The NWS has issued a Winter Weather Advisory for Saturday for the entire western New Jersey area.

Here are the details of the advisory:

Sussex-Warren-Morris-Hunterdon-Berks-Lehigh-Northampton-
Western Montgomery-Upper Bucks-
Including the cities of Newton, Washington, Morristown,
Flemington, Reading, Allentown, Bethlehem, Easton, Collegeville,
Pottstown, Chalfont, and Perkasie
337 AM EST Fri Jan 17 2020

...WINTER WEATHER ADVISORY IN EFFECT FROM 10 AM SATURDAY TO 1 AM
EST SUNDAY...

* WHAT...Snow expected. Total snow accumulations of 2 to 4
  inches.

* WHERE...Berks County, the Lehigh Valley, and adjacent portions
  of northern and northwest New Jersey.

* WHEN...From 10 AM Saturday to 1 AM EST Sunday.

* IMPACTS...Plan on slippery road conditions.

* ADDITIONAL DETAILS...Snow is expected to develop from late
  morning into the afternoon on Saturday. The heaviest snow will
  likely occur from mid to late afternoon. Snow may mix with sleet
  or rain by early Saturday evening before tapering off
  overnight.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling.

The NWS snow forecast graphic above has scaled back a little the higher snow amounts due to 1) warmer air arriving to mix the snow with sleet and rain and 2) limited amount of time snow will be falling

My forecast is 2-4″ for the I-78 corridor with amounts closer to the low end. Higher amounts will be further to the north and west where the mix/changeover will take longer.