Strong low pressure over the Midwest remained cutoff from the jet stream on the 16th. The warm front associated with this system passed through during the morning. Warm and moist southerly winds behind the front provided moderate amounts of instability. The instability combined with forcing from the low for showers and thunderstorms to develop.
There was enough instability along with strong winds aloft for some thunderstorms to become severe.

Thunderstorm Wind in CARROLL, MARYLAND
From 16-APR-11 16:40:00 to 16-APR-11 16:40:00 (EST-5)
Location: CEDARHURST
Magnitude: 50.00 EG
Property damage: 0.50K
Reported by: Fire Department/Rescue

A tree was down near Route 140.

Thunderstorm Wind in CARROLL, MARYLAND
From 16-APR-11 18:52:00 to 16-APR-11 18:52:00 (EST-5)
Location: WESTMINSTER CLRVW AR
Magnitude: 61.00 EG
Property damage: 1.00K
Reported by: Trained Spotter

A few trees were toppled along Benrose Lane.

Thunderstorm Wind in CARROLL, MARYLAND
From 16-APR-11 16:45:00 to 16-APR-11 16:45:00 (EST-5)
Location: HOUCKSVILLE
Magnitude: 50.00 EG
Property damage: 0.50K
Reported by: Trained Spotter

Large branches that were about three to four inches in diameter were brought down from thunderstorms winds near Carrollton.

Thunderstorm Wind in CALVERT, MARYLAND
From 16-APR-11 17:53:00 to 16-APR-11 17:53:00 (EST-5)
Location: HUNTINGTOWN
Magnitude: 50.00 EG
Property damage: 2.00K
Reported by: Emergency Manager

Several large trees were blown down.

Thunderstorm Wind in FREDERICK, MARYLAND
From 16-APR-11 18:43:00 to 16-APR-11 18:43:00 (EST-5)
Location: PLANE NUMBER FOUR
Magnitude: 56.00 EG
Property damage: 3.00K
Reported by: NWS Storm Survey

Several trees were snapped and down near the intersection of Woodville Road and Glissans Mill Road.

Thunderstorm Wind in CARROLL, MARYLAND
From 16-APR-11 19:03:00 to 16-APR-11 19:03:00 (EST-5)
Location: HOUCKSVILLE
Magnitude: 56.00 EG
Property damage: 1.00K
Reported by: Trained Spotter

Several small branches were brought down from thunderstorm winds.

Tornado in CARROLL, MARYLAND
From 16-APR-11 18:51:00 to 16-APR-11 19:05:00 (EST-5)
Location: MAYBERRY
Tornado F-scale: EF0
Property damage: 20.00K
Reported by: NWS Storm Survey

Dozens of trees were snapped along Deep Run Road. A roof was partially removed from a barn along Geeting Road and numerous trees were down. Several trees and large branches were also down at the Grand Valley Farms subdivision. A large tree fell on a home rendering the home uninhabitable. The tornado also snapped trees and partially removed another roof from a barn along Band Hall Hill Road.

Tornado in FREDERICK, MARYLAND
From 16-APR-11 18:38:00 to 16-APR-11 18:46:00 (EST-5)
Location: NEW LONDON
Tornado F-scale: EF1
Property damage: 50.00K
Reported by: NWS Storm Survey

Roofing panels were removed from a detached garage near Detrick Road and Old Annapolis Road.  Six or more softwood trees were snapped and pieces of large limbs and plywood were impaled in adjacent roofs.

Tornado in FREDERICK, MARYLAND
From 16-APR-11 18:37:00 to 16-APR-11 18:38:00 (EST-5)
Location: NEW LONDON
Tornado F-scale: EF1
Property damage: 50.00K
Reported by: NWS Storm Survey

A detached garage collapsed along New London Road. Shingles and siding were removed from a single-family home and softwood trees were snapped along New London Road.
Numerous hardwood trees were uprooted or snapped and barns were damaged or destroyed.

Tornado in CARROLL, MARYLAND
From 16-APR-11 18:48:00 to 16-APR-11 18:51:00 (EST-5)
Location: COVER
Tornado F-scale: EF1
Property damage: 5.00K
Reported by: NWS Storm Survey

Tree damage was found near the intersection of MD-26 and MD-27. A power pole was also snapped near the intersection.

Tornado in FREDERICK, MARYLAND
From 16-APR-11 18:47:00 to 16-APR-11 18:48:00 (EST-5)
Location: UNIONVILLE
Tornado F-scale: EF1
Property damage: 25.00K
Reported by: NWS Storm Survey

Substantial tree damage was noted near Talbot Run road. Pine trees were snapped near Buffalo Road and there was also a report of siding and trim torn from a home near Buffalo Road.