Near to slightly below average temperatures, along with dry conditions can be expected for this week. Cool High pressure now over the region will bring a pleasant day today, as temps reach the lower 60's. A cold front now over the Midwest will move southeast into the Delaware Valley on Tuesday. Overall this front will come through dry with only some clouds, but areas to our north could see a few light showers. Behind this front another shot of cool Canadian air, follows for Wednesday through Friday, as high pressure builds in. Temps will be in the mid to upper 50's both Wednesday and Thursday and near 60 on Friday. Fair and chilly nights can be expected, with lows in the 30's for the suburbs of PHL and near 40 for PHL. With High Pressure in control we can expect dry conditions.
10/27 through 10/31
A synoptic setup for unseasonably cold air, and possible stormy conditions look to be a good bet for next week. Both the EURO and GFS long range models, continue to show a deep trough for the central and Eastern US for the middle of next week into Halloween. A very strong, Cold core H5 low and trough, will slowly move SE out of Canada, and move into the NE and M/A States towards the middle of next week.
With this pattern and unseasonably cold air moving in, a threat for a coastal storm developing along the M/A coast is likely as this trough amplifies. As we get closer to the weekend, the details will become more clear of where this storm develops, and who is affected. I look for High temperatures Tuesday through Friday to be in the Upper 40's to lower 50's, which is about 10 to 15 degrees below average. Over night lows in the Upper 20's and low 3o's.
Most of the Delaware Valley will see a cold rain, and windy conditions if the coastal storm develops, followed by continued windy and cold conditions on a strong NW flow for later in the week. It's possible some areas could see there first flurries of the season later next week. Further north and the higher elevations of New England, Rain changing to snow is possible with this setup, Yes Snow !
EURO: H5 (500 mb)