Wednesday, 9 a.m.
A southerly flow of increasingly moist air is spreading up the I95 corridor, where the dawn was greeted by dreary dullness and dim, drab drippiness from Maryland to Massachusetts. There are also some showers from western New York to Ohio along a cold front that will reach the East Coast this evening. When that cold front arrives, it will usher in a dry air mass that pulls back the curtain of clouds to reveal brilliant sunshine that plays off the multicolored leaves in the Northeast from tomorrow into the weekend.
In New York City and Philadelphia, typical afternoon temperatures are well up in the 60s at this time of year. Nights cool to about 50 in the cities, but well down in the 40s in many suburbs. The air masses in place from tomorrow through Saturday will bring temperatures that run about a half-dozen degrees below those long-term averages. Saturday morning is apt to be frosty in the colder suburbs from Washington, D.C., to New York City and below freezing in upstate New York and much of New England's interior. However, a strong southwesterly flow of warmer air could boost temperatures to 70 degrees in these areas on Sunday afternoon.
A strong storm is likely to cut through the Great Lakes Saturday night and Sunday, and its associated cold front will trigger showers and even thunderstorms. However, the air coming in behind that storm should not be as chilly as the air that follows this week's fronts. The reason: this week's upper air flow into the Northeast can be traced back to northwest Canada. Next week's main upper air current looks like it will be straight west to east. The video has more.
The cold front that will cut off the heat will generate strong gusty thunderstorms as it moves southeastward today. The National Weather Service Storm Prediction Center highlights the most likely area for these severe thunderstorms today and tonight.
As the high pressure area in the Northeast moves away, the the southwesterly flow pattern will shift eastward. This means Wednesday could be the hottest day of the week from D.C. to Boston. A cold front will follow.
This is a satellite picture showing rather tame conditions off the South Atlantic coast at 7:45 AM ET today. The area is being watched for any signs of storm development.
When looked at this way, you can see two distinct flows in the East: one from the south with moisture, and one from the west that is dry. There is a problem, however: the model solutions evolve over time, and as we get closer to next Monday afternoon (the time the forecast maps are using), the lines and orientations will probably change.
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This map shows the scenario of hot air spreading across the northern Plains and north of the Great Lakes, while a pocket of cool air aloft gets stranded over the Middle Atlantic region.