I'm not a weather man, but my guess is rain so make sure if you shoot outdoors you have a bag or something for your gear.
You can try the glass museum, the studio would be okay and it's IN Tacoma. Mt. Rainier has many nice places. You could also head up to Snoqualamie Falls. It's always nice but is better during the spring run off. When done, head to the Casino
SnoqualmieFalls.com - The Official Snoqualmie Falls Web Site
All Glass, All the Time | Museum of Glass | Tacoma, Washington
Post your shots when you get back. I'd be interested to see.
Jason