There is a saying that it will snow a week after hearing thunder in the winter. This coming Saturday may put that to the test.
Many locations in our region heard thunder on Saturday, a record warm Jan. 11 with upper 60s highs that also brought damaging gusts in some places, and there is at least some chance of seeing snow on the upcoming Saturday as the atmospheric pattern begins a flip from unseasonably warm to a fairly prolonged period of at least seasonable cold.
After a cold front follows Tuesday’s mild, rainy system (which also brought thunder in spots), high pressure to the northeast may bank just enough cold air against the Appalachians ahead of the next wet storm system that a mix of snow, sleet and freezing rain may occur late Friday night into Saturday.
The low’s track to the north should be enough to pull in enough milder air to eventually change the precipitation to rain, but it is the start of changes that promise a much colder outlook to the final dozen days of January.
If you’ve lived in this region long enough, you should know by now that a surge of really warm weather in the middle of winter usually isn’t any kind of sign of an early spring, but instead often portends turbulence in the atmospheric pattern that will eventually bring down the cold air.
Roanoke has hit 60 degrees at least once in January about 90 percent of the time in its period of record, not doing so in only 11 of 109 previous years of weather data. The last time there wasn’t a 60-degree day in January, and so far the only such January of the 21st century, was in 2014.
Roanoke has averaged three 60-degree days in January over the past 10 years. The 10-year average for 60-degree days in January hit six about a decade ago, which was the highest point it had reached since peaking at seven in the 1950s and 1930s.
Through Tuesday, Roanoke has hit at least 60 degrees three days this month, and fourth may happen Wednesday, quite possibly the last of the month given the pattern ahead.
There were five 60-degree days in January 1960 before February and March unleashed a 57-inch snow barrage that ran the seasonal snowfall total to a record 62.7 inches. Even January 2010, in a break between December’s 18-inch snowstorm and two more 10-inchers in late January and early February, managed a couple of days above 60.
Obviously, hitting 60 degrees isn’t a magic barrier that triggers big snowfall some days later, nor is hearing thunder.
But January warmth capable of firing thunderstorms does often signal a jet stream pattern moving from a steady west-to-east flow, with middling temperatures, to something with more big ups and downs.
That is the case this time, as we have been under a huge northern swing of the jet stream that brought astounding lower 70s highs to Boston in January and spread severe storms over multiple states from the Mississippi River to the East Coast. But soon, as high pressure repositions over the Northern Pacific and Alaska, we’ll see cold air pressed deeply southward across much of the eastern U.S.
At least at the outset, this doesn’t appear to be a pattern that will threaten below-zero low temperatures in our region, as the polar vortex isn’t opening enough around the North Pole to let the really frigid stuff pour down. That may or may not come, but if it does it’ll be down the road.
But next week does look to be seasonably cold to a little below normal, with 40s highs and 20s lows most days.
It also appears the storm track will edge around this cold air mass to the south, bringing several wet storm systems, any of which could bring a round of snow and/or ice — or just cold rain — depending on the track and atmospheric particulars with each individual system.
Our winter has turned busy quickly. We may in fact get snow or wintry mix this weekend a week after thunder, but then, last weekend, we had thunder four days after snow.
Weather Journal appears on Wednesdays.