Here is a wonderful visible satellite picture.
It shows the very sharp delineation between places in southern PA that did and did not receive snow on 30 January 2010.
This picture is the perfect example of just how sharp the difference in local weather conditions can be.
Some of the spotter reports of the 30th show up to 3.5 inches of snow had fallen by late evening along the Mason-Dixon Line. Similar graphical summaries (and the text of the summary statements) are made in real-time as we receive the reports. They can be found through our Snowfall Info Page (available in the left-hand margin) - under the "Recent Snowfall" tab.
Visible satellite picture depicting the sharp snow line over southern PA.