Sleet has been falling across portions of north-central Virginia, the northern neck of Virginia and across southern Maryland since about 10 pm. The high-resolution models keep the sleet away from downtown DC (points north and west) for most of the event for now. Take a look at the latest high-resolution model depicting radar simulation (future radar) – you can see the time stamp in the upper right hand corner of the map: The pink colors indicate sleet mixing in.
My concern is that Fredericksburg, Stafford, Quantico, and southern Maryland may see their snowfall accumulations cut down depending on the million dollar question (how long does the sleet last before colder air moves back in at all levels of the atmosphere)?
Sleet (frozen raindrops) occur when a shallow layer of warm air in the mid levels of the atmosphere melts the snow flakes into a rain drop and then these rain drops re-freeze as an ice pellet as they travel into subfreezing air closer to the surface.
In my snowfall map I had 18 to 24″ across Fredericksburg, Stafford and Quantico. If the sleet keeps up most of the night in these areas they could see their totals cut down. The models still keep DC, points north and west in the snow during the entire event, so here I think totals of 18 to 24″ look reasonable.
Also of interest to me is how the heavy snow actually made it into south-central Pennsylvania. The snow always seems to head further north than the models initially show. Just like the sleet came into north-central Virginia and the northern neck (much further north and west than the high-resolution models had suggested earlier).