Conditions with temperatures at record or near-record warm levels on December 22 underwent a drastic change over a brief 24 hour period, as a sharp upper-level trough in westerly flow amplified while translating from the Pacific Northwest to the Plains. Low pressure developed and deepened rapidly while moving from South Dakota around 0000CST December 23 to the northern Great Lakes by 0600CST December 24.
Very steep lower to mid-level lapse rates and lift focused within a 200-250hPa deep layer supportive of effective dendritic growth resulted in intense precipitation banding over a 5 to 8 hour period. Winds in the lower mixed layer reached 40 to 60 knots as Arctic air surged into the area behind the system, producing numerous hours of widespread whiteout conditions.

Blizzard in BEADLE, SOUTH DAKOTA
From 23-DEC-20 05:00:00 to 23-DEC-20 14:00:00 (CST-6)
Reported by: ASOS

Winds gusted as high as 66 mph at Huron, 62 mph near Wolsey and 60 mph near Cavour, and despite a lack of pre-storm snow cover, snowfall which accumulated to 2.9 inches at Huron and 2.3 inches 2 miles southeast of Wessington resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in KINGSBURY, SOUTH DAKOTA
From 23-DEC-20 07:00:00 to 23-DEC-20 14:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 57 mph near Arlington and 46 mph 3 miles north northwest of De Smet, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.0 inches at De Smet and 2.5 inches at Iroquois resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in GREGORY, SOUTH DAKOTA
From 23-DEC-20 03:00:00 to 23-DEC-20 12:30:00 (CST-6)
Reported by: AWOS

Winds gusted as high as 66 mph near Dixon and 60 mph at Gregory, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.0 inches at Gregory and 4 miles south southwest of Pickstown and 3.5 inches 8 miles south southwest of Herrick and 4 miles southwest of Burke resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in MINNEHAHA, SOUTH DAKOTA
From 23-DEC-20 09:00:00 to 23-DEC-20 17:00:00 (CST-6)
Reported by: ASOS

Winds gusted as high as 63 mph near Dell Rapids and 62 mph at Sioux Falls, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.5 inches 6 miles south of Hartford, 3.0 inches at Colton and 2.8 inches at Sioux Falls resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.  At 1141CST, fifteen vehicles collided in whiteout conditions on northbound Interstate 29 around mile marker 99 which closed the road for 7 hours and resulted in 6 indirect injuries.  At 1252CST, another 30 vehicles crashed on westbound Interstate 90 three miles west of Sioux Falls (mile marker 393) which closed the roadway for 8 hours and resulted in 5 indirect injuries.  Another multi-car collision occurred on Interstate 29 in Sioux Falls, which was just one of several dozen other accidents.  All air traffic was cancelled for December 23 at Joe Foss Field in Sioux Falls.

Blizzard in BROOKINGS, SOUTH DAKOTA
From 23-DEC-20 09:00:00 to 23-DEC-20 15:00:00 (CST-6)
Reported by: AWOS

Winds gusted as high as 56 mph at Brookings and 52 mph at Volga, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.5 inches at Brookings and 3.0 inches 6 miles west of Bruce resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in JERAULD, SOUTH DAKOTA
From 23-DEC-20 04:00:00 to 23-DEC-20 13:00:00 (CST-6)
Reported by: AWOS

Winds gusted as high as 52 mph at Wessington Springs, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.0 inches at Wessington Springs resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in SANBORN, SOUTH DAKOTA
From 23-DEC-20 07:00:00 to 23-DEC-20 14:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 61 mph near Forestburg, and despite a lack of pre-storm snow cover, snowfall which accumulated to 5.0 inches at Woonsocket and 3.0 inches 4 miles north northeast of Forestburg resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in MINER, SOUTH DAKOTA
From 23-DEC-20 08:00:00 to 23-DEC-20 14:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 66 mph near Howard and 56 mph at Canova, and despite a lack of pre-storm snow cover, snowfall which accumulated to 1.5 inches at Howard resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in LAKE, SOUTH DAKOTA
From 23-DEC-20 09:00:00 to 23-DEC-20 15:00:00 (CST-6)
Reported by: AWOS

Winds gusted as high as 64 mph at Madison, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.2 inches 2 miles north of Chester and 2.8 inches at Madison resulted in widespread whiteout conditions for several hours. Travel was not recommended during the blizzard across all of southeast SD.

Blizzard in MOODY, SOUTH DAKOTA
From 23-DEC-20 09:00:00 to 23-DEC-20 16:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 68 mph 5 miles west of Ward and 54 mph at Flandreau, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.0 inches 11 miles north of Colman and 2.8 inches at Flandreau resulted in widespread whiteout conditions for several hours. Travel was not recommended during the blizzard across all of southeast SD.

Blizzard in BRULE, SOUTH DAKOTA
From 23-DEC-20 05:00:00 to 23-DEC-20 13:00:00 (CST-6)
Reported by: AWOS

Winds gusted as high as 66 mph at Kimball and 53 mph at Chamberlain, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.5 inches 2 miles south of Pukwana and 3.5 inches at Chamberlain resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in AURORA, SOUTH DAKOTA
From 23-DEC-20 06:00:00 to 23-DEC-20 13:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 53 mph at White Lake, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.0 inches 4 miles southwest of Stickney and 1.5 inches at White Lake resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in DAVISON, SOUTH DAKOTA
From 23-DEC-20 07:00:00 to 23-DEC-20 14:00:00 (CST-6)
Reported by: ASOS

Winds gusted as high as 66 mph at Mitchell, and despite a lack of pre-storm snow cover, snowfall which accumulated to 2.2 inches at Mitchell resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in HANSON, SOUTH DAKOTA
From 23-DEC-20 08:00:00 to 23-DEC-20 14:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 69 mph near Alexandria, and despite a lack of pre-storm snow cover, snowfall which accumulated to 1.1 inches at Alexandria resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in MCCOOK, SOUTH DAKOTA
From 23-DEC-20 08:00:00 to 23-DEC-20 16:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 67 mph near Montrose, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.0 inches at Bridgewater and Montrose resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in DOUGLAS, SOUTH DAKOTA
From 23-DEC-20 06:00:00 to 23-DEC-20 14:00:00 (CST-6)
Reported by: Emergency Manager

Winds gusted as high as 59 mph at Platte and 54 mph at Parkston, and despite a lack of pre-storm snow cover, snowfall which accumulated to 1.1 inches 11 miles west of Dimock resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in HUTCHINSON, SOUTH DAKOTA
From 23-DEC-20 07:00:00 to 23-DEC-20 15:00:00 (CST-6)
Reported by: Mesonet

Winds gusted as high as 67 mph at Freeman and 54 mph at Parkston, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.5 inches 11 miles south of Emery and 4.0 inches at Menno resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in TURNER, SOUTH DAKOTA
From 23-DEC-20 09:00:00 to 23-DEC-20 17:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 67 mph at Freeman and 63 mph near Davis, and despite a lack of pre-storm snow cover, snowfall which accumulated to 2.8 inches at Hurley resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in LINCOLN, SOUTH DAKOTA
From 23-DEC-20 09:00:00 to 23-DEC-20 17:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 63 mph near Davis and 45 mph at Tea, and despite a lack of pre-storm snow cover, snowfall which accumulated to 5.8 inches at Canton and 2.5 in southern Sioux Falls resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in UNION, SOUTH DAKOTA
From 23-DEC-20 10:00:00 to 23-DEC-20 17:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 64 mph 5 miles south of Beresford and 57 mph at North Sioux City, and despite a lack of pre-storm snow cover, snowfall which accumulated to 5.2 inches 6 miles north northeast of Elk Point resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in CLAY, SOUTH DAKOTA
From 23-DEC-20 09:00:00 to 23-DEC-20 17:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 67 mph at Yankton and 64 mph 5 miles south of Beresford, and despite a lack of pre-storm snow cover, snowfall which accumulated to 2.5 inches at Vermillion and 6 miles southeast of Centerville resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in YANKTON, SOUTH DAKOTA
From 23-DEC-20 09:00:00 to 23-DEC-20 17:30:00 (CST-6)
Reported by: AWOS

Winds gusted as high as 70 mph near Gayville and 67 mph at Yankton, and despite a lack of pre-storm snow cover, snowfall which accumulated to 5.0 inches at Yankton resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in BON HOMME, SOUTH DAKOTA
From 23-DEC-20 07:00:00 to 23-DEC-20 16:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 60 mph at Tyndall, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.5 inches at Tyndall and 4.0 inches 8 miles west northwest of Springfield resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.

Blizzard in CHARLES MIX, SOUTH DAKOTA
From 23-DEC-20 05:00:00 to 23-DEC-20 14:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 69 mph 10 miles west of Platte and 66 mph 5 miles west of Geddes, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.0 inches at Platte and 3.0 inches 2 miles northeast of Academy resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of southeast SD.