Snow in the D.C. forecast: How much could fall, and where?

UPDATE 4:20: I posted an updated snowfall accumulation map below. It shows 1 to 2 inches right around D.C. which may be "sloppy and at the tail end" of Saturday's "historic" storm, according to ABC7 senior meteorologist Bob Ryan. However, the thinking here is that what will fall in D.C. will be mostly rain, with just some slushy stuff on the ground by nightfall.

Meanwhile, Ryan's latest forecast has it that "areas above 500 feet in northern Montgomery County to western Fauquier Counties are likely to see a steady wet snow by mid-morning until late afternoon with 3-6" or more possible." Wow. Keep tuned for updates.

ORIGINAL: Hurry, there's still time to switch your Halloween costume to the Abominable Snowman! A Nor'easter moving up the East Coast this weekend is expected to unleash tons of the white stuff from Virginia up to New England, lending a credible backdrop to all faux yetis, snowman and Santa Claus outfits. (Latest ABC7 forecast, radar, weather alerts.)

This storm is nothing to scoff at: Snow is forecasted along the I-95 corridor, and everyone knows how drivers here like to freak out about that. And it may be time to check your candle supply. Says NOAA: "Heavy, wet snow combined with nearly fully-leafed trees could lead to extensive downed trees and power outages in a region extending from the borders of Virginia and West Virginia northeastward through the mid-Atlantic states and into southern New England." The Pepco PR machine is no doubt being oiled and warmed up this very moment.

The weekend forecast makes D.C.'s snow day practice run seem more important.

“We've been training year round for this, we're getting ready, today we're going to show we're ready,” said snow coordinator Robert Marsili.

D.C. crews expect the roads to stay warm enough that potential snow will not stick but say they'll be ready with plows and salt regardless.

About 250 vehicles were checked and sent out on what will be their snow clearing routes come winter. Some crews may be on the streets as early as Saturday.

In Prince George's county, plow drivers conducted an early-morning exercise. This year they will be using dash cameras to transmit live video of their snow clearing efforts to the county's command center.

The surface low that will be bringing the nasty weather is creeping up from the Gulf and should be whirling around near North Carolina beaches by Saturday morning. Winter Storm Warnings are in effect from tonight to Saturday evening for Loudoun, north Fauquier, and many other nearby counties; check the National Weather Service for a full list. Meanwhile, a fat line of Winter Storm Watches (for those who need to dust off their NWS terminology from last winter, watches are one degree of seriousness below warnings) runs from western Virginia all the way to Maine. Take a peek at this river of watches:

So, who gets to debut their shiny new snow boots on Saturday? And who will likely be left with a mere dusting of powder on the ground?

Rain and snow is already falling in the Appalachians and it will likely turn into all snow later today. (Blacksburg has sleet.) Some folks in the Virginia and West Virginia highlands may get 4 to 8 inches of snow before the storm's done. During Friday night, a heavier rainfall will soak the Mid-Atlantic while frigid air infiltrates the region. Early Saturday, snow will move out of the mountains and into lower areas, including along I-95 and westward.

NOAA's Hydrometeorological Prediction Center thinks that the thickest snow will drop in extreme northern Maryland up through north New Jersey and west Massachusetts; the agency says that 8 to 10 inches of snow in those areas is realistic. A few way-high-up spots in eastern Pennsylvania could even get a foot or more.

In D.C. proper, just a trace of crystals is more likely. According to ABC7 meteorologist Alex Liggitt's estimate, snow totals "will be on the order of a dusting around the D.C. Metro, to 1-2 inches in the western suburbs, to 5 inches or more in the higher elevations." Liggitt says to expect the liquid/solid changeover to occur around noon on Saturday (earlier out west), and to also prep for loads of cheer-drowning rain. All in all, it looks like a miserable day. Sorry, Marine Corps Marathon runners!

Here's a snow-accumulation map that our weather guys posted earlier today. Note the higher numbers in the mountains:{ }

The HPC also has a nifty experimental tool that generates maps showing the probabilities of snowfall. Here's are the places in the Mid-Atlantic that could get up to 2 inches of snow on Saturday, according to the program's calculations: