The last two weeks of weather in the Northeast have been rather stagnant, with a tropical airmass from the Deep South bringing rounds of heavy rain, flooding, severe storms and extreme heat to the region. While that pattern has finally come to an end, we’ll still be dealing with the heat and severe weather side of things for the next 48 hours.
Already this morning we’re watching a broken line of scattered showers mixed with pockets of heavier rain and lightning across the US/Canadian border. As this line crashes southeastward, a rather ripe and unstable atmosphere will allow for isolated severe storms to form.
The most recent mesoscale, short-range guidance is all pointing towards a similar story this afternoon, centered around scattered, severe storms forming mainly after 1 PM. A broken line of storms will be the main area we want to keep an eye on, but we’ll likely see more development ahead of this line in the form of isolated severe storms.
The good news is that atmospheric conditions shouldn’t be unstable enough to produce any storms that are extreme. Our main concern going into the afternoon and evening hours will be gusty winds, heavy rain, and some small hail. This will take place mostly between 1 PM and 7 PM ET, with the interior Northeast facing the highest risk. By time the storms move south of the line from Harrisburg PA to Albany NY, they should begin to fizzle out and become mostly just scattered heavier rain showers.
The entire region, from the central Midwest to western Pennsylvania and upstate New York to northern New England, will be the main area to watch for these type of scattered severe storms. This includes major cities such as Columbus OH, Pittsburgh PA, Syracuse NY, Albany NY, Concord NH, and Augusta ME. Closer to the coast and along the I-95 corridor, isolated storms will be possible, but the majority of action will move in after 7 PM, allowing for the severe threat to dwindle significantly. With that being said, we can’t totally rule out a few scattered strong storms ahead of the main line. Mesoscale guidance such as the NAM 3km is the most aggressive, with storms forming and lasting towards the coastline.
Tomorrow we look at yet another day of scattered severe storms, with the focus this time slightly further south and confined to a smaller region. A weak disturbance coming from the west will allow for more thunderstorms to bubble up and push towards the coastline. Rather than the standard line and movement of storms from the interior Northeast to the coast, we’ll be watching storms develop from the west, moving almost due eastbound towards the shore starting during the late afternoon and evening hours.
We’re looking at fairly similar types of storms overall during this day two event. There will be more in the way of scattered hail, gusty winds, and heavy rain. The isolated spin up of a storm or two cannot be ruled out. We may even see the SPC try and go ahead, with a smaller region highlighted in a slight risk on the northern and southern end of the larger marginal risk area. Mesoscale guidance is highlighting this event to start later than the one today, with the main timeframe for severe risk ranging from 4 PM to 9 PM ET.
Western Pennsylvania and the lower half of upstate New York will kick off the event, with scattered severe storms also impacting West Virginia, northern Virginia, and much of western Maryland. By the evening hours, eastern Pennsylvania, the Lower Hudson Valley and southern New England will be at risk as well. This will include cities from Erie PA to Binghamton NY, down to the extreme western suburbs of Washington DC and Baltimore. Scranton PA, Albany NY, and even the western-most suburbs of New York City will be at risk during the late evening and early overnight hours as well.
As we lose energy from the sun, these storms should quickly dissipate, leaving behind just some scattered rain showers for most of the I-95 corridor and immediate coastline. Again, depending on exactly how fast these storms move towards the shore, we could see a continued threat of stronger storms even to the ocean. We’ll be keeping a close eye out.