Thursday was a nice summer day(albeit it's now early September) with a low of 68 this morning at Philadelphia International Airport; sunshine and fair weather cumulus clouds filled the sky in the afternoon, but the high still managed to reach 87 shortly after 3:30pm(five degrees above average). This was thanks to high pressure on top of the region and also a southeasterly wind which meant that the further west you went today the warmer it was(as there was less of an onshore flow influence).
Overnight will be mostly clear with lows primarily in the upper 60s with a light and variable wind, but the dewpoints have creeped back into the lower and middle 60s which means the mugginess has returned as well; Friday will feature sunshine and then some clouds in the afternoon with a short wave pushing northward between the I-81 and I-95 corridors. This means there will be isolated showers and thunderstorms in the afternoon across southern areas, but elsewhere it will be hazy, hot, and humid with highs around 90 thanks to a continued southwesterly flow.
The heat and humidity continues for Saturday, but it will be mostly cloudy after lunchtime as a cold front inches closer; highs will be in the upper 80s with a southwesterly flow, but there will be widespread showers and thunderstorms in the afternoon as well. Behind the cold front we'll get a dry and northwesterly flow so with an unseasonably cool shot of air from Canada highs on Sunday will just be in the upper 70s!
That front will stall just to our south and then advect clouds and moisture northward on Monday; highs will be around 80 with an east-southeasterly flow and the best chance of rain staying along the shore. Tuesday will feature the same with highs in the lower 80s, but come Wednesday a cold front will approach from the west and not only provide more widespread showers and thunderstorms, but also push away this little coastal disturbance as well.
Don't forget that you can check out my 7-day forecast(as well as viewing the satellite and radar maps 24/7) at www.scottderekwx.com/forecast.html.