A fast moving system brought high winds to portions of central Wyoming. Some of the strongest winds included 81 mph west of Clark, 75 mph at Camp Creek and 61 mph along Wyoming Boulevard south of Casper.
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 fast moving system brought high winds to portions of central Wyoming. Some of the strongest winds included 81 mph west of Clark, 75 mph at Camp Creek and 61 mph along Wyoming Boulevard 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 20, 10:02 PM MST, 2 hours 33 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1002 PM MST Thu Dec 20 2018 .SHORT TERM...Tonight through Sunday Once again, the two concerns for the next few days are the same. I am sounding like a broken record. Oh wait, it is almost 2019, maybe a should say scratched CD or even corrupted MP3 file. Anyway, with the contrast in conditions, we will divide the discussion into West and East of the Divide. West of the Divide...The main concern here is snow. A fast moving wave and cold front will approach the area and bring snow to the area before daybreak. The atmosphere is unstable so there could be some decent snowfall rates for a few hours. However, this system is fast moving and this should limit snowfall amounts. In addition, most of the models have backed off QPF amounts just a bit. The NAM is the highest, but the orographic effects tend to be overdone. The model snow ratios also looked a bit too high. The previous shift issued a special weather statement and we will stick with that. There could be local advisory level amounts in the higher elevations of the Tetons and southwestern Yellowstone Park. However, this would only effect areas that would benefit from the fresh powder and the latter would only effect deer, elk and bears this time of year, oh my. There will be some gusty winds so there could be some blowing and drifting snow at times as well. The steadier snow should end by noon with only light snow showers lingering through the rest of the day and into the evening. A fast moving wave with some left front quadrant dynamics will then pass across southern Wyoming Friday night, mainly after midnight. All models are in agreement with timing, mainly from around 10 pm Friday and then out of the area by around 9 am. There are the some disagreements on how far north the best moisture gets though, and this is critical for effects, mainly on Interstate 80. For now, we have kept the higher POPs just south of I-80. but this could change. QPF is probably overdone, but a quick few inches of snow are certainly possible in southern Sweetwater County. Mainly dry conditions then move in for most of Saturday and Saturday night. Another wave then moves in for Sunday with another shot of snow. Like the others, this one is fairly fast moving and this should limit snowfall amounts somewhat. East of the Divide...The main concern here shifts to the thing that has an adverse effect on toupees and empty trash cans. With the shortwave passage, we will see the usual wind prone areas get rather windy once again. This includes Wyoming Boulevard south of Casper, the areas near Dubois and in the Lee of the Absarokas and the Cody Foothills, especially near everyone's favorite crossroad Clark. The things in favor include 700 millibar winds increasing to 50 to 55 knots. However, factors again include less of a pressure gradient across the state than on Tuesday and Wednesday. In addition, as the previous shift noted, the jet is not nearly as strong as the previous system. So again, we will stick with the special weather statement rather than a warning. There could be a high wind gust in the RAWS in the Green Mountains and possibly near Clark, but any impacts would be fairly minimal. Winds should decrease late Friday into Friday night as the pressure gradient lessens a bit. At this point, the period from Friday night through most of Sunday looks fairly dry and quiet. Winds will likely begin to increase again Sunday though as the next fast moving shortwave swings through the state from the west. As for snowfall, any snow would likely be restricted to the mountains and even here amounts would be fairly minimal. .LONG TERM... Overview...A couple of Pacific disturbances in westerly flow will bring chances of light snow to the west and southwest Sunday night and Monday along with breezy to windy conditions, mainly across the southern wind corridor. A stronger Pacific system will spread chances of snow across the area Christmas Day into Tuesday night. Colder conditions with chances of snow will follow on Wednesday. Discussion...A progressive WNW flow persists over the area Sunday and Monday with several weak, fast-moving shortwaves in the flow. GFS and ECMWF show enough spread to have low confidence in specific timing of these ripples, so we only made minor adjustments to the blended model guidance, namely to increase chances of snow across the southwest including the I-80 corridor that will be in the path of these systems. The next in this series of Pacific storm systems is forecast to dig down the west coast Monday night, carving out a deep trough across the Interior West on Christmas Day. GFS has slowed a bit from the previous run and now matches closer with the Canadian model, showing a low entering Northeast UT/North CO Tuesday night into Wednesday. Accordingly, southerly difluent flow sets up across the area late Christmas Day spreading chances of snow showers northward across the area. Any snow accumulations look light at this stage with the brunt of this system's energy remaining to our south. ECMWF may be too far north with lee cyclogenesis across eastern Colorado Wednesday morning, but we should see surface winds turn north-northeast across central and eastern Wyoming with some favored upslope areas (Casper, Lander, Thermopolis) standing the best chance of some light snow accumulations and travel impacts Wednesday-Wednesday night. Chances of snow will decrease west to east on Thursday with slight chances of snow showers lingering across Johnson and Natrona counties. Most highs will be in the 20s across the lower elevations Wednesday and Thursday, so colder but only around 5-10F below seasonal normals. && .AVIATION...For the 06Z TAFS through 06Z Saturday East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Routes VFR conditions will prevail through the forecast period. Areas of gusty wind will occur as a fast moving cold front sweeps across the region late Friday morning and early afternoon. KCPR will keep a gusty wind overnight through 00Z Saturday. All other areas will see light wind speeds by 01Z Saturday. West of the Divide...KBPI/KJAC/KPNA/KRKS Routes A fast moving weather system will spread snow across western WY from 12Z until 19Z, then lingering mountain snow showers until 00Z Saturday. Expect some mountain obscuration. MVFR to IFR conditions will occur at KJAC airport from 12Z to 21Z Friday, then conditions will improve to VFR after 21Z. KBPI and KPNA airports will see a quick period of snow with MVFR conditions Friday morning. Please see individual terminal sites for more details. VFR conditions will occur after 22Z through the remainder of the period. && .FIRE WEATHER... A fast moving weather system will move across the state late tonight into Friday. A period of snow will be likely in the western mountains. Areas East of the Divide will remain largely dry. Strong winds will be likely in the wind prone areas, including from the Red Desert through Casper, in the Lee of the Absarokas and in portions of the Wind River Basin. Mixing and smoke dispersal will range from poor in the deeper portions of the basins to fair to good in the breezy to windy locations. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...Hattings LONG TERM...Hulme/Meunier AVIATION...AR FIRE WEATHER...Hattings
Hazardous Weather Outlook National Weather Service Riverton WY 224 AM MST Thu Dec 20 2018 WYZ001>020-022>030-211000- 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- 224 AM MST Thu Dec 20 2018 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Friday and Friday night...Snow likely for the western mountains and the far west valleys. A chance for high winds to return to Cody Foothills and the Wind Corridor. Saturday and Sunday...Chances of snow showers across the west and south. Light accumulations are expected. Christmas Day and Wednesday...Snow showers are expected to spread across the area from the south and west by Christmas evening. Colder with chances of snow showers across mainly the south and central on Wednesday. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today and tonight.
Special Weather Statement National Weather Service Riverton WY 814 PM MST Thu Dec 20 2018 WYZ001-012-013-023-024-211100- 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, Alta, Jackson, Afton, Alpine, Star Valley Ranch, Thayne, and Fossil Butte National Monument 814 PM MST Thu Dec 20 2018 ...Snow returning late tonight through early Friday afternoon... * WHAT...Snow. 3 to 6 inches of snow in the far western mountains with locally higher amounts in the Tetons. 1 to 3 inches in the valleys. Areas of southwest winds 20 to 30 mph with blowing and drifting snow. * WHERE...Teton and Gros Ventre Range, Yellowstone National Park, Salt and Wyoming Ranges, Jackson and Star Valleys. * WHEN...Late tonight through early Friday afternoon. * ADDITIONAL DETAILS...Travel could be difficult. Areas of blowing and drifting snow could significantly reduce visibility and create slick, icy roads. The hazardous conditions will likely impact the morning commute, especially over Teton and Togwotee Passes. WYZ002-003-015-016-211100- Absaroka Mountains-Cody Foothills-Wind River Mountains East- Upper Wind River Basin- Including the cities of Pahaska, Cody, Meeteetse, and Dubois 814 PM MST Thu Dec 20 2018 ...Strong Wind to occur later tonight through Friday afternoon... * WHAT...West to northwest wind of 30 to 40 mph with gusts to 50 mph. Stronger wind gusts to near 60 mph are possible in the mountains and in the vicinity of Clark. * WHERE...Cody Foothills, Upper Wind River Basin, Wind River Mountains and South Pass. * WHEN....Late tonight through Friday afternoon. * ADDITIONAL DETAILS...Travel could be difficult. Areas of blowing snow could cause slick roads in the high country. WYZ019-020-211100- Green Mountains and Rattlesnake Range- Natrona County Lower Elevations- Including the cities of Jeffrey City and Casper 814 PM MST Thu Dec 20 2018 ...Strong Winds overnight through Friday afternoon... * WHAT...West to southwest wind of 30 to 40 mph with gusts around 55 mph. Outer Drive on the south side of Casper has seen wind gusts over 50 mph this evening. * WHERE...Southeast Fremont and much of Natrona County. * WHEN....Overnight through Friday afternoon. * ADDITIONAL DETAILS...These winds may cause loss of vehicle control or a blow over to high profile vehicles traveling empty or with a light load. Outer Drive on the south side of Casper will be impacted by the strong wind.
The national radar mosaic for the moment the first event began.
5 high wind. Local standard time, as filed.
The wind sensor along the Chief Joseph Highway recorded a few hurricane force wind gusts. The maximum wind gust recorded was 76 mph.
Hurricane force wind gusts were recorded west of Clark. The maximum wind gust recorded was 81 mph.
Multiple wind gusts over 58 mph were recorded along Wyoming Boulevard south of Casper. The maximum wind gust recorded was 61 mph.
A wind gust of 75 mph was recorded at the Camp Creek RAWS site. At Beaver Rim, a pair of 60 mph gusts were recorded.
A 59 mph wind gust was recorded at the Buffalo airport.
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: 798133, 798134, 798139, 798136, 798135.