After Philadelphia International Airport reached 90 on Tuesday I thought that we'd be able to do it again Wednesday afternoon with a southerly wind; apparently we were not able to as the high at the airport was just 89 after a morning low of 67. Although the day featured sunshine and then a few cumulus clouds in the afternoon I feel that the reason we didn't reach 90 was due to a higher dewpoint in the afternoon(Tuesday's dewpoint was in the lower 60s while the dewpoint Wednesday was in the middle 60s) that prevented maximum compressional heating compared to drier air.
There were a few isolated showers and thunderstorms pushing through by the late afternoon and surviving overnight thanks to the frontal boundary pushing southward; overnight will feature clouds and a passing sprinkle as lows will just be in the lower 70s(upper 60s in the suburbs). After morning clouds we'll have sunshine and much drier air thanks to high pressure providing a northerly wind; highs will be in the lower to middle 80s through the afternoon.
It will be a clear and cooler night overnight Thursday with lows in the lower 60s(upper 50s N&W) while Friday's highs will just be around 80 with an easterly wind. There will be a warm front pushing northward overnight into Saturday so there will be a few clouds with lows in the upper 60s while Saturday will be in the middle 80s with sunshine and a more southerly wind. Now with that also comes a frontal boundary to out west and may spark off some isolated showers and thunderstorms in the afternoon. Highs on Sunday as well as Labor Day itself will be around 90 with isolated showers and thunderstorms as that boundary pretty much stalls on top of the region. There won't be washouts, but there may be an interruption of 30-45 minutes for passing showers.
I'm just trying to keep it real and not get you upset if a shower does push through; I know some other meteorologists right now are going with a dry Saturday and Sunday, but I can't fault them on their forecasts at all. This is what makes all of us great as we may have varied forecast due to different model agreement(disagreement), past experiences, and confidence levels. I'll keep you posted about the weekend so keep checking my 7-day forecast(as well as obtain radar and satellite maps) any time at www.scottderekwx.com/forecast.html.