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.


Comments

Post a Comment

Popular posts from this blog

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

Strong Atmosphere River Heads into British Columbia and Southeast Alaska

Image
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska.   And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor.  You can see the current of moisture extending from near Hawaii into central BC.  This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California.   A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
Read more