Strong mid level winds mixed to the surface ahead of a cold front passage and brought high winds to the wind prone areas of central Wyoming. In central Wyoming, the Green Mountains, Eastern Wind River Range and Natrona County all saw wind gusts as high as 75 mph.
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.
Strong mid level winds mixed to the surface ahead of a cold front passage and brought high winds to the wind prone areas of central Wyoming. In central Wyoming, the Green Mountains, Eastern Wind River Range and Natrona County all saw wind gusts as high as 75 mph. A wind gust of 61 mph was reported in Clark in Park County, Wyoming.
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 Jan 6, 3:04 PM MST, 1 hour 58 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 304 PM MST Mon Jan 6 2020 .SHORT TERM...(This evening through Tuesday night) Issued at 302 PM MST Mon Jan 6 2020 West of the Divide...Abundant snowfall fell overnight last night in localized areas from heavy narrow snowbands ahead of a vigorous shortwave trough, one of these places being Alpine where up to 16 inches of snowfall fell in some areas there. The snowfall that is occurring now over the far west will be more of the steady light to moderate widespread type associated warm air advection and isentropic lift. The snow will spread from south to north through tonight, with more snowfall expected north of Salt River Pass. Weak QG forcing will aid in the forcing. Favorable dendritic growth is anticipated with this particular episode of snowfall. We are looking at another 1 to 4 inches in the valleys and Salt River Range along with 3 to 6 inches in the Tetons, Gros Ventre Range, and YNP where local amounts of 9 inches are possible by sunrise Tuesday. Then just light snow will resume later Tuesday morning before the next wave in the progressive flow, identified best by a bubble of QG forcing, initiates more light to moderate snowfall for a few hours Tuesday afternoon in the far west. This will be good for another couple of inches. Then another area of QG forcing in the westerly flow will add another 1-2 inches in the valleys Tuesday night after midnight and 3 to 5 inches in the mountains. During this entire time frame, the favorable upslope flow will aid in lift, especially on west facing slopes. However, 700mb temps will be a wee bit too mild for favorable dendritic growth Tuesday and Tuesday night. Will not issue any advisories since there is already a decent snowpack in the far west and the most abundant snowfall will occur where the ski resorts need it. East of the Divide...Wind is the main story here. One of the windiest spots in the CWA today was in t he Wind River Basin where the wind gusted to 51 mph at the Riverton Regional Airport at 1026 AM this morning. Sweetwater County also blew fairly strong with RKS gusting to 41 mph, and Tipton in eastern Sweetwater County, the wind gusted 51 mph. This wind was in response to the aforementioned vigorous shortwave with obvious and a sharp delineation of drying on the backside of the trough that tracked across the area this morning. The winds are slowly decreasing in these areas, but are still blowing fairly briskly in response to the 50 knot winds overhead at 700mb and the sfc gradient of 15mb developing between GCC and RKS as a 1040mb sfc high establishes itself over far southwest Wyoming and western Colorado. Five isoheight lines spaced apart every 30 decameters at 700mb were progged over Wyoming indicating a tight gradient at that level. We will keep the high wind warning now in progress for the Cody Foothills that is valid through 12Z Tuesday. The combination of a defined mountain wave, a weak mountain top inversion, 65 knot winds at 700mb leading into the event, as well as a gap flow component indicated by a 15C 700mb temp gradient between YNP and the Cody Foothills all point to a high wind event. Then on Tuesday. upper the flow will back from northwest to west as a flat ridge builds into the area. This backing brisk westerly flow will be channeled from the southwest along the southern wind corridor from the Green Mtns to Casper with the tight surface gradient continuing. twenty seven knots are indicated on the MAV MOS for Casper tuesday afternoon. Addressed this with an SPS and indicated that outer Drive could see a gust or two of 60 mph. .LONG TERM...(Wednesday through Monday) Issued at 302 PM MST Mon Jan 6 2020 Moist, southwest flow will reach western Wyoming Wednesday morning with snow rapidly increasing. Favorable orographics, instability, and mid-level temperatures should aid snow production during the daytime hours Wednesday. Valley temperatures around 30F may hinder accumulations during the day Wednesday. While conditions become less favorable overnight into Thursday there will still be accumulating snow. This event appears as though it will provide solid winter weather advisory amounts with the Tetons and southwest Yellowstone National Park poised to receive potentially 10-15 inches. A watch may be needed for these areas by early Tuesday morning if QPF amounts remain as they are currently. Areas east of the Continental Divide will be dry with wind in central Wyoming being the primary concern. West to southwest wind of 25 to 40 mph likely in the Wind Corridor for Wednesday. Overall, temperatures will be seasonal to slightly above seasonal in the snow-free basins east of the Divide. The upstream jet and another shortwave will help to carve a deepening trough across the western U.S. for Thursday. Temperatures will take a downturn with many locations below normal, but not bitter cold. Snow will continue across the western mountains Thursday. The 700mb flow veers to the northwest which will favor lingering snow in the Tetons and Jackson through the day Thursday. Areas east of the Divide will remain dry and wind is not expected to be a major player. A shortwave will drift across the northern Rockies Thursday night and early Friday morning. This feature could set off light snow across the far north and potentially the I-25 corridor during this time. The shortwave quickly clears the forecast area by midday Friday, but it would not be surprising to see an increase in snow chances in the Bighorns, northern Bighorn Basin, and Casper as this forecast develops. Friday will generally find temperatures slightly below normal throughout the forecast area. The attention then turns to the far west again for the weekend as another slug of Pacific moisture reaches the state. Accumulating snow will be widespread as temperatures will be plenty cold enough in the valleys, too. This storm has the potential to generate significant snowfall totals in the western mountains and valleys. A 100kt+ 300mb jet will be oriented west-to-east near southwest Wyoming Saturday with the left-exit region helping to initiate snowfall along I-80 Saturday. The jet departs and the trough deepens Saturday night, so the snow should end across the southwest. Otherwise, areas east of the Divide will remain dry and cold Saturday and Sunday. Heading into Monday, the latest deterministic solutions of both the GFS and ECMWF have backed off the bitter cold temperatures. West-northwest flow will keep it cold and unsettled to begin next week. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 302 PM MST Mon Jan 6 2020 West of the Continental Divide...KBPI/KJAC/KPNA/KRKS Terminals Conditions will become MVFR at KJAC early Monday evening as a weather disturbance moves through in northwest flow aloft. Other terminals will see lowering mid-deck ceilings. The best chance for light snow will be at KJAC until 09Z/Tuesday. However, northwest flow aloft could linger flurries into Tuesday morning. MVFR ceilings anticipated at KBPI and KPNA Tuesday morning in the wake of the disturbance before slowly improving to VFR in the afternoon. Mountain obscurations will be frequent through Tuesday morning, with frequent mountain top obscurations throughout the forecast period. Gusty westerly surface wind of 15-25kts to prevail at KRKS overnight with a slight decrease in speed anticipated for Tuesday. East of the Continental Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals The primary aviation hazard east of the Divide will be wind. Speeds have decreased at KRIW this afternoon, but still expect 15-25kts overnight. KCOD and KCPR will see westerly wind increase around or shortly after sunset Monday evening. These speeds will continue overnight and for KCPR through the day Tuesday. KLND has the potential for LLWS Monday evening as downsloping wind descends the east slopes of the Wind River Range. Westerly direction will not favor the stronger wind reaching KLND. VFR to reign at all terminals through Tuesday. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts.| && .FIRE WEATHER... Issued AT 302 PM MST Mon Jan 6 2020 A series of weather systems will impact areas west of the Continental Divide through at least midweek. Light snow will persist through Monday night but the snow will decrease Tuesday as an upper- level ridge moves into Wyoming. The better chance for snow will be in the west during the day Wednesday as a more vigorous weather system swings through the state. Accumulating snow will fall in the Teton and Yellowstone dispatch areas Wednesday into Wednesday night. Meanwhile, conditions are likely to remain dry through at least Wednesday night east of the Continental Divide. The primary hazard across the east will be gusty westerly wind across primarily zones 280 and 289. The gusty wind will increase smoke dispersal, but conditions will only be fair at best. Temperatures will remain seasonal with slightly above normal temperatures in the Absaroka and Bighorn mountain foothills and the snow-free lower elevations. && .RIW WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 5 AM MST Tuesday for WYZ003. && SHORT TERM...Lipson LONG TERM...Jones AVIATION...Jones FIRE WEATHER...Jones
Hazardous Weather Outlook National Weather Service Riverton WY 129 PM MST Mon Jan 6 2020 WYZ001>020-022>030-071400- 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- 129 PM MST Mon Jan 6 2020 ...High Wind Warning for the Cody Foothills Monday Afternoon and Evening... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Rest of Today and Tonight High winds will become likely in the Cody Foothills by Monday evening and persist overnight. The strongest winds are expected to occur after sunset Monday. Please see the High Wind Warning for specific details. Light to moderate snow will continue into early Tuesday morning in the western mountains with light snow persisting in the far west valleys. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Tuesday and Wednesday...Southwest wind 30 to 45 mph across central Wyoming, especially Natrona County. Wind gusts around 55 mph will be possible along Wyoming Boulevard on the south side of Casper. Wednesday and Thursday...Accumulating snow for the western mountains and valleys, particularly during the day Wednesday. Saturday and Sunday...Significant snowfall possible over the west. .SPOTTER INFORMATION STATEMENT... Weather spotters are encourage to report snowfall amounts. Team Riverton
Special Weather Statement National Weather Service Riverton WY 154 PM MST Mon Jan 6 2020 WYZ001-012-013-023-024-071400- Yellowstone National Park-Teton and Gros Ventre Mountains- Jackson Hole-Star Valley-Salt River and Wyoming Ranges- Including the cities of Lake, Mammoth, Old Faithful, Jackson, Afton, Alpine, Star Valley Ranch, and Thayne 154 PM MST Mon Jan 6 2020 ...Light Snow Persists Monday Night with More Snow Wednesday... * WHAT...Snow continues Monday night with new accumulations of 1 to 2 inches in the valleys and 3 to 5 inches in the mountains. Snow returns Wednesday and Wednesday night with possible valley accumulations of 3 to 6 inches and widespread mountain snowfall of 6 to 10 inches. * WHERE...Much of western Wyoming, including Jackson, the Star Valley, Teton and Togwotee passes, and the Teton Range. * WHEN...The first round of snow will continue through Monday night. After a break Tuesday afternoon and night, the second round of snow will arrive Wednesday morning with steady snowfall through Wednesday night. * ADDITIONAL DETAILS...Roadways over Teton and Togwotee passes will be covered by snow and ice.
Special Weather Statement National Weather Service Riverton WY 208 PM MST Mon Jan 6 2020 WYZ019-020-080100- Green Mountains and Rattlesnake Range- Natrona County Lower Elevations- Including the cities of Jeffrey City and Casper 208 PM MST Mon Jan 6 2020 ...Winds expected to increase once again from Jeffrey City to Casper on Tuesday... * WHAT...Southwest winds will likely increase to 30 to 40 mph with gusts to 50 mph. A few wind gusts will reach 60 mph along Outer Drive just south of Casper, as well as along some of the higher ridges. * WHERE...Along the Highway 287 corridor from Beaver Rim to Sweetwater Station and Jeffrey City, and along the Highway 220 corridor from Alcova to Casper. * WHEN...Tuesday with the strongest wind likely to occur from 11 AM to 6 PM. * ADDITIONAL DETAILS...Anyone traveling along Highway 20/26, 220, 287 and Interstate 25 on Tuesday should anticipate sudden strong cross winds. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
4 high wind. Local standard time, as filed.
A wind gust of 61 mph was reported in Clark, Wyoming.
Strong to high winds occurred through much of Natrona County. The highest wind gusts were 75 mph along Wyoming Boulevard on the south side of Casper, Wyoming.
The wind sensor at the Red Canyon reported wind gusts as high as 75 mph.
Wind gusts as high as 75 mph were reported at the Fales Rock RAWS site.
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: 868822, 868825, 868823, 868824.