An "ice storm warning" is in effect for Bucks, Chester and Montgomery Counties until 4 p.m. tomorrow, and "freezing rain advisory" for Philadelphia and South Jersey until 10 a.m.
But it's still not certain how much ice will accumulate, or how much of a factor it will be tomorow morning.
At last look the temperatures were right around freezing in Wilmington and Philadelphia, and just below to the north and west.
Those temperatures aren't going to budge much between now and when the heavier rain arrives late tonight.
In the city, the National Weather Service forecast calls for from 0.1 to 0.3 inches of ice before an early-morning changeover. That's quite a range.
It's even bigger outside the city. For example, the forecast range for Norristown is from 0.2 to 0.6, or anything from a pain to a power-outage disaster.
The key would be just how long the precipitation freezes on contact, and that's going to take longer the farther north and west one goes.
Tony Gigi at the National Weather Service in Mount Holly says that if you interpreted the models literally, the changeover to liquid would occur at 5 a.m.
He said the advisory would go until 8 a.m. in Philadelphia just to be on the safe side. Plus any effects would out-last the changeover.
At some point the ice is supposed to change to liquid rain everywhere, and it should all be winding down by late morning.
Still, this could end up being a non-event from Philadelphia south and east, and it's possible that most of the region will escape a commuter nightmare in the morning.
After the storm departs, it gets cold again, and expect frozen leftovers.
Another storm remains on the weekend horizon with snow or rain or both.