Ice Storm Alert: Classic Cold Air Damming (CAD) Set Up on Sunday

The coldest air of the season will infiltrate the Mid-Atlantic this weekend.

A storm system will pass to our west (Sunday through Monday) pulling mild southwesterly flow on top of the cold air at the surface. This set up is referred to as a Cold Air Damming (CAD) event, because the mountains “dam” or trap cold air at the surface while warmer air glides on top.

Bottom Line:  precipitation will likely begin as snow but will begin a transition over to sleet and freezing rain.

Winter Storm Watches may be issued across portions of the Mid-Atlantic states on Friday as odds are increasing that portions of the Washington Region may receive significant accumulations of snow, sleet and freezing rain.

Latest (subject to change) Global Forecast System (GFS) potential Snow, Sleet and Freezing Rain accumulations:

Potential Snow accumulations (subject to change)

Potential Sleet accumulations (subject to change)

Potential Freezing Rain accumulations (subject to change)

CAD events are tricky to forecast because the forecast models typically try to erode or scour out cold air that is trapped at the surface too quickly. 

Travel may be treacherous this weekend and with any potential ice storm, residents should be prepared for power outages.  I will provide updates as we continue to get closer to this potential winter storm.