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       An area of developing low pressure off the Florida coastline is expected to sweep up the southeastern coast and make landfall in the Mid-Atlantic this weekend. The National Hurricane Center is monitoring the subtropical system, which will bring plentiful rainfall, rough surf, strong gusty winds and coastal flooding, affecting the majority of major East Coast cities and bringing a dreary, dank weekend.

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       Tropical storm warnings have been issued from Cape Fear, N.C., to the Delaware-Maryland border on the Delmarva Peninsula, as well as for the Chesapeake Bay south of Smith Point. Albemarle and Pamlico Sounds in the Carolinas are also included. Similar regions are also under a storm surge watch.

       “There is a possibility of life-threatening inundation from rising water moving inland from the coastline,” the National Weather Service wrote. That’s especially true around Virginia Beach, the North Carolina Outer Banks and along the Chesapeake Bay. That’s where a storm surge of 3 feet or more is possible, due to strong onshore flow that will pile water against the coast.

       Some places could see a month’s worth of rainfall as the waterlogged system trudges north. The system appears likely to acquire subtropical characteristics and earn the name Ophelia. A subtropical storm is a hybrid storm sharing the characteristics of a nor’easter and tropical storm.

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       The wind-swept soaker will breeze into New England on Sunday, finally dissipating into early next week.

       Track and impacts

       The storm is expected to be located several hundred miles offshore of North Carolina on Friday afternoon, and then make landfall on or skim very close to the Outer Banks Saturday morning. Thereafter, it will continue parallel to or up the Chesapeake Bay and probably will continue to strengthen. It will then weaken Sunday into Monday.

       The storm is expected to deliver a slew of impacts, including:

       Strong winds. Subtropical storms have a broader wind field than their purely tropical counterparts. That means more people will face strong, gusty winds. Gusts of 40 mph will be common along the Interstate 95 corridor inland from the Carolinas to New York City, with gusts up to 50 to 60 mph along the coastline. The strongest winds will come Saturday for most locales. Storm surge/coastal flooding. Near and north of the storm’s center, onshore flow will pile water against the coastline. Given the more expansive wind field, storm surge will probably be more widespread and significant than with a traditional tropical storm. Many coastal tide gauges in the Mid-Atlantic are predicted to face moderate to major flooding. In some places, a surge of 3 to 4 feet and perhaps more is expected.

       Heavy rainfall. Most major East Coast cities will see 2 to 4 inches of rain, with a few areas topping 5 inches. That’s equivalent to perhaps a month’s worth of rainfall. There will be an abrupt western cutoff to the rain, but eastern North Carolina, eastern Virginia, the entire Delmarva Peninsula and far-southern New England will be drenched.

       Rough surf and rip currents. Offshore waves of 25 to 30 feet are likely, with dangerous rip currents for the entire East Coast. Entering the water will be perilous — even as far away as Florida or Cape Cod. Severe weather/isolated tornado risk. If the storm system’s center tracks farther inland, a ribbon of warm, moist air may be dragged northwestward across the Outer Banks and the southern Delmarva. With the changing winds with height associated with the parent storm system, an isolated rotating thunderstorm or tornado can’t be ruled out. This is a low risk but not zero.

       The setup

       A stationary front draped across south-central Florida has been a focal mechanism for daily afternoon thunderstorms. That same stationary front extends into the southwestern Atlantic Ocean. A weak wave of low pressure will develop on that front in the next 12 hours somewhere north of the Bahamas.

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       An approaching pocket of high-altitude cold air, low pressure and spin will sweep southeast out of the Plains, moving over our fledgling surface low. That will lift air up and away from the surface low, intensifying it. By midday Friday, it will be a solid storm.

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       Around that time, it will pass over the Gulf Stream on its way toward the Chesapeake Bay. The warm Gulf Stream waters will help an uptick in convection, or thunderstorm activity, near the storm’s center. That could lead to it being classified as “subtropical” — part nor’easter, part tropical.

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