The entire Northeast coast was told Friday to be prepared for flooding, high winds, widespread power outages and even snow early next week as Hurricane Sandy made its way north after killing 41 people in the Caribbean.
"It will be unpredictable until the last minute," Jim Cisco, a forecaster at the National Weather Service's prediction office, told NBC News. "That really is the truth of the situation ... we're not sure how it's going to behave."
That's because Sandy will be making a hard west turn from the Atlantic, a rare occurrence. "It's coming in at a sharper angle" than previous storms because cold air moving in from the Northern Plains is undercutting Sandy's circulation, Cisco added.
On top of that, a new lunar cycle will bring high tides Sunday, Monday and Tuesday -- adding to the storm surge from Sandy.
On Friday evening, Sandy was packing 75 mph winds and was centered about 90 miles north of Great Abaco Island and 400 miles southeast of Charleston, S.C. The hurricane was moving northward about 7 mph. Hurricane force winds extended 35 miles from Sandy's center; tropical storm force winds reached out 275 miles.
"We haven't had much precedent for a storm like this," Cisco said. "Its effects may surprise even us."
Here's a look at what some of those effects might be:
Storm surge: It's still too early to predict exactly where the surge will be worst, James Franklin of the National Hurricane Center told reporters Friday, but "somebody is going to get a significant surge impact from this."
NBC News meteorologist Bill Karins said current data indicates "the most likely location for this to occur is along Delaware/New Jersey shores followed by Long Island and coastal Connecticut."
High winds: Those will blow through an area "several hundred miles across," said Franklin, adding that New York City could see tropical storm force winds.
Karins expected "40-60 mph sustained winds over the region for 24-48 hours. Gusts along the coast could reach 80 mph, while inland gusts will likely peak in the 60-70 mph range."
Heavy snow: Parts of West Virginia and the Appalachian corridor are likely to see more than a foot and possibly up two two feet, Louis Uccellini, director of the National Centers for Environmental Protection, told reporters.
Rainfall: 5-10 inches are expected from the Outer Banks up into New York City, Karins said. "River levels are currently running low which helps, he added. "Flash flooding of small creeks and streams is certain due to high rainfall rates but major rivers have a better chance of staying within their banks."
Landfall: Sandy's core could hit anywhere between the Mid-Atlantic and the New York area. F or now, Cisco said, Sandy is projected to make landfall near Delaware Bay, just south of New Jersey.Video: Carolinas, East Coast on watch for Hurricane Sandy
Although Sandy is not forecast to be as strong as other recent storms to hit the Northeast -- such as Hurricane Irene in August 2011, which left $4 billion in damage -- it holds the potential to cause significant damage because it will be moving slowly.
Some experts predict at least $1 billion in damage in the United States.
"It's almost a weeklong, five-day, six-day event," Cisco said. "It's going to be a widespread serious storm."
Sandy could even weaken to below tropical storm status but "that doesn't matter much with respect to impacts," Uccellini said.
"The legacy of this storm will likely be coastal storm surge flooding and power outages," Karins said, while adding: "Everyone within 200 miles of the Northeast coast should hope for the best, but prepare for the worst: 5-7 days without power and short term loss of fresh water."
Sandy will also be hitting the Northeast on the 21st anniversary of the infamous "Perfect Storm" of Oct. 30, 1991, that killed six fishermen.
In related developments:
- Most of Florida was under a tropical storm warning, with coastal areas seeing high surf, winds and rain.
- In New Jersey, Cape May County urged people to leave its barrier islands by Saturday.
- Philadelphia urged residents of flood-prone neighborhoods to leave their homes by Sunday afternoon.
- Maryland and Virginia declared a state of emergency so as to free up resources ahead of time.
- New York City said it will suspend all construction work starting Saturday and until further notice. The worst for the city should be Monday through Tuesday, NBCNewYork.com reported.
Caribbean deaths, damage
Sandy was exiting the Bahamas on Friday, having weakend from a Category 2 to a Category 1 overnight.
The number of deaths blamed on Sandy's torrential rains and heavy winds jumped to 31. Below's a look by country.
Haiti: Sandy triggered flash floods and landslides that killed 26. The dead included a family of five in Grand-Goave, west of the capital Port-au-Prince, killed in a landslide that destroyed their home, authorities said.Slideshow: Recovering after Sandy (on this page)
Cuba: 11 deaths were reported, among them a 4-month-old baby, NBC News' Mary Murray reported from Havana. Most were killed by falling trees or in building collapses in Santiago de Cuba province and neighboring Guantanamo province. Hundreds of homes were destroyed or damaged.
Dominican Republic: Two deaths were reported but details were not available.
Bahamas: A death was reported and some islands saw extensive damage. "It was way stronger than we expected," said Joel Friese, general manager of the Stella Maris Resort on Long Island. "There are lots of downed trees and partial to heavy roof damage on some of the buildings." Several islands also saw power outages.
Jamaica: A man was crushed by a boulder and many areas were flooded or saw wind damage on the eastern side of the island.
The Associated Press and Reuters contributed to this report.