Another in a series of Pacific troughs crossed Wyoming and brought high wind and locally heavy snow to many areas. High wind occurred in Sweetwater and Natrona counties, where wind gusts of 70 and 58 mph were reported, respectively.
Every event with a place to put it; 6 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.
Another in a series of Pacific troughs crossed Wyoming and brought high wind and locally heavy snow to many areas. High wind occurred in Sweetwater and Natrona counties, where wind gusts of 70 and 58 mph were reported, respectively. A snow squall accompanied the cold front, producing wind gusts over 60 mph and heavy snow. This combination led to white-out conditions that closed Interstate 80 in Sweetwater County for a time. Heavy snow fell in Teton County where up to 13 inches was measured to the northwest of Jackson.
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 25, 3:30 AM MST, 6 hours 30 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 330 AM MST Sat Dec 25 2021 .SHORT TERM...(Today through Sunday) Issued at 330 AM MST Sat Dec 25 2021 The current active pattern remains in place over the next 36 hours. Strong southwesterly flow aloft with a longwave trough over the western CONUS will continue to bring snow to the western portion of Wyoming, with breezy conditions and isolated snow showers in the central portions of the state. Today will be relatively mild temperature-wise with clouds keeping morning temperatures fairly warm (but perhaps still a bit too cool for opening Christmas gifts outside). Strong mixing east of the Divide keeps afternoon temperatures a solid 10 plus degrees above seasonal averages. Expect widespread gusts in the 30 to 45 mph range, with localized higher gusts in the central Wyoming wind corridor. More widespread and more intense snow showers arrive overnight as lift ahead of the next shortwave trough moves in. Given increasing snowfall rates and multiple inch accumulations in the lower elevations of the west, have opted to issue Winter Weather Advisories for much of western Wyoming this afternoon through the day Sunday. Mountains and mountain passes will see enough new snow to make travel difficult and roads slick. Continue to exercise caution if traveling for holiday festivities. Snow continues in the west during the day Sunday. Relatively intense (but brief) scattered snow showers are also possible east of the Divide as a cold front pushes through. Strong westerly winds accompany the front, with gusts in the 40 to 50 mph range for most basins during the afternoon. Locally higher gusts are possible in the central Wyoming wind corridor from Rock Springs to Casper. Those traveling will want to stay alert as scattered snow showers could quickly reduce visibility while also bringing down higher momentum air (strong gusts) from the middle atmosphere. Winds and snow showers decrease after sunset. .LONG TERM...(Sunday night through Friday) Issued at 330 AM MST Sat Dec 25 2021 With the contrast in weather between West and East of the Divide, we will split the discussion today. West of the Divide...There will be a bit of break Sunday night with the snow showers. They will not stop, but since the area will be between waves showers should be less numerous for most locations. The break will be a short one though as the next, and probably final, in the series of waves will approach the west and bring another round of snow, especially Monday afternoon into Monday evening when the steadiest snow is expected before the trough axis swings through the area. Amounts at this point look to fall in the advisory range, but plenty of time for any needed highlights. Much colder air will then move in behind the system and bring some of the coldest air of the winter so far this season. Drier weather should then move in for most of Tuesday and Wednesday and even much of Thursday. North to northwest flow will continue to bring some snow showers to the western mountains. However, with the continental polar and even Arctic origin of this air, it is rather moisture starved. As a result, this will be a drier snow and amounts should remain on the light side for the most part. Most lower elevations should just be dry and cold. The next more substantial system will move in for later Thursday into Friday with a chance of more widespread accumulating snow. There is low confidence in precipitation details this far out though. East of the Divide...Any snow showers from the first trough should be moving away from the area during the evening Sunday. Dry conditions should then dominate from Sunday night through Monday. Temperatures will be cooler than recent days behind the cold front, but only back to seasonal levels for most areas. The main concern here will be wind. The pressure gradient will be tightening ahead of an advancing Arctic Front that will drop into the area Monday night. The models may actually be too slow, given the slow bias with advancing Arctic air masses. Guidance has backed off of high wind potential, but there are still some 50 knot 700 millibar wind barbs in the favored areas. We are not confident enough at this time for any highlights so future model guidance will be monitored closely. As for the chance of snow, most models are showing some. There is not a lot of moisture with the front though. It is also likely to be banded and hard to pin down where this far out. For now we have gone with slight to chance POPs for most areas until we can get a better handle on where any bands may develop. The most likely period for snow will be from later Monday evening through early Tuesday before the front moves away to the south and east. Quieter weather should then move in for most of the midweek period, although it will be cold, some of the coldest temperatures so far this winter for many areas. Guidance has backed off of the really cold temperatures from yesterday though. There is still a fair amount of uncertainty on how cold it will get since a lot depends on snow cover, and this could vary given the expected showery nature of the snow Monday night. For the most part, we strayed little from the previous forecast. These cold temperatures should continue for most through Thursday. Areas like Casper may mix out starting Wednesday night as the pressure gradient begins to tighten ahead of the next system moving in from the northwest. This system looks to arrive toward the later part of next week, possibly bringing a decent chance of snow to much of the area. && .AVIATION...(For the 12Z TAFS through 12Z Sunday morning) Issued at 330 AM MST Sat Dec 25 2021 East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals VFR conditions will prevail through the next 24 hours. Areas of strong winds gusting 35 to 40 kt will occur this afternoon, decreasing tonight. Scattered snow showers will develop over the region after 26/0300Z with local MVFR to IFR conditions through 26/1200Z. West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Periods of snow will occur through the next 24 hours. Terminals will see VFR conditions when the snow is not occurring and MVFR/IFR conditions when the snow is occurring. Gusty wind will occur this afternoon, decreasing in the evening. Snow becomes more widespread after sunset and into Sunday morning. KJAC, KPNA, and KBPI will see MVFR to IFR conditions prevailing after 26/0400Z through 26/1200Z. && .FIRE WEATHER... Issued AT 330 AM MST Sat Dec 25 2021 Expect snow to continue across western Wyoming throughout the day, as the weather pattern remains nearly unchanged. Winds in the wind corridor of central Wyoming will be in the 35 to 50 mph range this afternoon. Tonight into early Sunday brings higher snowfall rates to the west, as broad forcing associated with a shortwave trough arrives. Scattered snow showers are likely east of the Divide on Sunday with the passage of a cold front. Winds remain elevated Sunday afternoon, with gusts in the 40 to 55 mph range for most basins. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 11 AM this morning to 5 PM MST Sunday for WYZ001-002-012>015-023>025. Winter Weather Advisory from 11 PM this evening to 5 PM MST Sunday for WYZ027. && SHORT TERM...VandenBoogart LONG TERM...Hattings AVIATION...Hattings FIRE WEATHER...VandenBoogart
Hazardous Weather Outlook National Weather Service Riverton WY 340 AM MST Sat Dec 25 2021 WYZ001>020-022>030-261045- 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- 340 AM MST Sat Dec 25 2021 ...Winter Weather Advisories are in effect for western Wyoming Today through Sunday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Snow will continue throughout the day for the western mountains and valleys. A passing weather system will increase snow coverage and snowfall rates overnight into Sunday morning west of the Divide. Breezy winds gusting 35 to 45 mph will develop this afternoon, decreasing somewhat but remaining breezy after sunset. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Light to moderate snow in western Wyoming and breezy winds area- wide are likely through the middle of next week. The highest probability opportunities for more widespread strong winds are Sunday afternoon and evening, as well as Monday night into Tuesday morning. Much colder temperatures are forecast to move across the state on Tuesday, with temperatures below normal through midweek. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report snowfall totals.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RIVERTON WY
813 AM MST SAT DEC 25 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1244 AM NON-TSTM WND GST 8 SE RELIANCE 41.60N 109.07W
12/25/2021 M74 MPH SWEETWATER WY ASOS
ASOS STATION KRKS ROCK SPRINGS AIRPORT.
&&The national radar mosaic for the moment the first event began.
3 high wind, 2 winter weather, 1 winter storm. Local standard time, as filed.
An observer near Teton Village northwest of Jackson reported 13 inches of new snow.
A snow squall produced wind gusts over 50 mph and near zero visibility. The squall brought dangerous travel conditions that resulted in the closure of Interstate 80 for a time.
A wind gust of 70 mph occurred at Tipton along Interstate 80. A maximum wind gust of 63 mph occurred at the Southwest Wyoming Regional Airport east of Rock Springs.
A snow squall continued east along Interstate 80 through eastern Sweetwater County. The squall produced wind gusts over 50 mph and near zero visibility. The squall brought dangerous travel conditions that resulted in the closure of the interstate.
Wind gusts of 58 mph were reported along Wyoming Boulevard on the south side of Casper.
A wind gust of 58 mph was reported at a WYDOT wind sensor along Interstate 80 near Green River.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2021Every state in 2021This day in weather historyWarnings in Wyoming, December 2021
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: 997099, 997100, 997098, 997101, 997096, 997097.