A cold front and its associated trough of low pressure triggered showers and thunderstorms across Maryland. A southwest flow ahead of the front ushered in plenty of moisture from the Gulf of Mexico, resulting in an unstable atmosphere. The moderate amounts of instability combined with the forcing from the front and strong winds aloft for some thunderstorms to become severe.

Tornado in HOWARD, MARYLAND
From 31-JUL-09 13:42:00 to 31-JUL-09 13:43:00 (EST-5)
Location: ALPHA
Tornado F-scale: EF1
Reported by: NWS Storm Survey

Numerous trees were down.

Thunderstorm Wind in HARFORD, MARYLAND
From 31-JUL-09 14:05:00 to 31-JUL-09 14:05:00 (EST-5)
Location: SWAN CREEK
Magnitude: 55.00 EG
Reported by: Emergency Manager

Trees were down along Pulaski Highway near Oakington Road.

Thunderstorm Wind in HARFORD, MARYLAND
From 31-JUL-09 14:08:00 to 31-JUL-09 14:08:00 (EST-5)
Location: HAVRE DE GRACE
Magnitude: 55.00 EG
Reported by: Mariner

Boats were damaged due thunderstorm winds.

Thunderstorm Wind in ANNE ARUNDEL, MARYLAND
From 31-JUL-09 14:20:00 to 31-JUL-09 14:20:00 (EST-5)
Location: SEVERNA PARK
Magnitude: 50.00 EG
Reported by: Trained Spotter

A tree top fell into the driveway and large branches were down along Cypress Creek.

Thunderstorm Wind in CARROLL, MARYLAND
From 31-JUL-09 13:41:00 to 31-JUL-09 13:41:00 (EST-5)
Location: LAWNDALE
Magnitude: 60.00 EG
Reported by: Public

Damage was reported to mobile homes near Finksburg.

Thunderstorm Wind in FREDERICK, MARYLAND
From 31-JUL-09 13:05:00 to 31-JUL-09 13:05:00 (EST-5)
Location: PARK MILLS
Magnitude: 60.00 EG
Reported by: NWS Storm Survey

Several trees were uprooted along with large tree limbs near Park Mills.

Thunderstorm Wind in CARROLL, MARYLAND
From 31-JUL-09 13:40:00 to 31-JUL-09 13:40:00 (EST-5)
Location: GAMBER
Magnitude: 60.00 EG
Reported by: Emergency Manager

Trees and power lines were down on Klee Mill Road near Sykesville Road.

Thunderstorm Wind in CARROLL, MARYLAND
From 31-JUL-09 13:30:00 to 31-JUL-09 13:30:00 (EST-5)
Location: WESTMINSTER CLRVW AR
Magnitude: 56.00 EG
Reported by: Emergency Manager

Trees and power lines were down at Salem Bottom Road and Bloom Road.

Thunderstorm Wind in HARFORD, MARYLAND
From 31-JUL-09 14:33:00 to 31-JUL-09 14:33:00 (EST-5)
Location: ABERDEEN ARPT
Magnitude: 50.00 EG
Reported by: Emergency Manager

Trees were down at 20 Swan Street.

Thunderstorm Wind in HOWARD, MARYLAND
From 31-JUL-09 13:40:00 to 31-JUL-09 13:43:00 (EST-5)
Location: ALPHA
Magnitude: 65.00 EG
Reported by: NWS Storm Survey

Numerous trees were down near Alpha.

Thunderstorm Wind in BALTIMORE CITY (C), MARYLAND
From 31-JUL-09 13:58:00 to 31-JUL-09 14:10:00 (EST-5)
Location: LEAHIGH
Magnitude: 50.00 EG
Reported by: Trained Spotter

Numerous trees were down across the northern portion of Baltimore.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 31-JUL-09 13:11:00 to 31-JUL-09 13:11:00 (EST-5)
Location: HYATTSTOWN
Magnitude: 52.00 MG
Reported by: Mesonet

A wind gust of 52 knots was measured at Interstate 270 and Maryland Route 109.

Thunderstorm Wind in MONTGOMERY, MARYLAND
From 31-JUL-09 13:12:00 to 31-JUL-09 13:12:00 (EST-5)
Location: HYATTSTOWN
Magnitude: 52.00 EG
Reported by: Amateur Radio

Several one inch limbs were down from thunderstorm winds near Clarksburg.

Thunderstorm Wind in CARROLL, MARYLAND
From 31-JUL-09 13:24:00 to 31-JUL-09 13:24:00 (EST-5)
Location: MT AIRY
Magnitude: 60.00 EG
Reported by: Amateur Radio

Nine large hardwood trees were down near Mount Airy.

Thunderstorm Wind in ANNE ARUNDEL, MARYLAND
From 31-JUL-09 14:29:00 to 31-JUL-09 14:29:00 (EST-5)
Location: ARNOLD
Magnitude: 55.00 EG
Reported by: Trained Spotter

Trees were down in Arnold due to thunderstorm winds.

Tornado in CARROLL, MARYLAND
From 31-JUL-09 13:40:00 to 31-JUL-09 13:43:00 (EST-5)
Location: GAMBER
Tornado F-scale: EF0
Reported by: NWS Storm Survey

A large tree limb was down just west of Deer Park Road. Two pine trees were down on the westernmost portion of Constellation Way. Two residents suffered a significant loss of roof covering material. Several pine trees were uprooted at several locations along with numerous tree limbs broken. A portion of a corn field was blown over along Kays Mill Road.

Tornado in FREDERICK, MARYLAND
From 31-JUL-09 13:08:00 to 31-JUL-09 13:14:00 (EST-5)
Location: IJAMSVILLE
Tornado F-scale: EF1
Reported by: NWS Storm Survey

Several trees were snapped or uprooted along Ijamsville Road and Price Distillery Road. Several hundred hardwood and softwood trees were snapped or uprooted along Whiskey Road and Whiskey Court. One home bearing specialty shingles to withstand winds up to 100 mph suffered some dislodging of its shingles. A clubhouse on the golf Course also lost many shingles from its roof.

Tornado in FREDERICK, MARYLAND
From 31-JUL-09 13:06:00 to 31-JUL-09 13:13:00 (EST-5)
Location: URBANA
Tornado F-scale: EF1
Reported by: NWS Storm Survey

Sporadic tree damage was noted along Tabler Road, where large branches were broken from hardwood trees. The circulation impacted several residences along Ball Road between Tabler Road and Ijamsville Road. One residence suffered roof structure damage and broken windows. In this location the roof was uplifted and shifted northward. An air conditioner unit on the north side of the home was lifted and transported fifteen feet to the east.
Many trees were snapped along Mussetter Road. A large home suffered roof damage and structural damage and a barn was destroyed.

A second residence also experienced an uplift of roofing. Several metal-sided barns were also destroyed.

Thunderstorm Wind in FREDERICK, MARYLAND
From 31-JUL-09 13:06:00 to 31-JUL-09 13:06:00 (EST-5)
Location: FREDERICK JCT
Magnitude: 56.00 EG
Reported by: Mesonet

A wind gust of 56 knots was estimated at Crestwood Middle School.

Thunderstorm Wind in HOWARD, MARYLAND
From 31-JUL-09 13:31:00 to 31-JUL-09 13:31:00 (EST-5)
Location: GLENWOOD
Magnitude: 52.00 EG
Reported by: Emergency Manager

Multiple trees were down along Route 97 including at the intersection of Cattail Creek Drive.