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 LYON, IOWA
From 23-DEC-20 10:00:00 to 23-DEC-20 19:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 54 mph at Luverne and 60 mph at Sheldon, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.5 inches 3 miles north of Rock Rapids and 3.0 inches at Rock Rapids resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in OSCEOLA, IOWA
From 23-DEC-20 11:00:00 to 23-DEC-20 21:00:00 (CST-6)
Reported by: Department of Highways

Winds gusted as high as 55 mph at Worthington and 60 mph at Sheldon, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.0 inches at Sibley resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in DICKINSON, IOWA
From 23-DEC-20 11:00:00 to 23-DEC-20 21:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 49 mph at Lake Park, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.1 inches at Lake Park and Spirit Lake resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in SIOUX, IOWA
From 23-DEC-20 10:00:00 to 23-DEC-20 20:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 53 mph at Alton and 45 mph at Sioux Center, and despite a lack of pre-storm snow cover, snowfall which accumulated to 6.0 inches at Orange City and 3.5 inches 3 miles north of Sioux Center resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.  Sioux County law enforcement responded to 79 accidents as a result of blizzard conditions.

Blizzard in O'BRIEN, IOWA
From 23-DEC-20 11:00:00 to 23-DEC-20 21:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 60 mph at Sheldon, and despite a lack of pre-storm snow cover, snowfall which accumulated to 5.1 inches at Sanborn and 5.0 inches at Sheldon resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in PLYMOUTH, IOWA
From 23-DEC-20 10:00:00 to 23-DEC-20 18:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 52 mph at Le Mars, and despite a lack of pre-storm snow cover, snowfall which accumulated to 2.8 inches at Remsen and 2.2 inches at Le Mars resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in CHEROKEE, IOWA
From 23-DEC-20 11:00:00 to 23-DEC-20 18:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 52 mph at Le Mars and 51 mph at Storm Lake, and despite a lack of pre-storm snow cover, snowfall which accumulated to 4.0 inches at Cherokee and 4 miles north of Cleghorn resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in BUENA VISTA, IOWA
From 23-DEC-20 11:00:00 to 23-DEC-20 21:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 51 mph at Storm Lake, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.0 inches at Storm Lake and Sioux Rapids resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in WOODBURY, IOWA
From 23-DEC-20 10:00:00 to 23-DEC-20 17:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 67 mph at Sergeant Bluff and 56 mph at Sioux City, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.0 inches at Sioux City and 2.0 inches 4 miles north northeast of Hornick resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in IDA, IOWA
From 23-DEC-20 10:00:00 to 23-DEC-20 19:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 67 mph at Sergeant Bluff and 51 mph at Storm Lake, and despite a lack of pre-storm snow cover, snowfall which accumulated to 2.1 inches 3 miles northeast of Battle Creek and 1.0 inch 4 miles south southwest of Arthur resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.

Blizzard in CLAY, IOWA
From 23-DEC-20 11:00:00 to 23-DEC-20 20:00:00 (CST-6)
Reported by: COOP Observer

Winds gusted as high as 61 mph near Spencer, and despite a lack of pre-storm snow cover, snowfall which accumulated to 3.5 inches 3 miles west northwest of Everly and 3.0 inches near Spencer resulted in widespread whiteout conditions for several hours. Travel was not advised during the blizzard across all of northwest IA.  Prior to the development of snowfall, a brief period of light freezing rain produced ice-covered roadways.  A single-vehicle accident resulted in indirect injuries to the driver and three minor occupants as the pickup truck slid off Highway 18 east of Spencer and entered the ditch  around 0915CST.