A moist Pacific trough moved into western Wyoming on New Years Day and brought heavy snow to many areas. Amounts over a foot were common in the mountains with close to 2 feet in the Tetons, including 21 inches of new snow at Jackson Hole, Wyoming.
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.
A moist Pacific trough moved into western Wyoming on New Years Day and brought heavy snow to many areas. Amounts over a foot were common in the mountains with close to 2 feet in the Tetons, including 21 inches of new snow at Jackson Hole, Wyoming. Heavy snow also fell in the valleys, with 13 inches of snow at Alpine, Wyoming and 6 to 12 inches around the Jackson Valley. Meanwhile, strong mid level winds were forced to the ground by favorable jet dynamics in the wind prone areas East of the Divide. Wind gusts over 70 mph were recorded near Clark, Wyoming with wind gusts of 66 mph spreading into the west side of Cody, Wyoming. Wind gusts of 75 mph were reported south of Casper, Wyoming in Natrona County as well with 60 mph winds at Jeffrey City, Wyoming. In and around Cody, Wyoming, damage was reported. This included damaged fences, a destroyed metal shed that landed on a car and a roof torn off of a trailer.
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 31, 10:42 PM MST, 1 hour 18 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1042 PM MST Tue Dec 31 2019 .SHORT TERM...This afternoon through Wednesday night One last day of frigid temperatures for those areas that have been locked under inversions for the last few days.Highs will be slightly higher this afternoon, but will still be below 20 degrees over areas west of the Divide and the Wind River Basin. Gusty southwest winds will continue to blow across Natrona County this afternoon with gusts of 40 to 50 mph. Isolated gusts up to 60 mph could occur, but are unlikely. Stronger winds near Jeffrey City developed around sunrise this morning with gusts over 60 mph, creating ground blizzard conditions. A High Wind Warning is now in effect through this evening for this area. This warning may have to be extended through the morning New Year's Day. These winds in these areas will continue tonight and into midday New Year's Day, before beginning to subside in the afternoon. Gusty west winds also developed earlier this morning in the Cody/Clark area, with gusts of 35 to 45 mph. Similar conditions developed in the Upper Wind River Basin near Dubois and Crowheart. These conditions are also expected to continue through midday Wednesday, increasing slightly after midnight. Gusts over 60 mph cannot be ruled out, especially north of Cody toward Clark. Temperatures tonight will not be as cold, as clouds continue to increase over the area this evening. Light snow will be possible over northwest portions this afternoon and evening, but accumulations will remain light. Snow will increase just in time to ring in the new year, spreading southward during this time. The heaviest snow will occur during the morning Wednesday, continuing through the day and becoming light late Wednesday night. Snow chances will also increase across southern portions early Wednesday morning, staying more showery in nature through the day. Blowing snow will be the biggest impact over this area, as winds increase with gusts of 30 to 40 mph across Sweetwater and southern Lincoln counties late Wednesday morning and continue through the overnight hours. Snowfall amounts remain largely unchanged, however, amounts of 8 inches are possible near Jackson and the Star Valley. Locally higher amounts up to 11 inches possible. .LONG TERM...Thursday through Tuesday The snow in western Wyoming will continue through Friday, with the mountains still getting a couple of inches each day, but the main storm will be over. The valleys in the west will see flurries as well. The Bighorn Mountains and southern Wyoming will also have chances of light snow on Thursday. The bigger challenge for Thursday to Saturday will be the wind speeds and direction. Northwesterly winds on Thursday will switch to southwesterly on Friday and Saturday with a fast moving short wave trough moving across the forecast area. Strong, gusty winds will occur along the mountains, and the southern wind corridor from Rock Springs to Casper during the period, as well as along most of the mountain ranges east of the Divide. Snow and blowing snow will impact travel through Saturday. The one bit of good news is that the winds and change in primary flow will scour out the cold air in the basins for a bit of a warmup. Sunday will see a ridge build across the forecast area for dry, northwesterly flow, and a decrease in the winds. This will be short- lived as a new weather system will move in on Monday bringing more snow to the northwest and west. Models are still not in agreement for the timing and movement of this system, so confidence is low for the extreme long range forecast. Temperatures do look to stay on the warmer side next Monday and Tuesday with light winds. && .AVIATION...(For the 06Z TAFS through 06Z Thursday) Issued at 311 PM MST Tue Dec 31 2019 East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals VFR conditions will occur at the terminal sites through the period. Windy conditions at KCPR and KCOD airports will occur through 00Z, then decrease. Isolated snow showers are expected after 18Z through 06Z with local MVFR conditions. Mountains will be obscured at times due to snow and lower clouds. West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Snow will occur in the western mountains through the period. Expect mountains to be frequently obscured. The KJAC airport will see snow as well through Wednesday night, decreasing after 06Z Thursday. The other terminals in SW WY will see periods of snow Wednesday morning into the early afternoon with MVFR to IFR conditions at times. Snow will be decreasing after 03Z Thursday in southwest WY. Expect windy conditions at KRKS airport through the period. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Cold and dry conditions, with light winds across most of the area today. Southwest winds with gusts of 40 to 50 mph will occur this afternoon across the Wind Corridor from the Red Desert through southern Johnson County, continuing tonight into Wednesday. These winds will spread into Sweetwater County Wednesday morning and continue through the day. Strong winds will also occur in the Absaroka Mountains and Cody Foothills late tonight into Wednesday, with gusts as high as 65 mph in the mountains and 55 mph in the foothills. The next weather system arrives late tonight in the northwest, spreading south across areas west of the Divide through the day Wednesday. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 11 PM this evening to 5 AM MST Thursday for WYZ001-002-025. Winter Storm Warning from 11 PM this evening to 5 AM MST Thursday for WYZ012-013-023-024. && SHORT TERM...LaVoie LONG TERM...Swanson AVIATION...AR FIRE WEATHER...Hulme/LaVoie
Hazardous Weather Outlook National Weather Service Riverton WY 1008 AM MST Tue Dec 31 2019 WYZ001>020-022>030-011715- 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- 1008 AM MST Tue Dec 31 2019 ...High Wind Warning in effect through this evening for the Green Mountains... ...Winter Storm Warnings and Winter Weather Advisories in Effect late Tonight through Thursday Morning for the Western Mountains and Valleys... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Gusty winds will occur over the Wind Corridor, from the Red Desert to Casper, as well as along the cody Foothills. Wind gusts of 40 to 50 mph, with locally higher gusts, will occur through the day today and into tonight. Ground blizzard conditions and wind gusts over 60 mph will occur near Jeffrey City this afternoon. .DAYS TWO THROUGH SEVEN...New Years Day through Monday. New Year's Day...Snow will become widespread across the northwest mountains and western valleys early with light snow spreading into southwest and northern Wyoming later in the day. Strong winds are expected in the Cody Foothills with gusts as high as 55 mph and in the Wind Corridor from Rock Springs to Casper with gusts as high as 45 mph. Thursday through Saturday...Snow will continue in the west and southwest with increasingly gusty winds. The strongest wind will be Friday afternoon in the mountains and foothills as well as the Wind Corridor from Rock Springs to Casper. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged today to report significant weather conditions, according to standard operating procedures.
Special Weather Statement National Weather Service Riverton WY 619 PM MST Tue Dec 31 2019 WYZ003-011300- Cody Foothills- Including the cities of Clark, Cody, and Meeteetse 619 PM MST Tue Dec 31 2019 ...Strong Gusty Winds through New Year's Day... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...West to southwest wind of 30 to 40 mph with gusts 50 to 60 mph. The higher gusts will be from Clark to south of Clark. * WHERE...The Cody and Clark areas. * WHEN...Now through New Year's Day. * ADDITIONAL DETAILS...Travel could be difficult on Highway 120, especially for high profile vehicles. Strong cross winds will enhance the blowover risk for lightweight and high profile vehicles, including camping trailers. WYZ016-011300- Upper Wind River Basin- Including the city of Dubois 619 PM MST Tue Dec 31 2019 ...Strong Gusty Winds through New Year's Day... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...A Northwest wind 25 to 35 mph with gusts up to 45 mph. * WHERE...The Upper Wind River Basin, Dubois, and Crowheart. * WHEN...Now through New Year's Day. * ADDITIONAL DETAILS...Travel could be difficult over Highway 26. Patchy blowing snow could significantly reduce visibility. Roads may also become slick in spots. WYZ020-011300- Natrona County Lower Elevations- Including the city of Casper 619 PM MST Tue Dec 31 2019 ...Strong Gusty Winds through New Year's Day... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...A Southwest wind 30 to 40 mph with gusts up to 55 mph. Isolated gusts up to 60 mph are possible. * WHERE...Portions of Natrona County, including the Casper area. * WHEN...Now through New Year's Day. * ADDITIONAL DETAILS...Travel will be difficult, especially for high profile vehicles. Strong cross winds will enhance the blowover risk for lightweight and high profile vehicles, including camping trailers. WYZ019-011300- Green Mountains and Rattlesnake Range- Including the city of Jeffrey City 619 PM MST Tue Dec 31 2019 ...Strong Gusty Winds through New Year's Day... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...A Southwest wind 35 to 45 mph with gusts up to 55 mph. Isolated gusts around 60 mph are possible. * WHERE...Beaver Rim to Jeffrey City to Muddy Gap. * WHEN...Now through New Year's Day. * ADDITIONAL DETAILS...Travel will be difficult, especially for high profile vehicles. Strong cross winds will enhance the blowover risk for lightweight and high profile vehicles, including camping trailers. Some blowing snow is possible.
The national radar mosaic for the moment the first event began.
4 winter storm, 3 high wind. Local standard time, as filed.
Heavy snow of 1 to 2 feet fell throughout much of the Tetons and Gros Ventre mountains. This included 21 inches at the Jackson Hole Ski Resort.
Snowfall amounts through the Star Valley ranged from 6 inches at Afton to 13 inches at Alpine, Wyoming.
High winds occurred in Natrona County. The highest gusts were along the wind prone areas of Wyoming Boulevard along the south side of Casper, Wyoming, where the maximum wind gust recorded was 75 mph.
High winds occurred in the northern Cody foothills. The highest gust were in the wind prone areas near Clark, Wyoming, where a maximum gust of 76 mph was recorded. The high winds also reached into Cody, Wyoming, as well, with a gust of 66 mph on the west side of the city. The high winds damaged a trailer roof, fence, shed, car and storm door.
Heavy snow fell in the Salt and Wyoming Range. This highest amount was 19 inches at the Cottonwood Creek SNOTEL site.
Heavy snow fell in the Jackson Valley. Amounts ranged from 7 inches in the town of Jackson to 12 inches near Teton Village, Wyoming.
High winds occurred through the area. Wind gusts of 76 mph occurred at the high elevation sites of Camp Creek and Fales Rock. At the lower elevations, Jeffrey City, Wyoming, had a wind gust to 60 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2020Every state in 2020This day in weather historyWarnings in Wyoming, January 2020
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: 868610, 868614, 868616, 868617, 868611, 868613, 868615.