Chance of Thunderstorms This Evening

Forecast models are showing increased instability this evening, particularly in the mountains and South Puget Sound area.

At this time, the greatest threat for thunderstorms is from 5-10 PM. The forecast model below shows the CAPE (convective available potential energy...or instability) at 7 PM. 

You will notice that the CAPE values in the South Sound are 400-950 j/kg. That’s pretty unstable for our area. 

Why is this happening on a sunny day? Because it’s sunny. Sunny weather allows for daytime heating which greatly increases instability. (We didn’t have enough daytime heating this weekend to support thunderstorms). 

Some cells have already began in the Cascades, with some lightning reported as well. Expect some to move into the lowlands as the evening goes on. 

As always, expect gusty winds, heavy rain, and possible hail and lightning in any showers that move through tonight. Rain returns tomorrow...but from Thursday to Monday it will be sunny and 70-85 degrees!!!!