You can see the impact of this "first autumn storm" in the precipitation climatology Seattle. Below is the daily climatological probability of enjoying at least .01 inches at Sea-Tac. At the end of August the probability jumps to roughly 25%!
Rain comes in on Wednesday, associated with a robust Pacific front, with the 24 hr total ending 5 PM Wednesday being substantial over the Olympic Peninsula and north Cascades. On the coast, some locations could get several inches.
The Wednesday system is associated with a front connected with a very intense low center moving into southeast Alaska (see surface weather map at 2 AM Wednesday). Let's say that some of the Alaska cruises will be enjoying some rock and roll that has nothing to do with music.
Another system comes in late Friday and Saturday, with substantial amounts shown in the 24h total ending 5 AM Saturday.
All this rain will be associated with a massive reconfiguration of the atmosphere to a more fall-like pattern. To illustrate, here is the upper level map for around 30,000 ft ASL, showing the jet stream winds in colors. At 2 PM today, there is a ridge (higher pressure and heights) stretching from the Aleutians to California, and the jet stream (yellows and light green colors) is to our north.
But by 11 PM next Saturday everything is different, with a fairly strong jet stream heading right into our region. You won't have to worry about smoke in the Northwest. You will have to worry about finding your umbrella.
This pattern change will have a huge impact on wildfire potential, greatly reducing the changes of new fire initiation or the growth of old, smoldering burns.
from Cliff Mass Weather and Climate Blog https://cliffmass.blogspot.com/2019/08/the-first-autumn-storm-makes-landfall.html
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