A cold front sagged into Maryland during the afternoon of May 27th. Heavy rain trained to the northeast of Baltimore early in the afternoon, causing flash flooding. Then, later in the afternoon, the line completely stalled just west of Baltimore, producing 6-12 inches of rain in a very short period of time. Catastrophic flash flooding occurred in the Ellicott City and Catonsville areas, with significant flooding also observed in other nearby areas. Stream flooding continued through the next morning.

Flash Flood in BALTIMORE, MARYLAND
From 27-MAY-18 13:44:00 to 27-MAY-18 15:30:00 (EST-5)
Location: PARKVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

A swift water rescue was performed near Parkville along Herring Run.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 16:30:00 to 27-MAY-18 17:30:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video footage shows a second wave of floodwaters, with water 1-2 feet deep over the 8600 block of Frederick Road in Ellicott City's West End. The floodwaters entered and damaged homes and vehicles.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 17:16:00 to 27-MAY-18 17:45:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The culvert underneath Ellicott Mills Drive was undermined as the road was overtopped by floodwaters, washing out the road. Just downstream, the floodwaters caused the collapse of the historic stone cottage locals call The Old Courthouse, which was built in 1840.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 19:05:00 to 27-MAY-18 21:30:00 (EST-5)
Location: ELKRIDGE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

US Route 1 was flooded and closed at the Patapsco River due to rapid increases in the water level.

Flash Flood in CARROLL, MARYLAND
From 27-MAY-18 19:01:00 to 27-MAY-18 20:30:00 (EST-5)
Location: SYKESVILLE
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Lower Main Street in Sykesville flooded due to overwhelmed storm drains during torrential rain. Some water entered two structures in addition to water covering parking lots.

Flash Flood in BALTIMORE, MARYLAND
From 27-MAY-18 15:27:00 to 27-MAY-18 19:00:00 (EST-5)
Location: OELLA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on the Patapsco River near Catonsville rapidly exceeded the flood stage at the start time indicated. It rose more than seven feet above flood stage within 33 minutes of the flooding beginning, peaking at 27.03 feet. River Road was flooded, and damaged, as a result of this rapid rise.

Flood in HOWARD, MARYLAND
From 27-MAY-18 20:00:00 to 28-MAY-18 01:38:00 (EST-5)
Location: OAKLAND MILLS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on the Little Patuxent River near Columbia Town Center exceeded the flood elevation of 298.5 feet during the times indicated, and had already rapidly exceeded the flood stage due to flash flooding before this time. The peak elevation of 303.76 feet was observed at 8:20pm EST on May 27th. At the peak levels, US 29 was flooded by several feet of water on the southbound side. For the duration of the flood, South Entrance Road was flooded and closed.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 15:19:00 to 27-MAY-18 15:47:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The first of three waves of flash flooding affected lower Main Street in Ellicott City on the Tiber River. Video footage shows the Tiber escaping its banks near Tiber Alley at 4:19pm, and at the alley in the 8100 block at 4:22pm. Several feet of rushing water began inundating Main Street and buildings in the area. At 4:35pm, the force of the floodwaters buckled the floor within one business, and water pushed through the building, emptying its contents onto Main Street.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 16:39:00 to 27-MAY-18 17:30:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video footage shows a third and final flood wave pushing through the 8100 block of Main Street.  The water was nearly a foot deep on Main Street and then began entering buildings. Eventually overflow from the Tiber River caused the floodwaters of the Tiber and overland flow on Main Street to join with water surrounding and going through buildings.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 15:19:00 to 27-MAY-18 17:53:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 10.50M
Crop damage: 0.00K
Reported by: Emergency Manager

Catastrophic flash flooding occurred in Ellicott City as a result of torrential short-term rainfall of 6-10 inches.  One person died during a lull in the flooding when he attempted to help another person evacuate and was swept away. Floodwaters on the lower portion of Main Street in the 8000 block reached the bottom of second floors of businesses. In all, dozens of water rescues were performed, most from buildings.

Flash Flood in BALTIMORE CITY (C), MARYLAND
From 27-MAY-18 15:55:00 to 27-MAY-18 17:30:00 (EST-5)
Location: CATONSVILLE
Flood cause: Heavy Rain
Property damage: 3.00M
Crop damage: 0.00K
Reported by: 911 Call Center

Several roads flooded in Baltimore City. More than 20 people were rescued from vehicle rooftops during heavy rains. Six people were displaced from their homes, and Frederick Avenue was damaged in the Beechfield neighborhood.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 18:41:00 to 27-MAY-18 20:00:00 (EST-5)
Location: WOODSTOCK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

West Friendship Road flooded and closed south of Sykesville near the South Branch Patapsco River.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 18:05:00 to 27-MAY-18 20:00:00 (EST-5)
Location: OAKLAND MILLS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Flooding began of South Entrance Road in Columbia, after the Little Patuxent River rapidly came out of its banks. Shortly thereafter, the stream covered the southbound lanes of US 29, with at least one water rescue required.

Flash Flood in BALTIMORE, MARYLAND
From 27-MAY-18 13:09:00 to 27-MAY-18 14:00:00 (EST-5)
Location: PERRY HALL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

A swift water rescue was conducted on Seven Courts Drive where a man was trapped in rising flood waters, clinging to a tree. The man was successfully rescued.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 17:56:00 to 27-MAY-18 20:00:00 (EST-5)
Location: WATERLOO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Deep Run overflowed its banks, covering Mayfield Avenue in Elkridge.

Flash Flood in BALTIMORE, MARYLAND
From 27-MAY-18 17:00:00 to 27-MAY-18 19:00:00 (EST-5)
Location: CHADWICK MANOR
Flood cause: Heavy Rain
Property damage: 8.60M
Crop damage: 0.00K
Reported by: Broadcast Media

Widespread flash flooding in downtown Catonsville along Frederick Road.  Roads flooded and water entering buildings. Flooding was reported in local schools along with 12 swift water rescues.

Flash Flood in BALTIMORE, MARYLAND
From 27-MAY-18 15:16:00 to 27-MAY-18 17:46:00 (EST-5)
Location: HALETHORPE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on East Branch Herbert Run at Arbutus rapidly exceeded the 7 foot flood stage during the indicated times. There were two distinct peaks during the times indicated but the higher was the second peak, of 9.21 feet at 5:20pm EST on May 27th. Water levels rapidly fell thereafter.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 15:49:00 to 27-MAY-18 20:31:00 (EST-5)
Location: ILCHESTER
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on the Patapsco River at Patapsco Valley State Park rapidly exceeded the 15 foot flood stage during the indicated times. Widespread damage occurred within the park, with a peak level reached of 24.36 feet at 5:45pm EST on May 27th. This is preliminarily the highest value reached at this location since at least 2010.

Flood in HOWARD, MARYLAND
From 27-MAY-18 20:05:00 to 28-MAY-18 04:06:00 (EST-5)
Location: GUILFORD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on the Little Patuxent River at Guilford exceeded the 11 foot flood stage during the times indicated. The peak level of 15.22 feet was observed at 10:15pm EST on May 27th, and was the 3rd highest ever recorded at this location. Vollmerhausen Road was flooded.

Flood in HOWARD, MARYLAND
From 27-MAY-18 20:32:00 to 28-MAY-18 06:18:00 (EST-5)
Location: SAVAGE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on the Little Patuxent River near Savage exceeded the 10 foot flood stage during the indicated times. The peak level of 16.52 feet occurred at 11:30pm EST on May 27th. Brock Bridge Road significantly flooded during this event.

Flood in HOWARD, MARYLAND
From 27-MAY-18 15:16:00 to 27-MAY-18 15:23:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video footage shows Hudson Branch out of its banks near Court Avenue, flooding yards.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 16:37:00 to 27-MAY-18 17:53:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video footage shows a second, more significant flash flood wave moved down Hudson Branch during the times indicated. Cars, dumpsters, and other large debris were swept downstream. Water covered a second-floor deck and entered structures, and was at least a foot deep flowing over Court Avenue at the peak of the flooding. The stream was not fully back in its banks in this area until after 8:00pm due to debris blockage.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 15:47:00 to 27-MAY-18 16:20:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A second, more intense, flood wave pushed into the Tiber River, with water entering buildings in the 8100 block of Main Street. The water receded from this block of Main Street by 5:20pm.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 15:26:00 to 27-MAY-18 15:40:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video footage shows 6-12 inches of water flowing over the 8600 block of Frederick Road east of Rogers Avenue in Ellicott City's West End for a brief period before receding.

Flash Flood in BALTIMORE, MARYLAND
From 27-MAY-18 16:21:00 to 27-MAY-18 18:00:00 (EST-5)
Location: CHADWICK MANOR
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Moving water observed over the hoods of several cars in multiple locations in the Catonsville area along Frederick Road.

Flood in ALLEGANY, MARYLAND
From 27-MAY-18 16:37:00 to 27-MAY-18 18:00:00 (EST-5)
Location: WOLFE MILL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flooding of unknown depth was reported on Bedford Street in Cumberland.

Flash Flood in BALTIMORE, MARYLAND
From 27-MAY-18 16:49:00 to 27-MAY-18 18:00:00 (EST-5)
Location: OELLA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Several issues reported near Oella. There was a partial landslide on Old Frederick Road with the road also reported flooded and closed. River Road was flooded and closed. Thistle Road had a washout and was closed. A portion of Westchester Avenue was also flooded and closed.

Flood in CALVERT, MARYLAND
From 27-MAY-18 22:16:00 to 27-MAY-18 23:59:00 (EST-5)
Location: BOWENS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Buzzard Island Creek was out of its banks and running across Sixes Road.

Flash Flood in BALTIMORE CITY (C), MARYLAND
From 27-MAY-18 15:47:00 to 27-MAY-18 19:16:00 (EST-5)
Location: FREDERICK RD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on Gwynns Falls at Washington Boulevard in Baltimore rapidly exceeded the 13 foot flood stage, flooding portions of Gwynns Falls Park. The peak level of 17.09 feet was the 4th highest on record, and occurred at 5:31pm EST on May 27th.

Flash Flood in BALTIMORE, MARYLAND
From 27-MAY-18 13:54:00 to 27-MAY-18 16:00:00 (EST-5)
Location: WHITE MARSH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The stream gage on Whitemarsh Run at White Marsh rapidly exceeded the 11 foot flood stage during the times indicated. Parking lots near the stream, and Town Center Court, were flooded. The peak level of 13.42 feet was observed at 2:45pm EST on May 27th.

Flash Flood in HOWARD, MARYLAND
From 27-MAY-18 15:26:00 to 27-MAY-18 15:57:00 (EST-5)
Location: ELLICOTT CITY
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video footage shows water covering a deck and entering structures near Court Avenue. Water also flowed across Court Avenue during this time.

Flood in CALVERT, MARYLAND
From 27-MAY-18 22:16:00 to 27-MAY-18 23:59:00 (EST-5)
Location: PRINCE FREDERICK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Duke Street flooded and closed in Prince Frederick.

Flood in ANNE ARUNDEL, MARYLAND
From 27-MAY-18 18:33:00 to 27-MAY-18 20:00:00 (EST-5)
Location: GLEN BURNIE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Maryland Route 648 flooded and closed at Sawmill Creek in Glen Burnie.