The mid-Atlantic will miss the worst of the storm, though some effects were being felt Friday and expected into Saturday. Then, Florence’s remnants could pose some threats.
Gov. Larry Hogan declared a state of emergency this week ahead of the storm, and a spokeswoman said Thursday he would leave the executive order in place into next week, to help coordinate aid to other states and also to be ready for Florence’s remnants.
Here are the possible hazards Florence could still bring:
Florence, and a high pressure system over the Northeast, were both bringing an easterly flow into Maryland. That was pushing waters on shore and could raise high tides by as much as 3 feet on the western shore of the Chesapeake Bay.
A coastal flood advisory is in effect for Anne Arundel and Calvert counties through Saturday evening. On the Potomac River, a coastal flood warning is in effect for St. Mary’s County, with a coastal flood advisory for Charles County.
Florence’s outermost bands could bring periods of heavy rain in Southern Maryland on Friday, but otherwise, as the hurricane moves toward South Carolina and Georgia, the rain threat is expected to diminish by Saturday.
The National Hurricane Center predicts Florence will be a post-tropical depression over western Pennsylvania by Tuesday, headed for New England by Wednesday. Depending on how much moisture the system still packs by then, it could bring more heavy rain to a region that has already been soaked and flooded repeatedly this summer.
Dan Hofmann, a meteorologist with the National Weather Service’s Baltimore/Washington forecast office, said downpours are likely along the track of Florence’s remnants — the question is just how far south and east they will extend as what is expected to become a post-tropical depression heads toward New England by the middle of the week.
“There’s still uncertainty in the track itself, and the moisture field is very large,” Hofmann said. “We’re going to be in an environment favorable for heavy rain.”
More rain across Pennsylvania could mean another surge of rising waters down the Susquehanna River and into the Chesapeake Bay. Rising waters from rain earlier this week already forced Exelon Corp. to open as many as 14 floodgates on the Conowingo Dam, causing some flooding around Port Deposit.
Similar deluges of fresh water in July and August have sent large amounts of trash and debris down the Susquehanna into the Chesapeake, and pollution they carried could have long-term consequences for the health of the bay. Susquehanna flow hit a record in August, and another round of heavy rain could make an already extreme year on the river even worse.
The highest risks of flooding associated with Florence’s remnants is expected west of the Blue Ridge, in western Virginia and Maryland, the National Weather Service said.