The combination of a moist Pacific Air mass, strong jet dynamics and cold front passage brought heavy snow to portions of western and central Wyoming. The heaviest snow fell in northwestern Wyoming.
Every event with a place to put it; 8 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.
The combination of a moist Pacific Air mass, strong jet dynamics and cold front passage brought heavy snow to portions of western and central Wyoming. The heaviest snow fell in northwestern Wyoming. Some of the highest amounts of snow recorded were 27 inches at the Two Oceans Plateau SNOTEL site in Yellowstone Park, 21 inches at the top of the Jackson Hole Resort and 18 inches at South Pass in the Wind River Range. In the lower elevations of the west, amounts generally ranged from 4 to 9 inches. Heavy snow also fell around Casper in central Wyoming, where 7 to 10 inches of snow fell across the city. The snow was accompanied by strong winds over 50 mph in many places which resulted in blowing and drifting of the snow as well as some road closures.
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 4, 2:45 AM MST, 15 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 245 AM MST Sun Dec 4 2016 .SHORT TERM...Today through Tuesday night Imagery shows deep trof across central to west central CONUS with modest ridging over the far west and WY under NW flow aloft. Main trof axis stretches from central Canada down through the high/central Plains to northern Mexico where a nearly COL resides in the base of the trof. 100 kt plus jet located from northern WY to the PAC NW. Strong upstream shortwave trof coming into BC/northern WA...due to hit the WY area tonight. Modest moisture now advecting through the PAC NW and starting to pile up into NW WY. Light areas of snowfall across portions of west central to northwestern WY associated with this increasingly moist flow. SFC has high pressure across the Great Basin into southwest WY with a N/S trof located through the northern and central Plains. Decent P GRAD keeping gusty (at times) wind around the area east of the Divide. Today, the upper NW flow starts to flatten and will become nearly zonal by tonight in response to the approaching (now Gulf of AK) trof and associated strong 100+ kt jet. This will also allow additional EPAC moisture back into the western/northwestern FA along with increasingly good upper level forcing and a significant increase in precip chances across the western zones...especially from later this afternoon into Monday morning. Warning amounts of snow now look likely over the Teton...Gros Ventre mountains and across portions of YNP and the Jackson Valley. A Winter Storm Warning is now in effect for those previously mentioned areas. Advisory amounts of mountain/valley snow will surround this area...including the Salt, Wyoming, Wind River and Absaroka mountains in addition to the the Upper Green River foothills. Also, both the surface pressure and wind fields will respond to the increasing favorable upper level flow pattern as mid/upper wind flow becomes nearly normal to the mountain ranges and the surface P GRAD tightens as lee troffing deepens across central WY. Breezy to occasionally strong winds are expected over some of the FA's foothills and the wind corridor this afternoon and evening. SPSs address these winds. Monday, the main upper trof axis and strong cold front (Arctic) will move through the FA...with snow chances finally moving east of the Divide...albeit on the light side. Then, later overnight Monday/by sunrise Tuesday, post frontal very cold temperatures will be left along with a few flurries or ice crystals. Lows Tuesday morning will range from around 20 below in the western mountains to the single digits to near 10 deg in the basins east of the Divide. Tuesday will be cold post frontal with flurries around but skies trying to clear out except near the southern border region which will reside just on the northern side of the cold front and where small chances for snow will continue to exist. With rather flat NW flow continuing over the rest of the FA...small chances for light western mountain snow or flurries will continue periodically. Very cold daytime and overnight temperatures with Wednesday morning bottoming out as much as 25 below west of the Divide and over the Bighorn mountains. .LONG TERM...Wednesday through Sunday The polar express remains parked over the region Wednesday as high temps will struggle to warm up with those 700MB temps around -20 degrees C. It looks to be dry Wednesday all areas. Another cold night Wed night as a mostly clear sky will allow decent radiational cooling. The GFS has warming 700MB temps late Wed night while the ECMWF model is still very cold. If the GFS comes true, then temps will rise after midnight in some areas. If the ECMWF is correct, then a quite cold night will occur. This has been the scenario for 4 nights now. I will lean toward the colder solution but not as cold as Tue night. Plenty of time to watch this. The onset of precip in the west with the warm advection pattern starts Thursday afternoon and continues into Friday. The GFS is faster tonight with the next weather system and cold front, as it has it passing through the region Friday afternoon. The ECMWF model is Friday night with the cold front. Dry east of the divide Thursday and Thursday night with breezy to windy areas. High temps will moderate Thurs in all areas, but some of the colder valleys will not warm up as much as the inversion will hold. It is Friday when the inversion should break everywhere and milder highs all areas. Will add a precip chance to southern WY Friday afternoon ahead of the front. Fri night looks to have the cold front pass by and a chance of some snow in most places along with brisk wind. Some snow showers in the mountains on Saturday in the NW flow aloft. Cannot rule out some snow showers in the lower elevations Saturday. A little cooler high temps Saturday for the region. Next Sunday will see some light snow in the far west once again and mostly dry elsewhere. High temps will be near seasonal values. && .AVIATION.../12Z ISSUANCE/ EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES Winds aloft will increase ahead of an approaching trough/cold front Sunday morning with areas of LLWS developing 15z-18z. Surface southwest wind at 20-30 kt with gusts 40-45 kt will prevail from South Pass-50SM NE KRKS-KCPR 12z Sunday-06z Monday. Also, peaks above 9kft along the Continental Divide will be mostly obscured in -sn 12z Sunday - 12z Monday. A cold front will plunge south through KCOD-KBYG around 08z Monday and to near a KRIW-KCPR line by 12z Monday. Areas of MVFR/IFR -sn and gusty north wind will follow the cold front. WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES Snow, widespread IFR conditions and mountain obscurations will increase from north to south, to a vicinity and north of a KAFO-KDUB line by 12z Sunday. Ridgetop winds will also increase with LLWS becoming widespread by 17z across the area. IFR conditions will prevail vicinity and north of a KAFO-KPNA line through 06z Monday, with a cold front driving areas snow further south and east along the Interstate 80 corridor 06z-12z Monday. LLWS will subside behind a cold frontal passage with precipitation becoming more showery along with some improvement in ceilings and visibility vicinity and north of a KJAC-KDUB line by 12z Monday. && .FIRE WEATHER... Fire Danger low for the foreseeable future as cold unsettled conditions and general troughiness continue over the region, keeping RH levels on the high side. Precipitation chances will mainly occur across western WY through today and tonight before shifting east of the Divide later Monday. The mountains of the west may see up to a two feet of snow locally with 3 to 10 inches possible in the western valleys. The lower elevations east of the Divide will only see a trace to an inch with some foothill areas perhaps getting a couple of inches through the day Monday. Otherwise increasingly gusty, sometimes strong, winds will be the only real impact to fire weather as southwest wind of 10 to 20 mph gusting 30 to 40 mph today grows to gusts of 40 to 60 mph at times today and tonight over the western mountains...Cody foothills...and across the wind corridor from eastern Sweetwater, through eastern Fremont and across Natrona counties. Smoke dispersion will range from poor this morning and tonight to fair/good for a few hours this afternoon over northwest WY and portions of south central WY. Monday will see widespread good to excellent dispersion...mostly due to brisk winds across the forecast area. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 5 AM early this morning to noon MST Monday for WYZ002-014-015-023>025. Winter Storm Warning from 5 AM early this morning to noon MST Monday for WYZ001-012-013. && SHORT TERM...Braun LONG TERM...AR AVIATION...AEM FIRE WEATHER...Braun
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 300 AM MST SUN DEC 4 2016 WYZ001>020-022>030-051200- 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- 300 AM MST SUN DEC 4 2016 ...WINTER STORM WARNING FOR THE TETON AND GROS VENTRE MOUNTAINS IN ADDITION TO YELLOWSTONE NATIONAL PARK TODAY THROUGH MONDAY MORNING... ...WINTER WEATHER ADVISORIES FOR MUCH OF THE REST OF THE WEST TODAY THROUGH MONDAY MORNING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SIGNIFICANT SNOW AND WIND WEST OF THE CONTINENTAL DIVIDE... ESPECIALLY FROM THE TETONS NORTH THROUGH YELLOWSTONE NATIONAL PARK. WINDY TO VERY WINDY EAST OF THE DIVIDE TODAY INTO TONIGHT. SOME LIGHT SNOW IN THE NORTH AFTER MIDNIGHT. WINDY AREAS TONIGHT EAST OF THE DIVIDE. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY MONDAY...SIGNIFICANT SNOW AND WIND WEST OF THE CONTINENTAL DIVIDE IN THE MORNING...TAPERING OFF IN THE AFTERNOON AND EVENING. MUCH COLDER TEMPERATURES SETTLE IN ACROSS THE AREA MONDAY NIGHT AND TUESDAY...STAYING VERY COLD FOR TUESDAY NIGHT THOUGH WEDNESDAY NIGHT. THURSDAY NIGHT AND FRIDAY...A CHANCE OF SNOW IN THE WESTERN MOUNTAINS. MODERATING TEMPERATURES THURSDAY AND FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT SNOWFALL AMOUNTS. THANK YOU.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1245 AM MST SUN DEC 4 2016 WYZ003-042300- CODY FOOTHILLS- INCLUDING THE CITIES OF...CODY...MEETEETSE 1245 AM MST SUN DEC 4 2016 ...VERY WINDY CONDITIONS TODAY... WEST WIND WILL INCREASE EARLY THIS MORNING AHEAD OF AN APPROACHING COLD FRONT. AREAS OF WEST WIND 25 TO 35 MPH WITH GUSTS 45 TO 55 MPH WILL DEVELOP AND CONTINUE THROUGH EARLY THIS EVENING. LOCALLY HIGHER GUSTS TO 65 WILL BE POSSIBLE IN THE CLARK AREA. WINDS WILL DIMINISH AND SHIFT NORTHERLY AROUND MIDNIGHT SUNDAY NIGHT WITH A COLD FRONTAL PASSAGE. THESE WINDS MAY CAUSE LOSS OF VEHICLE CONTROL OR A BLOW OVER TO HIGH PROFILE VEHICLES TRAVELING EMPTY OR WITH A LIGHT ROAD FROM MEETEETSE TO THE CLARK AREA ON SUNDAY. WYZ019-020-022-042300- GREEN MOUNTAINS AND RATTLESNAKE RANGE- NATRONA COUNTY LOWER ELEVATIONS-CASPER MOUNTAIN- INCLUDING THE CITIES OF...JEFFREY CITY...CASPER 1245 AM MST SUN DEC 4 2016 ...VERY WINDY CONDITIONS TODAY... SOUTHWEST WINDS WILL INCREASE TO 25 TO 35 MPH WITH GUSTS 45 TO 55 MPH LATE THIS AFTERNOON AND CONTINUE THROUGH THIS EVENING. THE STRONGEST WINDS ARE EXPECTED THIS AFTERNOON THROUGH THIS EVENING. LOCALLY HIGHER GUSTS OVER 55 MPH ARE POSSIBLE ALONG WYOMING BOULEVARD...HIGHWAY 258...ON THE SOUTH SIDE OF CASPER. THESE WINDS MAY CAUSE LOSS OF VEHICLE CONTROL OR A BLOW OVER TO HIGH PROFILE VEHICLES TRAVELING EMPTY OR WITH A LIGHT ROAD.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 246 AM MST SUN DEC 4 2016 WYZ003-042300- CODY FOOTHILLS- INCLUDING THE CITIES OF...CODY...MEETEETSE 246 AM MST SUN DEC 4 2016 ...VERY WINDY CONDITIONS TODAY... WEST WIND WILL INCREASE EARLY THIS MORNING AHEAD OF AN APPROACHING COLD FRONT. AREAS OF WEST WIND 25 TO 35 MPH WITH GUSTS 45 TO 55 MPH WILL DEVELOP AND CONTINUE THROUGH EARLY THIS EVENING. LOCALLY HIGHER GUSTS TO 65 WILL BE POSSIBLE IN THE CLARK AREA. WINDS WILL DIMINISH AND SHIFT NORTHERLY AROUND MIDNIGHT SUNDAY NIGHT WITH A COLD FRONTAL PASSAGE. BETWEEN MIDNIGHT TONIGHT AND NOON MONDAY...LIGHT AREAS OF SNOW WILL MIX WITH THE WIND TO GIVE BLOWING SNOW AND SLICK ROADS AT TIMES. THESE WINDS MAY CAUSE LOSS OF VEHICLE CONTROL OR A BLOW OVER TO HIGH PROFILE VEHICLES TRAVELING EMPTY OR WITH A LIGHT ROAD FROM MEETEETSE TO THE CLARK AREA ON SUNDAY. WYZ019-020-022-042300- GREEN MOUNTAINS AND RATTLESNAKE RANGE- NATRONA COUNTY LOWER ELEVATIONS-CASPER MOUNTAIN- INCLUDING THE CITIES OF...JEFFREY CITY...CASPER 246 AM MST SUN DEC 4 2016 ...VERY WINDY CONDITIONS TODAY... SOUTHWEST WINDS WILL INCREASE TO 25 TO 35 MPH WITH GUSTS 45 TO 55 MPH LATE THIS AFTERNOON AND CONTINUE THROUGH THIS EVENING. THE STRONGEST WINDS ARE EXPECTED THIS AFTERNOON THROUGH THIS EVENING. LOCALLY HIGHER GUSTS OVER 55 MPH ARE POSSIBLE ALONG WYOMING BOULEVARD...HIGHWAY 258...ON THE SOUTH SIDE OF CASPER. THESE WINDS MAY CAUSE LOSS OF VEHICLE CONTROL OR A BLOW OVER TO HIGH PROFILE VEHICLES TRAVELING EMPTY OR WITH A LIGHT ROAD. WYZ010-011-042300- NORTHEAST JOHNSON COUNTY-SOUTHEAST JOHNSON COUNTY- INCLUDING THE CITIES OF...BUFFALO...KAYCEE 246 AM MST SUN DEC 4 2016 ...SOME LIGHT SNOW AND WIND FOR PORTIONS OF JOHNSON COUNTY FROM MIDNIGHT TONIGHT THROUGH MONDAY MORNING... A WEATHER SYSTEM MOVING THROUGH THE AREA MONDAY WILL BRING SOME LIGHT SNOW TO NORTHERN JOHNSON COUNTY. LIGHT SNOW WILL MIX WITH WEST TO NORTHWEST WIND...CAUSING SOME BLOWING AREAS OF SNOW MAINLY BETWEEN 2 AM AND 10 AM MONDAY...WITH LIGHT SNOW OR FLURRIES LINGERING THROUGH THE AFTERNOON. SNOWFALL WILL RANGE FROM 1 TO 2 INCHES...LOCALLY TO 3 INCHES WITH A WEST WIND OF 15 TO 30 MPH. THIS WILL CAUSE BLOWING AND DRIFTING SNOW IN SOME AREAS AND LOW VISIBILITY AT TIMES. THIS WILL IMPACT TRAVEL ON INTERSTATES 25 AND 90 AT TIMES.
The national radar mosaic for the moment the first event began.
8 winter storm. Local standard time, as filed.
Heavy snow fell in much of Yellowstone Park. Some of the highest amounts included 27 inches at Two Oceans Plateau and 16 inches at Lewis Lake Divide.
Heavy snow fell throughout the Tetons. The highest amounts were around the Jackson Hole Ski Resort where 18 to 21 inches was measured.
Snowfall amounts ranged from 7 to 10 inches around the Jackson Valley.
New snowfall in the Salt and Wyoming Range generally ranged from 8 to 15 inches; with a maximum of 15 inches at Blind Bull Summit.
Snowfall amounts in the Star Valley ranged from 3.6 inches in Afton to 9.5 inches near Smoot.
Heavy snow fell in portions of the Absaroka mountains. The highest amount recorded was 18 inches at the Blackwater SNOTEL.
Heavy snow fell in portions of the Wind River Range. The highest amount recorded was 18 inches at the South Pass SNOTEL.
Snowfall amounts ranged from 7 to 10 inches across the city of Casper.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2016Every state in 2016This day in weather historyWarnings in Wyoming, December 2016
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: 665685, 665686, 665687, 665689, 665688, 665691, 665690, 665692.