The combination of melting snow and heavy rain produced field, poor drainage and stream and creek flooding in southeastern Pennsylvania throughout the Philadelphia Metropolitan Area.  Rain began falling during the evening of the 25th and fell at a nearly steady rate. The heaviest rain fell during the late afternoon and early evening of the 26th. The rain ended late in the evening on the 26th. Event precipitation totals across eastern Pennsylvania averaged between 1.0 and 2.5 inches with the highest amounts in and around Philadelphia.
The steady rain was caused by a strong southerly flow of air from the Gulf of Mexico around an intense low pressure system that spent much of the 25th and 26th in Iowa before weakening and drifting to the northeast. The mild weather also rapidly melted the large snow pack that was present in southeastern Pennsylvania. The rain ended after this low's occluded front moved through the state.

Flood in PHILADELPHIA, PENNSYLVANIA
From 26-DEC-09 15:33:00 to 27-DEC-09 05:39:00 (EST-5)
Location: TACONY
Flood cause: Heavy Rain / Snow Melt
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The Wissahickon Creek at its mouth with the Schuylkill River was above its 5 foot flood stage from 333 p.m. EST on the 26th through 539 a.m. EST on the 27th. It crested at 6.10 feet at 145 a.m. EST on the 27th. The Pennypack Creek at the Rhawn Street Bridge was above its 7 foot flood stage from 730 p.m. EST on the 26th  through 306 a.m. EST on the 27th. It crested at 7.82 feet at 116 a.m. EST on the 27th. Event precipitation totals included 2.16 inches at the Northeast Philadelphia Airport and 2.06 inches at the Philadelphia International Airport.

Flood in CHESTER, PENNSYLVANIA
From 26-DEC-09 13:05:00 to 27-DEC-09 06:49:00 (EST-5)
Location: DOWNINGTOWN
Flood cause: Heavy Rain / Snow Melt
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The East Branch of the Brandywine Creek at Downingtown was above its 7 foot flood stage from 105 p.m. EST through 1113 p.m. EST on the 26th. It crested at 8.07 feet at 645  p.m. EST. The main stem of the Brandywine Creek at Chadds Ford was above its 9  foot flood stage from 551 p.m. EST on the 26th through 649 a.m. EST on the 27th. It crested at 9.72 feet at 1145 p.m. EST on the 26th. Event precipitation totals included 2.48 inches in West Chester, 2.22 inches in Unionville, 1.99 inches in Kenneth Square, 1.59 inches in Honey Brook and 1.52 inches in Glenmoore.

Flood in DELAWARE, PENNSYLVANIA
From 26-DEC-09 11:46:00 to 27-DEC-09 06:49:00 (EST-5)
Location: CHESTER
Flood cause: Heavy Rain / Snow Melt
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The Crum Creek at Newtown Sqaure was above its 6 foot flood stage from 1146 a.m. EST through 810 p.m. EST on the 26th. It crested at 6.17 feet at 3  p.m. EST on the 26th. The Chester Creek at Chester  was above its 8 foot flood stage from 127 p.m. EST through 928 p.m. EST on the 26th. It crested at 8.63 feet at 715  p.m. EST. The main stem of the Brandywine Creek at Chadds Ford was above its 9 foot flood stage from 551 p.m. EST on the 26th through 649 a.m. EST on the 27th. It crested at 9.72 feet at 1145 p.m. EST on the 26th. Event precipitation totals included 2.06 inches at the Philadelphia International Airport.

Flood in BUCKS, PENNSYLVANIA
From 26-DEC-09 18:00:00 to 27-DEC-09 06:00:00 (EST-5)
Location: LANGHORNE
Flood cause: Heavy Rain / Snow Melt
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The Neshaminy Creek flooded in Bucks County, but the gauge at Langhorne was not functioning properly during this event. Event precipitation totals included 2.24 inches in Doylestown, 2.22 inches in Bensalem, 1.84 inches in Penndel and 1.75 inches in Richboro.

Flood in MONTGOMERY, PENNSYLVANIA
From 26-DEC-09 19:08:00 to 27-DEC-09 12:48:00 (EST-5)
Location: FLOURTOWN
Flood cause: Heavy Rain / Snow Melt
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The Wissahickon Creek at Fort Washington was above its 9 foot flood stage from 708 p.m. EST on the 26th  through 1248 a.m. EST on the 27th. It crested at 10.53 feet at 10  p.m. EST on the 26th. Event precipitation totals included 2.35 inches in Blue Bell, 2.30 inches in Willow Grove, 2.07 inches in North Wales, 1.99 inches in Hatfield, 1.37 inches in Pottstown and 1.30 inches in Gilbertsville.