|An annular eclipse--the sun is not completely covered by the moon|
here) to see what proportion of the sun is covered and when. For Seattle, the answer was about 83% starting around 6:44 PM (time is in UTC/GMT).
Here is the official National Weather Service sky cover forecast for 5 PM Sunday:
What about our latest WRF weather model runs? Here is the predicted cloud liquid water integrated from the surface to the top of the atmosphere at 5 PM and 8 PM Sunday.. Bright white would be thick clouds, gray--thin clouds. If you believe this, there is a CHANCE for a thinning of the approaching clouds along a swatch over the southern and eastern portions of Washington.
here) and you will know the story.