Tuesday 10 a.m.
There's quite a contrast in conditions between Michigan and Massachusetts. At mid-morning, Detroit had some sunshine with south to southwest winds bringing in milder air. Meanwhile, in the I-95 corridor from Boston to Baltimore, dreariness greeted the dawn and dampness lingered. The surface pressure pattern helps explain this. Along the East Coast, the flow is coming from the Atlantic. The isobars bend around over the Appalachians, and the flow west of there is from southwest to northeast. The lines become closer together as you move north through Michigan, and the wind increases to match that. Finally, the isobars at the far upper-left corner of the map peel away from their tight packing and assume more of a west to east orientation. The change occurs along a cold front that will speed to the east and off the New England coast tomorrow night.
This video explores the current situation and how things should progress for the rest of the week and this weekend.
Now, drier air has arrived, and most of the Northeast will have abundant sunshine today and tomorrow.
A front that will usher in slightly less humid air for the Northeast tomorrow will trigger locally strong thunderstorms today.
Thunderstorms will continue to erupt near the northern edge of the heatwave, enhanced by a series of disturbances rippling along in the upper air flow. This is the NWS Storm Prediction Center's severe thunderstorm outlook for today
... the main upper air steering current moves eastward across the northern Plains, then dives southeastward toward the Middle Atlantic states. The core of this current defines the rim of the hottest weather and serves as a conduit for clusters of thunderstorms.
3. Hot air will be moving east from the Plains, reaching the major East Coast cities Friday and Saturday. This map shows the upper-air flow that will make this happen.
This map shows lightning strikes from 8 a.m. EDT yesterday until 7:20 a.m. EDT today. A concentration of thunderstorms can be seen in the Midwest ahead of the cold front.