It is not unusual to have a few warm days in early October, but with a cooling Arctic and shorter days, the atmosphere is rapidly moving into an autumnal configuration.
Tomorrow and this weekend will be wonderful, but major changes are in store for us starting on Monday.
On that day, a weak front will come through, resulting in general (light) rain over western BC, Washington, and Oregon (see total through 5 AM Tuesday)
Another weak front will come through on Tuesday, so that total precipitation through Wednesday at 5 PM will be more impressive, with the mountains getting several inches (see below)
The forecast highs for Seattle Tac will be in the 70s for a few days, but once the fronts start moving in, we won't get out of the 60s....sorry.
But perhaps what is more interesting are the global changes that are occurring now. The Arctic is rapidly cooling, while the subtropics are staying warm, with the result being that a large north-south temperature difference is developing. This temperature difference is not uniform in space but concentrated in the midlatitudes, something illustrated by the temperatures forecast for October 19th at around 5000 ft (pressure of 850 hPa).
The development of a strong north-south temperature change (or gradient) results in the development of strong winds in the mid to upper troposphere (from 15,000 to 40,000 ft)....also known as the jet stream.
The upper-level wind forecast at 5 PM Monday is shown below at around 35,000 ft. A wavy jet stream is evident, with the strong winds (greater than 125 knots in red) stretching from Japan to California. A very good time to fly from Tokyo to San Francisco.
This jet stream is not going away, with a powerful jet stream extending east of Japan on Saturday, October 14th (see below).
And the jet stream at 11 PM October 19th is not only huge, but headed right for Washington State!
Since storms and active weather are associated with the jet stream, you expect interesting weather on the West Coast....from rain to wind.
Enjoy!