For Sunday afternoon: Convergence zone showers persisting in a northwest-southeast line from Granite Falls to Skykomish and then deeper into the Cascades diminish with the arrival of high pressure at the surface and a ridge of high pressure beginning to build in aloft

For the remainder of today, expect partly to mainly sunny skies in the lowlands with a bit more cloud cover in the foothills and mountains.   With still a bit of an onshore flow and a cool post-frontal airmass in place, we'll still end up with temperatures a few degrees below seasonal norms despite the sunshine.

High pressure at the surface and ridging aloft will make for a very tranquil end to the day.  With low humidity, mainly clear skies, and light winds, we will have near-perfect conditions for radiational cooling tonight.  Monday will start out very chilly with morning lows near or just above freezing in Seattle and along much of the central and north Sound I-5 corridor and islands with widespread 20s in colder areas like the south Sound.  Frost looks to be widespread and there could be some slick spots of frost on elevated roadways early Monday.  

This will be the coldest night since Jan. 22 when it got down to 29 degrees at Sea-Tac.

Temperatures will quickly rebound Monday with good amounts of sunshine and an increasing offshore flow as high pressure moves to the east.   The difference between the high and developing low pressure in the Pacific will force an east-to-west air flow to set up during the day and downsloping out of the Cascades.  This will serve to keep us dry and mostly sunny Monday, and will also give us a boost to afternoon highs to above-average.   Highs will top out in the mid 50s for Seattle and many lowland spots, but some foothill locations will reach the upper 50s to perhaps near 60 where it will also be breezy at times.

High clouds will stream during the afternoon and evening Monday signaling an abrupt change for Tuesday.  A wet low pressure center will ease in from the Pacific bringing some showers early on Tuesday morning and continuing at times through the day.   Showers will persist in the forecast for Wednesday and early Thursday as the low gradually sinks southeastward.  Rainfall amounts around the Sound don't look heavy through the period with less than one-half inch total likely through Thursday.   More rain will fall in foothill locations (especially the southern faces of the Olympics), southern Hood Canal and across parts of the north.   The resorts will pick up some more fresh snow here and there.