The latest short-range, high-resolution North American Model (NAM) suggests that the onset of a wintry mix could hold off in the immediate DC Area until after 9AM. Several earlier runs indicated an earlier start time (pre-dawn) of sleet and freezing rain breaking out between 3 and 5AM.
Currently the models suggest that the outer, northern and western suburbs (western Loudoun, northern Montgomery, Frederick county Maryland) have the better chance of an earlier start time. This could still change and will need to be monitored.
Image below: 3AM – 10AM (North American Model) – Mix holds off in D.C. until 10AM.
Regardless, the threat of light icing primarily due to sleet and freezing rain warrants a Winter Weather Advisory for the morning rush-hour, especially for locations well north and west of downtown Washington.