Still under the influence of that Upper Low off the Coast of Oregon, morning showers with variable skies will be the name of the game again today...The unsettled waves of rain with sunny breaks will become more "settled" tonight into Friday. Unfortunately mother nature is going to settle on Rain not Sun until SUNday (how appropriate).
Patchy clearing today will add to the possibility of afternoon thundershowers popping up in this unstable air mass as another surface trough moves through. Best chance for this type of storm will be through the eastern southern interior. When they do happen they will track from south to north.
As Upper Low makes a move east, a significant amount of moisture from the south, will be drawn up over Northern Washington and into BC. Best chance of embedded thunderstorms is for areas south of the Canadian Border, however they can't be ruled out for the southern interior. The biggest issue with this move will be the volume of rain. Exact amounts and where the heaviest rainfall will occur is totally dependant of the track ( direction and speed) of this system but the potential exists for total accumulations of upwards of 40+mm for some areas. Make sure that water has a safe place to go, otherwise flood / washout damage may occur.