A moderate (4 out of 5) risk for severe weather exists across parts of Pennsylvania and New York this afternoon ahead of thunderstorms that could produce widespread damaging winds in excess of 75 MPH at times. In addition to the wind risk, hail the size of ping pong balls and even a tornado or two are possible.
A severe thunderstorm watch is in effect for a huge swath of real estate from upstate New York through central West Virginia, with a high risk for severe winds (greater than 58 MPH) and a moderate risk for winds greater than 75 MPH in and around the watch area.
The High Resolution Rapid Refresh (HRRR) model run from a couple of hours ago shows a strong line of thunderstorms developing ahead of a cold front moving across the moderate risk area.
The Storm Prediction Center notes in its latest forecast that the convection that develops on weather models resembles previous "serial derecho" events, or a long line of multiple bow echoes that can that can produce widespread wind damage. While serial derechos are often not as strong as progressive derechos — two examples of which occurred last week in the Midwest — they can produce damage over a much larger area.
Don't focus too heavily on the terminology, though. Calling a storm a "derecho" is mostly an argument for weather geeks to kill each other over; whether or not a storm is considered a derecho is immaterial to the people affected by wind damage.
It's worth noting that the same run of the HRRR model shows the squall line (above) surviving all the way east to the I-95 corridor by sunset. If this happens and how strong it'll be when it arrives remains to be seen, but folks anywhere from Greensboro, North Carolina to Burlington, Vermont should be aware that there's a chance of strong storms this evening.
The saving grace for the heavily populated metro areas is that the storms will have less instability to work with as the sun sets, so the storms probably won't be too strong by the time they make it this far east. It's still a good idea to keep an eye on the forecasts in case a warning is issued.
[Images via the SPC and WeatherBELL]