By Nic Loyd, WSU meteorologist, and Linda Weiford, WSU News
A rare weather phenomenon flashed and boomed over parts of the Palouse last Thursday night. Lightning and thunderclaps accompanied tumbling snowflakes in what meteorologists call a thundersnow.
The Nov. 16 event moved through areas including Moscow and Pullman within a 10-minute time period. Though brief, it presented an enthralling, seldom-seen show.
As the thundersnow moved into Pullman at 9:37 p.m., heavy rain was falling and previously calm winds had gusted to 28 mph. By 9:40 p.m., a rain and hail downpour dropped visibility to 1.75 miles, compared to the standard “clear” value of 10 miles.
By 9:48 p.m., the show was in full force.
![Thunderstorm lightning](https://s3.wp.wsu.edu/uploads/sites/609/2017/11/Thunderstorm-lightning-450p.jpg)
Bursts of light and rumbling thunder disrupted the quiet as many residents prepared for bed. Yanking back curtains or stepping outside, they experienced winter’s version of a summertime occurrence: Thunder and lightning combined with howling winds and a mix of snow and hail.
How did this happen? A precise convergence of circumstances involving layers of warm and cold air. The air closer to the ground was warmer than the layers above — but still cold enough to create snow. Also present was moisture from clouds and thermal instability.
Although thundersnow usually portends heavy snowfall, not this one. With temperatures in the mid-to-upper 30s, it was too warm. When we awoke Nov. 17, the only remnant of what we saw and heard the night before was a winter dusting on the ground.
Speaking of which, with the exception of the mountains, we probably won’t see more snow by Thanksgiving. Seattle, Spokane, Pullman-Moscow — you name it — all can expect more cloudiness, rounds of rain, warmer temperatures and plenty of breeze.