A Pacific system crossed Wyoming and brought heavy snow to portions of western Wyoming and high wind to central Wyoming. Over a foot of new snow fell at the Jackson Hole Ski resort with up to 10 inches reported around Alpine.
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 Pacific system crossed Wyoming and brought heavy snow to portions of western Wyoming and high wind to central Wyoming. Over a foot of new snow fell at the Jackson Hole Ski resort with up to 10 inches reported around Alpine. Meanwhile, East of the Divide high winds were the story. The highest wind gusts were the RAWS sites in the Green Mountains where gusts of 73 mph were recorded. In the lower elevations, the highest wind gust recorded was 71 mph along Wyoming Boulevard to the south of Casper.
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 11, 3:07 PM MST, 4 hours 53 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 307 PM MST Tue Dec 11 2018 .SHORT TERM...This evening through Friday Everything remains on track as our potent quick hitting storm system arrives in the west tonight and moves across the rest of the area during the day Wednesday. Ahead of it, winds are increasing rapidly in the Cody Foothills as mountain wave signature shows an increasing threat of wave breaking later this afternoon or evening. Winds have already gusted to 73 mph at Chief Joseph and 52 mph at our Clark sensor along highway 120 south of Clark. Signature looks as good or better than yesterday so beefed up wording a little more and included 90 mph wording. Also added in the lee of the Absarokas with 75kt showing up in the cross sections. Upstream mountain top inversion is solid again in the sounding and with increasing flow into the barrier up to around 40 mph, we could see the potential for triple digit wind speeds. Certainly not your average high wind event. Gap flow will also be a concern with 14-16C H7 thermal gradient. We've seen stronger with the strongest events showing around 20C or so but up to 16C is pretty impressive. Just that alone will produce high winds in the favored gap areas around Clark and just south of Cody (south of the T and towards the dump) but with mountain wave potential quite high, it all adds up to a potentially very significant event. And on top of that we may have another high wind event in the Cody Foothills later Wed night through Thu ngt. Will look at that again tomorrow. Flow into the barrier looks borderline (under 30kts) but gap flow looks weaker initially through early Thur before increasing again afternoon and evening. Out in the far west, it's more about snow although winds will be quite gusty and rather strong over the ridges (30-45 mph). Upgraded the Tetons to a warning with up to 15 inches expected in the favored nw flow areas and issued a warning for the Star Valley with warning amounts expected on the north end of the valley as unstable nw flow behind the front keeps potential of heavy snow continuing through the afternoon Wed. Other areas have advisories which should be good even as far south as southern Lincoln, especially west of the Bear River Divide. On Wednesday, the front blasts east of the divide with very strong to high winds for many areas. A several hour period of snow on I80 with 45 to 55 mph winds may make it interesting but it'll be short lived. As the front dives swd through Johnson County, there will likely be a band of snow where the nw winds meet the n winds along ern/sern Johnson down to about Midwest. Potential for 2 to 4 inches exists there and will cover that in afternoon SPS. High wind watches for the DUB to RIW corridor and BYG area where backed up to Wed aftn and evening as that still looks to be the best strong to high wind potential with and behind fropa. Dubois may also have some very strong winds through tonight and even Wednesday morning. Ridge builds in Thu and Fri for a dry period with those areas of gusty to strong w to sw flow with considerable lee troughing and increasing thermal gradient once again. More on that tomorrow! .LONG TERM...Friday night through Tuesday night Guidance has become split with the Friday night system, but will keep the forecast trend from the previous shift going for now. Will keep chance PoPs across the NW mountains and Far West valleys 6Z-18Z Saturday. Depending on whether this system comes to pass, will determine whether high winds occur east of the Divide Saturday. Guidance does come back in line with a ridge building back over the region. This will likely bring strong inversions back over western valleys and lower central basins Sunday and Monday. 700mb temperatures will warm to 0C to +2C Sunday, increasing to +3 to +5C over the central basins by Monday morning. Pattern becomes split over the western CONUS Monday night into Tuesday, with an atmospheric river impacting the PACNW by Tuesday. The southern branch of the jet stream will be well to the south, over northern Mexico and the Southeast. The valleys and basins could be trapped under inversions once again. && .AVIATION...For the 00Z TAFS through 00Z Thursday East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Routes VFR conditions will prevail through the TAF period. Gusty SW winds will continue at KCPR and KCOD, decreasing slightly after 18Z Wed. VCSH/-SN will be possible along and east of a KWRL-KCPR line after 12Z Wed, as the cold front moves through the area. This activity will end from north to south by 21Z. West of the Divide...KBPI/KJAC/KPNA/KRKS Routes Snow will return to NW WY by 06Z, expanding southward through 12Z Wed. Snow will continue to expand, reaching southern portions between 12Z and 18Z. KJAC will see snow and MVFR/IFR conditions return around 08Z Wed, with the remaining terminals impacted after 12Z. Blowing snow and snow is likely by 15Z at KJAC, as winds increase. MVFR conditions are expected at the remaining terminals, with snow activity decreasing and wind increasing after 18Z Wed. && .FIRE WEATHER... A strong storm system will push across the area later tonight through Wednesday with snow and wind out west and areas of snow and very strong wind east of the divide. A ridge of high pressure will return Thursday for a dry day with less wind for most areas but there will still be areas of gusty wind across the wind corridor and lee of most mountain ranges. Basin and valley inversions will return Thursday. && .RIW WATCHES/WARNINGS/ADVISORIES... High Wind Warning from 11 PM this evening to 2 PM MST Wednesday for WYZ019-020. Winter Weather Advisory from 11 PM this evening to 5 PM MST Wednesday for WYZ001-013. Winter Storm Warning from 11 PM this evening to 5 PM MST Wednesday for WYZ012. High Wind Watch from Wednesday afternoon through Wednesday evening for WYZ010-016-017. Winter Weather Advisory from 2 AM to 5 PM MST Wednesday for WYZ024. Winter Storm Warning from 2 AM to 5 PM MST Wednesday for WYZ023. Winter Weather Advisory from 5 AM to 5 PM MST Wednesday for WYZ027. High Wind Warning until 5 AM MST Wednesday for WYZ002. High Wind Warning until 5 AM MST Wednesday for WYZ003. && SHORT TERM...Skrbac LONG TERM...LaVoie AVIATION...LaVoie FIRE WEATHER...Skrbac
Hazardous Weather Outlook National Weather Service Riverton WY 1130 AM MST Tue Dec 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- 1130 AM MST Tue Dec 11 2018 ...Winter Storm Warning Teton and Gros Ventre Ranges 11 PM tonight through 5 PM Wednesday... ...Winter Storm Warning for the Star Valley 2 AM Wednesday through 5 PM Wednesday... ...High Wind Warning for the Absaroka Mountains through 5 AM Wednesday... ...High Wind Warning for Cody Foothills from 2 PM Today until 5 AM Wednesday... ...High Wind Warning for Southeast Fremont and Natrona Counties from 11 PM Tuesday night until 2 PM Wednesday... ...High Wind Watch for the WInd River Basin and Northeast Johnson County Late Wednesday Afternoon and Evening... ...Winter Weather Advisories for the rest of far west Wyoming late tonight through Wednesday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Very strong winds expected along the east slope of the Absaroka mountains and Cody Foothills through tonight. Strong southwest winds developing from southeast Fremont County through the Casper area late tonight. Please see High Wind Warnings for details. Snow increasing across the western mountains and Far West valleys tonight. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Wednesday...Significant snow expected in the far west mountains and valleys along with gusty to strong wind. A period of very strong wind and snow along the Interstate 80 corridor. A chance of snow showers with brief heavy snow showers possible across central Wyoming. Wednesday afternoon and evening...Strong northwest wind possible across the Wind River Basin and northeast Johnson County including Interstates 25 and 90. .SPOTTER INFORMATION STATEMENT... Please report wind gusts over 50 mph and any snow amounts. Team Riverton
The national radar mosaic for the moment the first event began.
5 high wind, 2 winter storm. Local standard time, as filed.
A 59 mph wind gusts was reported 8 miles south of Clark.
At the top of the Jackson Hole Ski Resort, 13 inches of new was measured.
The RAWS sites at Fales Rock and Camp Creek recorded maximum wind gusts of 73 mph. A wind gust to 59 mph was recorded at the WYDOT weather station at Red Canyon.
The wind sensor along Wyoming Boulevard recorded many wind gusts past 58 mph, including a maximum gust of 71 mph.
Trained spotters measured anywhere from 4 to 10 inches around Alpine. Other notable amounts included 8.5 inches north of Thayne and 6.5 inches at the Star Valley Ranch.
Wind gusts of 58 to 64 mph were recorded along Interstate 25 to the north of Kaycee.
A pair of 60 mph wind gusts were recorded along Interstate 90 to the southeast of Buffalo.
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, December 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: 797663, 797661, 797664, 797665, 797662, 797667, 797666.