January 29-30, 2010 Snowstorm Summary
The second major winter storm of the season blanketed all 40 counties in the Blacksburg County Warning Area (CWA) with at least 5-6" of snow, and in most cases much more than that. This was not quite as historic as the December 18-19 snowstorm that brought 1-2 FEET of snow to many locations, but it was still significant, and brought most locations well above their average snowfall for the season, if they weren't already there.
The following is a brief review of the evolution of the storm, the snowfall totals over our area, and where we stand with our snowfall totals for the season. Near the bottom of this page is a map of the final snowfall totals.
In contrast to the December 18-19 storm system which moved northeast out of the Gulf of Mexico and then strengthened quickly along the southeast U.S. coast ("Miller A cyclogenesis"), the late January storm moved on a more easterly course out of the southern Plains and across the deep South before heading out to sea off the Carolina coast. This path and evolution result in what we call an "overrunning" event, which does not usually pull in as much moisture from the Atlantic as a deepening cyclone, but often allows plenty of cold air to remain in place. Still, in this case there was ample moisture that had been pulled up from the Gulf, and much like the December event, there was a large area of cold/dry high pressure in place across the Great Lakes and northeast U.S. The loop below shows the track of the low pressure center and the radar composite from the morning of Friday January 29, through early morning Sunday January 31. (Click here for more information about "Overrunning" and "Miller A" storms, as well as other categories.)
Animation of surface pressure analysis and radar composites through the period the storm impacted the Carolinas and Virginia.
Forecasts from various computer guidance models began to come into agreement several days in advance, and suggested that the heaviest snow was aiming for southwest Virginia and northwest North Carolina, with a range of 4-5 inches across the far north, and as much as 10 inches across the south (the Virginia - North Carolina border consistently looked like the heart of the heavy snow area). A forecast map of snowfall made by this office on Thursday January 28 reflects this thinking.
Forecast snowfall from the NWS issued Thursday afternoon Jan 28.
A Winter Storm Watch was issued Wednesday afternoon January 27 (2 days before the storm reached the area), for the southern half of the CWA, and then early Thursday morning was expanded northward as indications were that heavier precipitation might make it farther north.. A Winter Storm Warning was posted on Thursday afternoon for all but two counties in the far north (where we had a winter weather advisory posted). This was 24 hours before the snow began in the far southwest portion of the area, and 30 hrs before it began in most locations (our goal is 15 hours ahead of time).
The image below shows the final snowfall totals from this event across the 40-county region covered by the Blacksburg/Roanoke NWS. The zone of highest amounts were slight farther north than the foreast from Thursday indicated, which was a result of some of the heavier snow bands shifting farther north than previously anticipated, and also due to the fact the sleet mixed in across the south, resulting in slightly lower totals. All in all, the forecast amounts were reasonably close to what occured, with a bit of an overforecast across the south and underforecast across the far north.
Storm total snowfall analysis map for Jan 29-30, 2010.
Summary of snow totals for the season compared to the 30-year average
The following table shows the totals from this storm at our five primary climate stations in our region. All stations are now above their 30-year average, and we still have two more months in which significant snow events have occurred in the past. Even early April has seen significant snowfall in the mountains.
Comparison to another significant "Overrunning" snowstorm
Most snow events in the overrunning category have produced rather modest snowfalls across the Blacksburg CWA, and in fact that last widespread overrunning snow event that impacted all 40 counties was on December 4, 2002. The snowfall analysis map for that event (below) shows that the January 2010 event was almost double in many locations. Most others have resulted in either less overall snowfall, or over smaller areas, so this was a pretty impressive snowfall for an overrunning event.