During the evening of the 11th widespread rainfall developed across the area.  As cold air was brought into the region by a strong upper level storm system over the area, the temperature fell below the freezing point causing the rain to change over to snow.  Due to the abundant moisture present, widespread heavy snowfall developed across the area during the early morning hours of the 12th.  Interstate 80 and Happy Jack Road were closed for a few hours during the early morning of the 12th due to blowing snow.

Heavy Snow in GOSHEN COUNTY, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

La Grange 4 ESE reported a measured snowfall amount of 7.0 inches at 600MST.

Heavy Snow in SOUTH LARAMIE RANGE FOOTHILLS, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

Cheyenne 17 WNW reported a measured snowfall amount of 9.0 inches at 600MST.

Heavy Snow in CENTRAL LARAMIE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

Burns 3 NW measured 9.3 inches of snowfall at 600MST, with a nearby CoCoRaHs site measuring 1.36 inches of liquid precipitation.

Heavy Snow in CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

Chugwater 2 NNW measured 8.0 inches of snowfall at 600MST.

Heavy Snow in CENTRAL LARAMIE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

Burns 6 WSW measured 7.5 inches of snowfall at 600MST, with a nearby CoCoRaHs site measuring 1.20 inches of liquid precipitation.

Heavy Snow in EAST PLATTE COUNTY, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: COOP Observer

The observer at Chugwater measured 6.8 inches of snowfall at 630MST, with a 24 hour liquid precipitation of 0.95 inches.

Heavy Snow in SOUTH LARAMIE RANGE, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: SNOTEL

An estimated 14.4 inches of snowfall was reported at Cow Creek at 700MST.  Elevation of the site is 8,330ft.  The snow water equivalent was 1.20 inches.

Heavy Snow in EAST LARAMIE COUNTY, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

A measured snowfall amount of 9.0 inches was reported at Pine Bluffs at 650MST.  Many tree limbs were broken and some houses are without power due to broken power poles and downed power lines.

Heavy Snow in SNOWY RANGE, WYOMING
From 11-MAY-10 11:00:00 to 12-MAY-10 12:40:00 (MST-7)
Reported by: SNOTEL

An estimated 13.5 inches of snowfall was reported at Brooklyn Lake at 700MST, with a snow water equivalent of 0.90 inches.  Elevation of the site is 10,240ft.

Heavy Snow in NIOBRARA COUNTY, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 13:40:00 (MST-7)
Reported by: Law Enforcement

An estimated 8.0 inches of snowfall was reported in Lusk at 520MST.

Heavy Snow in SHIRLEY BASIN, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 12:40:00 (MST-7)
Reported by: COOP Observer

The observer from Shirley Basin measured 5.5 inches of snowfall, with 24 hour liquid precipitation of 0.41 inches.

Heavy Snow in CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

Wheatland 1 W reported an estimated 8.0 inches of snowfall at 600MST.

Heavy Snow in SNOWY RANGE, WYOMING
From 11-MAY-10 11:00:00 to 12-MAY-10 12:40:00 (MST-7)
Reported by: SNOTEL

An estimated 15.6 inches of snowfall was reported at Cinnabar Park at 700MST, with a snow water equivalent of 1.30 inches.  Elevation of the site is 9,574ft.

Heavy Snow in CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

Wheatland 12 S reported an estimated 12.0 inches of snowfall at 800MST.

Heavy Snow in CENTRAL CARBON COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 12:40:00 (MST-7)
Reported by: COOP Observer

Rawlins 1 N measured 6.2 inches of snowfall at 800MST.

Heavy Snow in NORTH LARAMIE RANGE, WYOMING
From 11-MAY-10 11:00:00 to 12-MAY-10 12:40:00 (MST-7)
Reported by: Trained Spotter

Douglas 24 S reported an estimated snowfall of 12.0 inches at 830MST.

Heavy Snow in CENTRAL LARAMIE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Official NWS Observations

Measured 6.0 inches of snowfall at 430MST.  Four inches of snowfall occurred since midnight MST.

Heavy Snow in CONVERSE COUNTY LOWER ELEVATIONS, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 12:40:00 (MST-7)
Reported by: Trained Spotter

At Douglas 7 E an estimated 8.0 inches of snowfall was reported.

Heavy Snow in CONVERSE COUNTY LOWER ELEVATIONS, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 12:40:00 (MST-7)
Reported by: Public

Douglas 7 W reported an estimated 10.0 inches of snowfall at 830MST.

Heavy Snow in SIERRA MADRE RANGE, WYOMING
From 11-MAY-10 11:00:00 to 12-MAY-10 12:40:00 (MST-7)
Reported by: Public

An estimated 12.0 inches of snowfall was reported at Riverside 10 W at 1025MST.

Heavy Snow in EAST LARAMIE COUNTY, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: CoCoRaHS

Pine Bluffs 9 NW measured 7.4 inches of snowfall at 600MST, with a 24 hour liquid precipitation of 0.87 inches.

Heavy Snow in GOSHEN COUNTY, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: CoCoRaHS

La Grange 4 ESE measured 7.0 inches of snowfall at 600MST, with a 24 hour liquid precipitation of 0.63 inches.

Heavy Snow in CENTRAL LARAMIE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: CoCoRaHS

Carpenter 11 WNW measured 6.5 inches of snowfall at 600MST, with a 24 hour liquid precipitation of 1.20 inches.

Heavy Snow in EAST PLATTE COUNTY, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: CoCoRaHS

Wheatland observer measured 6.2 inches of snowfall at 600MST, with a 24 hour liquid precipitation of 0.83 inches.

Heavy Snow in CENTRAL LARAMIE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: NWS Employee

Cheyenne 2 E measured 9.1 inches of snowfall at 600MST, with a 24 hour liquid precipitation of 0.96 inches.

Heavy Snow in CENTRAL LARAMIE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

Cheyenne 18 E measured 10.0 inches of snowfall at 600MST.

Heavy Snow in SOUTH LARAMIE RANGE FOOTHILLS, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: Trained Spotter

Horse Creek 11 SE measured 9.0 inches of snowfall at 600MST.

Heavy Snow in CENTRAL LARAMIE COUNTY, WYOMING
From 11-MAY-10 17:00:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: NWS Employee

Cheyenne 9 N measured 9.4 inches of snowfall at 600MST.

Heavy Snow in GOSHEN COUNTY, WYOMING
From 12-MAY-10 00:18:00 to 12-MAY-10 08:40:00 (MST-7)
Reported by: CoCoRaHS

Yoder 6 SSE measured 7.1 inches of snowfall at 600MST, with a 24 hour liquid precipitation of 0.66 inches.