A combination of deep snowpack, a clear sky, light wind and an arctic air mass brought extremely cold temperatures to portions of western and central Wyoming. Low temperatures of -25F or below occurred in Sublette, Natrona and Lincoln Counties as well as in Yellowstone Park.
Every event with a place to put it; 4 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 combination of deep snowpack, a clear sky, light wind and an arctic air mass brought extremely cold temperatures to portions of western and central Wyoming. Low temperatures of -25F or below occurred in Sublette, Natrona and Lincoln Counties as well as in Yellowstone Park. The low temperature at the Casper airport on the morning of December 8th was especially noteworthy since it was the 6th coldest temperature ever recorded and the coldest since December 1990.
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 5, 10:30 PM MST, 1 hour 30 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1030 PM MST Mon Dec 5 2016 .UPDATE... Quick update to allow the winter weather advisory expire at 6 pm. Only some lingering snow band showery activity impacting eastern Fremont/Natrona Counties, but even these look to be shrinking in size. && .PREV DISCUSSION... /issued 202 PM MST Mon Dec 5 2016/ Short Term...Tonight Through Tuesday Snow should taper off and shift east of the area this evening with clearing. temperatures will be cold with most areas falling below zero and some western valleys could see -20. Some low stratus and patchy fog may develop but the east and south will remain breezy. Thursday will be dry and cold. Some wind in the south and east may mix the air mass there enough for some warming but the valleys and basins should be well trapped with temperature inversions. Long Term...Tuesday Night Through Monday A weak low pressure trough will move into the northwest from the Idaho Panhandle and western Montana bringing areas of light snow to the western and northern mountains Tuesday night and Wednesday. Snowfall amounts should be light. As this trough moves southeast across the west...into northwest Colorado some light snow may spread along and east of the Continental divide and across the southwest. Most areas will remain cold with lows below zero and highs in the single digits to teens. The cloud cover and light snow may hold up temperatures. The threat of light snow will continue in southern and central areas on Wednesday with clearing across the north and west. High pressure with cold temperatures will be in place Wednesday night into Thursday. In the west the leading edge of Pacific moisture should move into the mountains in the afternoon. There is potential for another strong Pacific jet to set up bringing a deep moist plume of pacific moisture into the west through Saturday night with potential very significant snowfall in the western mountains and valleys and another strong wind event east of the Continental divide. Temperatures will warm from thursday through Saturday. Saturday night and Sunday a cold front should move south east of the Continental divide spreading snow to the area and bring another shot of cold air into the region. Aviation.../06Z Issuance/ The main issue through 18Z will be patchy fog or stratocu mainly over the far western valleys. Otherwise mainly SKC with light winds through mid morning. This will quickly change this afternoon into the early evening as a quick moving upper wave, and a reinforcing cold front combine for increasing cloudiness and some snowfall. The best areal coverage/duration of snowfall is expected over Sweetwater County including RKS terminal where MVFR conditions are expected to develop around 22Z and last through much of the period. MVFR to Low VFR ceilings are expected to develop across much of the area east of the Divide shortly after sunset Tuesday with some flurries/light snow especially in favored upslope areas such as CPR/LND. Fire Weather... Snow should taper off and shift east of the area this evening with clearing. temperatures will be cold with most areas falling below zero and some western valleys could see -20. Some low stratus and patchy fog may develop but the east and south will remain breezy. Thursday will be dry and cold. Some wind in the south and east may mix the air mass there enough for some warming but the valleys and basins should be well trapped with temperature inversions. Most areas will have a very stable air mass with temperature inversions with overall poor smoke dispersal through Wednesday. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && UPDATE...WM SHORT TERM...C.Baker LONG TERM...C.Baker AVIATION...wm FIRE WEATHER...C.Baker
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 550 PM MST MON DEC 5 2016 WYZ001>020-022>030-061400- 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- 550 PM MST MON DEC 5 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TONIGHT MUCH COLDER TEMPERATURES SETTLE IN ACROSS THE AREA TONIGHT AND TUESDAY...STAYING VERY COLD FOR TUESDAY NIGHT THOUGH WEDNESDAY NIGHT. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THURSDAY THROUGH FRIDAY...SIGNIFICANT SNOW IN THE FAR WEST. MODERATING TEMPERATURES THURSDAY AND FRIDAY. SATURDAY AND SUNDAY...OCCASIONAL SNOW IN THE FAR WEST...ESPECIALLY IN THE MOUNTAINS. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT SNOWFALL AMOUNTS. THANK YOU. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
4 extreme cold/wind chill. Local standard time, as filed.
Very cold temperatures occurred across Yellowstone Park. The coldest temperature recorded was -33 at Grant Village on the morning of December 8th.
Temperatures fell to -25 in many locations. The coldest location was Bondurant where the temperature dropped to minus 33 on December 8th and -37 on December 6th.
The temperature fell to -33 at the Casper Airport. This was the earliest in the winter it had been this cold, the 6th coldest temperature ever recorded and the coldest temperature since December 1990.
The low temperature fell to -25 at the Box Y ranch.
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: 665820, 665818, 665821, 665819.