Kevin Myatt is The Roanoke Times' weather columnist.

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• We got graupel, but not on official record
• Moisture could get caught up in cold blast
• Forecast for Weather Journal: Partly print, with frequent Internet
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• Sprinkles or flurries possible Tuesday, but maybe something bigger for the weekend?
• For now, it looks like a quiet, mostly mild week ahead for SW Virginia
• Coldest morning of winter so far likely across much of Southwest Virginia; Tuesday precipitation looking doubtful
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@KevinMyattWx

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So why has winter decided to get so darn wintry again in Southwest Virginia?

For the second weekend in a row and the third in the past eight weeks, the region faces a winter storm expected to put down several inches of snow, possibly mixed with sleet and freezing rain, on Friday and Saturday as a complex storm system from the Gulf of Mexico moves our way.

By early February in some recent winters, Roanoke has trailed the likes of New Orleans and Victoria, Texas, in seasonal snowfall. A year ago on this date, Roanoke had four-tenths of an inch of snowfall for the season; today, Roanoke is within three-tenths of 30 inches.

This winter, the Star City finds itself keeping pace with Boston and Minneapolis in snow totals. And Blacksburg, at nearly 3 feet, is set to surge past Anchorage, Alaska, and Denver on the snowfall charts with even a moderate amount in this weekend's storm.

Very likely, this is not the last winter storm. We could be looking at more snow as early as Tuesday, and it appears likely that potential winter storms will be moving down the tracks one after the other like train cars through at least midmonth, possibly later, as even colder weather spills down from Canada.

This weekend's storm

Think of this weekend's storm as two runners in a relay race. One hands the baton to another.

A low pressure system moving northeastward into the Tennessee Valley, to our west, will transfer energy to a low developing off the coast of the Carolinas.

How quickly and smoothly that transfer occurs will determine how much snow, sleet and freezing rain we get.

An early, smooth transfer means we get more snow. The new low on the coast, spinning counterclockwise, will pull colder air southward through the upper layers of the atmosphere, ensuring what falls is snow.

A slower, clumsier transfer means the low to the west stays intact longer, allowing it to pull more warm air northward over the cold air at the surface. The longer that happens, the more sleet and freezing rain falls.

If we get all snow or mostly snow, amounts could top a foot. That is likely north of Interstate 64. Someplace up by Winchester or Front Royal will probably top 20 inches. Some of those 30-inch rumors that have been floating around may come true on the ridgetops along Skyline Drive.

The more freezing rain falls, the more the danger of damaging ice accumulations. This is of particular concern in an arc along the Virginia-North Carolina border curling northward west of Interstate 77 into the far Southwest Virginia coalfields and southern West Virginia.

Between those two zones -- including the Roanoke and New River valleys -- a mix of precipitation types is likely to occur, making accumulation forecasts very difficult. My best guess now is that at least 6 inches of snow/sleet mix will fall in the valleys, with more to the north and less to the south, beginning Friday morning and stretching into Saturday. Visit the Weather Journal blog on roanoke.com for the latest updates.

Slight changes in the movement of systems and the temperature of air high in the atmosphere could swing Roanoke and New River more toward damaging ice or toward another piling-up kind of snowstorm.

This winter overall

The push and pull between warm, moist air and cold, dry air evident with this storm is descriptive of the entire winter so far.

This battle occurs every winter, but it is rare that heavyweights show up for the fight in both corners.

El Nino, the periodic warming of central Pacific sea surface temperatures, is moderate to strong this year. That is juicing up the southern, or subtropical, branch of the jet stream, bringing wet storms out of the Pacific and across the southern half of the nation regularly.

Meanwhile, high pressure over Greenland has persisted most of the winter, causing the jet stream to buckle southward into the East, delivering repeated cold air masses.

It's a battle of the tropics vs. the tundra. When the tundra prevails, we have cold, dry weather with little precipitation. When the tropics prevail, we have mild weather with soaking rain.

We've had periods of each of those this winter, but most of the time the two heavyweights are slugging it out to a draw, and we're caught in the middle.

That's when we get snow and ice, when the cold air can't push away the moisture, but the moist warmth can't overcome the cold.

Lots of places to the north are cold enough. Lots of places to the south are wet enough. But, many times this winter, only the Southern Appalachians and Middle Atlantic regions have been both at the same time.

That's how Roanoke can have more snow than Boston.