An impressive transport of moisture (green, red areas) in the lower levels of the atmosphere associated with this developing storm system, but currently the radar is looking rather patchy across the Mid-Atlantic region and it appears as if there will be only occasional light snow through much of the morning across SE PA. Temperatures are generally in the upper 20’s across the suburbs of Philly this morning and they may drop a couple of degrees when the snow begins. The snow will then pick up in intensity from midday to mid-afternoon, and then the main action will begin. Heavy precipitation is likely in the period between the mid-afternoon and the latter part of evening (ie ~3pm to 10pm). Significant snow is likely to fall for a part of this time period in Bucks, Montgomery and Chester Counties to the N and W of Philly, but warmer air aloft will be advancing northward. The snow will change to sleet and freezing rain at some point by early tonight in all areas throughout the Philly metro region. The tricky part of the snow accumulation forecast is that in this 3-10pm time period there is liable to be heavy snow falling somewhere in the N and W suburbs of Philly while at the same time, just 20 miles or so away, there will likely be a wintry mix. A shift in this snow/wintry mix line in one direction or another or a shift in the timing by small amounts will make big differences in some localities with respect to snow accumulation as there will be a tight gradient. Current snowfall estimates are as follows: 3-6 inches of snow on average in Bucks, Montgomery and Chester Counties with a layer of ice deposited on top; 1-3 inches of snow across Delaware County and in the city of Philadelphia, and an inch or less at the Jersey Shore. This will be a “conventional” snow event in the Philly metro region in that there will be higher snowfall amounts as one goes farther and farther north and west of I-95 and lesser amounts closer and closer to the coastline.