Kevin Myatt is The Roanoke Times' weather columnist.

kevin.myatt
@roanoke.com
981-3341

Weather with Kevin Myatt

Recent columns

• Winter trying again to show up with snow
• We got graupel, but not on official record
• Moisture could get caught up in cold blast
• Column archive

Read the Weather Journal blog

• Many looking past mild, quiet week toward possibly wild weekend
• 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
• Weather Journal blog

#swvawx on Twitter

@KevinMyattWx

• Follow Kevin on Twitter at @KevinMyattWx

Six weeks later, the big snow of 2009 is about to gain a sequel.

Sequels usually aren't as memorable as originals, and the snowstorm likely to move into Southwest Virginia tonight and Saturday probably won't be.

While someone within the readership area of this newspaper will get a foot or more of snow, most folks will probably get a little less. Snowfall of 6 to 10 inches will be likely across most of Southwest Virginia, with the bulk of it falling between this evening and midafternoon Saturday.

This is what we would have called a "big snow" any winter before this one in the 2000s, back when we hadn't seen a snow that gave everyone a foot since 1996, back before December's 14 to 28 inches recalibrated Southwest Virginians' sense of snow bigness.

The coming winter storm is a little bit different species than the one in December.

This is not a tightly wrapped-up low pressure system arising from the Gulf of Mexico and roaring up the East Coast. Instead, it is a vigorous piece of atmospheric energy spinning eastward through the subtropical branch of the jet stream, the wet flow of air gushing out of the Pacific over the southern half of the United States.

A struggle is taking place between the warm wetness of the subtropical jet and the cold dryness of the polar vortex, a counterclockwise spinning core of extremely cold air that has dipped into southeast Canada.

The push and shove between these features has turned the forecasting of this storm into an atmospheric tennis match. At first, it appeared the subtropical jet might be overwhelming, driving the storm into the Ohio Valley, giving us another soaking rain. Then, it appeared the polar vortex might win out, pushing most or all of the snow to our south, leaving us with flurries or cold, dry winds. If you've followed along on the Weather Journal blog this week, you know all about this swinging pendulum.

After lots of flipping and flopping through the week, computer forecast models began converging Thursday on northern North Carolina and the southern half of Virginia as the best spot for truckloads of moisture to crystallize into tons of snowflakes in the Arctic air delivered from Canada.

Now that the large swirl of moisture became clearly visible in the south-central U.S. on Thursday night, it is highly unlikely this storm could simply miss us.

Based on many factors, it could still come in a little less or a little more than forecast. There is at least a slight risk that several more inches could fall than expected, putting this storm on the same plane as December's.

Looking ahead, it's unlikely this will be our last encounter with a winter storm. The overall pattern over the Northern Hemisphere favors continued wet storm systems moving across the U.S. and occasional intrusions of Arctic air into the East. Sooner or later in the weeks ahead, wet and cold will meet again near us.

So, in the end, this may not be merely a sequel, but another volume in a 2009-10 winter storm set.

Weather Journal runs on Monday, Wednesday and Friday.