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 May 2010 Climatic Summary

May Storm Summary...

On May 1…An upper level storm system brought 6 to 12 inches of snow to elevations above 5500 feet in the northern Black Hills and Bear Lodge Mountains.

On May 4…A deep low pressure system in North Dakota produced a strong pressure gradient across western South Dakota. Strong northwest winds of 35 to 45 mph with gusts in excess of 60 mph were common. The strongest wind gusts reported were 76 mph at Buffalo and 70 mph, 23 miles northeast of Newell.

On May 5 and 6…An upper level storm system brought 4 to 8 inches of snow to far northwest South Dakota, the Bear Lodge Mountains and far northern Campbell and Crook counties in northeast Wyoming.

On May 10 through 12…A slow moving upper level trough brought heavy rain and snow to the region. During the three days 10 to 18 inches of snow fell above 5500 feet in the Black Hills with 4 to 10 inches falling below 5500 feet. Snowfall of 1 to 4 inches fell on the plains of northeast Wyoming and southwest South Dakota. Rainfall totals of 1.5 to 3.3 inches were common across the region with the heaviest total along the northern and eastern foothills. Minor flooding occurred along the Belle Fourche river in Crook County in northeast Wyoming.

On May 18…An isolated thunderstorm dropped nearly 4 inches of rain in less than three hours over Crook County in northeast Wyoming. Flash flooding was reported along Oak Creek, Hay Creek and Beaver Creek. Oak Creek Road and Mona Road were severely damaged. At one crossing, during the worst part of the flooding, the water was at least 3 feet above the road and was over 30 feet deep around 630 PM. There was a lot of debris and the water cut away at the road base at all of the culverts in the area.

On May 21…Scattered thunderstorms brought heavy rain and large hail to portions of western South Dakota. Quarter size hail was reported across Fall River and Ziebach counties. Heavy rains produced minor flooding along small streams and creeks in Ziebach, Shannon, Custer and Pennington counties.

On May 22…Scattered thunderstorms brought large hail to central and south central South Dakota. There were several reports of nickel to quarter size hail. The largest hail reported was the size of golf balls 2 miles southeast of Winner in Tripp County.

On May 24…A strong low pressure system moved across the area producing tornadoes, large hail, damaging winds and widespread flash flooding. Tornadoes were reported 3 miles southeast of Plainview and 8 miles southwest of Faith in Meade County, and 6 miles northeast of Chance in Perkins county. The tornado in Perkins county destroyed a school and heavily damaged a ranch. There were also numerous reports of winds gusts of 60 to 70 mph. The strongest wind gust was 70 mph, 8 miles northwest of Usta in Perkins County. The thunderstorms produced heavy rains that caused flash flooding in Meade, Pennington, Fall River, and Custer counties. Numerous roadways were flooded with some roads being washed out. There were numerous reports of hail in excess of 1.5 inches in diameter. The largest hail reported was 4.25 inches in diameter near Maverick Junction in Fall River County and 4.00 inches in diameter 2 miles northwest of Buffalo Gap in Custer County.

On May 26…A strong upper level disturbance produced severe thunderstorms with large hail across northeast Wyoming. There were numerous reports of quarter size hail or larger. The largest hail to fall was the size of golf balls in downtown Gillette.

On May 29…A strong upper level disturbance produced severe thunderstorms with large hail and heavy rains across south central South Dakota. There were numerous reports of quarter size hail or larger. The largest hail to fall was the size of baseballs in Colome in southern Tripp County. Heavy rains of 2 to 4 inches produced minor flooding of streams and creeks in southern Tripp County.

LOCAL EXTREMES

REGIONAL EXTREMES

MONTHLY RECORDS

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