The latest high-resolution rapid refresh (HRRR) model (courtesy WxBell) shows very heavy snowfall rates of one to two inches per hour (dark blue colors in image below) developing across the Washington Region between 3 and 5 AM.
Note the very heavy sleet (orange) and freezing rain (pink) also showing up just south of the Capital Beltway around 10:00 on Thursday morning when the snow party should begin shutting down in the DC metro (points south and east) and the wintry mix of sleet and freezing rain begins in earnest.
Thump of Heavy Snow Accumulations Prior to Wintry Mix
The image below shows a solid 2 to 4″ across northern Virginia, D.C. and suburban Maryland (Prince Georges, Montgomery) before any mixing of sleet and freezing rain occurs.
Plows will not be able to keep up with the heavy snowfall rates on the Interstates causing secondary roadways to become snow-covered and treacherous. The heavy sleet and freezing rain will only exacerbate conditions making travel nearly impossible tomorrow – please stay off the roads!