A potent storm developed over Colorado and moved northeastward, spreading heavy snow across much of central Wyoming. The highest snowfall occurred at Midwest in northeastern Natrona County where 24 inches of snow was measured.
Every event with a place to put it; 11 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 potent storm developed over Colorado and moved northeastward, spreading heavy snow across much of central Wyoming. The highest snowfall occurred at Midwest in northeastern Natrona County where 24 inches of snow was measured. Amounts greater than 10 inches were also reported in Johnson, Fremont, and Sweetwater Counties. A tight pressure gradient developed as well, with the strongest wind occurring in northern Johnson County. Wind gusts past 50 mph occurred for several days, resulting in the closure of Interstate 25 for a few days. Many major roads were shut down at the height of the storm.
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 12, 11:16 AM MST, 44 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1116 AM MST Mon Dec 12 2022 .SHORT TERM...This afternoon through Wednesday night Issued at 1115 AM MST Mon Dec 12 2022 Potent winter storm remains poised to bombard WY, today through Wednesday. Latest model guidance has been increasing snowfall totals across the board and have added new Winter Weather Advisories to reflect the increased storm total snow expected. Winter Storm Warnings remain in place from eastern Sweetwater to southern Johnson County, and Hot Springs County. An upgrade to a Blizzard Warning has been made for northern Johnson County, with snowfall totals of 8" to 12" and strong northerly winds gusting over 40 mph. Travel is likely to be impossible in for much of Johnson County, due to the blizzard conditions from tonight through Wednesday. Another important change this morning is the onset of snow in the Wind River Basin by noon today. Snow has already been falling in earnest in eastern Fremont County and western Natrona County, with webcams showing accumulating snow and low visibility at Hiland and Waltman. The bulk of snow will fall in the Wind River Basin and Lander Foothills this afternoon into tonight. HRRR forecast soundings show a deep saturated dendritic growth zone for this area this evening, so snowfall rates could approach 1"/hr at times. The worry here is that amounts will reach warning criteria with significant travel impacts, if this occurs. Don't have enough confidence yet to pull the trigger on an upgrade from an Advisory to a Warning, but once snow begins it will be evaluated, once again. Initially, the main forcing will be diffluent upper-level flow and then isentropic ascent on the eastern side of the upper-low, which currently resides in western ID. There are two upper-lows in the longwave trough across the western US, evident on WV imagery. The first being the aforementioned low in western ID and another in southern CA. The northern low will be the driver for impacts across WY. Moisture is plentiful through the column, noted from WV imagery, so that will not be an issue initially. As the low progresses east tonight, winds will shift northeast, which is when the greatest upslope will occur for the Wind River Basin and eastern slopes of the Wind River Mountains. By Tuesday morning, the upper-low will be in the Central Plains with northerly winds across the area. Northerly winds then remain, turning a bit more northwesterly east of the Divide, as the upper- low slowly ejects into the Northern Plains. The NAM and ECMWF are a bit slower with the progression of the low, which would keep snow around longer and result in snowfall totals on the high- end of the forecast. This seems the more likely scenario with a quickly deepening low. Another important facet of the pattern is the expected swath of thunderstorms in the Southern and Central Plains later this afternoon into tonight. This could limit the amount of Gulf moisture that wraps around the backside of the low into WY, Tuesday into Wednesday. Regardless, current WV imagery values and PWATs of 0.2" to 0.35" (0.32" is in the 90th percentile for Dec 12) show that there is currently plenty of moisture to work with, so it shouldn't reduce snowfall amounts drastically. Wednesday afternoon isentropic ascent diminishes greatly for most of the CWA, so snow should be ending by that time for most areas. The exception is Natrona and Johnson counties, where some lingering light snow continues through Wednesday afternoon. At that point, wind will be the deciding factor on whether to extend any highlights. 700mb winds remain about 50 knots through Wednesday evening, so blowing and drifting snow is likely to continue until winds subside. .LONG TERM...Thursday through Sunday Issued at 415 AM MST Mon Dec 12 2022 Snow showers will linger Thursday mainly over northern portions and Natrona County. Snow showers may be enhanced as a shortwave trough will try to make its way down from Canada. A ridge looks to develop over the PACNW, which will help guide in potentially the coldest air of the season so far behind the shortwave. Starting Friday night, overnight lows look to drop well below 0, especially if there is more than a few inches of snow depth. Highs during the day Saturday/Sunday may struggle to get out of the single digits for some. The cold arctic air looks to remain over the region with well below normal highs/lows going into the start of next week. && .AVIATION...For the 18Z TAFS through 18Z Tuesday Issued at 1115 AM MST Mon Dec 12 2022 East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals Snow has developed over the central basins, filling in over Johnson and Natrona counties after 00Z. MVFR to IFR conditions will be prevailing, with local LIFR conditions. Mountain obscurations will be in place through the TAF period. Please see individual terminal forecasts for more details. West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Snow will occur over the area through 12Z, then slowly taper off through 18Z. MVFR to IFR conditions will prevail, with local LIFR conditions. Some improvement to VFR conditions will occur after 12Z Tue at KJAC. Frequent mountain obscuration will be observed. 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 1115 AM MST Mon Dec 12 2022 Snow continues for western zones through tonight, ending Tuesday morning, with several inches of snow at higher elevations and a couple of inches in the valleys. Snow begins across central and eastern zones this afternoon/evening and persists through Tuesday night. Most locations will receive several inches of snow through Tuesday night. Winds will be northerly for the next several days behind a cold front that is along the Continental Divide today. The strongest wind will be from Natrona to Johnson County with gusts of 30 to 45 mph from the north likely tonight through Wednesday. RH will be high through the middle part of the week with much colder temperatures to end the week. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 11 PM MST this evening for WYZ001- 012>014-023>025. Winter Weather Advisory from 2 PM this afternoon to 5 PM MST Tuesday for WYZ003. Winter Storm Warning from 3 PM this afternoon to 6 AM MST Wednesday for WYZ005-007. Winter Weather Advisory from 3 PM this afternoon to 6 AM MST Wednesday for WYZ006-008-009. Blizzard Warning from 5 PM this afternoon to 5 PM MST Wednesday for WYZ010. Winter Storm Warning from 5 PM this afternoon to 5 PM MST Wednesday for WYZ011-020-022. Winter Weather Advisory from 5 PM this afternoon to 6 AM MST Wednesday for WYZ015. Winter Weather Advisory until 6 AM MST Wednesday for WYZ017-018. Winter Storm Warning from 5 PM this afternoon to 6 AM MST Wednesday for WYZ019-030. Winter Weather Advisory until 6 AM MST Tuesday for WYZ026-027. Winter Weather Advisory until 11 PM MST Tuesday for WYZ028-029. && SHORT TERM...Rowe LONG TERM...Dziewaltowski AVIATION...LaVoie FIRE WEATHER...Rowe
Hazardous Weather Outlook National Weather Service Riverton WY 1124 AM MST Mon Dec 12 2022 WYZ001>020-022>030-131830- 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- 1124 AM MST Mon Dec 12 2022 ...Winter Weather Advisories in effect over the west until 11 PM... ...Multiple Winter Weather highlights for areas east of the Divide and southern areas Monday afternoon through Wednesday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Significant snow over the west spreading east of the Divide. Please see the winter weather statement for additional details. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Tuesday...Light to moderate snow will continue over areas east of the Divide and over the south. The heaviest snow occurring over Johnson and Natrona counties. Blizzard conditions expected to develop over northern Johnson County by Tuesday morning. Light snow will remain possible over western portions, but additional snowfall amounts expected to be minimal. Wednesday...Light snow will remain possible over portions of Johnson and Natrona counties. Strong winds will be possible over northern portions of Johnson County with significant blowing and drifting snow. Thursday to Sunday...Bitter cold temperatures, with readings 15 to 20 degrees below normal .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions, according to standard operating procedures. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
10 winter storm, 1 blizzard. Local standard time, as filed.
Snow amounts between Thermopolis and Luzerne generally ranged from 6 to 8 inches.
A combination of snow and strong wind caused the closure of the Highway 120 through the Wind River Canyon for several hours.
Snowfall amounts around the Lander foothills generally ranged from 6 to 9 inches.
Most of the area received over 6 inches of snow, including 8 to 11 inches around the city of Riverton.
A combination of strong wind and blowing snow resulted in the closure of Interstate 25 for several hours.
There were widespread reports of over 6 inches of snow in northern Johnson County, with 12 inches measures in Buffalo. The snow combined with frequent wind gusts past 40 mph to bring blizzard conditions at times, resulting in the closure of Interstates 25 and 90. The wind continued well after the snow ended, subsiding on December 14th.
Snowfall amounts in Natrona County ranged from 5 inches at Powder River to 10 inches at Casper to 24 inches in Midwest. The snow was accompanied by strong wind to bring the closure of Interstate 25 and US 20 26 for several hours.
The Casper Mountain SNOTEL measured 12 inches of new snow.
A combination of snow and gusty wind caused the closure of US 287 for over 48 hours.
A combination of heavy snow and strong wind brought low visibility to South Pass, resulting in the closure of Highway 28.
A trained spotter reported 13 inches of snow at Wamsutter. Interstate 80 was closed for many hours by a combination of strong wind an blowing snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2022Every state in 2022This day in weather historyWarnings in Wyoming, December 2022
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: 1070979, 1070981, 1070998, 1070997, 1070985, 1073353, 1070986, 1070987, 1070989, 1070996, 1070988.