A 31 year old man was back country skiing just south of the Jackson Hole Ski Resort, in an area called the Spacewalk Couloir. The man triggered an avalanche and he was tumbled the full length of the feature.
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The episode as NWS RIW wrote it up.
A 31 year old man was back country skiing just south of the Jackson Hole Ski Resort, in an area called the Spacewalk Couloir. The man triggered an avalanche and he was tumbled the full length of the feature. The man was not buried but suffered leg and hip injuries. He was rescued and brought a hospital in Jackson.
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 24, 9:47 AM MST, 2 hours 13 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 947 AM MST Mon Dec 24 2018 .SHORT TERM...(Today through Wednesday night) Snowfall has recently gotten underway in Far Western Wyoming ahead of a weak shortwave that is due to arrive around 12Z Monday. A second weak shortwave will arrive close to 00Z Tuesday. Weak isentropic lift will be ongoing during this time frame in the west. As a result, steady light snowfall, moderate at times, will continue in the far west now through the end of Monday. Aside from the weak isentropic lift, westerly upslope flow will contribute to the snowfall. By the end of Monday, we are looking at sub advisory amounts for the western valleys and most of the western mtn locations, although the Tetons, where the ski resorts are, will likely pick up advisory amounts. Namely 3 to 6 inches at the higher elevations of the far west and 2 to 4 inches in the valleys along with 10 inches on the higher west facing slopes of the Tetons. An SPS for this event should suffice. Lighter snow will continue in the Far West Monday night. As for the Christmas snow event, the splitting trough will still dig with a closed H5 low as far south as the Old Mexican Border. The models now want to open the low back up by 12Z Wednesday. With the main energy this far south, any snowfall associated with the related trough will be relatively light over the CWA. For starters, before the trough splits all the way, there will be a period of weak difluent flow as this trough first approaches 12Z Tuesday for a short period of light snow in the southwest zones late Monday night and Tuesday morning. Isentropic lift will also contribute to this light snowfall. Then a larger swath of isentropic lift will spread north across much of Wyoming Tuesday well north of the main energy (a warm front). This steady widespread light snowfall will spread north to most of Central and Western Wyoming Tuesday, Tuesday night, and Wednesday morning, with many lower elevations seeing an inch or less with foothills seeing 1 to 3 inches. At least that is our preliminary forecast, just enough to call it a White Christmas in many areas, even though it will be just "leftover scraps" from the southern stream system. The mountains will likely see sub advisory amounts during this time frame. The western valleys could see 1 to 2 inches. The GFS has been consistent in tracking a mid level circulation east along the Wyoming/MT border late Tuesday night and Wednesday morning along with some QG forcing asct with the northern stream shortwave that will track across the area Wednesday. Most of the snowfall should end Wednesday afternoon. However, a few snow showers will linger Wednesday afternoon with the leftover baggy main trough still overhead. .LONG TERM...Thursday through Monday Overview...A strong low pressure system will lift northeast across the central Plains on Thursday with snow on the backside of this system wrapping back into eastern Wyoming. Some light snow or flurries may extend as far west as Buffalo to Casper; significant impacts with this storm are expected to be over the Great Plains and Midwest. Another system will dive south across the western Great Basin on Thursday with more significant snowfall with this system expected to remain west and south of Wyoming. High temperatures will be 10F-15F below normal Thursday and Friday, with highs Friday only from 15F to 25F in the valleys and basins. Dry conditions with an overall warming trend are expected next weekend, but steep inversions will keep some western valleys and lower central basins trapped in colder air. Discussion...Synoptic pattern on Thursday will feature broad longwave trough from the West Coast to the Midwest, sandwiched between ridges across the eastern Pacific and eastern U.S. A strong shortwave is expected to dive south down the backside of the trough across the western Great Basin on Thursday, continuing to dig and possibly form a cutoff low over the SW U.S. by Saturday. Downstream, low pressure system over central Plains is expected to accelerate northeast into the Great Lakes Thursday- Thursday night. Cold Canadian high pressure will build south into the northern Plains behind the exiting low, bringing low level E-NE flow and possibly some low clouds, light snow or flurries backing up to the east slopes of the Divide Thursday night-Friday morning. Eastern Pacific ridge is expected to fold into the area on Saturday with lee side surface trough bringing gusty southwest winds and warmer temperatures through the wind corridor. Western valleys and lower portions of the Wind River and Bighorn Basins likely remain trapped in the teens to lower 20s for highs. ECMWF and GFS show significant spread with the synoptic pattern over the area Sunday and onward, with low confidence latching on to either solution. ECMWF is bringing an Arctic Front through the area on New Year's Eve, and GFS shows split flow across the west with dry and seasonably mild airmass over the area. We will need to see if models trend one way or the other over the next few runs before making any significant changes to the default SuperBlend output. && .AVIATION...For the 18Z TAFS through 18Z Tuesday East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Routes VFR conditions will prevail through the period. Some light snow to linger over the mountain tops of the Absaroka and Wind River mountains through much of the period with local MVFR conditions near the mountains. West of the Divide...KBPI/KJAC/KPNA/KRKS Routes Light snow will gradually end at the lower elevations this afternoon with MVFR/IFR conditions improving to VFR conditions by 00Z. KJAC airport will see improving conditions as well this afternoon. VFR conditions will then prevail at the terminal sites after 00Z through the rest of the forecast period. Some lingering light snow over the mountains will occur through tonight and Tuesday morning with local MVFR conditions at times. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... A series of weak weather system will move into western Wyoming through Christmas Eve and will bring light to moderate snow to western Wyoming while other areas should remain dry. On Christmas Day, light snow will fall over most of Western and Central wyoming. Gusty to possibly strong winds will occur over the lee of the Absarokas as well as from the Red Desert through Casper. Mixing and smoke dispersal will be generally poor but fair at times in windier areas. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...Lipson LONG TERM...Meunier AVIATION...AR FIRE WEATHER...Lipson
Hazardous Weather Outlook National Weather Service Riverton WY 223 AM MST Mon Dec 24 2018 WYZ001>020-022>030-251000- 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- 223 AM MST Mon Dec 24 2018 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Snow expected across the west. 1 to 3 inches of snowfall is expected in the western valleys with 3 to 6 inches in the mountains. .DAYS TWO THROUGH SEVEN...Christmas Day through Sunday. Christmas Day...Light snow accumulations across much of central and western Wyoming. Snow amounts will mostly range from less than an inch to around 2 inches across the lower elevations. .SPOTTER INFORMATION STATEMENT... Spotters are urged to report any snow accumulations. Thank you. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
1 avalanche. Local standard time, as filed.
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: 798165.