The most populous part of the US will be at risk for a few strong to severe storms Thursday afternoon. This region includes the I-95 corridor from Portland, ME to Washington, DC, and some of the storms may bring localized damaging winds with them.
This comes as a cold front associated with a shortwave trough moves east across the northeastern US and southern Canada. This cold front will move through the Northeast megalopolis in the afternoon, running into the hot and humid conditions. Temperatures in many areas will be in the 90s, spurring a Heat Advisory, while dew points rise to around 70 degrees. This will promote moderate instability, which will help storms to develop.
Not all of the ingredients will be in place, however, to promote the development of thunderstorms. Lapse rates will be weak, which is basically a measure of how much the temperature decreases by height. Wind shear will also be on the low end of the spectrum, so that will limit the risk for some of the more severe weather.
Nonetheless, there will be thunderstorms that form, bringing thunder and lightening. This morning, a line of scattered showers can be seen moving southeast ahead of the cold front, from the eastern Great Lakes to northern New England. By the mid-afternoon, those showers will run into the more conducive environment near the coast, allowing for the storms to rapidly develop. The most widespread of these storms looks to be hitting southern New England from 4 to 9pm EDT, while pther storms remain more hit or miss to the south across the Mid-Atlantic.
Heavy rain and localized flash flooding may also be an issue these storms may bring. Some towns may receive over an inch of rain, which has caused the Weather Prediction Center to issue a Slight Risk for excessive rainfall for coastal sections of the Northeast. This means there is a 10-20% chance for flash flooding to occur within 25 miles of a point in the area deemed a risk.
Once this front clears out, drier and cooler weather will prevail for the end of the week before a new round of heavy rain associated with Gordon’s remnants move in by early-next week.