A wave of low pressure passed by to the south on the 20th. At the same time, high pressure was building to the north and this caused cold air to filter in from New England. Rain changed to a wintry mix on the 20th. There was enough cold air for a period of heavier snow across northern Maryland with snow, sleet and freezing rain elsewhere.  A light wintry mix continued for all areas on the night of the 20th. Coastal low pressure developed along the Mid-Atlantic Coast on the morning of the 21st. This caused a round of heavier precipitation to fall mainly in the form of snow. The snow tapered off later in the day as the low moved off to the north and east.

Winter Storm in EXTREME WESTERN ALLEGANY, MARYLAND
From 20-MAR-18 05:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A round of heavy snow on March 20th totaled up to 8.5 inches at Ridgeley and 8.0 inches near Frostburg. Another round of snow occurred on the 21st and storm total snowfalls were 11 inches in both Ridgeley and Frosburg.

Winter Storm in NORTHWEST MONTGOMERY, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 5.3 inches in Damascus.

Winter Storm in CENTRAL AND SOUTHEAST MONTGOMERY, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 5.0 inches near Olney and 4.6 inches near Takoma Park.

Winter Storm in CENTRAL AND SOUTHEAST HOWARD, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 7.0 inches in Columbia and 5.5 inches near Scaggsville.

Winter Storm in CENTRAL AND EASTERN ALLEGANY, MARYLAND
From 20-MAR-18 05:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

Snowfall totaled up to 6.6 inches in Cresaptown on the 20th. Another round of snow occurred on the 21st and a storm total of 9.7 inches was reported in Cumberland. Storm total snowfall was estimated to be between 8 and 12 inches based on observations nearby.

Winter Storm in WASHINGTON, MARYLAND
From 20-MAR-18 07:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

Snowfall totaled up to 7.0 inches near Long Meadow on the 20th. Another round of snow occurred on the 21st and a storm total of 13.0 inches was reported near Maugansville. Snowfall totaled up to 12.5 inches in Long Meadow and 11.0 inches near Pecktonville.

Winter Storm in NORTHWEST HOWARD, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall was estimated to be between 4 and 8 inches based on observations nearby.

Winter Storm in PRINCE GEORGES, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 6.8 inches near Cheltenham and 6.5 inches near University Park.

Winter Storm in ANNE ARUNDEL, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 7.5 inches near Riva and 6.3 inches near Annapolis. Snowfall averaged between 4 and 8 inches across the county.

Winter Storm in FREDERICK, MARYLAND
From 20-MAR-18 07:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

Snowfall totaled up to 7.0 inches near Bloomfield and 6.5 inches near Thurmont on the 20th. Another round of snow occurred on the 21st and a storm total of 15.0 inches was reported near Sabillasville. Snowfall totaled up to 14.4 inches near Bloomfield and 12.0 inches near Braddock Heights.

Winter Storm in CARROLL, MARYLAND
From 20-MAR-18 07:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

Snowfall totaled up to 5.5 inches near Lineboro and 5.0 inches in Westminster on the 20th. Another round of snow occurred on the 21st and a storm total of 13.5 inches was reported near Lineboro. Snowfall totaled up to 12.5 inches near Millers and 11.5 inches near Westminster.

Winter Storm in NORTHERN BALTIMORE, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 9.0 nar Bentley Springs and 7.0 inches in Cockeysville.

Winter Storm in CHARLES, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 5.5 inches near Benedict and Bryantown. Snowfall averaged between 3 and 6 inches across the county.

Winter Storm in CALVERT, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 7.0 inches near Saint Leonard and 5.5 inches near Dunkirk.

Winter Storm in ST. MARY'S, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 5.2 inches near Mechanicsville and 5.0 inches near Clements.

Winter Storm in SOUTHERN BALTIMORE, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 6.4 inches near Pikesville and 6.0 inches near Pimlico.

Winter Storm in NORTHWEST HARFORD, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 11.0 inches in Norrisville and 8.0 inches in Whiteford.

Winter Storm in SOUTHEAST HARFORD, MARYLAND
From 20-MAR-18 12:00:00 to 21-MAR-18 13:00:00 (EST-5)
Reported by: Trained Spotter

A wintry mix occurred on the 20th before a round of heavier snow developed on the 21st. Snowfall totaled up to 5.8 inches near Perryman and 5.6 inches near Abingdon.