Low pressure passed through the area during the evening of the 20th into the morning hours of the 21st. There was enough cold air for precipitation to start off as snow, but warmer air eventually wrapped into the system, causing precipitation to change to a wintry mix.

Winter Weather in MONTGOMERY, MARYLAND
From 20-JAN-12 22:00:00 to 21-JAN-12 08:00:00 (EST-5)
Reported by: CoCoRaHS

Snow and sleet totaled up to between one and two inches across most of the county. A glaze of ice accumulation from freezing rain was also reported.

Winter Weather in PRINCE GEORGES, MARYLAND
From 20-JAN-12 22:00:00 to 21-JAN-12 08:00:00 (EST-5)
Reported by: CoCoRaHS

Snow and sleet accumulations totaled 2.0 inches near College Park.

Winter Weather in ANNE ARUNDEL, MARYLAND
From 20-JAN-12 22:00:00 to 21-JAN-12 08:00:00 (EST-5)
Reported by: CoCoRaHS

Snow and sleet accumulations were between one and two inches across most of the county. Ice accumulation from freezing rain was reported to be around five hundredths of an inch at Severn.

Winter Weather in CARROLL, MARYLAND
From 20-JAN-12 23:00:00 to 21-JAN-12 09:00:00 (EST-5)
Reported by: Trained Spotter

Snow and sleet totaled up to 2.0 inches near Manchester and 1.6 inches near Winfield.

Winter Weather in NORTHERN BALTIMORE, MARYLAND
From 20-JAN-12 23:00:00 to 21-JAN-12 09:00:00 (EST-5)
Reported by: Trained Spotter

Snow and sleet totaled up to between one and two inches across most of northern Baltimore County. Ice accumulation from freezing rain averaged between one and two tenths of an inch.

Winter Weather in SOUTHERN BALTIMORE, MARYLAND
From 20-JAN-12 23:00:00 to 21-JAN-12 09:00:00 (EST-5)
Reported by: Trained Spotter

Snow and sleet totaled up to between one and two inches across most of southern Baltimore County. Ice accumulation from freezing rain averaged between one and two tenths of an inch.

Winter Weather in HARFORD, MARYLAND
From 20-JAN-12 23:00:00 to 21-JAN-12 09:00:00 (EST-5)
Reported by: CoCoRaHS

Snow and sleet totaled up to 2.4 inches near Kingsville and 1.5 inches in Jarrettsville.

Winter Weather in CALVERT, MARYLAND
From 20-JAN-12 20:00:00 to 21-JAN-12 10:00:00 (EST-5)
Reported by: CoCoRaHS

Snow and sleet averaged less than one inch across the county. Ice accumulation from freezing rain was around one tenth of an inch.

Winter Weather in CHARLES, MARYLAND
From 20-JAN-12 20:00:00 to 21-JAN-12 10:00:00 (EST-5)
Reported by: CoCoRaHS

Snow and sleet averaged less than one inch across the county. A glaze of ice accumulation from freezing rain was estimated across the county.

Winter Weather in ST. MARY'S, MARYLAND
From 20-JAN-12 20:00:00 to 21-JAN-12 10:00:00 (EST-5)
Reported by: CoCoRaHS

Snow and sleet averaged less than one inch across the county. A glaze of ice accumulation from freezing rain was estimated across the county.

Winter Weather in EXTREME WESTERN ALLEGANY, MARYLAND
From 20-JAN-12 20:00:00 to 21-JAN-12 08:00:00 (EST-5)
Reported by: Trained Spotter

Snowfall totaled up to one inch near Eckhart Mines and Frostburg. Ice accumulation from freezing rain was generally between one and two tenths of an inch.

Winter Weather in CENTRAL AND EASTERN ALLEGANY, MARYLAND
From 20-JAN-12 20:00:00 to 21-JAN-12 08:00:00 (EST-5)
Reported by: Trained Spotter

Snowfall totaled up to one inch at Cumberland. Ice accumulation from freezing rain was  between one and two tenths of an inch.

Winter Weather in WASHINGTON, MARYLAND
From 20-JAN-12 20:00:00 to 21-JAN-12 08:00:00 (EST-5)
Reported by: Trained Spotter

Snowfall totaled up to 3.0 inches near Conococheague and 2.7 inches near Cavetown. Sharpsburg reported 2.0 inches of snow.
Ice accumulation from freezing rain was around one tenth of an inch near Cavetown.

Winter Weather in FREDERICK, MARYLAND
From 20-JAN-12 22:00:00 to 21-JAN-12 08:00:00 (EST-5)
Reported by: CoCoRaHS

Snowfall totaled up to 2.0 inches near Frederick and Thurmont.

Winter Weather in HOWARD, MARYLAND
From 20-JAN-12 22:00:00 to 21-JAN-12 08:00:00 (EST-5)
Reported by: CoCoRaHS

Snow and sleet accumulations averaged between one and two inches across the county. A glaze of ice accumulation from freezing rain was estimated across the county.