207
FXUS65 KRIW 151004
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
404 AM MDT WED APR 15 2026
KEY MESSAGES
- A POTENT LATE WINTER STORM WILL SWEEP ACROSS WYOMING THROUGH
THE REST OF THE WEEK, BRINGING WIDESPREAD SNOWFALL TO MOST OF
THE STATE. WINTER STORM WARNINGS ARE IN EFFECT FOR THE
NORTHWEST MOUNTAINS TONIGHT THROUGH FRIDAY.
- COLD AIR MOVES IN WITH THE WINTER STORM, WITH TEMPERATURES
LIKELY FALLING BELOW 28 DEGREES BOTH FRIDAY MORNING AND
SATURDAY MORNING (90% +). EXTENT OF TEMPERATURES BELOW
FREEZING COULD REACH 12 TO 15 HOURS FRIDAY NIGHT INTO SATURDAY
MORNING.
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 /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 359 AM MDT WED APR 15 2026
VFR CONDITIONS SHOULD CONTINUE THROUGH AROUND 20Z FOR ALL
TERMINALS. AN APPROACHING AREA OF LOW PRESSURE WILL BEGIN TO
SPREAD SHOWERS INTO THE WESTERN MOUNTAINS THIS AFTERNOON, WITH
SHOWERS POSSIBLE IN VICINITY OF KJAC STARTING AROUND 20Z.
PRECIPITATION SHOULD BEGIN AS RAIN, THEN TRANSITION TO SNOW
TONIGHT AS COLDER AIR MOVES IN BEHIND A COLD FRONT. OTHER
SHOWERS SPREAD INTO KPNA AND KBPI LATER TONIGHT. ALMOST ALL
SHOWERS SHOULD HOLD OFF UNTIL AFTER 12Z THURSDAY IN THE
TERMINALS EAST OF THE DIVIDE. MOUNTAIN OBSCURATIONS WILL BE
COMMON LATER TODAY AND TONIGHT TO THE WEST OF THE CONTINENTAL
DIVIDE.
WIND WILL INCREASE AT ALL TERMINALS THIS MORNING AS THE LOW
APPROACHES THE AREA. THE STRONGEST WIND WILL OCCUR IN VICINITY
OF KCPR AND KRKS WHERE GUSTS TO OVER 35 KNOTS WILL BE POSSIBLE
AFTER 18Z. WIND SHOULD DECREASE SOMEWHAT AT MOST TERMINALS AFTER
SUNSET BUT REMAIN STRONG IN VICINITY OF KCPR THROUGH MOST OF THE
NIGHT.
RIW WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM MDT FRIDAY
FOR WYZ001-002-012.
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM MDT FRIDAY
FOR WYZ014-015.
DISCUSSION...STRAUB
AVIATION...HATTINGS
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