Thursday 9 a.m.
A cold front will shift from the Lake Superior area southeastward to reach the Middle Atlantic coast by midday tomorrow. There are several bands and clusters of thunderstorms ahead of the front, but sunny and less humid air follows its passage.
Video for Great Lakes and Northeast:
When we have thunderstorms in the forecast, we are often asked whether any of them are severe. When we answer, we usually think of severe thunderstorms with winds exceeding 58 mph, and perhaps we think about large hail. However, it doesn't take anything that strong to have serious effects. A 20- to 30-mph wind gust can shake branches loose, and heavy rain can cause street flooding almost immediately. And, if a lightning strike hits where you, who cares how "severe" the storm was! The following pictures include a radar image showing thunderstorms not far from New York City and a lightning plot covering the period from 5 a.m. until just after 9 a.m. EDT. Pockets of heavy rain and active lightning were the two major hazards associated with these storms. This is the kind of situation where thunderstorms can align with the upper air steering winds and so it keeps pouring right underneath the train of storms. This setup is dangerous and life-threatening.
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.