A series of upper level disturbances and a supply of Pacific moisture brought locally heavy snow to portions of western Wyoming. In the mountains, they highest amounts fell in the Salt and Wyoming Range, including a maximum of 21 inches at the Willow Creek SNOTEL site.
Every event with a place to put it; 5 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 series of upper level disturbances and a supply of Pacific moisture brought locally heavy snow to portions of western Wyoming. In the mountains, they highest amounts fell in the Salt and Wyoming Range, including a maximum of 21 inches at the Willow Creek SNOTEL site. In the Tetons, the Jackson Hole Ski Resort had 16 inches of new snow. In the Jackson Valley, amounts generally ranged from 8 to 12 inches. The Star Valley also saw heavy snow, with amounts ranging from 5 inches at Afton to 12 inches at Alpine. Strong southwest wind also occurred with the system, with the Camp Creek RAWS in the Green Mountains experiencing a maximum wind gust of 84 mph.
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 11, 4:03 AM MST, 5 hours 57 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 403 AM MST Thu Jan 11 2018 .SHORT TERM...(Today and tonight) Issued at 332 AM MST Thu Jan 11 2018 The next Pacific shortwave now making landfall onto the Pacific coast will be advancing southeast toward Wyoming in the northwest flow today through tonight with the troughpa occurring around 12Z Friday. A substantial amount of snowfall is expected in the far west this afternoon, tonight, and Friday morning as a westerly difluent upper flow, strong 50 to 70 mph upslope flow, and isentropic lift all combine with the deep Pacific moisture to give far Western Mountains and valleys advisory amounts of snowfall with some local warning amounts in a relatively short period of time. The snow will diminish in intensity Friday afternoon. Only lighter amounts of snow will spill over the divide to the east, mainly in Northern WY over the mountains. This will be a colder weather system than the once on Tuesday night and Wednesday. 70 knot 700mb winds within the anticyclonic flow will surface along the southern wind corridor tonight as well as along the foothills along the east side of the Continental Divide. Strong northwest winds can be expected in the Upper and Lower Wind River Basin after midnight tonight once the winds veer at 06z Friday night. Most of the snowfall will end Friday night with only spotty light areas of snow expected in the northwest through Saturday night as light Pacific moisture streams in from the northwest up and over the building high to the west. Do not expect much in the way of of fluctuations in temperatures through the period as a sfc front osculates close to the divide. .LONG TERM...(Friday through Wednesday) Issued at 332 AM MST Thu Jan 11 2018 |Sharp ridge holds over the west to start this period but cold swd moving shortwave and arctic front will move into the nrn zones by Sunday afternoon and then move through most areas east of the divide by Sunday evening. Sharply colder temperatures, gusty north wind and a brief period of snow will be likely across our nrn and ern zones with areas a little further southwest like Fremont County more challenging. Big picture supports the best chances in our nern corner and the majority of the guidance has a period of light snow from the nrn and ern Bighorn Basin over to Johnson and south to Natrona County and that seems reasonable for now. Much colder Monday behind this system Monday with some lingering light snow or flurries in our nern/ern quadrant. Strong surface high that comes down will likely result in a cold day Monday east of the divide, especially Johnson County and possibly Natrona County. Lowered highs some in this area but not as much as they may need to be with time. Surface high near 1050mb and far nrn trajectory of this system should bring down some cold air that will likely not be flushed out that quickly on Monday as the blend gave us. Cold night Monday night with a clear sky and light wind and possibly some fresh snow cover east of the divide. Inversions for the basins and valleys Tuesday with shortwave ridging with some warming aloft for warming in the mountains. A weakening shortwave is expected to skim the far west around Tuesday night with a bout of light snow and gusty mtn top wind. The ridge is slowly weakening as the second half of next week and that may lead to a stronger system at the end of the period (next Thursday). Models are obviously struggling with the pattern change as we transition from the western U.S. ridge to a developing trough along or just off the west coast late next week and beyond but the odds of snow increase Thursday into Thursday night, especially across the west with increasing wind in many areas. One side note, expect some patchy fog in the basins east of the divide this morning. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) Issued at 332 AM MST Thu Jan 11 2018 West of the Continental Divide...KJAC, KBPI, KPNA and KRKS Northwest WY will see VFR conditions through 16Z with local MVFR ceilings. After 16Z, snow will be developing in NW WY and snow will continue through tonight. KJAC airport will see MVFR conditions around 19Z with snow developing around 21Z. IFR conditions will likely develop at KJAC airport around 00Z and continue through 12Z Friday. The mountains will be frequently obscured this afternoon and tonight. VFR conditions will occur in southwest WY through 03Z. Then KPNA and KBPI will see MVFR conditions develop after 03Z along with light snow developing after 06Z Friday. Please see individual terminal sites for more details. East of the Continental Divide...KCPR, KCOD, KRIW, KLND, and KWRL Fog may occur at the KWRL and KLND airports until 16Z with local MVFR/IFR conditions. Otherwise, VFR conditions will prevail through tonight. Gusty wind conditions will return to KCPR today and increase in speed tonight. Please see the Aviation Weather Center for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Issued AT 332 AM MST Thu Jan 11 2018 Another storm system will be moving into western Wyoming later today. Moderate to locally heavy snow will return to the west from this afternoon through the day Friday. Expect strong southwest to northwest winds over many areas tonight. Smoke dispersion will be very good for many locations today and fair to good both Wednesday and Thursday. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 11 AM this morning to 5 PM MST Friday for WYZ001-002-012>015-023>025. && SHORT TERM...Lipson LONG TERM...Skrbac AVIATION...Ross FIRE WEATHER...Lipson
Hazardous Weather Outlook National Weather Service Riverton WY 402 AM MST Thu Jan 11 2018 WYZ001>020-022>030-121200- 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- 402 AM MST Thu Jan 11 2018 ...Winter Weather Advisories for most of the western mountains and valleys from this afternoon until 5 pm Friday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Mid afternoon today through Friday...Another upper level disturbance will spread snow into the west, with locally heavy snow possible. Light snow expected east of the Divide Friday morning. Strong southwest to west winds are expected from Rock Springs to Casper as well as along the foothills east of the Continental Divide tonight. Strong northwest winds are expected after midnight tonight from Dubois to Riverton. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Friday...The snow in Western Wyoming will be decreasing in the afternoon. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report wind gusts of 50 mph as well as any snowfall amounts. Thank you. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
4 winter storm, 1 high wind. Local standard time, as filed.
Heavy snow fell throughout the Salt and Wyoming Range. The highest amount was 21 inches at the Willow Creek SNOTEL.
Snowfall amounts through the Jackson Valley generally ranged from 5 to 13 inches, including 8 inches in the town of Jackson.
Heavy snow fell through much of the Tetons and Gros Venture mountains. The highest amount measured was 16 inches at the top of the Jackson Hole Ski Resort.
Snowfall amounts in the Star Valley ranged from 5 inches at Afton to 12 inches at Alpine.
The RAWS site at Camp Creek recorded many wind gusts past 58 mph, including a maximum gust of 84 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2018Every state in 2018This day in weather historyWarnings in Wyoming, January 2018
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: 728999, 728996, 728998, 728997, 729000.