What has changed
No changes were made to the forecast. The Heat Advisory in effect for today expired as of 8PM. Additionally, the entire forecast area is under an Air Quality Alert for tomorrow as smoke from wildfires in Canada moves into the area.
What is an Area Forecast Discussion?
Area Forecast Discussions are the real forecasts, written 3 to 4 times daily by NWS meteorologists reading the models and interpreting what they mean for your area. They offer far deeper insight than any weather app, but they're written in dense meteorological shorthand. Plaincast uses Anthropic's Claude to summarize them into plain English, side by side with the annotated original.
Revised in 4 passages since the 2:40 PM discussion. See every revision.
Messages
1) Hot and hazy conditions persist through Friday with a chance of a couple strong storms through this evening.
2) A strong cold front brings the threat of severe weather Saturday, possibly lingering into Sunday to the south.
3) High pressure briefly returns Monday, then another strong frontal system crosses mid next week.
Discussion
KEY MESSAGE 1. Hot and hazy conditions persist through Friday with a chance of a couple strong storms through this evening.
Humidity has remained very elevated this afternoon, resulting in widespread heat indices of 100 to 109. Expect reduced mixing due to smoke aloft. Heat Advisories are in effect until 8pm for much of the area, with only a slow drop in temperatures this evening.
Satellite data has started flowing again as of early this afternoon. This reveals a large and rather thick plume of smoke emanating from wildfires in Canada. The thickest smoke is on the cool side of a front draped over PA to NJ, with a secondary weak boundary dangling down the west side of the Chesapeake Bay (enhanced by the bay breeze).
This conglomerate of boundaries, accentuated by differential heating along the edge of the thicker smoke, may be enough to ignite a few thunderstorms over northern to central MD heading into this evening. Given strong instability (MLCAPE 3000-4000 J/kg), DCAPE (1000-1500 J/kg), and ~40 knots effective bulk shear, any storms that form could produce very gusty winds. Large hail can't be ruled out given ample storm energy, sufficient shear, and mid- level lapse rates around 7 C/km.
The front will drop south tonight. North to northeast winds in its wake will advect drier air, but thick haze and smoke into the region. Air quality will become poor as a result through Friday. Visit airnow.gov for the latest air quality forecasts from the subject matter experts at state environmental agencies.
The front looks to stall near/south of I-64. A couple of thunderstorms may try to chance of rain up later in the afternoon near the Appalachians aided by orographic lift, but otherwise hazy and dry conditions will continue. temperatures rise into the 90s for much of the area, but lower humidity should keep heat indices below the century mark across the board.
This is the plain-text edition, decoded without AI so it loads anywhere. The full Plaincast experience — plain-English summaries beside the annotated original, with the forecast changelog — loads automatically with JavaScript, or open the interactive edition.