Discussion and Forecast:
For The Delaware Valley:
A return to chilly weather will be the rule for this week. Cold high pressure is now building in from the Great Lakes, and will bring, below normal temps and generally fair weather for Tuesday and Wednesday.
Expect M.Sunny and Chilly conditions for Tuesday with highs near 50. Tuesday night will offer another cold night as lows dip to the mid and upper 20's in the suburbs to the lower 30's in PHL. For Wednesday temps will continue Chilly with highs in the lower 50's. Some clouds will increase during the afternoon.
As our High Pressure system move NE and off the New England coast an easterly flow will develop Wednesday night into Friday. A continuation of Cool and increasingly moist air will develop at the surface during Wednesday night and will begin to bring in increasing cloudiness.
With a SW flow aloft and some ridging, an overrunning set up will begin as moisture and a wave of low pressure move NE into the region from the Tennessee Valley. Rainy and raw conditions are likely for Thursday and Thursday night as this set up evolves, and the moisture is pumped in from offshore, as our exiting High moves northeast. Temperatures will remain chilly and a NE wind develops and increases to 10 to 20 MPH with periods of rain and highs in the low to mid 50's for Thursday.
On Friday, We'll warm up to near 60, as The WAA (Warm Air Advection) takes over and more of a south and Southwest wind at the surface, ahead of an approaching U/L trough and strong cold front. So Friday will be Mostly Cloudy with showers and once again milder with highs near 60.
I'll update later this week with a weekend outlook, and touch more on some big changes to colder weather for much of next week. The AO and pattern change call I made on October 30th is looking good and many models and ensembles are in very good agreement for a much colder second half of November and Below normal temps. We are seeing the gradual changes taking place this week to cooler temps and stormy conditions developing later this week. Each trough moving in for down the road will have colder air and be more established in the east.