A period of snow will fall during the pre-dawn hours on Monday with accumulations likely across the colder northern and western suburbs of Washington (mainly along and north of interstate 66). Once rush hour concludes, snow will have mixed with or changed to sleet, freezing rain or plain rain as temperatures climb into the mid 30s.
Freezing rain, sleet and snow will likely remain the predominant precipitation type across the sheltered valleys well north and west of Washington and Baltimore (Frederick county Virginia to Carroll county Maryland) through at least the mid-afternoon hours.
The latest High Resolution Rapid Refresh (HRRR) simulated radar shows a band of some moderate/heavy snow moving into the metropolitan area between 2am and 6am, especially along and north of interstate 66 – this will need to be watched closely for the AM commute!
The forecast models disagree on how much snow will accumulate in D.C. during the pre-dawn hours, with the European dropping about one inch of snow in downtown Washington and the GFS (American model) showing nothing.
After 10 am, much of the immediate metropolitan areas should see mostly cold rain/sleet as temperatures climb into the middle 30s.
A wintry mix is forecast to hold on tough across the Shenandoah Valley, sheltered valleys along the Blue Ridge and in northern Maryland through the mid-afternoon hours. Widespread closings/delays are likely across the northern and western suburbs. Those of you in western Maryland should prepare for a nasty, prolonged ice storm (once the snow ends), with up to a quarter-inch or more of ice accretion (from freezing rain).