“It was one of the most extraordinary displays of lightning that I can remember," said KPLU weather expert Cliff Mass. "There were tens of thousands, not thousands ... of lightning strike yesterday over the region. Just startling."
What caused the atypical show? Not the usual culprit, says Mass, professor of Atmospheric Sciences at the University of Washington.
Thursday night's storm started with unstable air that, with a little nudge upward, is known to whip up thunderstorms, says Mass. And that's exactly what happened.
“It was just perfect. Unstable air, that lift from below, and that released these intense bands of showers," he said.
Normally, the heavy precipitation in our area is associated with atmospheric rivers—currents of warm air and strong water vapor content that start somewhere north of Hawaii then move into us.
“And as it is forced to lift by the mountains, it releases very heavy precipitation," he said. "That was not what happened,” he said.
Because the rain wasn’t triggered by a great atmospheric river, it didn’t rain as much as it could have with such a river, says Mass. Such storms sometimes reach rain totals of 15, even 20 inches.
But it sure did rain quite a bit. During the storm, Lewis County saw as much as 8 inches of rain in some places, Mass says, and a number of weather stations set new all-time daily records.
"It was an amazing concentration of heavy rain," he said.
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The weekly KPLU feature "Weather with Cliff Mass" airs every Friday at 9 a.m. immediately following BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KPLU Environment Reporter Bellamy Pailthorp. Cliff Mass is a University of Washington Professor of Atmospheric Sciences, a renowned Seattle weather prognosticator, and a popular weather blogger. You can also subscribe to a podcast of “Weather with Cliff Mass”shows.
