Winter storm warning

This undated handout photo provided by NOAA shows Louis Uccellini. The federal government Thursday selected Uccellini, an expert in winter storms to be the next director of the National Weather Service, just as a massive blizzard threatens New England. (AP Photo/NOAA)

In a rather dramatic shift from this morning, the National Weather Service has issued a winter storm warning for all of Montgomery and Bucks Counties and part of Chester County for 4 to 8 inches of snow late tomorrow into Saturday.

In the immediate Philadelphia area, the call is for 3 to 5 inches, with the changeover from to snow coming later.

When the change to snow occurs, forecasters are saying the precipitation will come fast and furious, perhaps at a rate of an inch or 2 an hour.

Snow is expected to creep across the region late tonight or during the early-morning hours and then change to rain.

By nightfall, the changeover will be under way, and probably complete in Philadelphia by late Friday night.

In all likelihood this will be the biggest snow of the season so far, especially considering the bar is situated at the 1.5-inch mark.

This morning, the forecast suggested that the old mark might stand ... but that has changed.