BIRMINGHAM, Ala. (AP) - Forecasters say a cold front is expected to bring frost and freezing temperatures to much of the state. The National Weather Service in Birmingham is projecting that wind chill values will plunge into the 20s in parts of Alabama by late this weekend. Wind Chill, commonly used to describe how cold it feels, is the combined effect of low temperature and wind. For Halloween night on Friday, forecasters expect mostly dry weather for trick-or-treaters. They say temperatures around 10 p.m. Friday will be around 44 degrees in metro Birmingham, and slightly cooler in areas to the northeast and to the south. By early Saturday morning -- when some of the coldest air arrives -- temperatures are expected to plunge into the lower to mid-30s in the Birmingham, Gadsden and Anniston areas.