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.
It appears that a large low pressure area will form in the Plains this weekend and then drift very slowly eastward next week. This could lead to a lot of rain over a large area. This map depicts the Euro model predicted rainfall between now at midday Saturday May 3rd.
Thunderstorms broke out in eastern New England this morning. Here is a lightning map showing strikes between 8 a.m. and 10:30 ET:
I'd like to think that my explanations of what was going on enlightened him, but we all know better! This map shows the distribution of lightning from around daybreak yesterday to the wee hours of the morning today.
Omega blocks are known for causing long periods of whatever kind of weather you had when the block was getting established. In other words, if it was rainy, you were in for more (perhaps a lot).
This satellite picture shows the storm that affected the Southeast on Saturday (1) , the frontal system that will reach the East Coast late tomorrow night (2) and a disturbance in the Pacific Northwest that may affect the Northeast at the end of the week (3) .
A deck of clouds about a half-mile overhead spread westward from the Atlantic to much of the I95 corridor from DC to Boston early this morning. These cloud decks can be a forecaster's nightmare in the spring because ...