Low pressure tracked to the west while a nearly stationary boundary was to the south. Warm and moist tropical air overran the surface cooler air in place, resulting in a moderate to heavy rainfall. Excess runoff from the rainfall led to flooding. One and a half to three inches of rain fell across northern Maryland late on the 8th into the 9th, followed by another one to three inches on the 9th into the 10th. This combination produced fairly widespread flooding, including of the mainstem rivers, which continued through the 11th and into the 12th.

Flood in ALLEGANY, MARYLAND
From 09-SEP-18 12:31:00 to 10-SEP-18 13:55:00 (EST-5)
Location: LONG
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The USGS stream gage on Wills Creek near Cumberland exceeded the 10 foot flood stage during the indicated period. This caused flooding of a car wash at Motor City, with water in parking lots in the same area. The peak level of 11.57 feet was observed at 4:45pm EST on the 9th.

Flood in MONTGOMERY, MARYLAND
From 10-SEP-18 23:21:00 to 12-SEP-18 01:52:00 (EST-5)
Location: KENWOOD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The USGS stream gage on the Potomac River at Little Falls Dam exceeded the 10 foot flood stage during the indicated period, flooding low lying areas and trails on the Maryland side of the river, especially near Chain Bridge. The peak level of 10.85 feet occurred at 1:30pm EST on the 11th.

Flood in HOWARD, MARYLAND
From 12-SEP-18 18:10:00 to 12-SEP-18 20:10:00 (EST-5)
Location: LISBON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Carrs Mill Road was flooded near Bush Park Road due to high water.

Flood in ANNE ARUNDEL, MARYLAND
From 09-SEP-18 07:26:00 to 09-SEP-18 09:26:00 (EST-5)
Location: CROFTON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

MD-455 Defense Highway was closed due to flooding between Huntwood Drive and Rutland road.

Flood in ALLEGANY, MARYLAND
From 09-SEP-18 09:22:00 to 09-SEP-18 11:22:00 (EST-5)
Location: ALLEGANY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

MD-36 Mount Savage Road northwest was closed due to flooding near MD-638.

Flood in MONTGOMERY, MARYLAND
From 10-SEP-18 11:01:00 to 12-SEP-18 13:03:00 (EST-5)
Location: WHITES FERRY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The USGS stream gage on the Potomac River at Edwards Ferry exceeded the 15 foot flood stage during the indicated period. The peak level of 20.31 feet occurred at 10:15am EST on the 11th. Several parking lots along the C&O Canal were flooded, along with the store at Whites Ferry and the basements of lockhouses along the C&O Canal.

Flood in ANNE ARUNDEL, MARYLAND
From 09-SEP-18 10:30:00 to 09-SEP-18 12:30:00 (EST-5)
Location: ARUNDEL GARDENS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Furnace Branch Road was closed due to flooding near Ritchie Street.

Flood in CARROLL, MARYLAND
From 09-SEP-18 13:28:00 to 09-SEP-18 15:28:00 (EST-5)
Location: NEW WINDSOR
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

MD-31 Main Street was closed due to flooding near Union Bridge Road.

Flood in ANNE ARUNDEL, MARYLAND
From 09-SEP-18 07:57:00 to 10-SEP-18 12:16:00 (EST-5)
Location: RAYNOR HGTS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on the Patapsco River at Elkridge exceeded the 16 foot flood stage during the indicated period. Hammonds Ferry Road flooded and was closed at the Patapsco River. Backwater flooding led to the closure of Furnace Avenue in Elkridge. The peak level of 19.64 feet occurred at 8:05 PM on the 9th.

Flood in FREDERICK, MARYLAND
From 09-SEP-18 14:16:00 to 09-SEP-18 16:16:00 (EST-5)
Location: WOODSBORO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

MD-550 Woodsboro Road was closed due to flooding near Council Drive.

Flood in ANNE ARUNDEL, MARYLAND
From 09-SEP-18 14:15:00 to 09-SEP-18 16:15:00 (EST-5)
Location: CHURCHTON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Broadwater Creek was out of its banks onto Battee Drive.

Flood in WASHINGTON, MARYLAND
From 09-SEP-18 15:23:00 to 09-SEP-18 17:23:00 (EST-5)
Location: CEARFOSS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

MD-63 Greencastle Pike was closed due to flooding near Bivens Lane.

Flood in ANNE ARUNDEL, MARYLAND
From 10-SEP-18 14:12:00 to 10-SEP-18 15:11:00 (EST-5)
Location: RAYNOR HGTS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on the Patapsco River at Elkridge exceeded the 16 foot flood stage during the indicated period. Hammonds Ferry Road flooded and was closed at the Patapsco River. Backwater flooding led to the closure of Furnace Avenue in Elkridge. The peak level of 17 feet occurred at 2:55 PM.

Flood in ALLEGANY, MARYLAND
From 09-SEP-18 11:58:00 to 10-SEP-18 09:24:00 (EST-5)
Location: LUKE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The river level surpassed flood stage at Georges Creek at Westernport, cresting at 8.83 feet on September 9th at 3:45 PM EST. Water reached the underside of the railroad bridge at downtown Westernport.

Flood in WASHINGTON, MARYLAND
From 09-SEP-18 18:13:00 to 11-SEP-18 13:43:00 (EST-5)
Location: FAIRVIEW
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gauge along the Conocochague Creek surpassed the flood stage of 10 feet. the gauge crested at 12.49 feet at 6:45 EST September 10th. Wishard Road and Kemp Mill Road were both flooded.

Flood in ALLEGANY, MARYLAND
From 09-SEP-18 15:40:00 to 10-SEP-18 15:40:00 (EST-5)
Location: OLDTOWN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

The Oldtown Toll Bridge was closed due to high water.

Flood in CARROLL, MARYLAND
From 09-SEP-18 15:53:00 to 09-SEP-18 17:53:00 (EST-5)
Location: CRANBERRY STATION
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Numerous Road closures were reported across Carroll County due to high water.

Flood in FREDERICK, MARYLAND
From 09-SEP-18 16:07:00 to 09-SEP-18 18:07:00 (EST-5)
Location: FREDERICK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Numerous road closures were across Frederick County.

Flood in WASHINGTON, MARYLAND
From 13-SEP-18 16:03:00 to 13-SEP-18 21:51:00 (EST-5)
Location: FAIRVIEW
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gauge along the Conocochague Creek surpassed the flood stage of 10 feet. the gauge crested at 10.58 feet at 6:30 PM EST September 13th. Wishard Road and Kemp Mill Road were both flooded.

Flood in WASHINGTON, MARYLAND
From 09-SEP-18 17:50:00 to 09-SEP-18 19:50:00 (EST-5)
Location: BROADFORDING
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Around a dozen roads were closed throughout the county due to flooding.

Flood in ALLEGANY, MARYLAND
From 10-SEP-18 13:48:00 to 10-SEP-18 15:48:00 (EST-5)
Location: WOLFE MILL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Country Club Road was closed near Christie Road due to flooding.

Flood in CARROLL, MARYLAND
From 09-SEP-18 11:15:00 to 10-SEP-18 01:40:00 (EST-5)
Location: KEYMAR
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The USGS stream gage on Big Pipe Creek near Bruceville exceeded the 8 foot flood stage during the indicated period, flooding Keysville-Bruceville Road. The peak level observed was 9.53 feet, which occurred at 3:30pm on the 9th.

Flood in WASHINGTON, MARYLAND
From 09-SEP-18 15:25:00 to 09-SEP-18 23:45:00 (EST-5)
Location: PEARRE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The USGS stream gage on Sideling Hill Creek near Bellegrove exceeded the 7.5 foot flood stage during the indicated period, flooding lowlands near the creek. The peak level of 8.37 feet was observed at 7:15pm EST.

Flood in FREDERICK, MARYLAND
From 10-SEP-18 13:50:00 to 12-SEP-18 00:45:00 (EST-5)
Location: BRUNSWICK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The river level surpassed the flood stage of 16 feet at Point of Rocks along the Potomac River. The river level crested at 19.92 feet at 7:30 AM EST September 11th.
Farmland behind the Tarara Vineyard was flooded. Water approached structures at the Brunswick campground. Water entered the comfort station at the Brunswick boat ramp parking area. The parking lots at both the McKimmey and Brunswick boat ramps were flooded. Flooding of an agricultural field adjacent to the McKimmey boat ramp occurred. About half the lower parking lot of the Point of Rocks boat ramp was also flooded.