Mid Atlantic Cold Wedge

One of the toughest forecast scenarios in the mid Atlatntic region involves cold air wedges. A cold air wedge is a result of warm air moving north and riding up and over the top of cold, dense air banked up against the Appalachian mountains. The cold, dense air hugs the eastern slope of the mountains and extends east across the piedmont to the coastal plain. As the warm air advances, it rides up and over the mountains, resulting in milder temperatures at the normally colder high elevations of West Virginia and western Maryland. Warm also sweeps up the bay and spreads over the coastal plain. The last parts of the cold wedge to give way are typically the pockets of air tucked in the mountain valleys and the chilly air that is trapped at the eastern base of the mountains, which can extend east nearly to the Chesapeake. The map shown here displays the warm front, the leading edge of the warm air, at 5:00pm on Friday afternoon, April 4, 2008 as it passes through West Virginia and western Maryland and rides up onto the eastern shore. A temperatures of 70° at Cambridge, MD, 71° at the Patuxent Naval Air Station in St. Mary’s County and 71° at Richmond, VA contrast with the cooler 52° at Westminster, MD, 47° at Hagerstown, MD and 49° at Harrisburg, PA. Computer models have a difficult time predicting the movement of warm fronts in this scenario because the wedge is a relatively small scale feature .

Tom Tasselmyer


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