During the past few days, we drifted back to the large-scale pattern of above-normal temperatures and ridging (high pressure) over the West Coast.
But that is over now.
We are moving back to a new configuration the atmosphere seems to like recently: high pressure over the central North Pacific and troughing (low pressure) over our region. As a result, expect cooler than normal and wetter than normal conditions for several days.
The upper level (500hPa pressure level) for Tuesday at 5 PM illustrates what we will deal with the next several days. BIG RIDGE south of the Aleutians and a trough over the Northwest. This is not a warm/dry pattern for us.
The precipitation forecast for the next 72h (through Wed. at 5 PM) shows rain stretching from western BC to northern California,
The extended forecast from the North American ensemble (many forecasts) system (NAEFS) for Seattle shows temperatures staying cool (20C is 68F) with lots of clouds through the end of the month.
The sun is rapidly weakening now, the nights are getting longer, and the atmosphere is increasingly showing fall-like circulations. No more 90s in the west, and I would not bet on seeing an 80F anytime soon. This is all very good news for the fire community. Cool, wet weather without lightning. Fire season is rapidly ending.
The city of Seattle can probably quit their ad campaign for water conservation. Our plants will be watered naturally and our reservoirs will start to fill. The level of Chester Morse Lake has greatly stabilized with the recent rains and conservation efforts. The rain this week will result in the levels rising.
The surface temperatures continue to cool offshore, which will influence our temperatures as well. And snow will fall over the high country of the North Cascades and southern BC mountains.
Enjoy the return to normality
Finally, it was really raining in Seattle this AM. Few tenths of inch in places. But it was sunny in Bellingham and Olympia and most every place else. Why? A localized Puget Sound Convergence Zone, with air passing around the Olympics and converging over central Puget Sound. Here is the satellite image around 1145 AM.
So if you are in Seattle and want sun, head out of town. Clouds should be reduced by mid-afternoon,