The combination of a deep Pacific trough and ample moisture brought heavy snow to portions of western and central Wyoming. The heaviest snow fell across the western mountains.
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The episode as NWS RIW wrote it up.
The combination of a deep Pacific trough and ample moisture brought heavy snow to portions of western and central Wyoming. The heaviest snow fell across the western mountains. The Tetons where especially hard hit with 23 inches of new snow at Grand Targhee and 20 inches at the Jackson Hole Ski Resort. Heavy snow also fell in the Star Valley with around 10 inches reported at Afton and the Star Valley Ranch. Upslope flow also brought heavy snow the eastern Bighorn Range with 19 inches at the Cloud Peak SNOTEL site. In the lower elevations, East of the Divide, snow bands developed in some areas. On particularly strong one developed over Fremont County and brought blizzard conditions for a short time. 6 to 8 inches of snow fell over a narrow strip, including the city of Riverton. Only five miles outside of the band, snowfall amounts dropped to almost nothing.
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 Apr 7, 1:34 PM MST, 4 hours 26 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 234 PM MDT Fri Apr 7 2017 .SHORT TERM...(This evening through Monday) Issued at 234 PM MDT Fri Apr 7 2017 Clouds and light mountain snow showers will increase across the western mountains, as temperatures warm and wind increases most areas east of the Continental Divide tonight and Saturday. Snow showers and clouds will increase across the western mountains with isolated thunderstorms in the early evening. A strong wet Pacific low pressure trough will bring periods of heavy wet snow to the Teton, Gros Ventre, Wyoming, Salt River and Wind River mountains tonight through Saturday night. Lighter snowfall is expected across Yellowstone National Park and the Absaroka mountains. Rain or a rain snow mix is expected below 7500 feet in the Star valley, Jackson Hole and the Green River Basin with local accumulations. The Tetons could see 10 to 20 inches of wet heavy snow with 8 to 16 inches in the Wyoming and Salt River, and Wind River mountains. Yellowstone National Park and the Absaroka mountains could see 6 to 12 inches of snow. Precipitation is expected to shift into the Bighorn mountains while decreasing in intensity over the west on Sunday but some additional accumulations will occur with snowfall spreading into the Bighorn mountains. Sunday night will be cold with clearing and northwest flow aloft. Dry and slight warming conditions will predominate on Monday. .LONG TERM...(Monday night through Friday) Issued at 234 PM MDT Fri Apr 7 2017 Another in the series of short waves will move into the west Monday night and bring some rain showers. However, it does not appear to have a lot of moisture to work with so we confined the showers West of the Divide. The models continue to have disagree in regards to any precipitation moving East of the Divide for Tuesday and into Tuesday night. At this point, the European is wetter and the GFS mainly dry. For now, we compromised and added some slight POPS across the northern part of the area for Tuesday afternoon into Tuesday evening. Temperatures should begin a moderating trend on Tuesday with most areas running fairly close to normal. The models have come into better agreement regarding Wednesday and Thursday with ridging across the area. As a result, we have removed the POPS and QPF. Temperatures will continue to warm with a mild day on Wednesday. Thursday at this point looks to be rather warm and dry. As a result we raised high temperatures a few degrees and they may need to be raised some more by future shifts. A gusty southwest wind may also develop across the usual areas favored in this pattern, mainly from Rock Springs through Casper. This may enhance fire danger somewhat so this has to be watched. The next system looks to move into the west on Thursday night or Friday. We say or because there continue to be some differences in timing with the models with the European running about 12 to 18 hours slower than the GFS. For now, we reduced POPS for Thursday night and kept them in the chance to slight chance categories through Friday. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 234 PM MDT Fri Apr 7 2017 WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES Ceilings will lower this evening with rain and snow moving into the western mountains with occasional to frequent mountain obscurations developing, especially in vicinity of KJAC. Largely VFR conditions should hold around other TAF sites through around 08Z before ceilings and visibilities begin to lower in snow and rain changing to snow. MVFR conditions with occasional IFR conditions are expected through Saturday with the exception of KRKS. However, a gusty southwest wind will be around KRKS early this evening and again on Saturday. Thunder is also possible although not enough confidence at this time to but it in the forecast. EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES Conditions will be VFR through the period. The main issue will be increasing south to southwest wind through this evening. Strongest winds will be at KCPR where southwest wind will blow 25-35kts by late Friday morning and continue until early in the evening. Areas of wind shear are possible in vicinity of KLND and KCPR late tonight and early Saturday. Mountain top obscurations will mainly be confined to areas along the Continental Divide beginning Friday afternoon. Showers will be possible tonight and tomorrow but most should hold off until after 18Z Saturday. Thunder will also be possible in some areas but not enough confidence to include in the forecast at this time. && .FIRE WEATHER... Issued AT 234 PM MDT Fri Apr 7 2017 Clouds and light mountain snow showers will increase across the western mountains, as temperatures warm and wind increases most areas east of the Continental Divide tonight and Saturday. Snow showers and clouds will increase across the western mountains with isolated thunderstorms in the early evening. A strong wet Pacific low pressure trough will bring periods of heavy wet snow to the Teton, Gros Ventre, Wyoming, Salt River and Wind River mountains tonight through Saturday night. Lighter snowfall is expected across Yellowstone National Park and the Absaroka mountains. Rain or a rain snow mix is expected below 7500 feet in the Star valley, Jackson Hole and the Green River Basin with local accumulations. The Tetons could see 10 to 20 inches of wet heavy snow with 8 to 16 inches in the Wyoming and Salt River, and Wind River mountains. Yellowstone National Park and the Absaroka mountains could see 6 to 12 inches of snow. Precipitation is expected to shift into the Bighorn mountains while decreasing in intensity over the west on Sunday but some additional accumulations will occur with snowfall spreading into the Bighorn mountains. Sunday night will be cold with clearing and northwest flow aloft. Dry and slight warming conditions will predominate on Monday. Mixing heights will lower across the west with generally poor smoke dispersal especially in the heavier showers. The unstable and windy areas east of the Continental divide will have good smoke dispersal in the afternoons. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from midnight tonight to 6 AM MDT Sunday for WYZ013-023-025>027. Winter Storm Warning from 6 PM this evening to 6 AM MDT Sunday for WYZ012-014-015-024. Winter Weather Advisory from 6 PM this evening to 6 AM MDT Sunday for WYZ001-002. Winter Weather Advisory from 3 AM Saturday to 6 PM MDT Sunday for WYZ008-009. && SHORT TERM...Baker LONG TERM...Hattings AVIATION...Hattings FIRE WEATHER...Baker
Hazardous Weather Outlook National Weather Service Riverton WY 637 PM MDT Fri Apr 7 2017 WYZ001>020-022>030-081100- 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- 637 PM MDT Fri Apr 7 2017 ...Winter Storm Warnings in effect for the Teton, Salt and Wyoming, and Wind River Ranges until 6 am Sunday... ...Winter Weather Advisories in effect for the Bighorn and Absaroka Mountains and western valleys through early Sunday morning... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Tonight A cold front will bring significant rain, snowfall and wind to the western mountains early this evening with snow levels initially between 8000 and 9000 feet . Snow levels will lower to below 7000 feet by early Sunday morning, so western valleys will likely see mainly rain showers until after midnight when a changeover to a rain snow mix or all snow is possible before sun up. Please see Winter Storm Warnings and Winter Weather Advisories for the latest information. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Saturday through Sunday...Periods of heavy wet snow will continue in the western and northern mountains through Saturday night. A rain and snow mix or heavy wet snow will occur below 7000 feet in the west through Saturday, and then a second cold front will change precipitation to all snow in the western valleys by Saturday evening. The cold front will spread snow showers into the central basins Sunday morning with some locally heavy, persistent snow-bands possible. .SPOTTER INFORMATION STATEMENT... Spotters are requested to report snowfall amounts or other significant weather. Thank you!
The national radar mosaic for the moment the first event began.
6 winter storm. Local standard time, as filed.
Heavy snow fell through much of the Tetons. The highest amounts of snow included 22 inches at the Grand Targhee SNOTEL and 20 inches at the top of the Jackson Hole Ski Resort.
The SNOTEL site at Gunsight Pass recorded 15 inches of new snow.
Heavy snow fell in portions of the Salt and Wyoming Ranges. Some of the highest amounts were at the Willow Creek and Cottonwood Creek SNOTEL sites where 20 and 18 inches of new snow fell, respectively.
Heavy snow fell in many portions of the Star Valley. Amounts ranged from 6 inches at the Box Y Ranch to 15 inches 5 miles SSE of Smoot.
Heavy snow fell over the east slope of the Bighorn range. The highest amount recorded was 19 inches at the Cloud Peak SNOTEL.
A narrow but intensive convective snow band developed over central Fremont County. Snow fell at rates of 2 inches an hour at times with wind gusts close to 60 mph at times. A NWS Employee measured 8 inches of snow about 5 miles NW of the Riverton airport with 6.2 inches of new snow in the city of Riverton. Amounts decreased rapidly outside of the band with generally 2 inches or less elsewhere.
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, April 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: 684342, 684343, 684344, 684345, 684346, 684347.