Feb 19, 2012 Snowstorm SummaryThe first significant winter storm of the season was long overdue, but final developed over the central Appalachian region on Sunday Feb 19, 2012. Temperatures had been unseasonably warm in the days leading up to the event (50s and 60s Saturday the day before), resulting in warm ground conditions. It took a timelycombination of colder air filtering back into the region from the north throughout the day Sunday, and then heavier bands of precipitation moving across the region late enough in the afternoon and into the evening, to get snow to begin sticking in earnest. The heavy wet snow that fell across the entire Blacksburg forecast area, including a few inches across north-central North Carolina, was enough to cause quite a few trees and tree limbs to fall onto power poles resulting in extensive power outages. Over 60,000 AEP customers across Virginia and West Virginia were reported without power at one point late Sunday evening. Numerous traffic accidents were also reported during the heaviest snowfall late in the day on the 19th. Snowfall totals are shown and listed at the bottom of this page, with 8 to 9 inches in a number of locations across the Appalachian mountains of Virginia and West Virginia, and 6 to almost 8inches as far east as Lynchburg. Here are a couple of high resolution satellite images showing the swath of snow across the region as observed the following Monday morning:
Meteorology Overview The storm system in general took a common track that passed just to the south of our region from the Gulf Coast to the Carolina Coast, before strengthening and moving northeast into the Atlantic. This track and surface low pressure development is know as a "Miller A" type system, and was common with many of our region's significant snowfalls during the 2009-2010 season. (More information about these kinds of winter storms click here). This storm track often occurs with cold air already in place across the region from an Arctic high pressure system anchorage over the Northeast U.S. That ingredient was NOT in place during the Feb 19, 2012 event, but colder high pressure was slowly building in from the northwest and some of it eventually spilled around the east side of the Appalachians as well. While adequate moisture was expected for a significant event, there were several concerns about just how much snow would accumulate. This depended on whether colder air would drag south fast enough, would the timing of the heavier precipitation (which would also help pull down colder air from aloft) would reach the area during the day time when the sun's energy would help keep the already warm ground above freezing, or would it come in late enough during the day where it would have a much better chance of sticking more quickly (and once that process begins it can accumulate more rapidly). Other questions concerned exactly where the heaviest band of precipitation would set up to bring these higher snowfall rates. Computer models first suggested this would take place more across the north and western portions of the region, and also more during the afternoon. Later computer forecasts suggested this favored zone shifting a little farther south, with colder air arriving from the north a little sooner and heaviest precipitation arriving later in the afternoon and into the evening. These trends resulted in National Weather Service Forecasts trending a little farther south with the heaviest snow (and thus the watches and warnings), as well as slightly higher amounts given the better timing with colder air and lowering sun (thus less melting from below). In fact, these ingredients all managed to come together just at the right time as the surface low moved to near the coast and an upper level wave of energy helped enhance the zone of heavier precipitation, with embedded heavier bands of snow arriving late in the afternoon with colder air now in place. The loop below shows the evolution of the surface features and the radar depiction of the precipitation. The time is labeled at the bottom in universal time (UTC or Z), with 1802Z being 1:02pm local time, and 210Z2 being 4:02pm, etc).
Here is a snapshot of the radar mosaic valid at about 21Z or 4pm, showing some heavier bands of precipitation beginning to move across parts of the New River Valley and north central NC).
Finally, here is the resultant map of snowfall totals as reported to the National Weather Service during and just after this event. Keep in mind that as the snow partially melted from below and also compacted since it was relatively wet and heavy, these amounts could ahve been much higher if it had been colderto begin with. We are extremely appreciate of ALL the many people that relayed snowfall reports to us via the phone, email, or Facebook. Thank you!
Storm Totals Text
|
