213
FXUS65 KRIW 130155
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
755 PM MDT SUN APR 12 2026
KEY MESSAGES
- LIGHT RAIN SHOWERS PRODUCING OUTFLOW WIND GUSTS 35 TO 45 MPH
FADE LATE SUNDAY EVENING, EXCEPT OVER NORTH-CENTRAL WYOMING
WHERE THE SHOWERS, WITH LESS WIND, LINGER OVERNIGHT.
- INTERMITTENT LIGHT PRECIPITATION PERSISTS IN THE FAR WEST
VALLEYS OVERNIGHT WHERE RAIN CHANGES TO SNOW. VALLEY SNOWFALL
WILL GENERALLY BE LESS THAN ONE INCH (ONLY A 20 PERCENT CHANCE
OF AN INCH).
- ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS OCCUR MONDAY
AFTERNOON IN CENTRAL WYOMING, MAINLY ACROSS FIRE ZONES 280
AND 283.
- THE PATTERN REMAINS UNSETTLED THROUGH THE WEEK, WITH MILD
AFTERNOON TEMPERATURES AND SEVERAL CHANCES FOR MOISTURE. A
LATE WEEK SYSTEM MAY DROP SOUTHEAST FROM CANADA AND PROVIDE A
BETTER CHANCE OF WIDESPREAD PRECIPITATION WHILE GENERATING
MUCH COLDER TEMPERATURES (OVERNIGHT LOWS 15-25 DEGREES).
UPDATE
ISSUED AT 1233 PM MDT SUN APR 12 2026
CURRENT SATELLITE IMAGERY SHOWS A GROWING CU FIELD AND A FEW SHOWERS
BEGINNING TO DEVELOP ACROSS WESTERN WYOMING AS A SHORTWAVE EJECTS
OFF THE UPPER LOW TO OUR WEST. DIURNAL HEATING WILL LEAD TO
MLCAPE VALUES PEAKING IN THE 100-300 J/KG RANGE OVER THE NEXT
FEW HOURS. THIS WILL EXPAND CONVECTIVE DEVELOPMENT FROM WEST TO
EAST ACROSS THE AREA, WITH THE MOST WIDESPREAD COVERAGE ACROSS
WESTERN WYOMING GIVEN INCREASED INSTABILITY AND A MORE FAVORABLY
SHEARED ENVIRONMENT. LIKE YESTERDAY, THE MAIN CONCERN WILL BE
STRONG OUTFLOW WIND GUSTS GIVEN THE STILL DRY, WELL-MIXED
BOUNDARY LAYER (FORECAST DLCAPE VALUES OF 400-800 J/KG). THIS
ACTIVITY WILL WANE WITH SUNSET.
FIRE WEATHER IS THE OTHER CONCERN TODAY, AND RECENT FORECAST TRENDS
HAVE INCREASED CONFIDENCE FOR REACHING CRITICAL CONDITIONS
ACROSS MUCH OF NATRONA COUNTY; A RED FLAG WARNING IS NOW IN
EFFECT THERE THROUGH SUNSET.
COLDER AIR AND THE NEXT WAVE AHEAD OF THE LOW WILL QUICKLY PUSH INTO
WESTERN WYOMING THIS EVENING. THIS WILL LEAD TO A QUICK SHOT OF
LIGHT SNOW ACROSS THE WEST TONIGHT, INCLUDING A TRACE TO A HALF INCH
ACROSS THE WESTERN VALLEYS BY SUNRISE.
DISCUSSION
ISSUED AT 130 AM MDT SUN APR 12 2026
WE ARE NOW WELL INTO APRIL. AND THIS MEANS WE ARE NOW
CLIMATOLOGICALLY THE WETTEST TIME OF THE YEAR, THE MONTHS OF APRIL,
MAY AND JUNE. THIS IS USUALLY WHEN WE RECEIVE OUR BEST RAINS AND
MOISTURE LADEN SNOWS, TO BUILD UP THE WATER FOR THE DRIER SUMMER AND
EARLY FALL MONTHS. THESE THREE MONTHS WE RECEIVE ON AVERAGE ANYWHERE
FROM 30 TO AS MUCH AS 53 PERCENT OF OUR ANNUAL PRECIPITATION.
AND WE DEFINITELY NEED IT THIS YEAR. ONLY GREYBULL IS ABOVE
NORMAL WITH PRECIPITATION THIS YEAR. THE REMAINDER OF THE AREA
IS ANYWHERE FROM 25 TO 80 PERCENT OF NORMAL. RIVERTON, LANDER,
BUFFALO AND CASPER HAVE RECEIVED LESS THAN HALF OF THE AVERAGE
AMOUNT OF PRECIPITATION THIS YEAR, WITH RIVERTON AND BUFFALO
ONLY AT AROUND A QUARTER OF NORMAL. THE GOOD NEWS IS, WE WILL
HAVE A FEW CHANCES OF PRECIPITATION THROUGH THE PERIOD.
AS I WRITE THIS AROUND 1 AM, THE RADAR IS LARGELY QUIET. TODAY WILL
BE ANOTHER DAY OF SCATTERED SHOWERS AND THUNDERSTORMS AS ANOTHER
SHORTWAVE CROSSES THE AREA. PRECIPITABLE WATERS, ESPECIALLY EAST OF
THE DIVIDE, ARE AROUND 25 PERCENT LESS THAN YESTERDAY THOUGH. SO,
THE VAST MAJORITY OF SHOWERS AND STORMS WOULD BE WEST OF THE DIVIDE
TODAY. AS FOR STRONGER STORMS, THERE IS A MARGINAL RISK ACROSS
ROUGHLY THE WESTERN THIRD OF THE AREA. AND GIVEN THE INVERTED V
SOUNDINGS ACROSS THE AREA, THE MAIN THREAT, LIKE YESTERDAY, WOULD BE
STRONG WIND GUSTS OVER 50 MPH. THERE IS ANOTHER CONCERN EAST OF THE
DIVIDE. THE 700 MILLIBAR WINDS ARE STRONGER EAST OF THE DIVIDE,
APPROACHING 40 KNOTS IN SOME LOCATIONS THIS AFTERNOON. HUMIDITY WILL
ALSO BE RATHER LOW, FALLING BELOW 20 PERCENT. HOWEVER, ENSEMBLE
FORECASTS GIVE AT MOST A 1 OUT 2 CHANCE OF RELATIVE HUMIDITY FALLING
TO 15 PERCENT OR UNDER AND ONLY FOR AN HOUR OF SO. SO, CRITICAL FIRE
WEATHER LOOKS UNLIKELY. HOWEVER, ELEVATED FIRE WEATHER LOOKS LIKELY
ACROSS MUCH OF SWEETWATER, FREMONT, NATRONA AND JOHNSON COUNTIES THIS
AFTERNOON. THERE WILL ALSO BE SOME SNOW IN THE HIGHER ELEVATIONS,
WITH THE HEAVIEST IN THE WIND RIVER RANGE. THE CHANCE OF OVER 6
INCHES IS RATHER SMALL THOUGH, AT MOST A 1 IN 3 CHANCE AND THIS OVER
THE HIGHEST ELEVATIONS WHERE IMPACTS ARE LIMITED.
THE CHANCE OF SHOWERS CONTINUES MONDAY AS WELL, ALTHOUGH SOMEWHAT
LESS MOISTURE SHOULD LEAD TO A SMALLER COVERAGE AND LARGELY WEST OF
THE DIVIDE AS WELL. CONVECTION SHOULD REACH A NADIR ON TUESDAY WITH
ONLY ISOLATED SHOWERS ACROSS THE AREA. THE ONE FLY IN THE OINTMENT
IS AN UPPER LEVEL LOW PASSING ACROSS COLORADO THAT WAS SHOWING A
DECENT AMOUNT OF QPF ACROSS SOUTHERN WYOMING. RECENT MODEL TRENDS
HAVE PUSHED THE SYSTEM FURTHER SOUTHWARD AND POPS WERE LOWERED AS A
RESULT, AT THIS TIME, ANY SHOWERS FROM THIS WOULD BE CONFINED TO THE
FAR SOUTH WITH A GREATER THAN 1 IN 3 CHANCE OF A TENTH OF AN INCH OR
RAIN CONFINED TO AREAS SOUTH OF INTERSTATE 80. TEMPERATURES THROUGH
TUESDAY AND EVEN WEDNESDAY WILL CONTINUE TO AVERAGE ABOVE NORMAL.
THEN HEADING INTO THE END OF THE WEEK, WE HAVE THE CHANCE OF
SOMETHING WE HAVE NEEDED FOR A WHILE, A CHANCE OF A DECENT
PRECIPITATION EVENT ACROSS MUCH OF THE AREA. THIS COMES COURTESY OF
AN UPPER LEVEL LOW MOVING INTO BRITISH COLUMBIA AND THEN MOVING INTO
THE NORTHERN ROCKIES FOR THURSDAY AND FRIDAY. MY GUT FEELING, GIVEN
THE FAST BIAS OF THE MODELS FOR PACIFIC SYSTEMS, IS THAT THIS WOULD
START MORE WEDNESDAY NIGHT OR THURSDAY, WITH WEDNESDAY LARGELY DRY.
THIS LOOKS TO BE A SLOWER MOVING SYSTEM WITH A GOOD AMOUNT OF
MOISTURE THAT COULD, EMPHASIS ON COULD, BRING A GOOD RAIN AND
SNOW TO MUCH OF THE AREA. THERE ARE STILL FAIRLY SUBSTANTIAL
DIFFERENCES WITH DETAILS IN REGARDS TO THE MOVEMENT OF THE UPPER
LEVEL LOW AND ANY LEE CYCLOGENESIS, AND THIS LEADS TO DIFFERENCES
IN PLACEMENT OF THE BEST UPSLOPE FLOW AND PLACEMENT OF THE
HEAVIEST PRECIPITATION. SO, I WILL NOT EVEN ATTEMPT TO PINPOINT
DETAILS THIS FAR OUT. THIS WILL BE A COOLER SYSTEM AS WELL,
WITH 700 MILLIBAR TEMPERATURES FALLING TO MINUS 10 OR LOWER,
DROPPING SNOW LEVELS TO VALLEY AND BASIN FLOORS THURSDAY NIGHT.
ENSEMBLE GUIDANCE GIVES AT LEAST A 2 OUT OF 3 CHANCE OF AT LEAST
AND INCH OF SNOW ACROSS MUCH OF THE AREA FROM THURSDAY THROUGH
FRIDAY NIGHT, WITH SIMILAR CHANCES OF AT LEAST A QUARTER OF AN
INCH OF PRECIPITATION THROUGH THE PERIOD. IT IS STILL SEVERAL
DAYS OUT BUT THINGS LOOK SOMEWHAT PROMISING RIGHT NOW, KEEP YOUR
FINGERS CROSSED.
AND THE FINAL CONCERN IS FOR A FREEZE. YES, IT IS ONLY MID APRIL NO
ONE SHOULD BE PLANTING GARDENS OR CROPS YET; LONGTIME RESIDENTS
KNOW BETTER. HOWEVER, MANY TREES HAVE BLOOMED AND MANY FLOWERS
ARE OUT. THIS COULD BE A CONCERN AS EARLY AS THURSDAY NIGHT WITH
THE SNOW. THE REAL TIME OF CONCERN MAY BE FRIDAY NIGHT,
ESPECIALLY IF THE SNOW ENDS EARLIER AND THERE IS SOME CLEARING.
EARLY ENSEMBLE GUIDANCE GIVES AT LEAST A 2 OUT OF 3 CHANCE OF
LOW TEMPERATURES BELOW 25 DEGREES IN THE LOWER ELEVATIONS BY
SATURDAY MORNING, WITH SOME AREAS HAVING A 1 IN 2 CHANCE OF LOWS
BELOW 20. A LOT DEPENDS ON HOW MUCH SNOW FALLS AND IF THERE IS
ANY CLEARING, BUT A LOT OF EARLY BLOOMING PLANTS WILL LIKELY
HAVE A TOUGH COUPLE OF NIGHTS TOWARD THE END OF THE WEEK.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 504 PM MDT SUN APR 12 2026
VFR FLIGHT CONDITIONS ARE LARGELY EXPECTED THROUGHOUT THE TAF
PERIOD. ISOLATED SHOWERS AND THUNDERSTORMS IN THE AREA OF KJAC AND
KCOD ARE EXPECTED TO LINGER THROUGH ROUGHLY 01Z/02Z. ALL OTHER
TERMINALS HAVE LESS THAN A 15 PERCENT CHANCE OF A SHOWER OR
THUNDERSTORM THROUGH 02Z. GUSTY 40KT WINDS ARE POSSIBLE AT ANY
TERMINAL IN OR WITH NEARBY SHOWERS OR THUNDERSTORMS. OVERNIGHT
AT KJAC, KPNA, AND KBPI, THERE IS A 30 PERCENT CHANCE OF LIGHT
SNOW WITH THE POTENTIAL (20 PERCENT CHANCE) FOR MVFR CEILINGS.
EXPECT MOUNTAIN OBSCURATIONS WITH ANY LIGHT SNOW. LATE IN THE
TAF PERIOD, THERE ARE LIGHT RAIN SHOWER CHANCES AT KRKS (30
PERCENT) AND KJAC (15 PERCENT). HOWEVER, OPTED TO ONLY MENTION
IN KRKS TAF AT THIS TIME GIVEN SLIGHTLY HIGHER CONFIDENCE.
GUSTY WINDS ARE EXPECTED TO DIMINISH BY 02Z, AT THE LATEST, AT ALL
TERMINALS. WINDS ARE FORECAST TO BE LIGHT THROUGH SUNRISE ON MONDAY.
WINDS INCREASE AGAIN AROUND SUNRISE/11Z ON MONDAY AT KCOD AND KCPR.
ALL OTHER TERMINALS BECOME GUSTY BETWEEN 16Z AND 19Z ON MONDAY.
AFTERNOON WIND GUSTS ON MONDAY ARE FORECAST TO BE BETWEEN 20KTS
AND 30KTS, EXCEPT AT KCPR. KCPR COULD SEE GUSTS BETWEEN 35KTS
AND 40KTS ON MONDAY AFTERNOON.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
FIRE WEATHER
ISSUED AT 130 AM MDT SUN APR 12 2026
A COMBINATION OF ABOVE NORMAL TEMPERATURE, HUMIDITY FALLING TO
BETWEEN 15 AND 20 PERCENT AND A GUSTY WEST TO SOUTHWESTERLY WIND
WILL BRING ELEVATION FIRE WEATHER ROUGHLY ALONG AND EAST OF A
ROCK SPRINGS TO RIVERTON TO CASPER LINE THIS AFTERNOON. ELEVATED
FIRE TO POSSIBLY CRITICAL FIRE WEATHER IS POSSIBLE AGAIN ON
MONDAY WITH LOWER DEW POINTS AND CONTINUED GUSTY WIND, BUT
SOMEWHAT LOWER TEMPERATURES.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...MYERS
DISCUSSION...HATTINGS
AVIATION...GERHARDT
FIRE WEATHER...HATTINGS
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