Break in the heat for early week, then back to dangerous heat on wednesday with a chance of severe weather

A refreshing airmass briefly overtakes the area Monday and Tuesday with temps mainly in the 80s on Monday and low 90s on Tuesday. Both days feature tolerable humidity and breezy-windy conditions with gusts possibly topping 30mph on Monday. No rain is expected either day.

By Wednesday, we shoot right back into the middle and upper 90s with heat index values over 100 once again. Luckily this will be short live as a stronger cold front moves through late evening and overnight, bringing thunderstorms and a cooler and drier airmass to end the week. Thursday and Friday should be mainly dry with increasingly sunny skies as well as temps only in the 80 to around 90ish with tolerable humidity. 

severe weather chances on wednesday

There is a good chance (a least 50%) of thunderstorms Wednesday late afternoon and evening, and its possible that some of these become severe. Temperatures along the east coast will rise well into the 90s, with middle and upper 90s likely in some areas. A belt of 20-30kts of wind shear also will overspread portions of the Northeast and Mid Atlantic states overlapping the northern portion of this hot airmass. Assuming dew points rise enough (they would need to reach the upper 60s at least), then there will be ample instability present. Since this instability will overlap this shear over portions of Maryland, Pennsylvania, and New Jersey, this is where a locally higher risk of perhaps some more widespread storms may occur. A cold front will approach from the west and as it intersects this modestly sheared and unstable airmass, thunderstorms will likely develop.

Looking at the parameters in place, the primary risk should be damaging winds as storms grow into clusters or line segments. There's enough wind shear present and some steepened mid level lapse rates that some small to perhaps even large hail could occur on an isolated basis. We currently are not expecting tornadoes to a concern but that's something we will closely monitor. Any storm will also be capable of producing frequent lightning and heavy rainfall. Again, this will all depend on how much instability develops which is reliant on both how much cloud cover there is and how high the dew points get. We will be able to fine tune this as we get closer.

There is no official outlook yet from the Storm Prediction Center, but I suspect that they will at least put us in a marginal risk (level 1/5) starting with the day 3 outlook issued at 3am Monday (for Wednesday).