A couple of storm systems moved through western Wyoming accompanied by heavy snow and gusty wind. Snowfall of one to around two feet was common.
Every event with a place to put it; 10 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.
A couple of storm systems moved through western Wyoming accompanied by heavy snow and gusty wind. Snowfall of one to around two feet was common. The heaviest snow was estimated to have fallen in the Salt and Wyoming mountain ranges. Up to 18 inches of snow fall across the higher elevations of the Tetons including the Jackson Hole Mountain Resort. Totals topped one foot in portions of Yellowstone National Park and the Wind River Range. Snowfall amounts in the Star Valley and Jackson Hole were generally 6 to 10 inches with a 15 inch total observed at Alpine. Strong winds also occurred across the peaks with gusts as high as 78 mph. In addition, east of the Continental Divide some areas saw very strong winds with gusts to 72 mph in the Green Mountains and 59 mph at the Casper 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 16, 3:25 AM MST, 1 hour 35 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 325 AM MST SUN DEC 16 2012 .SHORT TERM...SUNDAY THROUGH TUESDAY NIGHT PRESENTLY IT LOOKS LIKE THE ACTIVE WEATHER PATTERN WILL CONTINUE ROUGHLY THROUGH MONDAY NIGHT AS A SERIES OF WEATHER SYSTEMS MOVE ACROSS WYOMING. AS FOR TODAY...FOR THOSE AREAS WEST OF THE DIVIDE YOU WILL SEE OF MAINLY LIGHT TO MODERATE SNOW AS ANOTHER SHORTWAVE FORGES IN FROM IDAHO. MANY PLACES IN THE WEST WILL HAVE A FEW INCHES OF SNOW WITH THE STEADIEST SNOW FALLING THIS MORNING. SOME AREAS MAY REACH ADVISORY CRITERIA AND WITH THE MORE SUBSTANTIAL STORM EXPECTED TONIGHT AND MONDAY WILL NOT ISSUE ANYTHING FOR TODAY. ALSO...THERE HAS BEEN SOME PATCHY FOG ACROSS THE BIG HORN BASIN. FOG HAS ESPECIALLY BEEN FOUND WHERE LIGHT SNOW FELL THIS MORNING SO WE HAVE KEPT THE FOG FOR THIS EARLY THIS MORNING. EAST OF THE DIVIDE TODAY IT WILL BE A MAINLY DRY DAY WITH TEMPERATURES NEAR NORMAL. HOWEVER DUE TO AN INCREASING PRESSURE GRADIENT WITH THE SYSTEM FROM THE WEST SOUTHWEST TO WEST WINDS WILL INCREASE ACROSS THE WIND CORRIDOR. IN THE WEST SNOW WILL BECOME STEADY AND HEAVIER LATER TONIGHT AS A NEARING COLD FRONT...SHORTWAVE TROUGH AND A RATHER STRONG JET STREAK SLAM INTO WYOMING. A COMBINATION A FAVORABLE JET DYNAMICS AND WARM ADVECTION WILL COMBINE TO PRODUCE PERIODS OF HEAVY SNOW FROM SUNDAY NIGHT INTO MONDAY. IN ADDITION...GUSTY WINDS WILL CAUSE BLOWING AND DRIFTING OF THE SNOW. AS A RESULT...THE WINTER STORM WATCHES FROM YELLOWSTONE PARK SOUTHWARD THROUGH THE SALT RANGE AND WIND RIVERS HAVE BEEN CONTINUED. AS THE SYSTEM MOVES FURTHER EAST...SOME AREAS OF SNOW WILL SPREAD EAST AND ADVISORIES MAY BE NEEDED FOR PORTIONS OF SWEETWATER COUNTY AS WELL AS THE LOWER GREEN RIVER BASIN. WE WILL KEEP A CLOSE EYE ON THIS. EAST OF THE DIVIDE...THE ISSUE WILL BE WIND TONIGHT AND INTO MONDAY. LATEST MODELS CONTINUE TO SHOW VERY STRONG 700 MILLIBAR WINDS IN EXCESS OF 50 TO 55 KNOTS ACROSS PORTIONS OF CENTRAL WYOMING. GOOD MIXING CONDITIONS ARE LIKELY MONDAY WITH THE FRONT WITH STRONG WIND EXPECTED. THERE IS ALSO THE POSSIBILITY OF MOUNTAIN WAVE DEVELOPMENT NEAR THE LANDER FOOTHILLS AND WIND RIVER RANGE AS WELL AS WEST OF THERMOPOLIS SO WE WILL GO AHEAD AND EXPAND THE HIGH WIND WATCH ACROSS THE THESE AREAS. WITH STRONG DOWNSLOPING WE FELT LITTLE SNOW REACHES THE AREA EXCEPT FOR THE BIG HORN MOUNTAINS WHERE UPSLOPE MAY YIELD A BIT MORE PRECIPITATION AND PORTIONS OF THE BIG HORN BASIN. AS FOR SNOW CHANCES ON TUESDAY AND TUESDAY NIGHT...MODELS HAVE TRENDED FURTHER SOUTH WITH THE BEST ENERGY SO WE TRIMMED BACK POPS ACROSS THE PORTIONS OF CENTRAL WYOMING AND EVEN CUT BACK SNOW AMOUNTS ACROSS SOUTHERN WYOMING. STILL SOME UNCERTAINTY WITH THIS SOLUTION THOUGH SO WE ONLY BLENDED THE MODELS WITH CONTINUITY INSTEAD OF GOING ALL THE WAY. EXPECT COLDER TEMPERATURES TUESDAY AND TUESDAY NIGHT AS WELL AS COLD AIR MOVES IN BEHIND THE COLD FRONT. .LONG TERM...WEDNESDAY THROUGH SUNDAY STORM SYSTEM LIFTS OUT OF THE CENTRAL ROCKIES INTO THE PLAINS ON WEDNESDAY WITH THE BRUNT OF SNOWFALL WITH THIS SYSTEM REMAINING SOUTH OF THE AREA. COLDER AND DRIER AIRMASS PREVAILS ACROSS THE AREA WEDNESDAY/WEDNESDAY NIGHT. A RIDGE OF HIGH PRESSURE WILL BRING A PERIOD OF MAINLY DRY WEATHER THROUGH SATURDAY WITH A WARMING TREND THURSDAY AND FRIDAY. MEDIUM RANGE MODELS HAVE CONTINUED SOUTHERN TRACK WITH UPPER TROUGH PASSAGE ON WEDNESDAY...SHIFTING MAIN BAND OF PRECIPITATION ACROSS COLORADO INTO SOUTHEAST WYOMING. TO THE NORTH...WEST AND CENTRAL WYOMING ON COLD SIDE OF THIS SYSTEM...H5 -38C COLD POOL OVER AREA WEDNESDAY. LOW LEVEL NORTHERLY FLOW ON BACKSIDE OF EXITING LOW WEDNESDAY MORNING WILL FAVOR SOME LIGHT UPSLOPE SNOW IN THE CASPER/CASPER MOUNTAIN AREA WITH DRIER WEST NORTHWEST FLOW PREVAILING IN THE AFTERNOON. FORECAST REFLECTS 00Z ECMWF THURSDAY THROUGH SATURDAY WITH UPPER RIDGE BUILDING INTO AREA WEDNESDAY NIGHT. HIGH AMPLITUDE PATTERN TAKES SHAPE AFTERWARDS WITH UPPER LOW DIGGING OFF THE WEST COAST THURSDAY AND FRIDAY...EJECTING A SHORTWAVE NE INTO THE NORTHERN ROCKIES THURSDAY/THURSDAY NIGHT AS UPPER RIDGE AXIS PROGRESSES INTO HIGH PLAINS. UPPER RIDGE REBUILDS OVER ROCKIES BEHIND THIS SHORTWAVE FRIDAY AND SATURDAY. SHORTWAVE PASSAGE WILL RESULT IN LEE SIDE TROUGH AND BETTER MIXING THURSDAY/THURSDAY NIGHT...SO HAVE REMOVED MENTION OF FOG IN SW AND CENTRAL BASINS. FORECAST KEEPS CHANCES OF SNOW IN NW MOUNTAINS THROUGH FRIDAY WITH SHORTWAVE PASSAGE AND SW FLOW...WITH PACIFIC MOISTURE SHUTOFF BY SATURDAY AS RIDGE REBUILDS OVER AREA. ECMWF BRINGS EASTERN PACIFIC TROUGH INLAND ON SUNDAY AND FORECAST RETURNS LOW CHANCES OF SNOW POPS ACROSS THE FAR WEST. && .AVIATION.../12Z ISSUANCE/ SHORTWAVE AND ASSOCIATED TROUGH WILL SWEEP THROUGH WESTERN WYOMING LATER THIS MORNING. BETTER MOISTURE SURGE AND DYNAMICS WILL BRING A QUICK SHOT OF LIGHT SNOW TO KJAC AND THE STAR VALLEY WITH IFR CONDITIONS POSSIBLE FROM 15Z-20Z/SUN. MOUNTAIN TOP OBSCURATIONS WILL BE WIDESPREAD THROUGH AT LEAST MID-AFTERNOON TODAY ALONG AND WEST OF THE CONTINENTAL DIVIDE. NOT VERY FAVORABLE FOR PROLONGED PERIOD OF LIGHT SNOW AT KBPI AND KPNA...SO HAVE ONLY INDICATED A BRIEF PERIOD OF MVFR WITH THE TROUGH PASSAGE AROUND 18Z/SUN. TROUGH PASSAGE SHOULD ALLOW FOR WESTERN TERMINALS TO CLIMB TO LOW END VFR BEFORE 00Z/MON. KBPI...KPNA...AND KRKS WILL SEE GUSTY WEST TO NORTHWEST WIND BEHIND THE TROUGH THROUGH THE AFTERNOON. GUSTS OF 25-30KTS WILL BE COMMON. TROUGH PASSAGE WILL ALSO ALLOW FOR GUSTY WEST-NORTHWEST WIND DURING THE LATE AFTERNOON AT KRIW AND TO A LESSER EXTENT KLND. SOUTHWEST SURFACE WIND WILL INCREASE LATER THIS MORNING AT KCPR AND PEAK BY MID-AFTERNOON WITH GUSTS 25-35KTS. WIND SPEEDS WILL DROP OFF QUICKLY AS THE ATMOSPHERE DECOUPLES AROUND SUNSET. ALL TERMINALS EAST OF THE CONTINENTAL DIVIDE WILL BE VFR THROUGH THE FORECAST PERIOD. LIGHT SNOW WILL BEGIN AGAIN LATE THIS EVENING IN FAR WEST WYOMING BEFORE INCREASING BETWEEN 08Z-12Z/MONDAY. A STORM SYSTEM ON MONDAY HAS THE POTENTIAL TO GENERATE A MUCH MORE PROLONGED PERIOD OF SNOWFALL WEST OF THE DIVIDE ON MONDAY...ALONG WITH GUSTY DOWNSLOPE WINDS EAST OF THE DIVIDE. && .FIRE WEATHER... WINDS WILL BE ON THE INCREASE EAST OF THE DIVIDE TODAY INTO MONDAY WITH SNOW DEVELOPING IN THE SOUTH MONDAY. THE WEST WILL SEE PERIODS OF SNOW WITH A MAJOR STORM HITTING LATE SUNDAY NIGHT INTO MONDAY EVENING WITH SIGNIFICANT SNOW AND WIND. && .RIW WATCHES/WARNINGS/ADVISORIES... HIGH WIND WATCH FROM LATE TONIGHT THROUGH MONDAY EVENING WYZ019. HIGH WIND WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON WYZ005-018. WINTER STORM WATCH FROM THIS EVENING THROUGH MONDAY EVENING WYZ012>014-023-025. WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE MONDAY NIGHT WYZ027. HIGH WIND WATCH FROM THIS EVENING THROUGH MONDAY MORNING WYZ003. WINTER STORM WATCH FROM THIS EVENING THROUGH MONDAY AFTERNOON WYZ001. WINTER STORM WATCH FROM THIS EVENING THROUGH LATE MONDAY NIGHT WYZ024. HIGH WIND WATCH FROM LATE TONIGHT THROUGH MONDAY EVENING WYZ020. && SHORT TERM...HATTINGS LONG TERM...AEM AVIATION...CNJ FIRE WEATHER...HATTINGS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 500 AM MST SUN DEC 16 2012 WYZ001>020-022>030-171200- ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST- BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS- EAST SWEETWATER COUNTY-FLAMING GORGE- GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS- NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN- NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS- ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES- SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN- SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY- TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN- UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN- WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST- YELLOWSTONE NATIONAL PARK- 500 AM MST SUN DEC 16 2012 ...WINTER STORM AND HIGH WIND WATCHES ARE IN EFFECT FOR PORTIONS OF WESTERN AND CENTRAL WYOMING LATE SUNDAY NIGHT THROUGH MONDAY NIGHT... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT TODAY AND TONIGHT...SNOW...AREAS OF BLOWING SNOW...SLICK ROADS AND LIMITED VISIBILITY WILL BE LIKELY IN THE WESTERN MOUNTAINS AND FAR WEST VALLEYS. THE COMBINATION OF WIND AND SNOW COULD CAUSE PERIODS OF DIFFICULT TRAVEL...ESPECIALLY ALONG INTERSTATE 80. PLEASE SEE WINTER WEATHER PRODUCTS FOR DETAILS. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY MONDAY AND MONDAY NIGHT...STRONG WINDS WILL BE POSSIBLE ALONG THE EAST SLOPES OF THE WIND RIVER AND ABSAROKA RANGES AND ADJACENT FOOTHILLS AS WELL AS FROM ROCK SPRINGS TO CASPER. SNOW AND AREAS OF BLOWING AND DRIFTING SNOW ARE POSSIBLE IN THE WESTERN MOUNTAINS AND ACROSS THE SOUTH. PLEASE SEE WINTER WEATHER AND HIGH WIND PRODUCTS FOR DETAILS. TUESDAY AND WEDNESDAY...SNOW MAY INCREASE ACROSS SOUTHERN WYOMING ON TUESDAY WITH THE HEAVIEST SNOW ALONG AND SOUTH OF INTERSTATE 80. EXPECT COLD MORNING LOW TEMPERATURES IN THE WAKE OF THIS WEATHER SYSTEM. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 220 AM MST SUN DEC 16 2012 WYZ004>006-161600- NORTH BIG HORN BASIN-SOUTHEAST BIG HORN BASIN- SOUTHWEST BIG HORN BASIN- 220 AM MST SUN DEC 16 2012 AREAS OF FOG WITH VISIBILITY OF ONE-HALF MILE OR LESS WILL BE ENCOUNTERED ACROSS THE BIG HORN BASIN THROUGH 9 AM. THE FOG WILL BE MOST WIDESPREAD ALONG THE BIG HORN RIVER AND ALONG HIGHWAY 789 BETWEEN THERMOPOLIS AND COWLEY. BLACK ICE ON ROAD SURFACES IS LIKELY TO ACCOMPANY THE FOG...ESPECIALLY OVER BRIDGES. SLOW DOWN FOR THESE CONDITIONS AND ALLOW FOR EXTRA BRAKING DISTANCE THIS MORNING. AEM
The national radar mosaic for the moment the first event began.
8 winter storm, 2 high wind. Local standard time, as filed.
Heavy snow fell across the Star Valley. The maximum amount was at Alpine where 15 inches was recorded.
Heavy snow fell across the Salt River and Wyoming Ranges. Storms totals over a foot were common with the most at the Indian Creek Snotel where 25 inches was recorded. High winds were also common across the higher elevations where gusts to over 80 mph where recorded.
A series of storms brought heavy snow to Jackson Hole. Snowfall amounts generally ranged from 4 to 8 inches.
A series of storms left heavy snow over Yellowstone Park. The Lewis Lake SNOTEL station recorded 20 inches of new snow.
A series of storms brought heavy snow and high wind to the Teton and Gros Ventre Mountains. As much as 18 inches of snow was recorded at Jackson Hole Ski Resort. In addition, there were high winds across the mountain peaks with gusts as high as 78 mph.
Periods of snow fell across Southern Lincoln County. Amounts ranged from around 3 inches near Kemmerer to around 7 inches in Cokeville.
Heavy snow fell across the Western Wind River Range with snow amounts generally 6 to 12 inches.
Heavy snow fell across the Upper Green Basin Foothills with amounts ranging from 5 inches at Pinedale to 12 inches at Bondurant.
A tight pressure gradient and approaching cold front brought high winds. Winds gusted to 72 mph at Fales Rock and 62 mph at Camp Creek.
A 59 mph wind gust was reported at the Casper Airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2012Every state in 2012This day in weather historyWarnings in Wyoming, December 2012
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: 419425, 419426, 419423, 419421, 419422, 419428, 419424, 419427, 419429, 419430.