Terrain-induced heavy snowfall occurred across western Wyoming as a favorable moist, westerly flow aloft enveloped areas west of the Continental Divide. The heaviest snow fell in Teton County with frequent reports of 12 to 18 inches in Jackson Hole and in the Teton Range.
Every event with a place to put it; 7 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS RIW wrote it up.
Terrain-induced heavy snowfall occurred across western Wyoming as a favorable moist, westerly flow aloft enveloped areas west of the Continental Divide. The heaviest snow fell in Teton County with frequent reports of 12 to 18 inches in Jackson Hole and in the Teton Range. Snow totals of 6 to 10 inches were common across the lower elevations of Lincoln County. The nearby Salt River and Wyoming ranges received about one foot of snow. To the east of the Divide, high wind blew in Natrona County where speeds reached 74 mph on the south side of Casper and 61 mph at the city's international airport.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Riverton, WY wrote its last area forecast discussion before the first event at Dec 20, 10:47 PM MST, 2 hours 13 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 1047 PM MST SUN DEC 20 2015 .UPDATE... FOR WINTER STORM WARNING...HIGH WIND WARNING...AND WINTER WEATHER ADVISORIES. MORE TO FOLLOW ON MAIN EARLY MORNING PACKAGE. && .PREV DISCUSSION... /ISSUED 221 PM MST SUN DEC 20 2015/ SHORT TERM...TONIGHT THROUGH MONDAY MOIST WEST FLOW ALOFT AHEAD OF A PACIFIC LOW PRESSURE TROUGH MOVING INTO THE WEST COAST WILL PRODUCE WIDESPREAD SNOWFALL IN AND NEAR THE WESTERN MOUNTAINS WITH SEASONABLE TEMPERATURES EXPECTED. IN THE SHORT TERM SNOWFALL TONIGHT SHOULD BE IN THE 4 TO 6 INCH RANGE IN THE HIGHER ELEVATIONS WITH 3 TO 5 INCHES ON MONDAY. THE VALLEYS CAN EXPECT 2 TO 4 INCHES. EAST OF THE CONTINENTAL DIVIDE STRONG DOWNSLOPE WINDS WILL BRING WARMING. SOME DRIFTING AND BLOWING SNOW MAY BE ENCOUNTERED ESPECIALLY IN THE MOUNTAINS. MUCH OF THE LOW LEVEL SNOW HAS ALREADY BEEN BLOWN INTO DRIFTS AND IS RATHER HARD PACKED NOW. LONG TERM...MONDAY NIGHT THROUGH SUNDAY MODELS CONTINUE ON THEIR TREND OF DEMONSTRATING A VERY MOIST WESTERLY FLOW MONDAY NIGHT AND INTO WEDNESDAY. WITH ITS PIQUE EXPECTED TUESDAY EVENING AND INTO WEDNESDAY...IT REMAINS FAVORABLE FOR SIGNIFICANT SNOWFALL OVER THE WESTERN MOUNTAINS AND VALLEYS. MODELS AND NATIONAL GUIDANCES CONTINUE TO INDICATE IMPRESSIVE SNOWFALL AMOUNTS THROUGH WEDNESDAY MORNING. A WINTER STORM WATCH REMAINS IN EFFECT FOR THE MOST FAVORABLE AREAS...WITH NO CHANGES TO TIMING MADE DURING THIS FORECAST PACKAGE. AGAIN...IN ADDITION TO SNOWFALL...A STRONG APPROACHING JET WILL AID IN THE DEVELOPMENT OF STRONG WIND ACROSS THE AREA. MOST SUSCEPTIBLE IN THIS PATTERN WILL BE THE WIND CORRIDOR...ESPECIALLY BETWEEN ROCK SPRINGS AND CASPER. THE STRONGEST WINDS APPEAR TO BE EARLY TUESDAY MORNING...WITH WINDS RELAXING THROUGH THE AFTERNOON HOURS. THOUGH THE STRONGEST WINDS MAY TAPER OFF EARLY IN THE DAY...IT IS EXPECTED TO REMAIN GUSTY THROUGH WEDNESDAY. WHILE THE POTENTIAL FOR SIGNIFICANT SNOWFALL AND POTENTIAL FOR STRONG WIND REMAINS THE MOST NOTABLE FORECAST CONCERNS DURING THE FORECAST PERIOD... IT SHOULD BE NOTED THAT WIDESPREAD COOLER TEMPERATURES WILL IMPACT THE AREA TUESDAY AND INTO WEDNESDAY. MINIMUM TEMPERATURES TUESDAY NIGHT WILL COOL ANYWHERE FROM 5 TO 15 DEGREES FROM THEIR VALUES MONDAY NIGHT. BECAUSE OF THE ANTICIPATED GUSTY WINDS...THERE IS GOOD POTENTIAL FOR SUBZERO WIND CHILLS WEDNESDAY MORNING FOR MUCH OF WESTERN AND CENTRAL WYOMING. THIS POTENTIALLY IMPRESSIVE WINTER SYSTEM WILL EXIT THE AREA WEDNESDAY EVENING...THOUGH SOME LINGERING SNOWFALL IS EXPECTED AS ADDITIONAL MOISTURE MOVES INTO WESTERN WYOMING. A SURGE OF MOISTURE FROM AROUND THE UTAH/COLORADO BORDER IS THEN ANTICIPATED TO MOVE NORTHEAST THROUGH THE AREA ON CHRISTMAS DAY...POTENTIALLY BRINGING LIGHT SNOWFALL AS IT PROGRESSES THROUGH THE STATE. THE POTENTIAL FOR FRESH SNOWFALL RELATED WHITE CHRISTMAS DOES STILL EXIST...THOUGH SOME AREAS MAY NOT SEE SNOWFALL UNTIL THE AFTERNOON HOURS. GENERALLY BENIGN CONDITIONS MOVE OVER THE AREA BY SATURDAY WITH A BUILDING AREA OF HIGH PRESSURE. AVIATION.../06Z ISSUANCE/ EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES THE MAIN AVIATION CONCERNS THROUGH THE TAF PERIOD WILL BE STRONG WINDS...LOW LEVEL WIND SHEAR...AND GENERAL MOUNTAIN TURBULENCE. THE STRONGEST WINDS WILL OCCUR FROM SOUTH PASS TO CASPER...WHILE LLWS WILL IMPACT KCOD AND KLND TERMINALS. THE STRONG WINDS COULD ALSO SURFACE ONCE IN A WHILE AT THOSE TERMINALS. OTHERWISE EXPECT VFR CONDITIONS WITH VARIABLE MID/HIGH LEVEL CLOUDINESS. ROUTES GOING WEST OVER THE DIVIDE WILL ENCOUNTER SNOW...LOW CEILINGS AND SEVERE TURBULENCE. WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES LIGHT SNOW/FLURRIES AND MOUNTAIN OBSCURATIONS WILL CONTINUE TONIGHT...MAINLY OVER THE FAR WEST. THIS ACTIVITY WILL CONTINUE MONDAY MORNING. HOWEVER A POTENT WINTER STORM PUSHING ACROSS THE REGION MONDAY AFTERNOON AND TONIGHT WILL RESULT IN CONSIDERABLE SNOWFALL AND WIND...WITH SEVERELY REDUCED VISIBILITIES AT TIMES IN SNOW AND BLOWING SNOW. THE PEAK IN SNOWFALL IS EXPECTED TO OCCUR BETWEEN 23Z AND 06Z...WITH THE WORST IMPACTS OVER THE FAR WESTERN VALLEYS INCLUDING KJAC. HOWEVER EVEN OTHER TERMINALS WILL LIKELY SEE MVFR/IFR CONDITIONS IN LOW CEILING OR LOW VSBY IN SNOW. STRONG SOUTHERLY WINDS ARE EXPECTED TO DEVELOP LATER THIS AFTERNOON...AND CONTINUE INTO THE NIGHT. THIS WIND WILL BE STRONG ENOUGH FOR SOME BLOWING SNOW. MOUNTAINS WILL BE OBSCURED MUCH OF THE TIME WITH IFR/LIFR CONDITIONS MOST OF THE TIME. SOUTH PASS LOOKS TO BE A BIT BETTER...BUT SHOULD ALSO GO DOWN BY AROUND 00Z AS THE MAIN BRUNT OF THE STORM OVERSPREADS THE REGION. FIRE WEATHER... MOIST WESTERLY FLOW WITH A SERIES OF SHORT WAVE LOW PRESSURE TROUGHS WILL BRING PERIODS OF SNOW TO THE WESTERN MOUNTAINS OF WYOMING THROUGH MUCH OF THE WEEK AHEAD. THE HEAVIEST PERIOD OF SNOW IS EXPECTED LATE MONDAY NIGHT THROUGH WEDNESDAY MORNING. IN THE SHORT TERM SNOWFALL TONIGHT SHOULD BE IN THE 4 TO 6 INCH RANGE IN THE HIGHER ELEVATIONS WITH 3 TO 5 INCHES ON MONDAY. SIGNIFICANT ACCUMULATIONS WILL BE POSSIBLE INTO NEXT WEEKEND. EAST OF THE CONTINENTAL DIVIDE STRONG WINDS WITH SOME WARMING CAN BE EXPECTED. TEMPERATURES WILL BE SEASONABLE WITH FAVORABLE RELATIVE HUMIDITY. INVERSIONS WILL BE IN PLACE OVER THE VALLEYS AND BASINS WITH LOW MIXING HEIGHTS AND POOR SMOKE DISPERSAL. EAST OF THE CONTINENTAL DIVIDE IN THE WINDY AREAS...MARGINAL GOOD SMOKE DISPERSAL MAY RESULT DUE TO THE WIND EVEN WITH LOW MIXING HEIGHTS. && .RIW WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 5 PM MONDAY TO 5 PM MST TUESDAY FOR WYZ026-028>030. HIGH WIND WARNING FROM 9 AM MONDAY TO 9 AM MST TUESDAY FOR WYZ019-020. WINTER STORM WARNING FROM 1 PM MONDAY TO 5 PM MST TUESDAY FOR WYZ025. WINTER STORM WARNING FROM 9 AM MONDAY TO 5 PM MST TUESDAY FOR WYZ012>014-023-024. WINTER STORM WARNING FROM 5 PM MONDAY TO 5 PM MST TUESDAY FOR WYZ027. WINTER WEATHER ADVISORY FROM 9 AM MONDAY TO 5 PM MST TUESDAY FOR WYZ001-002-015. && SHORT TERM...C.BAKER/BRAUN LONG TERM...BRANHAM AVIATION...WM FIRE WEATHER...C.BAKER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 1031 PM MST SUN DEC 20 2015 WYZ001>020-022>030-220545- YELLOWSTONE NATIONAL PARK-ABSAROKA MOUNTAINS-CODY FOOTHILLS- NORTH BIG HORN BASIN-SOUTHWEST BIG HORN BASIN- SOUTHEAST BIG HORN BASIN-OWL CREEK AND BRIDGER MOUNTAINS- BIGHORN MOUNTAINS WEST-BIGHORN MOUNTAINS SOUTHEAST- NORTHEAST JOHNSON COUNTY-SOUTHEAST JOHNSON COUNTY- TETON AND GROS VENTRE MOUNTAINS-JACKSON HOLE- WIND RIVER MOUNTAINS WEST-WIND RIVER MOUNTAINS EAST- UPPER WIND RIVER BASIN-WIND RIVER BASIN-LANDER FOOTHILLS- GREEN MOUNTAINS AND RATTLESNAKE RANGE- NATRONA COUNTY LOWER ELEVATIONS-CASPER MOUNTAIN-STAR VALLEY- SALT RIVER AND WYOMING RANGES-UPPER GREEN RIVER BASIN FOOTHILLS- UPPER GREEN RIVER BASIN-SOUTH LINCOLN COUNTY- ROCK SPRINGS AND GREEN RIVER-FLAMING GORGE-EAST SWEETWATER COUNTY- 1031 PM MST SUN DEC 20 2015 ...WINTER STORM WARNING FOR THE WESTERN MOUNTAINS AND VALLEYS BEGINNING LATE MONDAY MORNING...CONTINUING THROUGH THE DAY TUESDAY... ...HIGH WIND WARNING FOR PORTIONS OF CENTRAL WYOMING BEGINNING MONDAY MORNING...CONTINUING THE TUESDAY MORNING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT LIGHT TO MODERATE SNOW ACROSS THE WEST TODAY AND TONIGHT. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY MONDAY...LIGHT TO MODERATE SNOW ACROSS THE WEST. BREEZY TO WINDY IN THE MOUNTAINS...FOOTHILLS AND EAST OF THE DIVIDE. MONDAY NIGHT THROUGH WEDNESDAY MORNING...A MAJOR WINTER STORM IS EXPECTED ACROSS THE WEST. SIGNIFICANT SNOW AND VERY STRONG WIND IS EXPECTED TO DEVELOP MONDAY NIGHT AND CONTINUE INTO WEDNESDAY MORNING. STRONG WINDS WITH GUSTS OVER 50 MPH POSSIBLE ACROSS MUCH OF CENTRAL AND SOUTHERN WYOMING. CHRISTMAS DAY...A SLIGHT CHANCE OF SNOW. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT ANY SNOWFALL AMOUNTS OR WIND GUSTS IN EXCESS OF 50 MPH. THANK YOU.
The national radar mosaic for the moment the first event began.
5 winter storm, 2 high wind. Local standard time, as filed.
Very heavy snow fell across the Tetons from a long lived winter storm. Some areas such as Grand Targhee Ski Resort and Jackson hole received around 3 feet of new snow.
Heavy snow fell across the Salt and Wyoming Range during a long lived winter storm. The heaviest snow fell at the Indian Creek SNOTEL where as much as 15 inches was estimated.
Heavy snow fell throughout the Jackson Valley. Around 12 inches was the average in Jackson with as much as 18 inches in Moose.
Heavy snow of up to around 8 inches fell in Star Valley.
Heavy snow fell across portions of southern Lincoln county. A spotter reported 10 inches of new snow at Kemmerer.
The RAWS site at Fales Rock recorded many wind gusts over 58 mph, including a maximum of 67 mph.
The wind sensor along Outer Drive recorded many wind gusts over 58 mph including a maximum of 74 mph. The ASOS at Casper Airport reported a maximum gust of 61 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2015Every state in 2015This day in weather historyWarnings in Wyoming, December 2015
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 607358, 607360, 607361, 607362, 607365, 607370, 607371.