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.
This map shows the pressure pattern at 9 a.m. ET. As the high moves closer and the storm moves farther away tomorrow and Wednesday, there should be an increase in sunshine with milder afternoons.
This map is the GFS forecast for when weekend rain makes its most northward advance early Sunday. The model then shows drying from north to south during the day Sunday. The ensemble mean has the northern edge in the same area. Looking ahead, it appears that warmer air is coming when May starts.
This map shows the GFS model forecast for Saturday evening. In the last day or two, the models have trended northward with the precipitation. If it trends even farther north, the issue of possible snow would need to be addressed. Check back later for updates, please.
The GFS (U.S. Model) predicts a major storm for the Middle Atlantic in the middle or late part of next week. This map is the GFS forecast for next Thursday (April 30) at 8 a.m. ET. Just to put you in a better mood, the second map (for May 4) shows what would be a sunny and pleasantly warm spring day.
This map shows the pressure pattern earlier this morning. You can see the extensiveness of the area of west to east winds. As a storm north of the Upper Great Lakes moves eastward, the flow will become more northwesterly.
This year, the "slight" category has been divided in two: slight and enhanced. When seen together on an SPC map, the progression makes sense. When the term "enhanced" is used alone, it can be a challenge, at least until we get used to it.