(CNN)A powerful storm in the Washington DC-Baltimore area could cause significant tidal flooding over the next two days, according to forecasters.
“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 (NWS) said in a tweet.
With two to four feet of coastal flooding expected, more than 20 million people are under alerts, including residents of Baltimore and Washington. Parts of northern Virginia are also under a flood watch through Friday afternoon, NWS said.
To help Baltimore residents prepare for the potentially historic storm, the city’s Department of Transportation will distribute sandbags to residents from 9 a.m. to 3 p.m. 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 that 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 already preparing for flooding
By 1 a.m. Friday, the Potomac River in Washington, DC, experienced minor flooding, which was expected to get worse into Saturday before subsiding, according to the NWS. The Severn River in Annapolis, Maryland, will also see similar conditions.
And high wind warnings and wind advisories are also in effect for several counties as wind gusts are expected to reach as high as 60 miles per hour.
“Damaging winds will blow down trees and power lines. Widespread power outages are expected. Travel will be difficult, especially for high profile vehicles,” the local NWS said.
Businesses were bracing for the impact by placing sandbags to protect their premises.
In Alexandria, Stu Robinson, the general manager at Misha’s Coffee, removed all outdoor furniture and started loading sandbags, CNN affiliate WTTG reported.
Konrad Karandy, who manages Mission BBQ in Annapolis, told CNN affiliate WJZ that he’s doing everything he can 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 that 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 will close due to the potential flooding, according to the the affiliate.
CNN’s Allison Chinchar contributed to this report.
