Heavy Rain Could Bring Flash Flooding to the Coast From Virginia to Massachusetts

The rain is here in the Northeast. After weeks of dry conditions and pleasant autumn weather, a cold front is bringing noticeably cooler temperatures and rain to this corner of the country. Here is a look at what is happening now and what to expect this weekend.

Dry and Warm Streak Over in the Northeast

It was a toasty day in the biggest cities in the Northeast on Wednesday, making the arrival of the cool front on Thursday even more dramatic. Temperatures hovered in the upper 70s in Pittsburgh, Buffalo, and Boston just ahead of the weather change.  

The cooler temperatures will be accompanied by a surge of moisture, including the threat of thunderstorms across the Appalachians, the Great Lakes, the mid-Atlantic, and up into New England. It has been weeks since many areas of the East have seen measurable rainfall. This means that roads are likely to be slippery at the onset of the rain due to the buildup of oil and other residue. Motorists are being advised to allow extra space for stopping as tires may not have as much grip.

In addition to the residue buildup, wet leaves will also contribute to the slippery roadways. The recently fallen leaves may also clog storm drains in areas where rain comes down at a fast clip.

The heaviest rainfall is forecast to fall along a narrow corridor stretching from southeastern Virginia and to the north through the Delmarva Peninsula, New Jersey, coastal New York, and into southeastern Massachusetts. The stalling of the front along the coastline of this region late Friday and into Saturday will be the culprit of this persistent rain.

The precise spot where this front stalls will determine which major cities become targets for the torrential rain. Forecasters are warning that the major metro areas of New York City, Washington, D.C., Philadelphia, and Boston may end up on the fringe of this heavy rain zone. Flash flooding is a possibility in this zone, particularly in areas where the most potent rain bands refuse to budge.

Widespread rain totals of 1 to 4 inches are possible along this narrow rain corridor. The moisture began to pick up late Thursday and is forecast to continue through the day and night on Friday. Rainfall rates of about an inch an hour will quickly overwhelm drainage systems and raise the threat of flooding.

The best-case scenario will send the heaviest rain bands offshore, limiting the amount of moisture that falls.

Mercury on a Downward Trajectory

Residents of the Northeast will also see significantly cooler temperatures heading into the weekend. In addition to the arrival of the cold front, a shift in the polar vortex will also allow some of the coldest air at the North Pole to escape and creep to the south. However, the timing of this vortex breakdown in early November means that the air will not be nearly as cold as when this happens in the dead of winter.

The chilliest air this weekend will be found over the Great Lakes and into the interior Northeast. Highs across these regions will top out in the 40s and near 50 degrees, coming in slightly below the historical average for the first weekend in November. The air will be cold enough in the higher terrains for a few snowflakes to mix in with the rain.

Intermittent peeks of sunshine may bring the temperatures up into the 50s or low 60s along the mid-Atlantic coastline. These readings are right about normal for this time of the year.

Winds will also pick up as the storm comes together. When combined with the clouds, real feel readings are likely to slide even lower. The good news is that the surge of precipitation and the cooler temperatures will lower the wildfire risk across the region even in light of the breezy conditions.

A more pronounced mass of cold air will dive down from Canada beginning the middle of next week. This influx of colder temperatures could bring the first real chance of snow to some parts of the northern U.S. We will continue to follow this potential development in the days ahead.

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