Rain Shadow Storms

I notice the SPC has outlooked a large chunk of Washington state and central Oregon in a slight risk of severe weather. That's out of the ordinary in itself, but the large part of Washington that is outlooked is in the rain shadow of the Cascades. The rain shadow doesn't mean no rain is ever measured, but most of eastern Washington is a desert climate with annual rainfall totals less than 15". Contrast that with the windward side of the Cascades that receive well over 100" of rain every year!

The images below compare and contrast the vegetation and scenery of both sides of the state. I took these last summer while instructing an 8-day field course, and Washington quickly earned one of the top spots in my favorite U.S. states.

Eastern Washington

Western Washington

Upslope flow in central Washington combined with a Pacific Northwest trough will provide the needed lift for thunderstorm development later this afternoon. Moderate to strong instability (for this area) will be present across the slight risk area with MLCAPE values up to 2,000 J kg-1! Additionally, deep layer wind shear will enhance the potential for organized thunderstorm development and the possibility of damaging winds and hail. The tornado threat looks very slim, but it is not zero. Did I really just type that while referring to Washington? As crazy as it sounds, given 0-3 km SRH values between 150-300 m^2 s^-2, some low-level rotation is possible in north-central Washington with any storms that develop. It should be interesting to watch this event unfold today.