June 15, 2021

Thunderstorms Possible This Afternoon

 The final stage in our wet interval is about to begin:  the potential for thunderstorms in western Washington.

Lightning has been no stranger to our region the past two days.  For the 24-h ending Monday at 1 AM, eastern Washington was hit by hundreds of cloud to ground lightnining strokes.

And the next 24h, ending 1 AM this morning, continued to show lightning hits over the region east of the Cascade crest.

 I suspect that some of you on the western side will get to enjoy a few "boomers" as well. today...but, let me be clear:   the thunderstorms will be scattered.

Before I go into that, I note that the precipitation over the past 72h has been substantial (see below), with 1-2 inches over SW Washington, where spring had been the driest.  And there has been a nice wetting of the slopes in eastern Washington, which should help to delay the wildfire threat.  And enough rain in Palouse to assist dryland farming a bit (but they still need more).  June precipitation will be above normal over much of the region, partially balancing out the earlier dry spring.

Oregon has been similarly blessed with rain, with SW Oregon being inundated in places and some locations getting 3-8 inches:

Back to lightning.   The recent radar image  (below) shows lots of scattered showers over the region, including a line coming in off the ocean and more substantial convection over northeast Oregon.  There are some lightning strikes with the latter.

The air above us now is quite unstable, meaning that a little upward motion can result in the development of convection, including thunderstorms. A measure of this potential instability is called CAPE:  Convective Available Potential Energy and values will be moderately high over western Washington this afternoon (purple and blue areas).  Not Midwest high, mind you.

And to get instability going it helps to have something that gives the air parcels an initial shove upwards...and we have that today:  an approaching upper-level trough (see map for 500 hPa--about 18,000 ft).

Anyway, some scattered thunderstorms are quite possible later this afternoon over western Washington and I certainly expect some thunderstorms over eastern Washington.


  1. Yep, Enumclaw here. We just had a good thunderstorm with lots of lightning and gusty winds with hail pass over us!

  2. I'm rooting for thunderstorms here in the convergence zone, but experience has taught me not to get my hopes up. Not in W. Washington.

    1. Thunderstorms in the spring and summer in western Washington is like snow in the winter here. It's rare.

    2. Yeah, I know, but it doesn't stop me from wishing. I have lived numerous places with more "entertaining" weather.

  3. I noticed a lot of the convective showers formed south west of seattle but then dissipated when they got into the seattle area. any explanation for this?

  4. June rain totals look to end up above normal in western Washington, but unless there is more rain before the end of the month, most of Eastern Washington will be below normal.

  5. Hi Cliff, looking at the extended it seems that summer is starting early? No "June gloom" this year so far.
    One thing that concerns me is that I have noticed the snow levels at Mt Rainier in my usual hiking spots are lower than previous years at the exact same time despite this being a higher snow year. Is this because the sun has been so strong and has melted the snow quicker than usual?


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

Mountain-Top Instability

Over the lowlands of Washington State,  today was sunny and generally clear.  Not a drop fell out of the sky. But something very different h...