Today’s weather pattern is a real treat to look at on satellite. We have marginally unstable air moving inland, and this air is just unstable enough to give crustal clear, bluebird skies over the ocean but heavy thundershowers over land. Why is this?
The Pacific Ocean is only in the mid-50s, and the air over the Pacific is nearly the same temperature (or just a few degrees warmer). Meanwhile, the air over Western Washington/Oregon is about 10 degrees warmer, with Portland currently sitting in the upper 60s. As this air moves over land, the upper levels stay cool while the surface warms, destabilizing the atmosphere and causing convection. Uplift from the Coast Range, Willapa Hills, and Olympic Mountains also helps surface air parcels tap into some of the instability at the mid and upper levels of the atmosphere. This convection results in clouds and showers, some of which have been quite heavy and contained a few bolts of lightning.
Additionally, there are numerous “mountain waves” in the lee of the Cascades and even over the Rockies. Mountain waves form when air is forced upward by terrain and oscillates around a stable layer on the other side, much like a weight oscillates up and down on a spring.
Just another example of how terrain plays such a huge role for our weather. And the imagery from the new GOES-17 satellite is absolutely captivating.
