This evening I start out with the satellite animation, it tells the story pretty well, a nice defined trough over the eastern US and another trough is dropping out of Canada, which is causing an upper level low to develop over the Great Lakes region.
This trough and upper level low will make for a wet and stormy period from Thursday night through Saturday evening. A strong cold front will extend south from the upper low and come east. Meanwhile you can see a massive ridge over the western Atlantic, this will force the cold front to move VERY SLOWLY east , which has been the case since the end of July.
Showers and thunderstorms are developing with this storm system from Western PA through the Great Lakes, everything will slowly shift east and begin to impact our area tomorrow night
The thing to remember through the period is that this will not be a steady rain, but more in the way of waves of showers and thunderstorms, strong to severe thunderstorms will be possible with each of these waves with the best shot being late Thursday night into Friday as the atmosphere will be most unstable during this time period,
I think the threat of severe weather will be very isolated Friday night through Saturday due to cloud cover and rain keeping the atmosphere somewhat stable.
The main threat with these waves will be heavy rain and training thunderstorms, with a slow-moving cold front, a SW to NE flow aloft, parallel to the front will lead to likely training of storms in spots, so flash flooding will be a concern for some. We will be in the warm sector of this storm, meaning the warm front extending from the low over te great lakes will be north of us, so the flow will be out of the south leading to a lot of humidity and moisture in the air, basically a tropical air mass will take hold, this is why heavy rain will be te main concern
I can’t rule out isolated storms tomorrow afternoon for our western sections like East PA, but The first of these waves will impact us late Thursday night into Friday, again this is when I expect the best threat of severe weather , I still don’t think it will be very widespread, I expect more in the way of showers to strong thunderstorms.
Any storms will bring heavy rain , gusty winds and potentially dangerous lightning but we see here that the flow will be out of the SSE off the Atlantic, that’s not a very good flow if you want severe wather which is why im not impressed with and do not any widespread severe weather.
This wave will continue to impact the area through Friday afternoon with widespread showers and storms, which will be slow-moving and capable of dumping a lot of rain in a short period of time, flash flooding will be a concern for some.
We then see a little break in the action Friday later in the afternoon through the evening hours before wave 2 comes along and showers and storms move back in by late evening Friday
Another break will be possible Saturday morning before the actual cold front comes along by early afternoon with showers and thunderstorms training SW to NE over the area through the evening
By late Saturday night into early Sunday the storm over the Great Lakes will move NE and the cold front will move off the coast.
Overall I expect an average area wide of 0.50 to 1.25 inches however this model shows the potential for training storms well and areas that get stuck under training could easily exceed 2 inches and potentially exceed 3 inches through the period. I can’t tell you where the training storms will occur, this model says northern NJ and NE PA but that will be nearly impossible to pin point for sure until the situation unfolds.
Highs on Thursday will be in the low 80s interior and along the immediate coast, mid to upper 80s for the rest with high humidity, Friday with more clouds and rain in the picture highs in the upper 70s to mid 80s are expected with very high humidity and Saturday with even more clouds and rain highs will only be in the mid to upper 70s but again very high humidity with a tropical air mass in place. Lows Thursday and Friday night will not fall much with only low to mid 70s expected, Saturday night a much more comfortable regime will begin to take hold, lows in the low 60s interior to upper 60s along the coast with decreasing humidity
Behind this system a very comfortable regime will take hold with highs Sunday through Tuesday in the lower to mid 80s and lows in the upper 50s interior to mid 60s along the coast before we watch our next potential storm system by mid-week.