[NOAA's HRRR model forecast map for radar reflectivity at 4pm today]
A squall line is now forming across eastern Ohio and it will intensify over the next couple of hours as it moves into western Pennsylvania, western New York and West Virginia. The combination of a strong cold front, very humid air mass, and impressive upper level support will help to generate strong-to-severe thunderstorms as the afternoon progresses. While the squall line should weaken slightly by the time it reaches the I-95 corridor, some nasty storms should make it all the way into the northern and western suburbs by this evening. NOAA’s latest High Resolution Rapid Refresh (HRRR) computer forecast model predicts the squall line will be in western Pennsylvania at 4pm (above) and then it'll reach the I-95 corridor by 8pm (below) - albeit in a slightly weakened state. The timetable for the arrival of this line of thunderstorms in the big cities along I-95 is as follows: 6-9pm in DC, 7-10 pm in Philly, and 8-11pm in the NYC metro region. Any storm that makes it into the I-95 corridor can produce damaging wind gusts, hail, and brief heavy rainfall with the highest chance for severe weather to the north and west of I-95.
[NOAA's HRRR model forecast map for radar reflectivity at 8pm today]