The pendulum appears to be swinging back toward a snowier outcome for the winter storm forecast for the mid-Atlantic states Wednesday.
The National Weather Service is now predicting minor accumulations for BWI Marshall, as forecast models finally begin to converge on a common solution that would increase the chances for some accumulation as the storm departs.
The official BWI forecast calls for a 50 percent chance of snow and rain, beginning after midnight Wednesday morning. Any snow before 9 a.m. would gradually change to rain and snow, or all rain during the day Wednesday. But the forecast now has the precipitation switching to all snow after 9 p.m. Wednesday. Temperatures will fall into the upper 20s.
The snow forecast map shows as much as 4 inches piling up in northern parts of Carroll, Baltimore and Harford counties, fading to 2 or 3 inches in the closer Baltimore suburbs, and less as you move south and east. The morning forecast discussion from Sterling gives you a sense of how complex this event will be.
AccuWeather.com now has Central Maryland firmly in the snow bands of its snow map, too. The "wintry mix" would be confined to Southern Maryland and the Eastern Shore. The 1-to-3 band lies just south and east of Baltimore; the 3-to-6 band is just north and west.
Three to six inches are possible for western Maryland, too, by their reckoning. Six to 12 are possible in some mountain counties of Maryland and West Virginia. The biggest hit from this storm would land on Massachusetts, with 12 to 16 inches possible there. Once the storm passes by, they're expecting another surge of cold Canadian air next week.
Eric the Red has the snowiest solution this morning: "A burst of moderate to heavy snow Weds eve. The timing of the changeover will be critical to the final snow tally; obviously, the sooner it changes over to snow, the more snow you'll get. Well Duh. But pinpointing when that will occur is the tricky part. I like the 4-8" range I mentioned yesterday.. but this could be lower if the precip stays rain/sleet longer, and be higher if it stays mostly snow."
Unconvinced? Here's another contribution, from Jeff Halverson, associate professor of geography and environmental systems, at UMBC's Joint Center for Earth Systems Technology. On the jump:
"Part 1, the coastal low coming up from the south, will bring bring a period of light-moderate rain during the day tomorrow, with the heavy corridor of moisture staying east of the metro region.
"Part 2 is an upper level disturbance - a combination of energy (spin) and deep cold air - that will sweep in from the Ohio Valley and merge with the back-side of the exiting coastal low. Part 2 will impact the region late Wed into Wed night.
"The cold air will change precip over to snow, and the energy is such that moderate to heavy snowbands could create a 6-hour burst of significant snowfall across the metro areas. Totals could range from 4"-6", but accumulation will be initially reduced by standing water on roads, and any pre-treatment that is put down.
"Eventually, though, the rate of snowfall and cold air moving in should cause snow to stick. Could be a messy Thurs AM rush."