A deep low pressure system tracked across the Lower Great Lakes northeastward into the St. Lawrence Valley from the evening of the 20th into the daytime of the 21st. Its associated strong cold front swept eastward through the Mid Atlantic region and across Pennsylvania during the early morning of the 21st. In addition, a secondary area of low pressure formed along the frontal boundary, west of Delaware Bay, and deepened rapidly. The approaching cold front and the deepening secondary low pressure produced a strong southeasterly flow the reached into the local Philadelphia area and resulted in peak wind gusts of around 50 mph in the far southeast part of the state and knocked down weak tree limbs and wires.  In addition, the significant southeast flow allowed water to pile up along the New Jersey shore and into the Delaware Bay and Delaware River and produced major tidal flooding.on the morning of the 21st. Lastly this southeast flow also brought moderate to heavy rain into the state with storm totals ranging between 1 to 3 inches. The rain began during the afternoon of the 20th and fell at its heaviest between Midnight EST and 6 a.m. EST on the 21st. The rain ended between 7 a.m. EST and 9 a.m. EST on the morning of the 21st. This rain resulted in poor drainage flooding as well as minor to moderate flooding of streams and creeks in Eastern Pennsylvania.

In Philadelphia, the tidal flooding forced the closure of the southbound lanes of Interstate 95 at Columbus Boulevard. Columbus Boulevard/Delaware Avenue was flooded and closed in both directions between Washington and Fairmount Avenues.  In Bucks County,  tidal flooding affected the Radcliffe, Cedar and Mill Street areas of Bristol Township. The high tide swamped the backyards and basements of stores in the business district along Radcliffe and Cedar Streets   The Mill Street parking lot was under water as was the Landmark Wharf on Mill Street. The high tide in Philadelphia reached 10.35 feet above mean lower low water. This was the third highest tide on record. Major tidal flooding starts at 10.2 feet above mean lower low water.  The high tide  reached  12.13 feet above mean lower low water at Newbold Island (Bucks County). There are no established flood categories for this site.
Strong winds occurred in the southeast part of the state, beginning a few hours prior to daybreak and ending soon after sunrise on the 21st. Winds decreased by mid-morning following the passage of the surface cold front. In Delaware County, downed utility lines forced the closure of U.S. Route 30 in both directions in Radnor Township and the southbound lanes of U.S. Route 1 in Chadds Ford. Peak wind gusts included 55 mph in Newbold Island (Bucks County) and 52 mph at the Philadelphia International Airport.

Flood in CHESTER, PENNSYLVANIA
From 21-DEC-12 04:30:00 to 21-DEC-12 15:30:00 (EST-5)
Location: VINCENT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The Valley Creek at Valley Forge was above its 7 foot flood stage from 430 a.m. EST through 845 a.m. EST on the 21st. It crested at 7.49 feet at 645 a.m. EST.  The main stem of the Brandywine Creek at Chadds Ford was above its 9 foot flood stage from 1157 a.m. EST through 330 p.m. EST on the 21st. It crested at 9.12 feet at 240 p.m. EST. Event precipitation totals included 2.34 inches in West Chester, 2.23 inches in Malvern, 2.21 inches in Devon-Berwyn, 2.20 inches in West Grove and 2.02 inches in Exton.

Flood in MONTGOMERY, PENNSYLVANIA
From 21-DEC-12 05:30:00 to 21-DEC-12 16:30:00 (EST-5)
Location: MARBLE HALL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The Wissahickon Creek at Fort Washington had moderate flooding and was above its 9 foot flood stage from 533 a.m. EST through 1220 p.m. EST on the 21st. It crested at 11.29 feet at 1045 a.m. EST. The East Branch of the Perkiomen Creek at Schwenksville had moderate flooding and was above its 7 foot flood stage from 632 a.m. EST through 416 p.m. EST on the 21st. It crested at 9.72 feet at Noon EST. The Main Stem of the Perkiomen Creek at East Greenville was above its 4 foot flood stage from 709 a.m. EST through 1151 a.m. EST on the 21st. It crested at 4.45 feet at 10 a.m. EST.  Event precipitation totals included 2.86 inches in Conshohocken, 2.66 inches in North Wales, 2.64 inches in Norristown, 2.52 inches in Blue Bell, 2.49 inches in Ambler, 2.30 inches in West Norriton and 2.04 inches in Perkiomenville.

Flood in BUCKS, PENNSYLVANIA
From 21-DEC-12 05:41:00 to 22-DEC-12 18:55:00 (EST-5)
Location: CORNWELLS HGTS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The East Branch of the Perkiomen Creek at Dublin was above its 5 foot flood stage from 541 a.m. EST through 849 a.m. EST on the 21st. It crested at 5.75 feet at 745 a.m. EST. The Neshaminy Creek at Langhorne had moderate flooding and was above its 9 foot flood stage from 945 a.m. EST through 655 p.m. EST on the 21st. It crested at 10.08 feet at 315 p.m. EST.  Event precipitation totals included 2.33 inches in Doylestown, 2.09 inches in Springtown, 1.98 inches in Sellersville and 1.32 inches in Penndel.

Flood in BERKS, PENNSYLVANIA
From 21-DEC-12 10:45:00 to 21-DEC-12 12:15:00 (EST-5)
Location: PINE FORGE
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 1050 a.m. EST through 1211 p.m. EST on the 21st. It crested at 6.04 feet at 1130 a.m. EST.  Event precipitation totals included 2.10 inches in Alburtis, 1.70 inches in Hamburg, 1.62 inches in Fleetwood, 1.45 inches at the Blue Marsh Dam, 1.34 inches in Wyomissing and 1.23 inches at the Reading Airport.

Flood in PHILADELPHIA, PENNSYLVANIA
From 21-DEC-12 06:30:00 to 21-DEC-12 16:45:00 (EST-5)
Location: ROXBOROUGH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The Wissahickon Creek at its mouth was above its 5 foot flood stage from 637 a.m. EST through 452 p.m. EST on the 21st. It crested at 6.39 feet at 2 p.m. EST on the 21st. The Pennypack Creek at the Rhawn Street Bridge was above its 7 foot flood stage from 652 a.m. EST through 118 p.m. EST on the 21st. It crested at 7.77 feet at 11 a.m. EST.
Event precipitation totals included 1.84 inches at Franklin Institute in Center City, 1.60 inches in Rockledge, 1.58 inches at the Philadelphia International Airport and 1.45 inches at the Northeast Philadelphia Airport.

Strong Wind in DELAWARE, PENNSYLVANIA
From 21-DEC-12 03:00:00 to 21-DEC-12 06:00:00 (EST-5)
Magnitude: 43.00 EG
Property damage: 2.50K
Crop damage: 0.00K
Reported by: Mesonet

Strong Wind in PHILADELPHIA, PENNSYLVANIA
From 21-DEC-12 04:00:00 to 21-DEC-12 07:00:00 (EST-5)
Magnitude: 45.00 MG
Property damage: 2.50K
Crop damage: 0.00K
Reported by: ASOS

Coastal Flood in PHILADELPHIA, PENNSYLVANIA
From 21-DEC-12 06:00:00 to 21-DEC-12 10:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Coastal Flood in DELAWARE, PENNSYLVANIA
From 21-DEC-12 05:00:00 to 21-DEC-12 09:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Flood in NORTHAMPTON, PENNSYLVANIA
From 21-DEC-12 06:00:00 to 21-DEC-12 12:00:00 (EST-5)
Location: KEPLERS MILL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Heavy rain caused the flooding of the Bushkill Creek along the Forks and Palmer Township border on the morning of the 21st. Bushkill Drive was flooded and closed. A vehicle became trapped in the flood waters near the intersection of Zucksville Road and Bushkill Drive. The woman was able to get out of the car and walk away.  The northbound side of Bushkill Drive was reopened at 830 a.m. EST, the southbound side later that day. Event precipitation totals included 2.08 inches in Bethlehem, 2.06 inches in Hellertown, 2.00 inches in Glendon and 1.93 inches in Nazareth.

Flood in DELAWARE, PENNSYLVANIA
From 21-DEC-12 04:31:00 to 21-DEC-12 15:30:00 (EST-5)
Location: MARCUS HOOK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

The heavy rain and flooding forced the termination of the SEPTA Sharon Hill Trolley Service at McDade Boulevard. in Darby. The Crum Creek at Newtown Square was above its 6 foot flood stage from 431 a.m. EST through 942 a.m. EST on the 21st. It crested at 7.41 feet at 715 a.m. The Chester Creek near Chester was above its 8 foot flood stage from 608 a.m. EST through 815 a.m. EST on the 21st. It crested at 8.4 feet at 7 a.m. EST. The Brandywine Creek at Chadds Ford was above its 9 foot flood stage from 1157 a.m. EST through 330 p.m. EST on the 21st. It crested at 9.12 feet at 240 p.m. EST. Event precipitation totals included 2.31 inches in Media.

Coastal Flood in LOWER BUCKS, PENNSYLVANIA
From 21-DEC-12 07:00:00 to 21-DEC-12 11:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Strong Wind in LOWER BUCKS, PENNSYLVANIA
From 21-DEC-12 05:00:00 to 21-DEC-12 08:00:00 (EST-5)
Magnitude: 48.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Mesonet