Before sitting down for turkey dinner, Bloodworks Northwest is urging everyone to roll up their sleeves and donate blood.Bloodworks Northwest issued a plea for donations this week as the organization braces for the holiday season downturn, when the number of donors drops by 15 to 20 percent. Blood donor centers across the state will operate extended hours to make donating more convenient.The Bloodworks Northwest Vancouver Donor Center, 9320 N.E. Vancouver Mall Drive, Suite 100, is typically open Tuesday through Saturday. All centers are closed on Thanksgiving, but the local center is open 8 a.m. to 4 p.m. Wednesday, Friday and Saturday.The Vancouver Donor Center will also be open additional days and hours throughout December. Here are the additional holiday hours:• Monday, Dec. 18: 8 a.m. to 4 p.m.• Saturday, Dec. 23: 8 a.m. to 8 p.m.• Saturday, Dec. 30: 8 a.m. to 8 p.m.All centers are closed Christmas Day.All blood and platelet donors are welcome, but there’s always a demand for type O blood and for platelets, according to Bloodworks Northwest. Donation takes about one hour.Donors can schedule an appointment by vising the website, schedule.bloodworksnw.org, or calling 800-398-7888.Because blood can be broken down into three components — red cells, platelets and plasma — each one-pint donation can potentially save three lives.Bloodworks Northwest supplies blood and blood products for both Clark County hospitals that are used for patients having surgeries, trauma care, organ transplants and cancer treatment.