A few locations in the lee of the Absarokas had high winds. The maximum wind gusts included 76 mph along the Chief Joseph Highway and 59 mph to the west of Clark.
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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 few locations in the lee of the Absarokas had high winds. The maximum wind gusts included 76 mph along the Chief Joseph Highway and 59 mph to the west of Clark.
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 18, 4:02 PM MST, 2 hours 3 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 402 PM MST Tue Dec 18 2018 .SHORT TERM...(This evening through Wednesday) Issued at 301 PM MST Tue Dec 18 2018 Snowfall has increased during the past couple of hours in far Western Wyoming. Web cams indicate that around 2 inches of snowfall have already likely fallen at Grand Targhee. This snowfall is in response to a vigorous shortwave now pushing rapidly across the Pacific Northwest. Increasing westerly difluent upslope flow and isentropic lift are rapidly enhancing the snowfall in these areas. In addition, left front quad dynamics from a 135 knot jet will be providing extra lift by 06Z tonight as the jet stream lifts north, and the strong shortwave digs on the front side of the ridge that will eventually amplify over the Pacific states Wednesday. By 09Z tonight, the asct strong Pacific cool front will push across Western Wyoming and by 11 or 12Z it will push across areas east of the Divide. Winds will come to a crescendo once the front pushes on through with the west winds at the top of RPK likely reaching 65 mph. Even the Jackson Valley will blow from the SSW with 50 to 55 mph winds expected to gust there as the 65 mph wind component is forced down into the valley during the fropa. The airmass will be weakly unstable once the front rushes through and snow showers will continue post frontal, mainly in the far west through 18Z Wednesday. Snow advisory amounts are slated for the far western mtns and valleys tonight through Wednesday morning along with considerable blowing and drifting. Lingering flurries are expected over the western mtns Wednesday afternoon with clearing skies by Wednesday evening. As for wind, in addition to the winds directly asct with the front, several areas are likely going to see strong to high winds, especially areas east of the divide as we trade snowfall for wind in these areas. The Cody Foothills (and the Absarokas which are already under a winter weather advisory) will have the potential to blow high wind through 15Z Wednesday during which time a high wind warning is in effect. A persistent mtn top inversion is in place along with a decent temp gradient between YNP and the Cody Foothills along with a froude number of 1. The Southern Wind corridor from South Pass to Casper will blow sub warning criteria in response to a 13mb sfc pressure gradient from GCC to RKS> Casper Outer Drive could see isolated high wind gusts tonight and Wednesday morning. The potential for high post frontal northwest winds will likely occur within the Wind River Basin and Northern Johnson County as these areas have a propensity for strong post frontal northwest winds, given the 5 and half H7 height lines spaced out over Wyoming every 30 decameters. Sweetwater County is also under the gun Wednesday with their typically strong post frontal westerly winds with both the MET and MAV MOS indicating over 30 knots for a sustained wind for a period of 6 to 9 hours. the MAV peaks the wind gusts at RKS at 36 knots at 21Z Wed. We have a high wind watch out for Sweetwater County, the Wind River Basin, and Northern johnson County for Wednesday. winds will diminish toward evening. Any snow that makes it over the divide will be relatively light with only 2 to 4 inches expected in the Big Horn Mtns by Wednesday. Expect clearing skies with continued diminishing winds Wednesday night as the aforementioned ridge builds east. .LONG TERM...(Thursday through Tuesday) Issued at 301 PM MST Tue Dec 18 2018 Shortwave ridging and dry to start the period Thursday. Another strong shortwave trough will approach the west Thursday night and blast east of the divide Friday. The west will see a period of snow and gusty to strong w/sw wind during the day Friday. Some lcl advsry amounts are possible but system is a quick hitter. Eventual high wind watches will likely be needed for the Cody Foothills and wind corridor Thursday night and Friday ahead of the front. As the cold front moves east of the divide, a chance of snow will shift east of the divide along with strong west (shifting to north winds up north and east) wind. Models are struggling with the mean pattern and whether there will two systems very close to each other or a gap before the Saturday one. The GFS 5-wave shows a general trough over the central Rockies so it would favor another quick hitting Saturday system or the Friday one lingering or held back as the next system moves into the 'mean' trough. This idea is depicted more in the Euro and GEM. So once the snow starts out west Friday, we may see periods of at least light snow through Saturday. On Sunday, a weak disturbance may brush through the area or at least the nrn part with some light snow/flurries in the west and possibly north. Some warm advection/upglide snow may fall out west Monday with flat ridging ovhd ahead of our digging Christmas storm. Details remain all over the board but they all generally have a fairly strong system digging into the Great Basin Christmas Day and then possibly lifting newd next Wednesday as another system drops down the back side of the trough to hold it from racing away. The main trend with the GFS this morning is to have more of a nwd extension of this upper low into ern ID and WY increasing the chances of snow across the area on Christmas day into Christmas night. Still a week out so we'll just have to watch the details with time but like I said yesterday, the big picture supports a trough/upper low in the area even if it ends up being in pieces. The main trough may hang around beyond this period as another shortwave drops swd into the mean trough next Wednesday. Complex and interesting weather around Christmas for sure! && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 301 PM MST Tue Dec 18 2018 East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Routes The main aviation concern again through this evening will be windy to strong southwest to west wind and/or low-level wind shear in the South Pass to Casper wind corridor, lee side of mountain ranges into adjacent foothills. Otherwise, variable mid-high level cloudiness is expected with VFR conditions through this evening. After 06Z Wednesday, a cold front will begin to sweep across the area with windy conditions developing in some locations that were relatively light for much of the period such as KRIW and KBYG. There could also be a few showers along and behind the cold front, but coverage is not enough to include any precip at any terminal. VFR conditions are expected after 18Z Wednesday. West of the Divide...KBPI/KJAC/KPNA/KRKS Routes Ceilings will vary between 020-050 kft agl over the far western terminals including KJAC with some light snow/flurries through the rest of the afternoon today. A winter storm will continue to approach the area with increasing snowfall and wind overspreading western Wyoming. MVFR and IFR conditions are expected at KJAC after 00Z Wednesday from snow and blowing snow, and last through the night. Farther southeast, the snow will be much lighter, but windy west to northwest will develop. Mountains will be obscured much of the time, with the best conditions occurring across South Pass. Some areas of MVFR conditions will persist in far Western Wyoming through 18Z Wednesday. After 18Z Wednesday, expect mainly VFR conditions with some lingering flurries in the far Western Mountains. 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 301 PM MST Tue Dec 18 2018 Strong cold front and weather system will blast east across the area tonight through Wednesday. Snow and wind will fall out west tonight through Wednesday. East of the divide, there will be strong to high wind and pockets of light snow in the far northern part of the district. Thursday will be dry behind this system with areas of gusty southwest to west wind in the foothills and wind corridor from Jeffrey City to Casper. The basins will see temperature inversions returning Thursday. && .RIW WATCHES/WARNINGS/ADVISORIES... High Wind Watch from late tonight through Wednesday afternoon for WYZ010-016-017-028>030. Winter Weather Advisory until noon MST Wednesday for WYZ001-002- 012-013-023-024. High Wind Warning until 8 AM MST Wednesday for WYZ003. && SHORT TERM...Lipson LONG TERM...Skrbac AVIATION...Lipson FIRE WEATHER...Skrbac
Hazardous Weather Outlook National Weather Service Riverton WY 224 AM MST Tue Dec 18 2018 WYZ001>020-022>030-191215- 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 Tue Dec 18 2018 ...High Wind Warning for the Cody Foothills late today into early Wednesday... ...High Wind Watch for some areas East of the Divide Wednesday... ...Winter Weather Advisory for western Wyoming late today through noon Wednesday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Light snow continuing in the west today. Moderate to possibly heavy snow will occur tonight in the western mountains. Please see Winter Weather Products for details. High winds are likely late tonight and tonight in the Cody Foothills. Please see High Wind Warning for details. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Wednesday...Strong winds possible in northern Johnson County, the Wind River Basin and Sweetwater County. Please see High Wind Products for details. Snow continuing in the west, decreasing in the afternoon. Friday and Friday night...A chance of snow for the mountains and the far west valleys. Sunday...A chance of snow in the western mountains. .SPOTTER INFORMATION STATEMENT... Spotters are urged to report snowfall amounts and wind gusts over 50 mph. TEAM RIVERTON
Special Weather Statement National Weather Service Riverton WY 250 PM MST Tue Dec 18 2018 WYZ019-020-191000- Green Mountains and Rattlesnake Range- Natrona County Lower Elevations- Including the cities of Jeffrey City and Casper 250 PM MST Tue Dec 18 2018 |..Strong winds this afternoon through Wednesday... * WHAT...Strong west to southwest wind of 30 to 40 mph with gusts to 55 mph. Local gusts over 60 mph on Outer Drive in Casper are possible. * WHERE...Southeast Fremont and Natrona County, especially around Outer Drive. * WHEN....For the rest of this afternoon through tonight and Wednesday. * 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. WYZ025-191000- Upper Green River Basin Foothills- Including the city of Pinedale 250 PM MST Tue Dec 18 2018 ...Periods of snow tonight into Wednesday... * WHAT...Periods of snow. One to three inches of snow expected, with the highest amounts near Bondurant and around an inch expected at Pinedale. * WHERE...The Green River Foothills, including Pinedale and Butternut. * WHEN....Early this evening through the rest of tonight and and into Wednesday morning. * ADDITIONAL DETAILS...Travel could be difficult. Expect slick and snow covered roads if traveling tonight and Wednesday. WYZ027-191000- South Lincoln County- Including the cities of Kemmerer and Cokeville 250 PM MST Tue Dec 18 2018 ...Periods of snow tonight into Wednesday... * WHAT...Periods of snow. One to three inches of snow expected, with less than an inch expected in the extreme south portion of the county. * WHERE...The lower elevations of Southern Lincoln County. * WHEN....Early this evening through the rest of tonight and and into Wednesday morning. * ADDITIONAL DETAILS...Travel could be difficult. Expect slick and snow covered roads if traveling tonight and Wednesday. WYZ014-015-191000- Wind River Mountains West-Wind River Mountains East- Including the city of Atlantic City 250 PM MST Tue Dec 18 2018 |...Periods of snow tonight into Wednesday... * WHAT...Periods of snow. Four to nine inches of snow expected above 9500 feet including Togwotee Pass with 1 to 3 inches expected below 9500 feet. South Pass on the southern end of the range will likely only receive an inch or less of snow. However, wind gusts of 50 mph over South Pass will likely combine with the snowfall, effectively lowering the visibility. * WHERE...The east and west slope of the Wind River Mountains. * WHEN....Early this evening through the rest of tonight and and into Wednesday morning. * ADDITIONAL DETAILS...Travel could be difficult. Expect slick and snow covered roads if traveling tonight and Wednesday. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
2 high wind. Local standard time, as filed.
Winds were sustained at over 50 mph for over an hour and a half along the Chief Joseph highway. The maximum wind gust recorded was 76 mph.
A 59 mph wind gust was reported to the west of Clark.
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: 798131, 798132.