Friday, October 30, 2009
Weather columnist Kevin Myatt: Prediction: A wetter, whiter winter is ahead

MATT GENTRY The Roanoke Times
An unidentified couple walk at the snow-covered Blacksburg Municipal Golf Course in Blacksburg on March 1. Last winter's only widespread snowstorm in Southwest Virginia dumped 4 to 10 inches across most of the region.
Kevin Myatt is The Roanoke Times' weather columnist.
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@roanoke.com
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Fact or fiction: In Roanoke's biggest snow months on record, snow usually makes up more than half of the total precipitation for the month.
January 1996 is generally considered the last really big snow month for Roanoke and most of Southwest Virginia. The Star City got 28 inches of snow that month, with 2 feet of it on Jan. 6 and 7.
Melted snow equaled 2.67 inches of liquid at Roanoke in January 1996; rainfall totaled 4.2 inches. In that snowy month, rainfall was about three-fifths of the month's precipitation total.
January 1966 is still Roanoke's snowiest month on record with 41 inches. But it also rained more than 4 inches than month, while melted snow totaled 3.28 inches.
So it would seem that, after a quick look on a couple of the most extreme examples, the opening statement of this column is fiction.
It certainly is fiction regarding a "normal" winter that would produce about 22 inches of snow in Roanoke. Snowfall makes up only about a quarter to a third of total precipitation in January and February during a statistically normal winter.
Eventually you will find an exception to any rule. Melted snow did total more than rain in February 1960, which included the first two weeks of the incredible five-week, 58-inch snow blitz that stretched well into March. But it still rained more than 3 inches in early February before melted snow totaled a little less than 4 inches of liquid the rest of the month.
The truth about Roanoke winters is this: More often than not, when it snows big, it rains even bigger.
That is what has me thinking that this winter, more so than any in recent years, maybe more than a decade, has a decent shot at being a 1960s-style big-snow winter for Southwest Virginia.
Abundant moisture is essential for big snows in Southwest Virginia. Cold air is needed too, obviously, but a lot of cold air and little moisture means weeks of cracked hands with very little snow. Thick moisture and just a few shots of marginally cold Arctic air can, if timed right, deliver a few big snows amid lots of rain.
I definitely think this winter is going to be wet. El Nino is active, and we've already seen earlier this week how seemingly weak storms can quickly become soakers with a little extra subtropical energy. I think we'll see more soaking rains and dreary winter days than snow lovers or sun seekers want.
The big question is how often cold air will be there to meet the moisture, and just how thick that cold air will be.
We have seen repeated occurrences of high pressure near Greenland forcing the jet stream southward into the United States. That's what brought repeated unseasonably cool shots into the central and eastern U.S. this summer.
If this event, called the negative phase of the North Atlantic Oscillation, becomes a pattern, we will have repeated intrusions of Arctic air this winter.
A concern of mine about this winter is getting situations where abundant Gulf moisture is flowing on top of a thin but frigid layer of Arctic air trapped against the mountains. A scenario like that could trigger a major ice storm.
My best guess: We will see frequent abundant precipitation events this winter. About two-thirds will be primarily rain. It's the timing and potency of the remaining third that will determine how winter 2009-10 is remembered.
I think this winter has one pretty big storm in it, with widespread 8 inches-plus, two or three 4-to-8-inch type storms, and perhaps as many as a half-dozen light snows and mixed winter storms. In my opinion, the risk of at least one major ice storm this winter is high, and the risk of a foot-plus monster snowstorm is moderate.
There will probably be at least one borderline wet snow that buries higher elevations while brushing or missing the lower elevations, but probably fewer northwest-wind upslope snow events that hammer the mountains' western slopes while leaving areas east of Interstate 81 mostly dry, like what happened frequently last winter.
My picks: Roanoke 23 inches, first 1-inch snow on Dec. 3; Blacksburg, 30 inches, first 1-inch snow on Dec. 4.
Now it's time to enter your picks for the 2009-10 Weather Journal snowfall prediction contest.
Snowfall prediction contest
(1) You must give the following information to be entered:
Your name
City or town of residence (nearest town or section of county if rural). School affiliation is OK for students.
Projected date of first 1-inch snow in Roanoke, as reported by the official snowfall measuring station at WDBJ (Channel 7) studio.
Predicted total inches (rounded to nearest whole number) of snowfall between Nov. 15 and April 15 in Roanoke.
Projected date of first 1-inch snow in Blacksburg, as reported by the National Weather Service office.
Predicted total inches (rounded to the nearest whole number) of snowfall between Nov. 15 and April 15 in Blacksburg.
(2) E-mail above information to weather@roanoke.com before the end of Friday, Nov. 6. Entries will not be accepted after midnight on Nov. 7.
(3) Each entrant’s score will be calculated by adding the number of inches off each snowfall seasonal prediction and the number of days off the first 1-inch snow predictions. The lowest score wins.
It is OK to send multiple people’s entries on one e-mail, such as a family or a classroom. It is also OK to send an attachment … such as a Word document or an Excel spreadsheet … with many individual entries, as long as you identify the group they are coming from (such as a school).
The first 1-inch snow means the date on which there is at least 1 inch of snow on the ground. That means that if it snows nine-tenths of an inch before midnight on Dec. 12 and one-tenth of an inch after midnight on Dec. 13, Dec. 13 is the date that will count.
We are using official statistics, which means that sleet also counts as snowfall. If there is an inch of sleet, it counts as a 1-inch snowfall whether or not there are any snowflakes mixed in, because it will be recorded as an inch of snowfall in official records. Glaze ice from freezing rain does not count as snowfall.




