A backdoor cold front stalled out over the region on the 12th while and upper-level disturbance passed through the area. A hot and humid air mass ahead of the cold front produced moderate amounts of instability. Some thunderstorms that developed were able to produce damaging wind and large hail.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 05:22:00 to 12-AUG-10 05:22:00 (EST-5)
Location: MONROVIA
Magnitude: 61.00 EG
Property damage: 15.00K
Reported by: Public

Structures were damaged at a drag racing facility near Green Valley.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 05:22:00 to 12-AUG-10 05:22:00 (EST-5)
Location: FOUNTAIN MILLS
Magnitude: 61.00 EG
Property damage: 5.00K
Reported by: Trained Spotter

Numerous trees were down along Routes 80 and 75.

Thunderstorm Wind in PRINCE GEORGE'S, MARYLAND
From 12-AUG-10 07:25:00 to 12-AUG-10 07:25:00 (EST-5)
Location: ASHBOX
Magnitude: 52.00 EG
Property damage: 0.50K
Reported by: Public

A large limb was blown down on Brandywine Road.

Hail in MONTGOMERY, MARYLAND
From 12-AUG-10 06:15:00 to 12-AUG-10 06:15:00 (EST-5)
Location: WHEATON HILLS
Magnitude: 1.00 
Reported by: Public

Quarter size hail was reported near Glenmont.

Hail in PRINCE GEORGE'S, MARYLAND
From 12-AUG-10 07:09:00 to 12-AUG-10 07:09:00 (EST-5)
Location: MEADOWS
Magnitude: 1.75 
Reported by: Public

Golf ball size hail was reported near Andrews Airforce Base.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 15:50:00 to 12-AUG-10 15:50:00 (EST-5)
Location: UNIONVILLE
Magnitude: 61.00 EG
Property damage: 5.00K
Reported by: Fire Department/Rescue

Several trees and wires were down. Most of the trees were six inches in diameter.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 15:58:00 to 12-AUG-10 15:58:00 (EST-5)
Location: UNIONVILLE
Magnitude: 61.00 EG
Property damage: 5.00K
Reported by: Emergency Manager

Trees were down in Unionville.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 16:14:00 to 12-AUG-10 16:14:00 (EST-5)
Location: PLANE NUMBER FOUR
Magnitude: 61.00 EG
Property damage: 10.00K
Reported by: Emergency Manager

Numerous large trees were blown down along and across Woodville Road and also near the intersection of Woodville Road and Old Annapolis Road.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 16:13:00 to 12-AUG-10 16:13:00 (EST-5)
Location: NEW LONDON
Magnitude: 56.00 EG
Property damage: 1.00K
Reported by: Public

Smaller branches were blown down due to thunderstorm winds. A flag pole was bent at its base on Charles Drive.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 15:47:00 to 12-AUG-10 15:47:00 (EST-5)
Location: JOHNSVILLE
Magnitude: 52.00 EG
Property damage: 2.00K
Reported by: Public

Large limbs were down along Beaver Dam Road.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 16:13:00 to 12-AUG-10 16:13:00 (EST-5)
Location: NEW LONDON
Magnitude: 56.00 EG
Property damage: 1.00K
Reported by: Public

A tree was down on Old Annapolis Road near Charles Drive.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 16:15:00 to 12-AUG-10 16:15:00 (EST-5)
Location: PLANE NUMBER FOUR
Magnitude: 70.00 EG
Property damage: 5.00K
Reported by: Public

Several trees were topped in thunderstorm winds along Amys Terrace.

Thunderstorm Wind in CARROLL, MARYLAND
From 12-AUG-10 15:47:00 to 12-AUG-10 15:47:00 (EST-5)
Location: KEYMAR
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: Fire Department/Rescue

Trees and wires were down near Keymar.

Thunderstorm Wind in CARROLL, MARYLAND
From 12-AUG-10 15:50:00 to 12-AUG-10 15:50:00 (EST-5)
Location: MC KINSTRYS
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: Fire Department/Rescue

Trees and wires were down anear Linwood.

Thunderstorm Wind in CARROLL, MARYLAND
From 12-AUG-10 15:52:00 to 12-AUG-10 15:52:00 (EST-5)
Location: NEW WINDSOR
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: Fire Department/Rescue

Several trees and wires were down near New Windsor.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 04:47:00 to 12-AUG-10 04:47:00 (EST-5)
Location: BRADDOCK HGTS
Magnitude: 50.00 EG
Property damage: 1.00K
Reported by: Fire Department/Rescue

A tree was down along Old Receiver Road.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 05:04:00 to 12-AUG-10 05:04:00 (EST-5)
Location: REELS MILL
Magnitude: 52.00 EG
Property damage: 1.00K
Reported by: Fire Department/Rescue

A tree was down along Reichs Ford Road.

Thunderstorm Wind in FREDERICK, MARYLAND
From 12-AUG-10 05:24:00 to 12-AUG-10 05:24:00 (EST-5)
Location: URBANA
Magnitude: 61.00 EG
Property damage: 5.00K
Reported by: Fire Department/Rescue

Trees were down near Urbana.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 12-AUG-10 06:05:00 to 12-AUG-10 06:05:00 (EST-5)
Location: SPENCERVILLE
Magnitude: 50.00 EG
Property damage: 1.00K
Reported by: Trained Spotter

Small trees were down near Spencerville.

Thunderstorm Wind in WASHINGTON, MARYLAND
From 12-AUG-10 15:21:00 to 12-AUG-10 15:21:00 (EST-5)
Location: (HGR)HAGERSTOWN RGNL
Magnitude: 50.00 MG
Reported by: ASOS

A wind gust of 50 knots was reported at the Hagerstown Airport.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 12-AUG-10 05:15:00 to 12-AUG-10 05:15:00 (EST-5)
Location: PURDUM
Magnitude: 52.00 EG
Property damage: 1.00K
Reported by: COOP Observer

Several eight inch tree limbs were down due to thunderstorm winds near Damascus.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 12-AUG-10 05:53:00 to 12-AUG-10 05:53:00 (EST-5)
Location: MONTGOMERY VLG
Magnitude: 50.00 MG
Reported by: Mesonet

A wind gust of 58 mph was measured at Montgomery Village.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 12-AUG-10 05:58:00 to 12-AUG-10 05:58:00 (EST-5)
Location: GAITHERSBURG
Magnitude: 70.00 EG
Property damage: 5.00K
Reported by: NWS Employee

Numerous trees and branches were down, including a snapped large Oak Tree and an uprooted Pine Tree.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 12-AUG-10 06:00:00 to 12-AUG-10 06:00:00 (EST-5)
Location: GAITHERSBURG
Magnitude: 78.00 EG
Property damage: 7.00K
Reported by: County Official

Widespread damage to trees was reported in the vicinity of Old Towne Avenue in Gaithersburg.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 12-AUG-10 06:22:00 to 12-AUG-10 06:22:00 (EST-5)
Location: WHITE OAK
Magnitude: 61.00 EG
Property damage: 5.00K
Reported by: NWS Storm Survey

Tree damage was reported between Northwest Drive and Prelude Drive along US-29.

Thunderstorm Wind in PRINCE GEORGE'S, MARYLAND
From 12-AUG-10 07:09:00 to 12-AUG-10 07:09:00 (EST-5)
Location: MEADOWS
Magnitude: 61.00 EG
Property damage: 5.00K
Reported by: Public

Large sections of trees were blown down and shutters were blown off from a residence near Andrews Airforce Base.

Thunderstorm Wind in PRINCE GEORGE'S, MARYLAND
From 12-AUG-10 07:21:00 to 12-AUG-10 07:21:00 (EST-5)
Location: ASHBOX
Magnitude: 52.00 EG
Property damage: 1.00K
Reported by: Public

Large limbs were blown down just off of Cedarville Road.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 12-AUG-10 05:55:00 to 12-AUG-10 05:55:00 (EST-5)
Location: CLOPPER
Magnitude: 66.00 EG
Property damage: 25.00K
Reported by: Broadcast Media

A tree fell into the Garden Apartments. The tree was eighty feet tall.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 12-AUG-10 05:25:00 to 12-AUG-10 05:25:00 (EST-5)
Location: DAMASCUS
Magnitude: 52.00 EG
Reported by: NWS Employee

A wind gust of 60 mph was estimated by a National Weather Service employee near Damascus.

Thunderstorm Wind in CARROLL, MARYLAND
From 12-AUG-10 15:48:00 to 12-AUG-10 15:48:00 (EST-5)
Location: BARK HILL
Magnitude: 52.00 EG
Property damage: 2.00K
Reported by: Fire Department/Rescue

Trees and wires were down anear Linwood.

Tornado in FREDERICK, MARYLAND
From 12-AUG-10 16:03:00 to 12-AUG-10 16:04:00 (EST-5)
Location: UNIONVILLE
Tornado F-scale: EF0
Property damage: 15.00K
Reported by: NWS Employee

Numerous trees were uprooted and large limbs were snapped. The damage to trees and debris showed a convergent and weakly rotational pattern which suggests there was a weak tornado near and just north of Westvale Court.