The storm that brought substantial rainfall to the Northeast will depart through eastern Canada today, and a high pressure area will take its place. Ahead of the high, tomorrow will be a cool day with northwesterly breezes in New England and the Middle Atlantic states. However, with the high pressure area offshore and another cold front approaching, there will be an increasing southwesterly flow of much warmer air on Thursday. This video shows that sequence of events then proceeds through the coming weekend.
A cold front will approach the I-95 corridor on Thursday night, but computer models show differing ideas on whether it moves right through or instead stalls and prolongs a shower threat into Saturday. It appears the weekend will start on the cool side, but that much warmer air will sweep into the Northeast on Sunday.
However, after the warmup, another cold front will move through the Great Lakes and Northeast with at least some rain. This map contains the forecast for Sunday evening, and includes precipitation predicted for 2 p.m. through 8 p.m. ET.
In this picture, the sun had set as seen from the ground. However, sunlight was able to light up the clouds from below to create this look outside my home:
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.