Article and Forecast by Meteorologist Peter Forister
Graphics by Denver Murray
— Peter Forister ❄️☃️❄️ (@forecaster25) February 17, 2021
A very strong arctic airmass has setup to the northeast of the Mid-Atlantic, and is forcing a layer of cold air to run down the spine of the Appalachians. This “CAD” (Cold air damming) ensures that temperatures at the surface will remain below or near freezing for most of the day Thursday.
A low pressure system will track through Tennessee and to the south of the Mid-Atlantic, bringing with it plenty of moisture. This moisture will “Overrun” the cold air at the surface. The remarkable thing about this particular storm system is that the mid levels of the atmosphere will be unseasonably warm (possibly exceeding 50 Degrees several thousand feet up) and will be transported north over Virginia by VERY strong mid level winds (over 80mph). This process of moisture and temperature movement is called “WAA” (Warm Air Advection) by meteorologists, and is what will make the forecast so tricky and potentially dangerous on Thursday.
Sleet: Bad for roads. In areas of heavy sleet, even treated roads will quickly be covered with a layer of ice. This can easily cause widespread traffic accidents, but will not impact electricity lines.