I don’t know about you, but I was glad to see the tail end of last week. I can’t remember seeing such a variety of weather. Advisories, watches and warnings were in place for snow, rain, freezing drizzle, freezing rain, blowing snow, Wreckhouse winds and Suetes winds…all at the same time! These things did all take place…and more. The more is thunderstorms. The reports started to come in around noon on Wednesday– first from the south shore region of Nova Scotia, then from the Valley and before the end of the day, pockets of thundershowers had popped up everywhere…on the warm side of the system of course. At the height of the storm, a reader reminded me about what Grandma would say. If Grandma heard thunder in the winter, she believed there would be a snow storm 7 days later. Can there be any truth to this?
Perhaps a little grain of truth. Thunder in the winter comes when certain frontal boundaries interact and that might give us a glimpse at what’s to come.
Cold air and low-pressure systems from the north, displacing warm air and high pressure in the south, form an unstable atmosphere and the vertical lift along the frontal line is enough to trigger thunderstorms. That kind of instability is created as a cold front pushes in. The cold front opens the arctic pipeline ahead of a high pressure system. Cold winter highs can sit for 3 days or more. Behind every high there’s another low. It might take a day or two to build into the region. Now we’re close to 6 days. That next, moist weather system could conceivably bring snow.
The "seven days" thing should not be taken literally but in my experience, it’s not usually too far off.
What do I think? Well, I believe that winter thunder does tell us a bit more about how the weather might behave than, say, a groundhog that sniffs its way out of a burrow once a year.