Today will be pleasant break in the weather with some sun and temps getting into the mid-50s. But things are going to change in a big way.
A very moist pattern will set up for a few days and flooding will probably occur along some of the local rivers. A warm front will approach the region tomorrow am...and we should be cloudy and raining on Tuesday morning. This will bring a warmer air mass in and the winds will strengthen during the day from the south. Particularly strong SE winds over NW Washington from Everett, across Whidbey, into the San Juans. The mountains will get several inches from this first pulse. The rain will lessen a bit in the afternoon, before the second and stronger system hits. This one will be very wet and some windward slope regions will be hit by 5-10 inches. You can bet on river flooding. The saving grace for the central and northern sound is that we will be somewhat rain shadowed because the winds will have a large westerly component.
The graphic you see shows the 24-h rainfall ending Wednesday morning at 4 AM. The reds are 5-10 inches--enough to cause the rivers to really surge. What makes this event even more of a problem is that is the two rain events have very little separation...the soils will be saturated from the first and then they will be hit hard by the second.
Wednesday morning will see drying. The end of the week should be relative dry with normal temps and a huge ridge of high pressure builds in Friday and Saturday (see figure for Friday upper air pattern and huge ridge along the west coast). The weekend may be extraordinarily nice...dry and fairly warm. But it is too early to be sure about this.