Drought conditions in Washington, Idaho and Oregon should improve this winter, but worsen in much of the West, the National Oceanic and Atmospheric Administration predicted Thursday. NOAA primarily based its outlook for December, January and February on a La Nina expected to prevail for a third straight winter. La Nina winters are typically cold and wet in the northern U.S., but warm and dry in the southern U.S. La Nina’s effects are most pronounced in the Lower 48 in far north or far south. For regions in between, such as Southern Oregon, Southern Idaho and Northern California, La Nina winters can be mild, harsh or average. Climatologists consider it a toss-up.