Kevin Myatt is The Roanoke Times' weather columnist.

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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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Many parts of Southwest Virginia will "hit for the cycle" with this next round of precipitation, expected to begin early Tuesday and continue through Wednesday.

It will likely start as snow, change to sleet, then freezing rain and finally to rain. The tricky part is figuring out how long each stage of precipitation lasts, and how much falls during that time.

The lacking part of Tuesday's winter weather scenario is strong cold air damming. There is no really strong high pressure system positioned correctly to keep pressing the cold air southward as the moisture arrives from the southwest.

As a result, the cold air will be eroded as warmer, moist air pushes in aloft. First in the middle layers of the atmosphere, and then at the surface, temperatures will rise, likely getting above freezing by sometime late Tuesday or Wednesday.

That is all that stands between us and a major winter storm. If for some reason the cold air is deeper or more stubborn than expected, the frozen precipitation types may last longer. If it is not as cold as expected to start with or the warm air rushes in faster, the periods of frozen precipitation may be brief.

The best guess at what will happen is that snow and sleet will collect an inch or two before a few hours of freezing rain put about a quarter-inch layer of ice down, before changing to plain old rain. Expect more snow and sleet to the north of the Roanoke-Blacksburg corridor and less to the south.

Because there are so many variables, what actually happens will probably vary at least some from the forecast. All I feel comfortable saying is that this will be a messy system.