Eastern U.S. Flood Threat to Continue No Matter Where Hurricane Joaquin Tracks (FORECAST)

Chris Dolce
Published: September 30,2015
The forecast for the East Coast is looking increasingly ominous as a complex weather pattern promises to deliver more heavy rainfall to a region that is already dealing with flooding from recent deluges.
Thursday through this weekend, deep tropical moisture from the Caribbean Sea and the western Atlantic will be involved in this soaking setup as a front stalls near the East Coast.
Significant impacts are likely in portions of the East, whether Hurricane Joaquin tracks towards the United States or not, due to the large-scale weather pattern taking shape. This will include, flash flooding, river flooding, gusty winds, high surf, beach erosion and some coastal flooding at high tide.
(MORE: Latest on Joaquin)
Heavy rain that impacted northern New England on Wednesday has since moved out of the area. This batch of moisture-rich air came from the Gulf of Mexico and fueled torrential downpours along a slow-moving cold front. This brought significant flooding to parts of Virginia, New York, North Carolina, Maine, Maryland, Pennsylvania and Ohio.
Several daily rainfall records were set on Wednesday in New England, some of which include Portland, Maine with 5.56 inches (previous record was 2.14 inches in 1920), Boston, Massachusetts with 2.46 inches (previous record was 1.26 inches in 1899) and Providence, Rhode Island with 2.02 inches (previous record was 0.95 inches in 1946).
(MORE: Serious Flooding Reported in Multiple States)

Rainfall Totals Since Sept. 23

The National Weather Service continues flood watches through Thursday morning for parts of Maine.
(MAPS: Interactive Radar | Flood Alerts)

Current Radar

Thursday Through This Weekend: More Heavy Rain; Wind, Coastal Impacts Possible

As the aforementioned front stalls, a jet stream dip will dig south across the eastern states. This will allow one or more waves of low pressure to develop along the front, helping to pull more rain into parts of the East.

Setup Late Week-Weekend

At the same time, strong high pressure in eastern Canada will help create a large pressure gradient along the East Coast, increasing the potential for gusty winds, coastal flooding, high surf and beach erosion.
The rain and coastal impacts would begin in advance of any threat from Hurricane Joaquin. Uncertainty remains high on where Joaquin will eventually track. However, even if the center does not make a direct hit on the U.S., rich tropical moisture will still be involved in the soaking setup in the East. For more details on the uncertainties with Joaquin, click the link below.
(MORE: Latest Forecast for Hurricane Joaquin)
Here are the potential impacts on the table starting Thursday and lasting through this weekend, no matter whether Joaquin approaches the U.S. or not:
Rainfall, Flooding: River flooding and flash flooding are both likely in parts of the East. There is uncertainty regarding where the heaviest rain may occur; however, areas from the Mid-Atlantic to the central Appalachians and the Carolinas appear to be the epicenter for the heaviest rainfall amounts. Totals could exceed 5 inches in many locations, with some areas having the potential to see a foot of rain. Areas farther north into New England should also monitor this situation as well.

Rainfall Forecast: Next 7 Days

Increasing Winds: The gradient between lower pressure near the stalled front and a strong area of high pressure anchored from eastern Canada into the Midwest will help increase winds late this week. Depending on how this weather pattern unfolds, the strong winds could impact coastal areas of the Northeast and Mid-Atlantic right through this weekend. If Joaquin approached the U.S. coast, there would be a core of much stronger winds, but that remains very uncertain.
The National Weather Service has already hoisted high wind watches valid Friday and Saturday for parts of southern New Jersey in anticipation of this windy setup, which could produce gusts of 50 to 60 mph.
Coastal Impacts: The winds could contribute to high surf, beach erosion and coastal flooding in some locations along the Northeast and the Mid-Atlantic coast.
The National Weather Service has issued coastal flood watches for the Jersey shore, the Delaware beaches, and areas surrounding Delaware Bay and the tidal section of the lower Delaware River, including Philadelphia.
According to the watch bulletin, major coastal flooding may occur along the Delaware beaches and the Atlantic-facing coastlines of Cape May and Atlantic counties in southern New Jersey. This means flooding may be severe enough not only to flood numerous roads in coastal areas, but also to flood homes and businesses.
Check back with weather.com for updates in the days ahead as we provide more specifics on this forecast.

MORE: Retired Atlantic Hurricane Names