End of meteorological winter doesn't guarantee snow's all done
Posted March 1, 2016
You've probably heard us mention "meteorological" seasons that are a little offset from the traditional ones that are marked with astronomical passages.
They are three-month periods that divide the year a little more neatly with regard to typical weather conditions and temperatures, and there is also some element of convenience in keeping records that don't split individual months into different parts.
As we ended leap day for 2016, we also closed out meteorological winter, but of course, as with any change of season, the process is gradual and the fact that we're heading into meteorological spring doesn't preclude the potential for a few more bouts with cold weather, or even some wintry precipitation.
It does mean that from a historical perspective, we're moving past the part of the year with the highest chances of snow. A week or two ago, Greg Fishel put together a graph to show on the evening news that captured those statistics for the Raleigh area in an interesting way.
He broke the prime "snow season" into a four-month period, and then looked at three 10-day periods centered on the early, middle and latter portions of each month. The numbers on the graph represent the average for each of those 10-day periods of the probability of measurable snow occurring on any one day.
So, to take one example, the middle 10 days in January have about a 4.1 percent chance of measurable snow (so you'd expect any individual date in that time frame to have measurable snow about once in 24 years). You can see that while there's some variation (owing in part to the relative rarity of snowfall here), the trend, as you'd imagine, is for snow chances to peak from around mid January through late February/early March, then trend downward rather quickly by the time we get to April. It might surprise some of you, though, to find that the chance for the first part of March isn't much different from the first half or so of January.
While chances for additional significant snow do ramp down as we head on into Spring, there have been some rare but notable snowstorms during that time frame, including, as just a few examples, snows in Raleigh like the 7 inches that fell on March 24, 1983, 5 inches on March 26, 1971, 10 inches on April 3, 1915 and almost 2 inches on April 18, 1983.
As for this year in particular, there simply isn't a way to know with any confidence whether we'll see any more significant snows.
As I write this, there are hints of some possible wet snow, mainly north of the Triangle, developing Thursday night into early Friday, March 4th, but that system remains a few days away and subject to significant uncertainty.