SHOWERS TO LINGER INTO MONDAY, OTHER FAVOR
FLOW TURNING MORE TO THE WEST-SOUTHWEST FOR A WARMER AND DRIER
PATTERN. FOR MOST OF THE NEXT WEEK, THE CONSENSUS SEEMS TO BE FOR
WARM BUT NOT HOT WEATHER AND A COUPLE OF CHANCES OF MAINLY DIURNAL
SHOWERS AND THUNDERSTORM AS SHORTWAVES MOVING THROUGH THE LARGELY
ZONAL FLOW.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 428 AM MDT FRI MAY 29 2026
VFR CONDITIONS ARE EXPECTED THROUGH AROUND 06Z FOR ALL
TERMINALS. WIND WILL INCREASE THIS AFTERNOON WITH GUSTS TO 15 TO
25 KNOTS AT MANY TERMINALS, BUT WIND WILL BE A BIT LESS THAN
YESTERDAY AFTERNOON. KCOD AND KCPR HAVE THE BEST CHANCE OF A
SHOWER OR THUNDERSTORM THIS AFTERNOON AFTER 20Z, AND WE HAVE
MAINTAINED THE PROB30 GROUPS FOR THESE LOCATIONS. AT THE OTHER
TERMINALS, THE CHANCE IS GENERALLY 10 PERCENT OR LESS THROUGH
THE DAY. A WEATHER SYSTEM WILL BEGIN TO MOVE IN FROM THE
SOUTHWEST AFTER SUNSET TONIGHT AND SPREAD SHOWERS FROM SOUTHWEST
TO NORTHEAST ACROSS THE AREA, GENERALLY AFTER 06Z SATURDAY.
MVFR CONDITIONS ARE POSSIBLE IN WEST OF THE DIVIDE AFTER AROUND
08Z TONIGHT WITH SOME MOUNTAIN OBSCURATIONS.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HATTINGS
AVIATION...HATTINGS
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