(CNN)A powerful storm is flooding some Mid-Atlantic coastal areas Friday evening, and flooding is expected to continue in Washington, DC tonight -- part of what forecasters said could be the area's worst tidal flooding in the past two decades.
Strong winds are pushing water into Chesapeake Bay and Delaware Bay, and moving water inland, flooding the coasts of Maryland, Virginia, Delaware and New Jersey.
By late morning, water levels were running 3-4 feet above normal along parts of the Chesapeake -- and higher levels are expected later in the day or night, especially if stronger winds coincide with local high tides.
In Maryland's bayside capital of Annapolis, water was flowing over the City Dock area on Friday -- deep enough that a couple of people were paddling down Main Street in kayaks, CNN affiliate WBAL reported.
"One of the biggest tidal flood events of the past 10-20 years (possibly since Hurricane Isabel at some locales), is expected Friday & Saturday. Those along tidal shores should get ready for exceptional tidal inundation!" the local National Weather Service office in the Washington-Baltimore said in a tweet.
Coastal flood warnings and watches have been issued from Virginia to New Jersey, including for the residents of Washington, Baltimore and Philadelphia.
Friday evening Maryland's governor declared a state of emergency for all counties in coastal flood warnings.
Washington itself was facing a double threat Friday afternoon: Flooding not only from winds pushing water up from the Potomac River, but also heavy rain.
The rainfall, by itself, was expected to cause "creeks and streams to rise through late (Friday) afternoon," the weather service said.
The Potomac already reached major flood levels just southeast of the Jefferson Memorial Friday afternoon for the first time since 2003. Major flood stage is 7 feet and the gauge topped out at 7.12 feet. It could reach just above that height again after midnight, by which time parts of the Navy Yard and much of East Potomac Park already would have been flooded, according to the weather service.
People wade through floodwaters in downtown Annapolis, Maryland, on Friday.
To help Baltimore residents prepare for the potentially historic storm, the city's transportation department was distributing sandbags to residents Friday on a first-come, first-served basis, CNN affiliate WJZ reported.
The last time conditions were this bad was during Hurricane Isabel in 2003.
During the storm, Fell's Point in Baltimore, the US Naval Academy, downtown Annapolis, and the Belle View neighborhoods of northern Fairfax County, Virginia, all experienced severe storm surge flooding, according to the National Oceanic and Atmospheric Administration.
Businesses prepare for flooding
High wind warnings and wind advisories are also in effect for several counties as wind gusts are expected to reach as strong as 60 mph.
"Damaging winds will blow down trees and power lines. Widespread power outages are expected. Travel will be difficult, especially for high-profile vehicles," the weather service said.
Businesses were bracing for the impact by placing sandbags to protect their premises.
A man walks past an art gallery through floodwaters in downtown Annapolis, Maryland, on Friday.
In Alexandria, Stu Robinson, the general manager at Misha's Coffee, removed all outdoor furniture and started loading sandbags, CNN affiliate WTTG reported Thursday.
A day later, streets in historic Old Town Alexandria were flooded.
"We have a couple of blocks closed off down by the river due to flooding," Amanda Paga, Alexandria Police Department spokesperson, told CNN. "We have another high tide coming through overnight, and we will continue to monitor the area and stay on top of it. We are prepared."
Alexandria police shared photos of coastal flooding that closed several streets
Konrad Karandy, who manages Mission BBQ in Annapolis, told CNN affiliate WJZ Thursday he was doing everything he could to keep the water away from his business, including piling sandbags.
"We're prepping for the worst. My personal guess is four feet (of water), something like that," Karandy told the news outlet.
Sharon Mahaffey who works with Storm Bros. Ice Cream in Annapolis added: "We've already gotten sandbags out. We're moving supplies that could potentially get wet."
D.C. Homeland Security and Emergency Management Director Christopher Rodriguez told the outlet businesses along the coast will likely need their flood insurance documents ready.
"We want to make sure that our businesses that are along those coastal areas of our region, in particular our city, make sure you know where your insurance papers are, because flood insurance is going to be really helpful as we recover from this event over the next 48 hours," Rodriguez said.
And in Maryland, schools in Calvert and Harford counties announced Thursday night they would close due to the potential flooding, according to the affiliate.
