A southerly flow around high pressure off the east coast produced hot and humid conditions. The hot and humid conditions combined with colder air aloft associated with an upper-level trough to produce moderate amounts of instability. Some thunderstorms that developed produced damaging wind gusts and large hail.

Hail in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 17:52:00 to 18-AUG-11 17:52:00 (EST-5)
Location: MARYLAND CITY
Magnitude: 1.00 
Reported by: Trained Spotter

Quarter sized hail was reported near Laurel.

Hail in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 18:20:00 to 18-AUG-11 18:20:00 (EST-5)
Location: MARLEY
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported at Glen Burnie.

Hail in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 18:09:00 to 18-AUG-11 18:09:00 (EST-5)
Location: PIONEER CITY
Magnitude: 1.00 
Reported by: Broadcast Media

Quarter sized hail was reported near Severn.

Hail in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 18:07:00 to 18-AUG-11 18:07:00 (EST-5)
Location: PIONEER CITY
Magnitude: 1.00 
Reported by: Broadcast Media

Quarter sized hail was reported at Fort Meade.

Thunderstorm Wind in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 16:08:00 to 18-AUG-11 16:08:00 (EST-5)
Location: SEVERN
Magnitude: 52.00 EG
Reported by: Trained Spotter

Wind gusts were estimated to be around 60 mph.

Thunderstorm Wind in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 16:40:00 to 18-AUG-11 16:40:00 (EST-5)
Location: CONAWAYS
Magnitude: 56.00 EG
Property damage: 15.00K
Reported by: Public

A tree was blown onto a garage crushing the roof. A car was also damaged in the garage. Multiple 150 year old trees were blown down.

Thunderstorm Wind in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 17:15:00 to 18-AUG-11 17:15:00 (EST-5)
Location: MAYFIELD
Magnitude: 52.00 EG
Property damage: 1.00K
Reported by: Public

A tree that was one to one and one half feet in diameter was blown down.

Hail in CARROLL, MARYLAND
From 18-AUG-11 16:26:00 to 18-AUG-11 16:26:00 (EST-5)
Location: MT AIRY
Magnitude: 1.00 
Reported by: Other Federal Agency

Hail up to quarters in size was reported near Mount Airy.

Hail in BALTIMORE, MARYLAND
From 18-AUG-11 17:12:00 to 18-AUG-11 17:12:00 (EST-5)
Location: PLEASANT GROVE
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported near Boring.

Hail in HARFORD, MARYLAND
From 18-AUG-11 16:34:00 to 18-AUG-11 16:34:00 (EST-5)
Location: EMMORTON
Magnitude: 1.75 
Reported by: Public

Hail up to the size of golf balls was reported.

Hail in HARFORD, MARYLAND
From 18-AUG-11 16:40:00 to 18-AUG-11 16:40:00 (EST-5)
Location: CALVARY
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported.

Thunderstorm Wind in HARFORD, MARYLAND
From 18-AUG-11 16:36:00 to 18-AUG-11 16:36:00 (EST-5)
Location: CALVARY
Magnitude: 56.00 EG
Property damage: 1.00K
Reported by: State Official

A tree was down along MD-543 and Calvary Road.

Hail in MONTGOMERY, MARYLAND
From 18-AUG-11 17:19:00 to 18-AUG-11 17:19:00 (EST-5)
Location: KEN GAR
Magnitude: 1.00 
Reported by: Trained Spotter

Quarter sized hail was reported at the intersection of Connecticut Avenue and Viers Mill Road.

Hail in HARFORD, MARYLAND
From 18-AUG-11 17:01:00 to 18-AUG-11 17:01:00 (EST-5)
Location: HAVRE DE GRACE
Magnitude: 1.00 
Reported by: Public

Hail up to quarters in size was reported.

Hail in MONTGOMERY, MARYLAND
From 18-AUG-11 17:33:00 to 18-AUG-11 17:33:00 (EST-5)
Location: FAIRLAND
Magnitude: 1.75 
Reported by: Trained Spotter

Golf ball sized hail was reported in Calverton.

Hail in MONTGOMERY, MARYLAND
From 18-AUG-11 17:24:00 to 18-AUG-11 17:24:00 (EST-5)
Location: GLENMONT
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported near Glenmont.

Thunderstorm Wind in HARFORD, MARYLAND
From 18-AUG-11 16:43:00 to 18-AUG-11 16:43:00 (EST-5)
Location: PLEASANTVILLE
Magnitude: 50.00 EG
Property damage: 1.00K
Reported by: State Official

A tree was down along High Point Road.

Hail in HARFORD, MARYLAND
From 18-AUG-11 17:00:00 to 18-AUG-11 17:00:00 (EST-5)
Location: LAPIDUM
Magnitude: 1.75 
Reported by: State Official

Golf ball sized hail was reported at the Steppingstone Museum.

Hail in MONTGOMERY, MARYLAND
From 18-AUG-11 17:15:00 to 18-AUG-11 17:15:00 (EST-5)
Location: WHEATON
Magnitude: 1.00 
Reported by: Trained Spotter

Quarter sized hail was reported at Wheaton.

Hail in MONTGOMERY, MARYLAND
From 18-AUG-11 17:35:00 to 18-AUG-11 17:35:00 (EST-5)
Location: FAIRLAND
Magnitude: 1.75 
Reported by: Public

Golf ball sized hail was reported.

Hail in PRINCE GEORGE'S, MARYLAND
From 18-AUG-11 17:36:00 to 18-AUG-11 17:36:00 (EST-5)
Location: AMMENDALE
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported.

Thunderstorm Wind in HARFORD, MARYLAND
From 18-AUG-11 16:26:00 to 18-AUG-11 16:26:00 (EST-5)
Location: EMMORTON
Magnitude: 50.00 EG
Property damage: 1.00K
Reported by: Trained Spotter

A tree was blocking the roadway near Patterson Mill Road and Route 924.

Hail in MONTGOMERY, MARYLAND
From 18-AUG-11 17:15:00 to 18-AUG-11 17:15:00 (EST-5)
Location: KEN GAR
Magnitude: 1.25 
Reported by: Broadcast Media

Half dollar sized hail was reported in Wheaton.

Hail in MONTGOMERY, MARYLAND
From 18-AUG-11 17:20:00 to 18-AUG-11 17:20:00 (EST-5)
Location: HOMEWOOD
Magnitude: 1.50 
Reported by: Public

Hail up to the size of ping pong balls was reported near Wheaton.

Hail in MONTGOMERY, MARYLAND
From 18-AUG-11 17:38:00 to 18-AUG-11 17:38:00 (EST-5)
Location: FAIRLAND
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported.

Hail in PRINCE GEORGE'S, MARYLAND
From 18-AUG-11 17:47:00 to 18-AUG-11 17:47:00 (EST-5)
Location: LAUREL
Magnitude: 1.50 
Reported by: Broadcast Media

Hail up to the size of ping pong balls was reported in Laurel.

Hail in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 17:56:00 to 18-AUG-11 17:56:00 (EST-5)
Location: GREEN HAVEN
Magnitude: 1.00 
Reported by: Trained Spotter

Quarter sized hail was reported near Green Haven.

Lightning in HARFORD, MARYLAND
From 18-AUG-11 16:53:00 to 18-AUG-11 16:53:00 (EST-5)
Location: SINGER
Reported by: Fire Department/Rescue

A person was injured by lightning while using an ATM machine.

Hail in WASHINGTON, MARYLAND
From 18-AUG-11 20:40:00 to 18-AUG-11 20:40:00 (EST-5)
Location: CLEAR SPG
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported.

Thunderstorm Wind in WASHINGTON, MARYLAND
From 18-AUG-11 21:15:00 to 18-AUG-11 21:15:00 (EST-5)
Location: FUNKSTOWN
Magnitude: 56.00 EG
Property damage: 5.00K
Reported by: State Official

Multiple reports of trees were down across the eastern parts of Washington County.

Hail in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 15:50:00 to 18-AUG-11 15:50:00 (EST-5)
Location: PIONEER CITY
Magnitude: 1.00 
Reported by: COOP Observer

Quarter sized hail was reported in Fort Meade.

Thunderstorm Wind in WASHINGTON, MARYLAND
From 18-AUG-11 20:44:00 to 18-AUG-11 20:44:00 (EST-5)
Location: CLEAR SPG
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Trees and large limbs were down in Clear Spring.

Thunderstorm Wind in BALTIMORE, MARYLAND
From 18-AUG-11 23:04:00 to 18-AUG-11 23:04:00 (EST-5)
Location: BENTLEY SPGS
Magnitude: 56.00 EG
Property damage: 2.00K
Reported by: Public

Large limbs were down due to thunderstorm winds.

Hail in HARFORD, MARYLAND
From 18-AUG-11 16:48:00 to 18-AUG-11 16:48:00 (EST-5)
Location: ALDINO ARPT
Magnitude: 2.25 
Reported by: Public

Large hail 2.25 inches in diameter was reported.

Thunderstorm Wind in WASHINGTON, MARYLAND
From 18-AUG-11 21:44:00 to 18-AUG-11 21:44:00 (EST-5)
Location: KEEDYSVILLE
Magnitude: 56.00 EG
Property damage: 2.00K
Reported by: Public

Several Sycamore trees were snapped off due to thunderstorm winds.

Hail in WASHINGTON, MARYLAND
From 18-AUG-11 21:45:00 to 18-AUG-11 21:45:00 (EST-5)
Location: KEEDYSVILLE
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported near Keedysville.

Hail in WASHINGTON, MARYLAND
From 18-AUG-11 21:15:00 to 18-AUG-11 21:15:00 (EST-5)
Location: ROXBURY
Magnitude: 1.00 
Reported by: Public

Quarter sized hail was reported near Funkstown.

Thunderstorm Wind in ANNE ARUNDEL, MARYLAND
From 18-AUG-11 16:15:00 to 18-AUG-11 16:15:00 (EST-5)
Location: MAYFIELD
Magnitude: 52.00 EG
Reported by: Trained Spotter

A tree about one to one and one half feet in diameter was blown down from thunderstorm winds.