Before this heat takes hold, a complex of thunderstorms, with a long history of producing damaging winds, could impact the region tonight.
The storm complex, or mesoscale convective system, is currently moving through central Ohio. If it holds together, it would probably impact the metro region some time between 7 p.m. and midnight.
The illustration to the left illustrates that there is 70% chance of the presence of the ingredients - namely instability and wind shear - needed for severe thunderstorms this evening around the region (i.e. that the Craven-Brooks significant severe weather parameter will exceeed 20,000 m3/s3). Note: this does not mean there is a 70% chance of severe thunderstorms - it just means there’s a good chance the atmosphere could support them if they survive their journey through the mountains - about a 40-50% chance.
If you’ve forgotten how to interpret dew points, here’s a chart we posted a couple years ago which serves as an easy-to-understand guide:
How Humid it Feels (and subjective description)
|Below 55||Dry (Pleasant)|
|55-60||Hint of humidity (Still comfortable)|
|65-70||Sticky (Becoming unpleasant)|
|Above 75||Sultry (Oppressive and unbearable)|
Humidity levels will be similarly high tomorrow, and the storm risk returns. Of course, many will anxiously await the storms to snap what could be record-breaking heat. Tuesday’s record highs of 99 (from 1908) at Reagan National, and 97 at BWI and Dulles (from 1908 and 1986) will all be in play.