Since the Piedmont runs through it, the Philadelphia region is a land of many microclimates.
We all know that the city is situated on a self-made heat island, and that an accumulating snowfall in Gladwyne could be nothing more than white rain in South Philly.
The National Weather Service has long recognized this phenomenon by dividing the region into winter-warning zones.
But acknowledging that in any given storm the weather in, say, Quakertown, Bucks County can be radically different from that in Bensalem, at the other end of the county, the weather service is going a step farther.
In December, the weather service is going to split Bucks, Chester, and Montgomery Counties in half and create new warning zones and criteria.
Here is the new map.
The new criteria will be as follows, according to Mike Gorse, meterologist in the Mount Holly office:
Eastern Chester -- Winter storm warning, 4 inches; winter-weather advisory, 2 inches.
Western Chester -- warning, 6; advisory, 3.
Eastern Montgomery -- warning, 4, advisory, 2.
Western Montgomery -- warning, 6, advisory, 3.
Lower Bucks -- warning, 4, advisory, 2.
Upper Bucks -- warning, 6, advisory, 3.
Supermarket-stampede criteria remain the same for all counties.