624
FXUS65 KRIW 151857
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1257 PM MDT WED APR 15 2026
KEY MESSAGES
- WINDY SOUTHWEST WINDS ARE EXPECTED TODAY, WITH WIDESPREAD
GUSTS OF 25 TO 40 MPH. WIND PRONE LOCATIONS COULD SEE GUSTS UP
TO 50 MPH. OTHERWISE, AFTERNOON TEMPERATURES WILL BE MILD
ACROSS THE AREA.
- SNOW CHANCES (70-90%) INCREASE THIS AFTERNOON ACROSS WEST AND
NORTHWEST WYOMING. PRECIPITATION (RAIN THEN SNOW) SPREADS EAST
ACROSS THE ENTIRE AREA MIDDAY ON THURSDAY. STRONG WINDS AND
SNOW COULD CREATE HAZARDOUS TRAVEL CONDITIONS THURSDAY EVENING
THROUGH FRIDAY MORNING, ESPECIALLY ALONG I-25, US 20/26, AND
US 287.
- THERE IS HIGH CONFIDENCE (95%+) IN A HARD FREEZE (28 DEGREES
OR BELOW) FRIDAY MORNING AND SATURDAY MORNING. WIDESPREAD
MORNING LOWS IN THE LOW 20S AND TEENS ARE EXPECT ON SATURDAY
MORNING.
UPDATE
ISSUED AT 1257 PM MDT WED APR 15 2026
1PM/19Z RADAR IMAGERY SHOWS LIGHT SNOW SHOWERS OVER THE TETONS,
INDICATING THAT THE FIRST PUSH OF PACIFIC MOISTURE, ASSOCIATED WITH
THE WINTER WEATHER SYSTEM, HAS ARRIVED. EXPECT ONLY RAIN ACROSS
JACKSON VALLEY AND STAR VALLEY THIS AFTERNOON WITH TEMPERATURES IN
THE 40S. SNOWFALL RATES FOR THE NORTHWEST MOUNTAINS AND THE WIND
RIVER MOUNTAINS WILL INCREASE BY 6PM MDT TODAY AS THE UPPER LEVEL
TROUGH BEGINS TO PUSH INTO THE NORTHERN ROCKIES, WITH MODERATE TO
HEAVY SNOW EXPECTED. ANTICIPATE WINTER TRAVEL CONDITIONS ACROSS
TETON PASS, TOGWOTEE PASS, AND SOUTH PASS WITH SNOW AND GUSTY 30 TO
50 MPH WINDS. AS FOR THE WESTERN VALLEYS, TEMPERATURES ARE FORECAST
TO REMAIN ABOVE FREEZING UNTIL AFTER MIDNIGHT TONIGHT. THIS MEANS
THAT RAIN WILL CHANCE OVER TO SNOW AFTER MIDNIGHT AS WELL. EXPECT
ONLY LIGHT ACCUMULATIONS OF 1 TO 3 INCHES FOR THE WESTERN VALLEYS
THROUGH THURSDAY NIGHT.
AS MENTIONED IN THE MORNING DISCUSSION, PRECIPITATION WILL SPREAD
EAST ACROSS THE STATE DURING THE DAY ON THURSDAY AS THE POTENT COLD
FRONT PUSHES EAST. EXPECT PRECIPITATION TO BEGIN AS RAIN AHEAD OF
THE COLD FRONT WITH TEMPERATURES IN THE 50S. ON THURSDAY, THE COLD
FRONT IS EXPECTED TO PASS THROUGH SOMETIME IN THE NOON TO 3PM
TIMEFRAME FOR JOHNSON COUNTY AND 3PM AND 7PM TIMEFRAME ELSEWHERE AND
QUICKLY DROP TEMPERATURES. RAIN WILL QUICKLY CHANGE OVER TO SNOW DUE
TO THE QUICK TEMPERATURE DROP DURING THESE TIMEFRAMES. ALSO,
WIDESPREAD WINDY CONDITIONS ARE EXPECTED DUE TO THE TIGHT
TEMPERATURE GRADIENT BOTH AHEAD AND BEHIND THE FRONT. GUSTY 30 TO 50
MPH ARE FORECAST FOR MOST LOW ELEVATIONS. NEAR AND IN BUFFALO,
NORTHERLY GUSTS OF 60 MPH ARE POSSIBLE BEHIND THE FRONT THURSDAY
NIGHT.
ALTHOUGH SNOW AMOUNTS FOR FREMONT, NATRONA, AND JOHNSON COUNTIES ARE
IN THE GENERALLY IN THE 1 TO 5 INCH RANGE, WINTER WEATHER ADVISORIES
HAVE BEEN ISSUED FOR THESE AREAS DUE TO WIND AND SNOW. THE GUSTY 30
TO 50 MPH WINDS COMBINED WITH LIGHT SNOW WILL NO DOUBT CAUSE REDUCED
VISIBILITIES AND PERIODS OF HAZARDOUS TRAVEL. ADDITIONALLY, DUE TO
THE STRONG TEMPERATURE DROP WITH THE COLD FRONT, AND THUS INCREASED
FRONTOGENESIS, CONVECTIVE SNOW BANDS/SNOW SQUALLS ARE POSSIBLE
ACROSS EASTERN FREMONT, JOHNSON, AND NATRONA COUNTIES ALONG THE
FRONT THURSDAY EVENING AND OVERNIGHT. THIS BANDING COULD ALSO OCCUR
ACROSS EASTERN SWEETWATER, INCLUDING ALONG I-80, BUT CONFIDENCE IS
TOO LOW TO INCLUDE THIS AREA IN THE HAZARD. ANY SNOW SQUALL OR
CONVECTIVE SNOW BAND WILL CAUSE SUDDEN DROPS IN VISIBILITY AND
CREATE VERY HAZARDOUS TRAVEL CONDITIONS. CONFIDENCE REMAINS VERY
HIGH (95%+) IN A HARD FREEZE (28 DEGREES OR LESS) FRIDAY MORNING AS
WELL. IT IS NECESSARY TO NOTE THAT WINTER WEATHER ADVISORIES HAVE
ALSO BEEN ISSUED FOR THE BIGHORNS, CASPER MOUNTAIN, AND THE
RATTLESNAKE MOUNTAINS FOR THE SAME REASONS.
DISCUSSION
ISSUED AT 109 AM MDT WED APR 15 2026
FOR MOST OF THE STATE, THE MILD TEMPERATURES WILL BELIE THE
ABRUPT AND SHIFT WEATHER SHIFT APPROACHING. MOST OF THE STATE
WILL AGAIN SEE MILD TEMPERATURES AND GUSTY WINDS TODAY, WITH
HIGHS IN THE 60S.
AND THEN THE BOTTOM FALLS OUT OF THE FORECAST. THE NEXT WINTER
SYSTEM IS COMING ASHORE ALONG THE PACNW THIS MORNING, AND WILL
ALREADY START TO SPREAD SNOWFALL INTO THE NW MOUNTAINS BY THIS
AFTERNOON. THIS SNOWFALL WILL ONLY INCREASE THROUGH THE NIGHT
TONIGHT AS THE COLD AIR PUSHES INTO THE STATE. THE MAIN COLD
FRONT WILL RACE ACROSS THE STATE DURING THE DAY THURSDAY,
BRINGING A STUNNING DROP IN TEMPERATURES FROM THE LOW TO MID 50S
AROUND NOON TO THE UPPER 30S BY 6PM. AS THE FRONT SWEEPS
THROUGH, PRECIPITATION WILL COME ALONG AS WELL. PRECIP WILL
START AS RAIN FOR THE LOWER ELEVATIONS BRIEFLY, BEFORE SWITCHING
TO ALL SNOW BY EARLY EVENING. SNOW WILL CONTINUE ACROSS THE
STATE THROUGH THE NIGHT INTO FRIDAY, CONTINUING THROUGH SUNSET
BEFORE TAPERING OFF. MAIN FORECAST ISSUE IS HOW MUCH OF THE
INITIAL SNOWFALL WILL MELT OFF, DUE TO GROUND TEMPERATURES
ALREADY BEING VERY WARM. PUTTING ALL THESE FACTORS TOGETHER,
HAVE GONE AHEAD AND UPGRADED CURRENT WINTER WATCHES TO WINTER
STORMS WARNINGS FOR THE NW MOUNTAINS, INCLUDING THE WIND RIVER
RANGE. WILL NEED TO CLOSELY MONITOR THE SNOW FORECAST FOR THE
BIGHORNS, ALONG WITH LOWER ELEVATIONS OF JOHNSON, NATRONA, AND
FREMONT COUNTIES FOR LAST MINUTE MODEL SHIFTS FOR ACCUMULATIONS.
AS THIS SYSTEM SWEEPS SOUTHEAST, SKIES WILL GRADUALLY CLEAR WEST
TO EAST FRIDAY NIGHT. THE COLD POOL MOVING IN BEHIND THE SYSTEM
IS PARTICULARLY COLD FOR THIS TIME OF YEAR, AND A COUPLE FACTORS
WILL DETERMINE JUST HOW COLD TEMPERATURES FALL. FIRST IS HOW
FAST CLOUD COVER CLEARS OUT, ALLOWING BETTER RADIATIONAL
COOLING. SECOND IS IF THERE'S ANY CONSIDERABLE SFC SNOWPACK
INSULATING THE COLD POOL AS IT MOVES THROUGH. CURRENT FORECAST
IS FOR LOWS IN THE MID TO UPPER TEENS. WITH CLOUDS CLEARING SELL
BEFORE SUNRISE, AND SNOWPACK HOLDING FOR MOST AREAS. CURRENT
FORECAST HAS TEMPERATURES IN MOST LOWER ELEVATIONS FALLING
BELOW 28 DEGREES (HARD FREEZE) FOR 9 TO 12 HOURS. THIS WILL HAVE
A SIGNIFICANT IMPACT ON ALREADY FLOWERING PLANT LIFE, ANIMALS,
LAWN SPRINKLER AND IRRIGATION SYSTEMS, AND THE LIKE. PLEASE TAKE
ANY AND ALL PRECAUTIONS FOR A LATE-SEASON COLD SNAP.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1127 AM MDT WED APR 15 2026
VFR CONDITIONS ACROSS NEARLY ALL TERMINALS TO START THE TAF PERIOD.
KJAC IS THE ONLY EXCEPTION AS SHOWERS BEGIN TO MOVE INTO THE AREA
LEADING TO LOWERED CEILINGS AND MVFR CONDITIONS. A NEARING
DISTURBANCE WILL BRING ROUNDS OF PRECIPITATION TO WESTERN TERMINALS
AND INCREASED WINDS TO NEARLY ALL TERMINALS THIS TAF PERIOD. KJAC AS
MENTIONED EARLIER WILL SEE SHOWERS THROUGH THE AFTERNOON INTO THE
EVENING. THERE MAY BE SOME SPOTTY SHOWERS AFTER 02Z THURSDAY WITH
ANOTHER ROUND OF PRECIPITATION LIKELY BY 09Z. BY THIS TIME
TEMPERATURES SHOULD DROP TO NEAR OR BELOW FREEZING LEADING TO SNOW
SHOWERS. OTHERWISE, WINDS INCREASE FOR THE START OF THE PERIOD
AT NEARLY ALL TERMINALS WITH GUSTS OF 20 TO 35 KNOTS POSSIBLE
THROUGH THE EVENING. WINDS DECREASE SLIGHTLY AFTER SUNSET WITH
BREEZY WINDS OF 10 TO 20 KNOTS PERSISTING THROUGH THE OVERNIGHT.
A COLD FRONT BEGINS TO ENTER THE STATE THURSDAY MORNING WHICH
WILL BRING PRECIPITATION CHANCES TO KCOD, KPNA, KBPI, AND KJAC
AROUND THE END OF THE TAF PERIOD. WINDS WILL START TO INCREASE
AHEAD OF THE FRONTAL PASSAGE WITH MANY TERMINALS SEEING WINDS
INCREASE BY AROUND 15Z THURSDAY. ASIDE FROM INCREASING WINDS ALL
TERMINALS WILL LIKELY SEE LOWERING CEILINGS AROUND THIS TIME.
MOUNTAIN OBSCURATION WILL BE PERSISTENT THROUGH THE TAF PERIOD
ESPECIALLY ACROSS WESTERN MOUNTAINS WITH OBSCURATION INCREASING
BY THE END OF THE TAF 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
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM MDT FRIDAY
FOR WYZ001-002-012.
WINTER WEATHER ADVISORY FROM 9 AM THURSDAY TO 6 AM MDT FRIDAY
FOR WYZ008-009.
WINTER WEATHER ADVISORY FROM NOON THURSDAY TO 6 AM MDT FRIDAY
FOR WYZ010-011.
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM MDT FRIDAY
FOR WYZ014-015.
WINTER WEATHER ADVISORY FROM 3 PM THURSDAY TO 6 AM MDT FRIDAY
FOR WYZ016>018.
WINTER WEATHER ADVISORY FROM 3 PM THURSDAY TO NOON MDT FRIDAY
FOR WYZ019-020-022.
UPDATE...GERHARDT
DISCUSSION...STRAUB
AVIATION...DZIEWALTOWSKI
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