A wet, winter-like frontal system is now approaching the Northwest and will arrive on Friday, but before I discuss it, let's consider the substantial thunderstorm activity that struck the regional mountains on Wednesday.
The weather radar image around 2 PM Wednesday showed a strong thunderstorm over the northeast Olympics and a line of convective showers over the eastern slopes of the Cascades.
The Seattle Space Needle panocam showed the extensive scale of the Olympic Peninsula thunderstorm:
And the Space Needle cam also indicated a line of storms over and east of the Cascades.
The Wednesday thunderstorms were associated with hundreds of lightning strokes, as illustrated by a one-hour sample during the mid-afternoon on Wednesday:
Why is there so much lighting on Wednesday afternoon?
The air above us was unusually unstable, meaning that a rising parcel of air would tend to accelerate upward if lifted. A measure of such potential instability is called CAPE (Convective Available Potential Energy), and values of CAPE were unusually high over the region (see plot below).
High for the Northwest, but the folks in the Midwest would laugh.
Convection tends to release at the surface warms, but yesterday the process was aided by increasing westerly winds (from the west), which provided strong upslope flow over the high terrain. It helps to give the air a kick upwards to get the instability going.
Finally, a wet, winter-like system is now approaching our region, as illustrated by the latest infrared satellite image (below). Looks like winter!
The total forecast precipitation over the region through Sunday morning is substantial (see below), and should both moisten the surface, add to the water supply, and reduce wildfire potential.
I noticed those massive clouds over the Cascades yesterday afternoon from Seattle and wondered if big storms were happening over the mountains. And I saw the radar action over the NE Olympic Pennisula on the UW’s weather map app, after noticing what looked like a big storm brewing from the south on the Dungeness Spit online webcam.
ReplyDeleteLast night at sunset I was on my front deck near the arboretum reading, looked up, and noticed what looked like popcorn clouds floating high above the east side. It caught my attention so I grabbed a camera. Combined with the fading sky light it was quite beautiful in its own way. The clouds just looked like they derived from unstable air conditions.
I don’t know if I can send a link here to the photograph I posted to Instagram this morning (Thursday) but I’ll try. If it can be viewed, the white peak right of center on the Cascades crest line is Glacier Peak for reference.
https://www.instagram.com/p/DaBKqanmmQ4/?utm\_source=ig\_web\_copy\_link&igsh=MzRlODBiNWFlZA==
This is why I rarely leave the safety of my man cave.
ReplyDeleteWe were on top of Sahale Peak when we noticed a lot of instability in the sky.... The storm caught us surprise on the descent to Cascade Pass.... It was... Exciting :)
ReplyDeleteSahale Peak. Kind of a loose rock mountain as I remember.
DeleteLightening sparked a wildfire in the Olympics. Good timing on cool and rainy weather
ReplyDeleteYes there is always more action over the mountains. Apparently lightning has started a fire in the Western Olympics. Meanwhile here in Bothell there has been only intermittent light rain so far, and no lightning.
ReplyDelete