GREENSBORO, N.C. – The City of Greensboro will activate White Flag warming centers tonight in response to expected freezing overnight temperatures. Address: 305 W. Gate City Blvd. Open for: Men and women. Glenwood Recreation Center. Address: 2010 Coliseum Blvd. Hours: 8 p.m. to 6:30 a.m. on December 6. Open…