10:45 p.m. update: As some spotty light rain and drizzle moves back into the area, we don’t see any late-breaking changes in the latest model data. Temperatures should stay right about where they are now, until they start to slowly rise after 8 a.m. or so. That means for the immediate metro area, locations generally north and west of the Beltway (zone 2 above) have the best chance of seeing icy spots on untreated surfaces overnight into the early morning, with more significant icing expected to continue far north and northwest of D.C. (zone 1 above). That said, with temperatures so close to freezing, everyone should use caution when they first venture out onto sidewalks, driveways and streets in the morning, even those inside the Beltway and to the south and east.
8:30 p.m. update: Radar has quieted over the D.C. metro area for now. Spotty rain, perhaps mixed with a bit of sleet in our northern suburbs, should redevelop later this evening, possibly becoming a bit steadier at times overnight. Pavement should remain just wet inside the Beltway and to the south and east, although isolated icy spots are possible on untreated surfaces, as described in this special weather statement issued by the National Weather Service. But temperatures north and west of the Beltway could be cold enough for more numerous slick spots on untreated surfaces into the Tuesday morning commute. Further north, a winter storm warning is now in effect for Frederick, Carroll, and northern Baltimore counties, where “travel may become extremely difficult” due to snow, sleet, freezing rain, and temperatures around 30-32.
Original post from 3 p.m.
Moisture will continue to funnel into the Washington region Monday night and Tuesday, meaning more rainy weather. But cold air wedged into our north and west areas could lead to an icy mix of precipitation overnight Monday into early Tuesday morning.
Precipitation may be intermittent and spotty at times overnight, but where temperatures fall low enough, wet surfaces could freeze.
Iciness and slick travel are most likely Monday night into Tuesday morning in our Zone 1 from northwest Virginia through northern Maryland. In this area, temperatures hovered close to freezing even into Monday afternoon while the rest of the area warmed. Snow even fell in northern Maryland north of Interstate 70.
In this zone, lingering snow and sleet are likely to change to freezing rain overnight. And, with temperatures falling back to 30 or 31 degrees, icy spots are likely on untreated areas. It may take until mid-morning to early afternoon Tuesday for these areas to rise above freezing.
Zone 1 includes Winchester, Frederick and Westminster, and is under a winter weather advisory.
In Zone 2, which borders Zone 1 to the south and east, temperatures are likely to fall to 31 or 32 degrees, cold enough for some rain to freeze on untreated surfaces. We don’t expect widespread hazardous icing in this zone, but scattered slick spots are possible.
Pedestrians should be careful on sidewalks and motorists especially cautious on bridges, ramps and overpasses, which freeze before other road surfaces. In this zone, most locations should see temperatures rise above freezing by mid-morning Tuesday.
Zone 2 includes Warrenton, Reston, Rockville, Columbia and Baltimore’s north and west suburbs. This zone is under a winter weather advisory.
Lastly, in our Zone 3 (just south and east of Zone 2) temperatures should bottom out around 32 or 33 degrees, high enough for most surfaces to remain wet rather than turn icy. However, we cannot rule out a few icy areas.
In this zone, we urge motorists and pedestrians to check temperatures before heading out overnight into Tuesday morning, and use caution taking their first steps out.
Any locations that are near freezing in this zone early Tuesday should rise above freezing an hour or two after sunrise.
Zone 3 include Manassas, Fairfax, Northwest Washington, Bethesda, Silver Spring and Laurel. The northern part of this zone is under a winter weather advisory.
Locations south and east of Zone 3 should see mostly if not all plain rain.