As pockets of snow work through Western Washington, a few of them have been vigorous enough to produce something very unusual in Western Washington: lightning, thunder, and even a waterspout while snow is going on!
Even though temperatures barely budged today, the combination of slight “daytime heating” and cooling aloft increased the instability in the atmosphere. That’s the ability of pockets of air to rise faster and higher in the atmosphere. This brings heavier precipitation to areas briefly, but also the more quickly-rising air can produce weak areas of rotation in a snow shower. This happened off Birch Bay in Whatcom County today where a brief waterspout was sighted.
Also in Whatcom County and again in South King County Sunday evening, a few lightning strikes were produced. That’s thundersnow! It’s fairly rare but sometimes occurs when there is a heavy pocket of snow. Once again, quickly rising air is responsible for this, as within the fast-rising air, snowflakes bouncing off one another form a static charge — the same kind of static electricity that can give your finger a shock on a doorknob on a cold, dry day! However, the charges that produce a lightning bolt in thundersnow is far more powerful, and is as dangerous as a lightning strike in a traditional thunderstorm.
Interestingly, the thunder produced by thundersnow often has a different type of sound from a typical thunderclap. The sound waves are muffled by the snowflakes, instead of the sound waves reflecting off raindrops. So it will sometimes wind up being a slow rumble of thunder heard over a wide distance, though there is still a sharp “clap” of thunder in the immediate vicinity.
As we have seen with thundersnow on Sunday, when that occurs, it is associated with very heavy snowfall rates and even with snow mixing with sleet. This can produce treacherous driving conditions in a big hurry.