A cold front dropped southward over Wyoming and combined with ample moisture to bring heavy snow to portions of northern and central Wyoming. The heaviest snow fell in the favored north to northeast facing slopes of the mountain ranges as upslope flow developed.
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The episode as NWS RIW wrote it up.
A cold front dropped southward over Wyoming and combined with ample moisture to bring heavy snow to portions of northern and central Wyoming. The heaviest snow fell in the favored north to northeast facing slopes of the mountain ranges as upslope flow developed. Over 2 feet of snow fell in portions of the Wind River Range and the Lander foothills. Over a foot of snow also fell in the higher elevations south of Casper in Natrona County. Over 6 inches of snow fell in the lower elevations in portions of Park, Sublette, Natrona and Hot Springs county.
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 17, 1:50 AM MST, 10 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Riverton WY 250 AM MDT Thu Apr 17 2025 .KEY MESSAGES... - Late season cold front racing southward, with widespread snow in its wake. - Gusty winds behind the front will bring hazardous conditions through the day today. Winter Storm Warnings and Winter Weather Advisories are in effect for a large portion of northern and central Wyoming. - Snowy conditions continue into Friday morning, with a gradual decrease by afternoon. && .DISCUSSION... Issued at 224 AM MDT Thu Apr 17 2025 The initial edge of the cold front continues to push southward across central WY this morning, with precipitation beginning to fill in across the north. The precip currently is a mix of rain and snow, but falling temperatures will switch this precip over to all snow by sunrise. As the north sfc winds increase later this morning, overrunning precip will begin to build across central Wyoming, and with temperatures steady in the low to mid 30s, precip will be nearly all snow through the day. Favored areas for accumulation will be against any north to northeast facing slopes. Latest model runs come in similar to previous forecast, with 6 to 12 inches across central Wyoming, and 12 to 24 inches of snow for higher elevations of the Wind River, Absaroka, and Bighorn ranges. Will need to monitor Sweetwater County for snowfall accumulations, as precip amounts shifted a bit later into the evening, bringing a slightly better opportunity for snowfall with colder temperatures. Precip gradually fades during Friday morning, as the gusty north winds relax, decreasing any remaining overrunning. Saturday should be mostly sunny and cool behind this system, but highs remain well below normal in the 40s during the day. Winds shift back from the southwest, bringing a return of milder temperatures into Sunday. A weaker trough sweeps across the northern Rockies later Sunday and Monday, with another round of precip. Less cold air is associated with this system, so most precip will be rain, with higher elevation light snow. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1000 PM MDT Wed Apr 16 2025 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Shortwave energy within a broad trough of low pressure dives toward southwest Wyoming by 12Z/Thursday, aiding the development of widespread precipitation between 12Z-16Z/Thursday. MVFR conditions and areas of IFR are anticipated across the region, developing last at KRKS around 18Z/Thursday as a vigorous cold front arrives. The cold front shifts the wind at KRKS to the east-northeast at 18-30kts producing localized blowing snow during the afternoon. The presence of a mid-level low allows for snow to continue through the afternoon, with the start of a downturn in precipitation coming 00Z-03Z/Friday. Mountains becoming obscured between 10Z-16Z/Friday. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals A cold front and accompanying wind shift are progressing south through the forecast area Wednesday evening. Upslope and overrunning moisture begin to overspread the region between 09Z-14Z/Thursday as an upper-level low takes shape just to the west of Wyoming. This low and an associated mid-level circulation over southwest Wyoming by Thursday morning will increase snowfall across the region between 12Z-16Z/Thursday. Right-entrance region jet dynamics will aid heavier snow during the late morning and afternoon hours, especially at KLND, KRIW, and KCPR where upslope flow is favorable. IFR conditions will be widespread during this timeframe and into the evening hours Thursday. Snow chances decrease late in the period at KCOD and KWRL, where MVFR may become more common after 00Z/Friday. Mountains becoming obscured between 08Z-14Z/Thursday across the entire region. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until noon MDT Friday for WYZ002- 007>009. Winter Storm Warning until 3 AM MDT Friday for WYZ003-005. Winter Storm Warning from 6 AM this morning to noon MDT Friday for WYZ010-011-016>020-022. Winter Storm Warning until noon MDT Friday for WYZ015. && DISCUSSION...Straub AVIATION...CNJ
Hazardous Weather Outlook National Weather Service Riverton WY 522 AM MDT Wed Apr 16 2025 WYZ001>020-022>030-171530- Yellowstone National Park-Absaroka Mountains-Cody Foothills- North Bighorn Basin-Southwest Bighorn Basin-Southeast Bighorn 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- 522 AM MDT Wed Apr 16 2025 ...WINTER WEATHER ADVISORY AND WINTER STORM WARNING IN EFFECT TONIGHT THROUGH FRIDAY MORNING... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and tonight. Elevated fire weather conditions possible in the afternoon from Muddy Gap through Casper due to gusty southwest wind and low relative humidity. A cold front will bring much colder temperatures late tonight, with rain changing to snow east of the divide. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Thursday through Friday...Turning much colder with widespread accumulating snowfall, especially in the mountains and across lower elevations east of the Continental Divide. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The national radar mosaic for the moment the first event began.
10 winter storm. Local standard time, as filed.
A COOP observer reported 6.9 inches o snow near Meeteetse.
At Cora, 9.2 inches of new snow fell. Around Pinedale, 7 to 9 inches of snow fell.
Winter storm conditions reported in Jeffrey City.
The public reported 8 inches of snow to the south of Manderson. Amounts elsewhere were generally less than 6 inches.
A CocoRaHs observer reported 10 inches of snow near Fort Washakie. Amounts in Riverton generally ranged from 4 to 8 inches.
Heavy snow fell throughout the Lander foothills. Amounts ranged from 11 to 20 inches, including 15.3 inches at the Lander airport.
A COOP observer reported 7 inches of snow in Thermopolis.
A retired Weather Service meteorologist measured 26 inches of new snow at Bruce's Campground. Numerous SNOTEL sites reported 12 to 20 inches of snow. Highway 28 along South Pass was closed at the height of the storm.
Snowfall amounts ranged from 6 to 12 inches around Casper, with the highest amounts on the south side of Casper closer to Casper Mountain.
The Casper Mountain SNOTEL site reported 13 inches of new snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2025Every state in 2025This day in weather historyWarnings in Wyoming, April 2025
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: 1247968, 1247976, 1248707, 1247970, 1247972, 1247973, 1247969, 1247971, 1247974, 1247975.