The May outlook was issued Thursday from NOAA's Climate Prediction Center. Warmer than average temperatures are expected from the Southwest and southern Plains into the Southeast and Middle Atlantic states. Odds favor the final month of spring to end cooler than normal in the Great Lakes and northern Plains. A wet month is in the forecast for the eastern third of the nation, with above average precipitation predicted. Most of the West and Plains are expected to see drier than average weather, which may expand and worsen the drought conditions found in those areas. A persistent La Nina was one the driving factors in the forecast for May and the Climate Prediction Center expects conditions to last for several months.  La Nina occurs when the waters of the Pacific Ocean show a general trend of cooling, the opposite of an El Nino. During La Nina periods, the Jet Stream is not usually active in the Southern U.S. This usually leads to less storms systems and below average precipitation. Cooler than normal weather typically occurs across the northern tier of the country and occasionally wetter periods as well. The latest model guidance, current global patterns, soil moisture/drought conditions, and the current snowpack also impacted the May outlook.