The medium range model forecast for the weekend sems to be in flux as details of the development of several systems seem to have changed over the past few days – a storm expected to develop Friday into Saturday is now forecast for Saturday into Sunday. It appears that we will get rain from this system.  I would not be surprised if the timing changes again.

There’s also a small impulse forecast for this Thursday into Friday which keeps changing intensity and track.

So a very uncertain weather outlook for this weekend in Philadelphia.

The models are consistent in the appearance of a deep dive in the jet stream for much of next week caused by arctic high pressure. As a result, well below average temperatures are likely for much of next week. Storm development with this jet dip is expected to be off-shore, but that could change.