March weather in the Middle Atlantic states can be very changeable as winter and spring battle one another for dominance. Today's highs will reach near 70 degrees in Baltimore and Washington, but snow will be falling within 36 hours. The National Weather Service at Sterling VA has issued a Winter Storm Watch for much of Maryland south of the Mason-Dixon line and west of Chesapeake Bay effective Sunday afternoon through Monday afternoon for the potential of "five or more inches of snow." As noted in the watch, the heaviest snow is expected to fall across the southern portion of the region from Washington to Annapolis on southward. A Winter Storm Watch does not mean that these conditions are imminent, but that the weather pattern is favorable for five or more inches of snow. The watch may be upgraded to a warning, or downgraded to an advisory, if conditions warrant.
Meanwhile, various features on the national weather will converge to produce snow in these same areas on Sunday night and Monday. The first feature is another shot of arctic air that will surge southeast into the Mid-Atlantic region by Sunday night. Today's highs near 70 will fall into the middle 30s by Sunday morning, and highs on Sunday will only rise a few degrees to near 40. This cold, dry air on a north wind will set the stage for overrunning precipitation to develop on Sunday in the form of rain showers as afternoon temperatures will be in the lower to middle 40s. At the same time, an area of low pressure is expected to develop to the southwest and move across North Carolina on Sunday night and off Cape Hatteras NC on Monday. As the center of low pressure intensifies, colder air will be drawn into the system and will change rain to snow across the region by late Sunday night. Snow may continue into Monday morning, perhaps mixing with or changing to rain on Monday in Virginia. Precipitation will taper to flurries on Monday afternoon.
Although computer forecast models have recently begun to shift the heaviest band of snow to the south of Washington DC, a slight change in the track of the storm will have significant implications upon where snow accumulates. With the majority of the snow falling at night, and with temperatures plunging into the 20s overnight, snow will easily accumulate not only on unpaved surfaces but on roads as well. Road conditions may improve late Monday morning as the snow tapers to flurries and as the high March sun angle heats the surface. At this time, I am expecting a minimum accumulation of 1 to 2 inches in Baltimore with 2 to 4 inches in Washington DC and Annapolis. Amounts may reach 6 inches at some locations. Southern Maryland looks to receive 4 to 6 inches with isolated amounts of 8 inches.
I'll provide more updates through the weekend as new data becomes available.
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