347
FXUS65 KRIW 310227
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
827 PM MDT FRI MAY 30 2025
KEY MESSAGES
- WARM AND MOSTLY DRY THROUGH THE WEEKEND. TEMPERATURES RISE TO NEAR
OR ABOVE 90 DEGREES BY SUNDAY FOR MUCH OF THE AREA.
- RIVER AND STREAM FLOODING POTENTIAL WILL CONTINUE TO INCREASE
THROUGH THE WEEKEND AS SNOWMELT IS EXACERBATED BY WARMING
TEMPERATURES.
- SHOWER AND THUNDERSTORM CHANCES INCREASE ON SUNDAY ACROSS
NORTHWESTERN WYOMING AS THE NEXT SYSTEM APPROACHES.
- COOLER AND WETTER CONDITIONS EXPECTED MONDAY THROUGH THE
MIDDLE OF NEXT WEEK, THOUGH PRECIPITATION AMOUNTS REMAIN
HIGHLY UNCERTAIN.
UPDATE
ISSUED AT 207 PM MDT FRI MAY 30 2025
NOT MUCH CHANGE TO THE FORECAST TODAY. SATELLITE AND RADAR IMAGERY
ARE SHOWING A FEW STRUGGLING SHOWERS EARLY THIS AFTERNOON IN
RESPONSE TO A WEAK SHORTWAVE CLIPPING WYOMING. THIS ACTIVITY WILL
REMAIN LIMITED, AND NEARLY ALL OF THE AREA WILL STAY WARM AND DRY.
AS DISCUSSED BELOW, THIS TREND WILL LARGELY CONTINUE THROUGH THE
WEEKEND, THOUGH WITH INCREASING CONVECTION CHANCES ACROSS THE
NORTHWEST ON SUNDAY AS THE NEXT SYSTEM APPROACHES. THE UNCERTAINTY
WITH THIS SYSTEM CONTINUES, PARTICULARLY WITH PRECIPITATION AMOUNTS
EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 202 AM MDT FRI MAY 30 2025
QUIET WEATHER IS THE RULE FOR A CHANGE TONIGHT ACROSS WESTERN AND
CENTRAL WYOMING AND HERE AT THE HUMBLE RIVERTON WEATHER ABODE. MOST
AREAS SHOULD STAY MAINLY QUIET TODAY, BUT WE HAVE ONE CONCERN. THAT
IS A FAST MOVING SHORTWAVE / UPPER LEVEL LOW DIVING OUT OF
SASKATCHEWAN AND MOVING INTO THE PLAINS STATES. GUIDANCE HAS
FINALLY COME INTO BETTER AGREEMENT IN MOVING ACROSS MONTANA AND
INTO THE DAKOTAS. THIS, PLUS THE FACT IT IS OF CONTINENTAL
ORIGIN AND AS A RESULT IS MOISTURE STARVED, WILL KEEP ANY
CONVECTION TO A MINIMUM. WE HAVE KEPT SOME MINIMAL POPS FOR
JOHNSON AND NATRONA COUNTIES AND THE EASTERN SLOPES OF THE
ABSAROKAS, BUT EVEN HERE THE CHANCE OF A SHOWER OR THUNDERSTORM
IS AT MOST 1 OUT OF 5. ALL SHOWERS SHOULD END BEFORE SUNSET.
THE OTHER CONCERN IS FOR GUSTY WIND IN THE FAVORED NORTHWEST
FLOW LOCATIONS, ESPECIALLY JOHNSON COUNTY, WHERE THERE IS A 4
OUT OF 5 CHANCE OF WIND GUSTS PAST 40 MPH THIS MORNING FOLLOWING
THE PASSAGE OF A WEAK COLD FRONT. THE CHANCE OF GUSTS PAST 50
MPH IS LESS THAN 1 OUT OF 10 THOUGH, SO NO WIND HIGHLIGHTS WILL
BE NEEDED. AND, WITH THE RIDGE BUILDING, IT SHOULD KEEP MOST OF
THE SMOKE FROM THE WILDFIRES IN CANADA TO THE EAST OF THE AREA.
IT WILL BE A NICE AND SUMMERY START TO THE WEEKEND AND THE LAST DAY
OF METEOROLOGICAL SPRING WITH RIDGING OVER THE AREA. TEMPERATURES
WILL PUSH INTO THE 80S, IN SOME CASES WELL INTO THE 80S FOR HIGH
TEMPERATURES FOR THE LOWER ELEVATIONS. THIS COULD BE THE DAY WE
SEE OUR FIRST 90 DEGREE HIGH. HOWEVER, THERE IS A MUCH BETTER
CHANCE ON SUNDAY AS SOUTHWEST FLOW INCREASES AHEAD OF AN UPPER
LEVEL LOW APPROACHING FROM THE SOUTHWEST. MANY LOWER ELEVATION
LOCATIONS EAST OF THE DIVIDE WILL HAVE AT LEAST A 1 OUT OF 2
CHANCE OF 90 DEGREES FOR A HIGH ON SUNDAY, AND AS HIGH AS A 4
OUT OF 5 CHANCE IN THE BIGHORN BASIN. THIS APPROACHING UPPER
LEVEL LOW AND ASSOCIATED COLD FRONT WILL ALSO INCREASE THE
CHANCE FOR CONVECTION. THE STORM PREDICTION CENTER HAS ISSUED A
DAY 3 MARGINAL RISK ACROSS NORTHWESTERN WYOMING, SO WE COULD
SEE A FEW STRONGER STORMS. AND, WE HAVE THE CONCERN OF SOME
RISING CREEK AND RIVERS AS LEFTOVER HIGH ELEVATION SNOW MELTS.
IT DOES NOT LOOK LIKE MAJOR FLOODING AT THIS TIME, BUT WE WILL
WATCH IT.
WE HAVE THE SAME REASONING FOR EARLY NEXT WEEK AS YESTERDAY AT THIS
TIME. WE ARE CONFIDENT OF TRANSITIONING TO A COOLER PERIOD STARTING
ON MONDAY AND CONTINUING INTO THE MIDDLE OF NEXT WEEK. HOWEVER,
DETAILS ON PRECIPITATION AMOUNTS AND TIMING OF THE
PRECIPITATION REMAINS HIGHLY UNCERTAIN. SOME GUIDANCE, LIKE THE
ECMWF, KEEPS THE ENERGY SPLIT AND GIVES WYOMING ONLY A GLANCING
BLOW FOR SHOWERS. OTHERS, LIKE THE GFS, IS MORE IMPACTFUL WITH
A DECENT RAIN MONDAY INTO TUESDAY. PROBABILISTIC GUIDANCE STILL
GIVES A GREATER THAN 1 IN 2 CHANCE OF GREATER THAN HALF INCH OF
QPF FOR MOST OF THE NORTHERN HALF OF THE AREA. THERE COULD BE A
FEW INCHES OF SNOW IN THE BIGHORNS, WHERE 700 MILLIBAR
TEMPERATURES FALLING TO MINUS 1C MAY LOWER SNOW LEVELS DOWN TO
8000 TO 8500 FEET ON TUESDAY. HOWEVER, THIS SYSTEM HAS MORE
MOVING PARTS THAN A RUBE GOLDBERG MACHINE SO DETAILS WILL BE
HARD TO HASH OUT UNTIL PROBABLY SUNDAY AT THE EARLIEST.
FOLLOWING THAT, THERE IS MORE UNCERTAINTY WITH SOME GUIDANCE
SHOWING RIDGING AND DRIER WEATHER AND OTHERS HAVING ZONAL FLOW
WITH SHORTWAVES BRINGING FURTHER CHANCES OF CONVECTION. SO,
UNCERTAINTY IS HIGH IN THE LONG RANGE.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 449 PM MDT FRI MAY 30 2025
VFR CONDITIONS WITH ONLY FEW TO SCT HIGH CLOUDS THROUGH THE TAF
PERIOD FOR ALL TERMINALS. WINDS REMAIN MOSTLY LIGHT (LESS THAN
10KTS) THROUGH THE PERIOD, WITH A FEW SITES SEEING SOME LINGERING
GUSTS TAPERING OFF WITHIN THE FIRST FEW HOURS OF THE PERIOD. THE
EXCEPTION HERE WILL BE KRKS, WHERE A NORTH-EASTERLY WIND PUSH IS
EXPECTED BETWEEN 05Z AND 06Z THIS EVENING. HI-RES GUIDANCE STILL
SUGGESTS THAT THIS WILL BRING GUSTY WINDS FOR A FEW HOURS OVERNIGHT,
WITH GUSTS TO 20 TO 25KTS. MOS AND NBM GUIDANCE ALSO CONTINUE
TO INDICATE THIS NORTH-EASTERLY PUSH MOVING IN AROUND THE SAME
TIME FRAME, BUT WEAKER AND WITHOUT THE GUSTS. HAVE CONTINUED TO
GO WITH HI-RES GUIDANCE FOR THE KRKS TAF FOR THIS ISSUANCE WITH
GUSTS 20 TO 25KTS THROUGH 11Z. WINDS DIMINISH AT THAT POINT,
REMAINING LIGHT EASTERLY THROUGH THE REMAINDER OF THE PERIOD.
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...MYERS
DISCUSSION...HATTINGS
AVIATION...HENSLEY/DZIEWALTOWSKI
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