A cold front moving southward across Wyoming brought heavy snow mainly to the mountainous areas of western and central Wyoming although a few areas in the lower elevations also saw heavy snow. Portions of the Bighorns and Absarokas saw over a foot of snow.
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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 cold front moving southward across Wyoming brought heavy snow mainly to the mountainous areas of western and central Wyoming although a few areas in the lower elevations also saw heavy snow. Portions of the Bighorns and Absarokas saw over a foot of snow. A few locations in the lower elevations also saw heavy snow with over 6 inches of snow reported at Meeteetse, DuBois, Thermopolis and near Kaycee.
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 Oct 31, 9:35 PM MST, 2 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1035 PM MDT Tue Oct 31 2017 .SHORT TERM...(This evening through Thursday) Issued at 234 PM MDT Tue Oct 31 2017 Imagery shows broad longwave trof across the CONUS with a few embedded disturbances within the flow...with one embedded wave moving east of WY into the Plains today and the next more significant system to impact WY just now moving sse through scntrl Canada/into MT. SFC has broad area of low pressure across the Desert SW and into the 4 corners area with high pressure over the nw CONUS into the cntrl Rockies ahead of a strongly developing cyclone over swrn Canada with an attending warm front now moving ewd through MT. All precipitation activity currently north of WY. Rest of today and tonight: With the approach of a strong jet (100 to 130 kt) from the north and eventual arrival of an associated embedded shortwave and cold front, the first likely result of this system will be a significant increase in the winds across the Absaroka Mountains and Cody Foothills tonight...with a strong P, T and Omega GRAD developing across the mountains and foothills of northern WY. Strong high wind is probable between mid evening and midnight...continuing into Wednesday morning until FROPA. The Wind River Mountains will begin to see the same increases in winds some time after midnight tonight...followed by the Lander foothills, Western Wind River Basin and across the Wind Corridor from eastern Sweetwater and southern Fremont Counties through the lower elevations of Natrona County during the day and early evening Wednesday. A High Wind Warning has now replaced the Watches for these areas to support this possibility (zones 7 and 17 have, however, been removed). Dynamics from the jet poking into northern WY tonight will give some additional lift, in addition to that of the terrain, to moisture increases flowing in from the PAC NW region...with areas of light to moderate snow breaking out across the northern mountains overnight tonight into/through Wednesday and at least Thursday morning...possibly longer. Snowfall up to 18 inches may be possible across portions of the northern Absaroka and Bighorn Mountains by end of the day Thursday. A Winter Storm Warning has been issued for the Absaroka and Bighorn Mountains beginning Wed morning and continuing through the day Thursday. With and behind FROPA, occurring late Wed afternoon/evening, rain and snow chances will begin to move south across central WY. The boundary between the shallow cold front coming down from the north and deeper warmer drier air across the southern half of Wyoming will keep precip out of most of the region south and east of the Big Horn Basin through the end of the forecast period. That said, Winter WX Advisory or low end/marginal Winter Storm conditions (snowfall) will be possible from Wed night through the day Thursday for the Cody Foothills and lower elevations of Johnson County with total snowfall generally ranging from 3 to locally 8 inches by end of day Thursday. A Winter Storm Watch continues for these two areas with the determination between Warning and Advisory in the second period of the forecast will be made. A few instability rain/snow showers possible into central/southeastern WY Thursday morning/afternoon. .LONG TERM...(Thursday night through Tuesday) Issued at 234 PM MDT Tue Oct 31 2017 Synopsis...A digging longwave trough over the PACNW/EPAC will continue to dig Friday, before beginning to fill as it makes its way eastward Friday night into Saturday. As this system passes through the region on Sunday, another system will develop over the same area of the PACNW/EPAC. This system will also quickly fill, as it transitions eastward over the forecast area Monday night into Tuesday. In the wake of this system, a ridge will develop over the Northern Rockies by Tuesday night. Discussion...A moist Pacific flow pattern will bring a persistent upslope flow across the far west Thursday night into Friday and Saturday. Significant precipitation is still expected, with periods of moderate to heavy snow possible for the higher elevations above 8000 to 9000 feet for the Tetons, Absarokas, Gros Ventres and much of Yellowstone. Temperatures will be warm Friday and Saturday, so do not expect much snow accumulation in the lower elevations at this time. Warm and dry east of the Divide Friday and Saturday, with breezy to windy conditions impacting the Wind Corridor, from Rock Springs to Casper. Strong winds could impact this area on Saturday ahead of the cold front, with 700mb SW winds at 40-50kt flowing over the area. Isolated to scattered showers will be possible east of the Divide Saturday night across mainly southern portions, as the cold front blasts through. Rain showers Saturday afternoon will change over to snow or a rain/snow mix across the I80 corridor and continue through the day on Sunday. Precipitation will be confined across the south and west Monday and possibly Tuesday. The ECMWF pushes through trough out of the area during the day Tuesday, while the GFS brings a second trough along the southern branch of the jet and impacts southern WY Tuesday night. && .AVIATION...(For the 06Z TAFS through 06Z Thursday) Issued at 1030 PM MDT Tue Oct 31 2017 Gusty wind will be common at the terminal sites overnight through most of Wednesday. Expect areas of LLWS through Wed afternoon. A cold front will push into Northern WY around 21Z Wed and progress south into Central WY Wed night. VFR conditions will occur at the terminal sites through 00Z Thurs. Snow will develop over Northern WY Wednesday with snow developing from KCOD to KBYG by 00Z Thursday. Then snow will increase in coverage over Northern WY Wed night. Expect IFR conditions in this area after 00Z Thurs with mountains frequently obscured. && .FIRE WEATHER... Issued AT 234 PM MDT Tue Oct 31 2017 Fuels remain at critical levels across over Fremont, Johnson and Natrona Counties. (Please see the Fire Weather Forecast product for more information). Today will have warmer temperatures for all locations with generally lower minimum RH values ranging from the upper teens to 25 percent across the valleys and basins and 25 to 40 percent in the mountains. Wind speeds across most of the forecast area will range out of the south to southwest 5 to 25 mph except for strong/high winds developing across the Cody Foothills and Absaroka Mountains this evening...continuing into Wednesday morning. Seasonally cool overnight with lows in the 20s and 30s for most locations. Increasing chances for snow across the northern mountains later tonight. Wednesday, high temperatures increase at all locations with the exception of the northern border area. Minimum RH values will be similar to to higher everywhere when compared to those of today, ranging from the upper teens to 45 percent over the lower elevations...30 to 70 percent in the mountains. Winds becoming west to southwest 15 to 35 mph for most locations east of the Divide (except the Big Horn Basin and Johnson County which will remain light southerly) on Wednesday with gusts in the afternoon 40 to 60 mph. West of the Divide, wind will range out of the southwest 10 to 25 mph with gusts 30 to 40 mph. Increasing chances for rain and/or snow chances across the northern half of WY Wednesday and Wednesday night...decreasing through the day Thursday. && .RIW WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 6 AM MDT Wednesday for WYZ002-003. Winter Storm Warning from 6 AM Wednesday to 6 PM MDT Thursday for WYZ002-008-009. High Wind Warning from 6 AM to 9 PM MDT Wednesday for WYZ016- 018>020-030. Winter Storm Watch from Wednesday evening through Thursday afternoon for WYZ003-010. High Wind Warning from midnight tonight to 9 PM MDT Wednesday for WYZ015. && SHORT TERM...Braun LONG TERM...LaVoie AVIATION...AR FIRE WEATHER...Braun
Hazardous Weather Outlook National Weather Service Riverton WY 243 PM MDT Tue Oct 31 2017 WYZ001>020-022>030-012045- 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- 243 PM MDT Tue Oct 31 2017 ...HIGH WIND WARNING TONIGHT THROUGH WEDNESDAY FOR PORTIONS OF NORTHERN AND CENTRAL WYOMING ALONG AND EAST OF THE DIVIDE AND ALSO FOR EASTERN SWEETWATER COUNTY... ...WINTER STORM WARNING FOR THE ABSAROKA AND BIGHORN MOUNTAINS WEDNESDAY THROUGH THURSDAY... ...WINTER STORM WATCH FOR THE CODY FOOTHILLS AND JOHNSON COUNTY WEDNESDAY NIGHT THROUGH THURSDAY... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Tonight. Becoming very windy tonight along the east slope of the Continental Divide as well as along the adjacent foothills from Cody to Dubois to Lander. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Wednesday through Thursday...Becoming very windy along the southern wind corridor from Rock Springs to Casper as well as other portions of Central Wyoming. Heavy snow possible in the northern mountains Wednesday through Thursday and in the Cody Foothills and Northern Johnson County Wednesday night and Thursday. Friday through Saturday...Significant mountain snowfall possible in the northwest mountains. Strong winds from Rock Springs to Casper much of this period. Strong winds in the mountains and east slope of most mountain ranges on Saturday. .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report wind speeds greater than 50 mph. Thank you.
The national radar mosaic for the moment the first event began.
8 winter storm. Local standard time, as filed.
The Shell Creek SNOTEL site measured 16 inches of new snow.
The Cloud Peak Reservoir SNOTEL site measured 13 inches of new snow.
The Evening Star SNOTEL measured 16 inches of new snow.
The Evening Star SNOTEL measured 16 inches of new snow.
A trained spotter measured 7.5 inches of snow at Meeteetse.
COOP observers and trained observers reported anywhere from 6 to 9 inches of snow around southern Johnson County.
Trained spotters measured anywhere from 3 to 9 inches around Thermopolis.
A trained spotter measured 8 inches of snow in DuBois.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2017Every state in 2017This day in weather historyWarnings in Wyoming, November 2017
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: 723809, 723810, 723811, 723812, 723813, 723816, 723814, 723815.