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 Maryland 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 during the early morning on the 21st that resulted in peak wind gusts of around 45 mph across the Eastern Shore and knocked over weak tree limbs and wires. In Grasonville (Queen Anne's County), the strong winds not only snapped a tree, but also damaged a greenhouse. Peak wind gusts included 49 mph in Salisbury (Wicomico County) and 43 mph at the Baltimore-Washington International Airport.
In addition, the significant southeast flow allowed water to pile up into Chesapeake Bay. Once the winds shifted to the west, the higher tidal departures shifted to the Eastern Shore and producing moderate tidal flooding in Queen Anne's, Talbot and Caroline Counties and minor tidal flooding in Kent and Cecil Counties at the time of high tide during the daytime of the 21st. Moderate to heavy rain also fell across the Eastern Shore, with storm totals ranging between 1 to 2 inches.  In Queen Anne's County, Maryland State Route 18 was covered with water from exit 42 at Kent Narrows to exit 43A in Grasonville. Tidal flooding along Maryland State Route 18 also occurred in Queenstown adjacent to the Little Queenstown Creek. Flood waters nearly reached one home. In the Kent Narrows area, tidal flooding also occurred in and around Mears Point Marina north of U.S. Route 50. People were wading through the flood waters with boots.
Minor to moderate tidal flooding occurred in the Chesapeake Bay during the morning and afternoon high tide cycle on the 21st. High tide in Cambridge (Dorchester County) reached 4.70 feet above mean lower low water. Moderate tidal flooding starts at 4.5 feet above mean lower low water.  High tide at Tolchester Beach reached 4.17 feet above mean lower low water. Minor tidal flooding starts at 3.5 feet above mean lower low water.

Coastal Flood in CAROLINE, MARYLAND
From 21-DEC-12 10:00:00 to 21-DEC-12 13:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: WLON

Coastal Flood in TALBOT, MARYLAND
From 21-DEC-12 11:00:00 to 21-DEC-12 13:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: WLON

Coastal Flood in QUEEN ANNES, MARYLAND
From 21-DEC-12 12:00:00 to 21-DEC-12 15:00:00 (EST-5)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: WLON

Strong Wind in CAROLINE, MARYLAND
From 21-DEC-12 01:00:00 to 21-DEC-12 05:00:00 (EST-5)
Magnitude: 42.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Mesonet

Strong Wind in TALBOT, MARYLAND
From 21-DEC-12 01:00:00 to 21-DEC-12 05:00:00 (EST-5)
Magnitude: 42.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Mesonet

Strong Wind in CECIL, MARYLAND
From 21-DEC-12 01:00:00 to 21-DEC-12 05:00:00 (EST-5)
Magnitude: 40.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Mesonet

Strong Wind in QUEEN ANNES, MARYLAND
From 21-DEC-12 01:00:00 to 21-DEC-12 05:00:00 (EST-5)
Magnitude: 42.00 EG
Property damage: 6.00K
Crop damage: 0.00K
Reported by: Mesonet

Strong Wind in KENT, MARYLAND
From 21-DEC-12 01:00:00 to 21-DEC-12 05:00:00 (EST-5)
Magnitude: 40.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Mesonet