Saturday, February 09, 2013
Weather columnist Kevin Myatt: This time, Roanoke Valley got biggest snowfall totals
Rebecca Barnett | The Roanoke Times
Dottie, a horse at Mount Regis Stables in Salem, wears a blanket to protect her from the cold as she runs in the snow Friday morning. The Roanoke Valley experienced a snowfall of 3 to 5 inches Thursday night, while areas that usually receive more snow than Roanoke got less.
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Roanoke Valley residents know the drill. We wake up to an inch of slushy muck, puddles of cold rain or a bare ground, and see photos from our Southwest Virginia friends of pristine snow several inches deep covering the landscape 30 or 50 miles away.
Our schools aren't in the long list of closings and delays. Commuters from the New River and Roanoke valleys pass each other on the highways, each noting upon their arrival how much more snow there is in the New River Valley than there is in Roanoke.
On Friday morning, that oft-repeated winter scenario flipped on its head.
The Roanoke Valley was in the circle of heaviest snowfall from an overachieving storm system rushing through Thursday night on its way to becoming part of a historic New England blizzard.
Snowfall of 3 to 5 inches was reported across the Roanoke Valley and surrounding areas from a storm system projected to drop less than an inch of snow, sleet and ice mix — which is what it did in many places to the south, east and west of Roanoke, including many spots that almost always get more snow.
Roanoke's official snowfall, measured at the WDBJ (Channel 7) studios, measured 3.5 inches. Blacksburg's official snowfall totaled only 0.8 inch at the National Weather Service office.
You may never again see Roanoke's snowfall total more than quadruple Blacksburg's.
This from a storm system that until about 36 hours beforehand looked like it would only bring rain with temperatures in the 40s. And even when it became apparent that temperatures would be colder, an icy mix looked far more likely than significant snow.
Temperatures from just below the clouds to the ground were very close to the freezing mark Thursday night as precipitation moved in. With some pockets of air above freezing, snow melted on its way to the ground, either refreezing into pellets of sleet before hitting the ground, or reaching the surface as liquid rain.
It all started just as expected in Roanoke on Thursday evening, with rain and sleet.
But about midevening, temperatures dropped a few critical degrees in the layers of the atmosphere above the Roanoke Valley that had been above freezing. Snowflakes leaving the clouds began reaching the surface. And then, lots of snow started plopping all the way to the ground, and began piling up.
That level of consistent cold was not achieved through the atmosphere over the New River Valley, or most of Southwest Virginia south of Floyd, or areas east of the Blue Ridge, so mixed precipitation or rain continued in those locations.
North of Roanoke, the thick moisture continued only so far, about to the middle of Botetourt County. So while it was cold enough for snow farther north, snow amounts dropped off quite a bit.
In short, Roanoke was perfectly placed Thursday night with just the right depth of cold air and the right amount of moisture so that it neither stayed too warm nor dried up too much.
We look to the mountains surrounding the Roanoke Valley and know they have a major impact on our weather. But the atmosphere is much higher than the mountains, and its actions sometimes overrule the topography, and our meteorological expectations.