Florence continued its path toward the East Coast overnight Monday, maintaining its monstrous Category 4 storm status and 140-mph winds.

The National Hurricane Center is calling the storm “extremely dangerous,” and predicts it could still strengthen to near Category 5 intensity on Tuesday. The center issued hurricane and storm surge watches for the East Coast from Edisto Beach, South Carolina, northward to the North Carolina-Virginia border, including the Pamlico and Albemarle sounds.

Computer-model forecasts generally project the storm to make landfall between northern South Carolina and North Carolina’s Outer Banks as a Category 4 on Thursday, although shifts in the track are possible and storm impacts will expand great distances beyond where landfall occurs. More than 1.5 million people have already evacuated coastal areas ahead of the storm.

The center is warning of an “extremely dangerous” triple threat in the Carolinas and Virginia:

1) A “life-threatening storm surge” at the coast – a rise in ocean water over normally dry land.

2) “Life-threatening freshwater flooding from a prolonged and exceptionally heavy rainfall event” from the coast to interior sections.

3) “Damaging hurricane-force winds” at the coast and some distance inland.

Like Hurricane Harvey, which stalled over Texas in 2017, Florence could linger over the Southeast for several days after landfall. Forecast models suggest that more than two feet of rain could fall over the higher elevations of the Carolinas and Virginia, which would generate dangerous flooding downstream. The flooding might be similar to what the Carolinas experienced during Hurricane Matthew in 2016.

At 5 a.m. Tuesday, Florence was tracking west-northwest at 15 mph, and located about 975 miles east-southeast of Cape Fear, North Carolina. Its zone of hurricane-force winds doubled in size Monday as it explosively strengthened.

If Florence makes landfall as a Category 4 in North Carolina, it would be the strongest storm to come ashore that far north on record.

In coastal areas of the Southeast and Mid-Atlantic, heavy surf and elevated water levels are expected to arrive by Wednesday morning, and rainfall could begin by Thursday morning.

Tropical-storm-force winds could reach the coastline as early as Wednesday night, at which point all outdoor preparations should be completed. Extremely dangerous hurricane-force winds could batter coastal locations Thursday into Friday. Hurricane-to-tropical-storm-force winds could extend inland, depending on the storm’s track.

Models have come into agreement that a northward turn before reaching the United States is unlikely and that a building high-pressure zone north of the storm will cause it to slow or stall once it reaches the coast or shortly thereafter. Rainfall could begin Friday or Saturday and continue into the following week. Where exactly the zone of heaviest rain will be is a big uncertainty. It could reasonably occur anywhere between the mountains and the coast.

If the storm stalls, some areas could see feet of rain, especially if downpours focus over the higher terrain in western North Carolina and southwestern and central Virginia.

This region will be particularly susceptible to flooding because of far-above-normal rainfall in the region since May. In addition, because the ground is likely to be saturated, trees will be vulnerable in strong winds.

Parts of the Mid-Atlantic, especially from Virginia to Pennsylvania, have received 150 to 300 percent of their normal rainfall since May.

Residents farther north in coastal and inland areas in the Delmarva Peninsula, New Jersey, Pennsylvania and New York should also monitor the storm and prepare in case the forecast shifts to the north and east.

Where the storm makes landfall has implications for where the strongest winds and biggest rise in water at the coast occurs, but strong winds and extreme rainfall could occur at great distances from the landfall location. Keeping this in mind, here is the likelihood of landfall at different locations based on our evaluation of model data:

– 70 percent in the Carolinas;

– 10 percent between Virginia and New York;

– 10 percent offshore; and

– 10 percent between northern Florida and Georgia.

Even in the unlikely event that the storm center remains just offshore, it will almost certainly come close enough to bring dangerous wind and flooding to coastal areas. Inland areas may be somewhat spared in this scenario.

If a major hurricane (Category 3 or higher) does make landfall along the Southeast coast, the rarity of such an event is relevant. Since 1851, only 10 major hurricanes have done so, and the most recent was Fran in 1996, 22 years ago. Hugo in 1989 was the one before that and was a Category 4 at landfall. No hurricane has made landfall as a Category 5 in this region on record.

Many people in the Southeast and Mid-Atlantic probably have not experienced a storm of the potential magnitude of Florence.