Heavy rain caused poor drainage flooding in Eastern Pennsylvania and mainly minor to moderate creek and  river flooding in Berks County and Southeastern Pennsylvania. The rain began during the morning of the 16th and fell at its heaviest during thunderstorms on the evening of the 16th. The rain ended during the early morning of the 17th. Precipitation totals averaged 1.5 to 3.0 inches with the highest amounts along the interstate 95 corridor and the Poconos.
The heavy rain was caused by a deep low pressure system that emerged from the Rockies on the 14th and moved northeast and reached the Great Lakes on the morning of the 16th and then north into Canada that evening. A strong high pressure system preceded it across southeast Canada and both pumped considerable moisture into the region from the Gulf of Mexico and the Atlantic Ocean. The rain ended shortly after the low's occluded front moved through Pennsylvania.

Flood in BERKS, PENNSYLVANIA
From 16-APR-11 21:48:00 to 17-APR-11 04:18:00 (EST-5)
Location: GREISEMERSVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The Manatawny Creek at Spangville was above its 6 foot flood stage from 1048 p.m. EDT on the 16th through 518 a.m. EDT on the 17th. It crested at 6.72 feet at 130 a.m. EDT on the 17th.  Storm precipitation totals included 2.41 inches in Bechtelsville, 2.08 inches in Hamburg, 1.85 inches in Fleetwood, 1.79 inches in Berne, 1.69 inches in Bethel, 1.67 inches in Wyomissing, 1.61 inches in West Lawn, 1.47 inches in Reading and 1.26 inches in Oley.

Flood in PHILADELPHIA, PENNSYLVANIA
From 16-APR-11 19:54:00 to 17-APR-11 06:50:00 (EST-5)
Location: FOX CHASE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Heavy rain caused poor drainage flooding as well as flooding along several creeks within Philadelphia. Moderate flooding occurred along the Pennypack and Frankford Creeks and minor flooding occurred along the Wissahickon Creek. Flooding along the Wissahickon Creek closed Lincoln Drive. The eastbound lanes of the Schuylkill Expressway were closed near Montgomery Drive because of a mudslide. Flooding also occurred in the city's Bridesburg section near the Frankford Creek. A man had to be rescued from the top of a vehicle at the intersection of Hadley and Richmond Streets. Tidal flooding also occurred along the Delaware River.
The Frankford Creek at Castor Avenue was above its 7 foot flood stage from 902 p.m. EDT through 1027 p.m. EDT on the 16th. It crested at 9.84 feet at 930 p.m. EDT. The Pennypack Creek at the Rhawn Street Bridge was above its 7 foot flood stage from 929 p.m. EDT on the 16th through 620 a.m. EDT on the 17th. It crested at 10.18 feet at 1130 p.m. EDT on the 16th. The Wissahickon Creek at its mouth was above its 5 foot flood stage from 854 p.m. EDT on the 16th through 750 a.m. EDT on the 17th. It crested at 6.91 feet at 230 a.m. EDT on the 17th. Storm precipitation totals included 3.12 inches at the Philadelphia International Airport, 2.98 inches at the Northeast Philadelphia Airport, 2.78 inches in Wyndmoor and 2.51 inches in Rockledge.

Flood in DELAWARE, PENNSYLVANIA
From 16-APR-11 19:04:00 to 17-APR-11 10:17:00 (EST-5)
Location: CHADDS FORD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Heavy rain caused poor drainage flooding as well as minor flooding along the Brandywine, Chester and Crum Creeks in Delaware County. The Chester Creek in Chester was above its 8 foot flood stage from 937 p.m. EDT on the 16th through 1205 a.m. EDT on the 17th. It crested at 8.74 feet at 1030 p.m. EDT on the 16th. The Crum Creek at Newtown Square was above its 6 foot flood stage from 804 p.m. EDT on the 16th through 1246 a.m. EDT on the 17th. It crested at 7.44 feet at 10 p.m. EDT on the 16th. The main stem of the Brandywine Creek at Chadds Ford was above its 9 foot flood stage from 502 a.m. EDT through 1117 a.m. EDT on the 17th. It crested at 9.58 feet at 815 a.m. EDT on the 17th. Storm precipitation totals included 3.12 inches at the Philadelphia International Airport and 2.32 inches in Chadds Ford.

Flood in MONTGOMERY, PENNSYLVANIA
From 16-APR-11 19:43:00 to 17-APR-11 02:30:00 (EST-5)
Location: NIANTIC
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Heavy rain caused poor drainage flooding as well as moderate flooding along the Wisshaickon Creek and parts of the East Branch of the Perkiomen Creek and minor flooding along parts of the main stem of the Perkiomen Creek. The Wissahickon Creek at Fort Washington was above its 9 foot flood stage from 9 p.m. EDT on the 16th through 303 a.m. EDT on the 17th. It crested at 11.47 feet at at 1245 a.m. EDT on the 17th. The East Branch of the Perkiomen Creek at Schwenksville was above its 7 foot flood stage from 930 p.m. EDT on the 16th through 330 a.m. EDT on the 17th. It crested at 8.97 feet at 115 a.m. EDT on the 17th. The main stem of the Perkiomen Creek at East Greenville was above its 4 foot flood stage from 843 p.m. EDT on the 16th through 246 a.m. EDT on the 17th. It crested at 4.88 feet at Midnight EDT on the 17th. Storm precipitation totals included 2.43 inches in Wynnewood, 2.36 inches in Pottstown. 2.25 inches in Plymouth Meeeting, 2.24 inches in Gilbertsville, 2.05 inches in North Wales, 1.95 inches in Blue Bell, 1.81 inches in Graterford, 1.72 inches in Green Lane, 1.70 inches in Norristown, 1.66 inches in Harleysville, 1.56 inches in Hatfield and 1.47 inches in Schwenksville.

Flood in CHESTER, PENNSYLVANIA
From 16-APR-11 18:36:00 to 17-APR-11 10:17:00 (EST-5)
Location: CHADDS FORD JCT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Heavy rain caused poor drainage flooding as well as moderate flooding along sections of the East Branch of the Brandywine Creek and minor flooding along the main stem of the Brandywine Creek and the Valley and French Creeks in Chester County.  The East Branch of the Brandywine Creek at Downingtown was above its 7 foot flood stage from 853 p.m. EDT on the 16th through 529 a.m. EDT on the 17th. It crested at 9.38 feet at 1215 a.m. EDT on the 17th. The main stem of the Brandywine Creek at Chadds Ford (Delaware County) was above its 9 foot flood stage from 502 a.m. EDT through 1117 a.m. EDT on the 17th. It crested at 9.58 feet at 815 a.m. EDT on the 17th. The French Creek in Phoenixville was above its 8 foot flood stage from 757 p.m. EDT on the 16th through 7 a.m. EDT on the 17th. It crested at 8.66 feet at 1230 a.m. EDT on the 17th. The Valley Creek at Valley Forge was above its 7 foot flood stage from 736 p.m. EDT through 1135 p.m. EDT on the 16th. It crested at 7.62 feet at 830 p.m. EDT on the 16th. Storm precipitation totals included 2.54 inches in Glenmoore, 2.03 inches in Valley Forge, 1.91 inches in Modena, 1.81 inches in Northbrook and West Chester and 1.45 inches in Unionville.

Flood in BUCKS, PENNSYLVANIA
From 16-APR-11 21:54:00 to 17-APR-11 08:35:00 (EST-5)
Location: LANGHORNE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

In addition to the tidal flooding along the Delaware River, the heavy rain caused poor drainage and creek flooding inland in Bucks County. The Neshaminy Creek had major flooding at Langhorne. In East Rockhill Township, Stone Hedge Road was closed because of creek flooding. In Plumstead Township, the intersection of Pennsylvania State Route 32 and Point Pleasant Pike was partially blocked by a mudslide. In Richland Township, flooding was reported along Pike and Ebert Roads.
The Neshaminy Creek at Langhorne was above its 9 foot flood stage from 1054 p.m. EDT on the 16th through 935 a.m. EDT on the 17th. It crested at 12.14 feet at 5 a.m. EDT.  Precipitation event totals included 3.20 inches in Neshaminy Falls, 2.81 inches in Penndel, 2.60 inches in Richboro, 2.52 inches, 1.86 inches in Perkasie, 1.81 inches in Doylestown and 1.56 inches in Sellersville.