The atmosphere out ahead of Monday’s storm system will be very dry with dew points likely starting out in the single digits and teens. As warmer air aloft begins to glide on top of the very cold, dry air at the surface, some forecast models (such as the latest NAM model below) are hinting at a nasty ice storm developing, especially for locations north and west of interstate 95 .
Even in DC, advisory level icing of up to a tenth of an inch is looking likely if the current forecast models are accurate. Snow and sleet will likely break out on Monday afternoon, rapidly changing over to freezing rain in the metro area with snow potentially holding on a bit longer across northern Maryland before the change over to ice.
Temperatures may rise into the middle 30s on Monday afternoon but as precipitation begins to fall, evaporation cooling will likely drive temperatures to at or below freezing across much of the DC region (outside of southern Maryland and central Virginia). The image below (courtesy WxBell) shows temperatures from 2pm Monday through 1am Tuesday. Notice how many locations are forecast to rise slowly above freezing before falling again as precipitation begins to fall.
Potential Ice Accretion from Freezing Rain
Winter Storm Watches are likely to be issued Sunday afternoon/evening across the Potomac Highlands, the West Virginia panhandle, northern Maryland and parts of Northern Virginia where over a quarter-inch of ice could accumulate on trees and power lines making for very treacherous travel conditions on Monday through Tuesday morning.
Ice accumulations of over a half-inch are likely across the Shenandoah Valley, Skyline Drive and western Maryland. Now is the time to begin thinking about preparing for potential power outages across these locations.
I’ll have updates tomorrow as the latest model date comes in, I’m also watching (as is everyone else) the potential for a Nor’easter (with Snow) Wednesday night into Thursday. It’s too early to tell if this system will have major impacts on DC or miss our region to the south.