It’s blue skies, why the weather advisory? A couple of reasons: 1) there can be some snow showers today that can leave anywhere from a coating to an inch or two and b) the strong winds of today that will cause blowing and drifting of the snow resulting in reduced visibility.

...WINTER WEATHER ADVISORY NOW IN EFFECT UNTIL 8 PM EDT THIS EVENING...

* LOCATIONS...Most of eastern Pennsylvania and northwestern New   Jersey.

* HAZARDS...Snow and blowing snow.

* ACCUMULATIONS...Up to 2 inches of new snow accumulation.

* IMPACTS...Blowing and drifting snow will lead to reduced   visibility especially in open areas. In addition, isolated snow 
  squalls today could lead to additional quick snow accumulations,   reduced visibility and exacerbating already hazardous driving conditions.

* WINDS...Northwest 15 to 25 mph with gusts up to 40 mph.

* TIMING...Blowing snow is possible through the day. Snow squalls will be possible from mid morning through early this evening.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Weather Advisory for snow and blowing snow means that visibilities will be limited due to a combination of falling and
blowing snow. Use caution when traveling, especially in open areas.