A powerful storm system moved from the Southern Plains on Wednesday morning into Michigan by early Friday morning. This brought a wide array of weather to northwest Illinois through the period. Precipitation began as rain on Wednesday evening and quickly changed over to snow along and north of a line from Keokuk County to Linn County to Johnson County to across Carroll, Jo Daviess, and Stephenson Counties. Snow continued heavy at times through the night across Carroll, Jo Daviess, and Stephenson Counties while to the south rain with isolated thunderstorms occurred. A powerful cold front swept through northwest Illinois on Thursday morning changing the precipitation over to all snow from west to east by afternoon. In addition, winds switched to the northwest and increased rapidly to 25 to 35 mph with gusts as high as 60 mph.  This created blizzard conditions across all of northwest Illinois as the front passed, reducing visibility to a half mile or less for several hours.  Conditions began to improve rapidly from west to east on Thursday evening as the storm system departed to the east.

Blizzard in CARROLL, ILLINOIS
From 19-DEC-12 22:00:00 to 20-DEC-12 21:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter in Thomson reported 4.0 inches of snow. The AWOS site in Savanna reported a peak gust of 37 knots.

Blizzard in MCDONOUGH, ILLINOIS
From 20-DEC-12 13:00:00 to 20-DEC-12 22:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter snow reports ranged from 4.0 inches at Colchester to 5.0 inches one mile southwest of Macomb. The AWOS at Macomb reported a peak wind speed of 47 knots.

Blizzard in HENRY, ILLINOIS
From 20-DEC-12 13:00:00 to 20-DEC-12 22:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotters snowfall reports ranged from 3.4 inches of snow 1 mile east of Kewanee to 4.7 inches of snow 2 miles southeast of Colona.

Blizzard in MERCER, ILLINOIS
From 20-DEC-12 12:00:00 to 20-DEC-12 22:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter 2 miles north of New Windsor reported 4.5 inches of snow.

Blizzard in PUTNAM, ILLINOIS
From 20-DEC-12 14:00:00 to 20-DEC-12 22:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Blizzard in JO DAVIESS, ILLINOIS
From 19-DEC-12 22:00:00 to 20-DEC-12 20:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Snowfall reports in Jo Daviess County ranged from 8.0 inches 3 miles southeast of Galena to 11.0 inches in Apple River Canyon State Park. The ASOS at Dubuque Iowa had a peak wind gust of 42 knots.

Blizzard in STEPHENSON, ILLINOIS
From 19-DEC-12 23:00:00 to 20-DEC-12 20:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reports ranged from 5.0 inches at Freeport to 12.0 inches 2 miles northwest of Lena.

Blizzard in HANCOCK, ILLINOIS
From 20-DEC-12 12:00:00 to 20-DEC-12 21:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A COOP Observer in Augusta, Illinois reported a storm total snowfall of 6 inches. The AWOS in Fort Madison, Iowa reported a peak gust of 46 knots.

Blizzard in WHITESIDE, ILLINOIS
From 20-DEC-12 12:00:00 to 20-DEC-12 22:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter 1 mile west northwest of Morrison reported 3.5 inches of snow.

Blizzard in HENDERSON, ILLINOIS
From 20-DEC-12 12:00:00 to 20-DEC-12 21:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Blizzard in ROCK ISLAND, ILLINOIS
From 20-DEC-12 12:00:00 to 20-DEC-12 20:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

The NWS observer at the Quad Cities Airport recorded 4.9 inches of snow. The ASOS at the airport reported a peak gust of 45 knots.

Blizzard in BUREAU, ILLINOIS
From 20-DEC-12 13:00:00 to 20-DEC-12 22:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reports ranged from 1.0 inch at Walnut to 1.5 inches in Princeton.

Blizzard in WARREN, ILLINOIS
From 20-DEC-12 13:00:00 to 20-DEC-12 22:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter