Unusual summer nor’easter brings heavy rain, gales and rough seas to the coastal Atlantic

An abnormally strong low pressure system impacted the Mid-Atlantic States over the weekend. During the time of year when attention usually turns to the tropics, a winter-like Nor’easter lashed areas from D.C. to Atlantic City. The storm was spawned by a broad 500mb Analysis valid 12z 29 July 2017deep-layer trough diving into the northeastern United States from Ontario. An extended area of surface low pressure formed on Friday morning. This low stretched from Boston southwestward through West Virginia before becoming organized over Virginia during the afternoon hours. Above average sea-surface temperatures allowed ample moisture to push across the Delmarva Peninsula toward the nation’s capital. Widespread heavy rain showers developed Friday afternoon and evening, and flash flood warnings were issued from D.C. to Baltimore. Before the storm wound down on Saturday, over four inches of rain had fallen across Maryland’s most populous city, with areas to the east seeing almost six inches of rainfall.

Conditions were no better offshore, where Gale Warnings were issued from Morehead City, North Carolina to Cape Cod, Massachusetts. As the system was developing, model guidance indicated the potential for wind gusts near 70mph offshore, which is near hurricane force. Fortunately, these extreme winds did not materialize, but widespread sustained winds in excess of 35mph were noted from the Chesapeake Bay northeastward toward Rhode Island. This allowed seas to become quite rough, with significant heights pushing 12 feet just off the coast of Delaware Saturday evening.

The unseasonable strong storm finally subsided on Sunday while quickly moving east of the region. Although not tropical in nature, this weekend’s system was a reminder that the East Coast is entering the time of year where weather becomes the forefront of the mind, and this could be even more the case this August, as it looks to be particularly active in the tropics. Stay tuned!

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