With a strong La Nina forecast for the winter and dryer warmer temps expected for NC, what will the snows be like out west?
Posted November 6, 2007
MIKE MOSS SAYS: Marcus, There isn't a whole lot to go on that allows a very confident projection about snow for the NC mountains this winter season. Forecasts for the La Nina episode that is underway in the Pacific vary from weak to strong as we move on into the heart of the winter, and there is some significant variation in historical tendencies depending on the intensity of the event. Weak La Nina events (Oceanic Nino Index of -.5 to -.9) have tended to produce little departure from normal for temperatures in that area, and actually correlate to slightly above normal precipitation. Moderate to strong La Nina episodes (ONI -1.0 to -2.0) on the other hand have tended to average a little above normal for temperatures and near to a little below normal for temperatures. However, La Nina is also known for its volatile upper air patterns, which may include some very significant swings to colder and warmer temperatures and wetter or drier periods regardless of how the seasonal averages end up.
Note that the tendencies toward drier than normal winter conditions when La Nina is moderate to strong are more pronounced across central and especially eastern NC than they are toward the mountains, while the temperature response is similar across the state.
If you'd like to explore some composite maps that illustrate La Nina impacts across the U.S. for each season, see
Note that those maps are for precipitation anomalies. There is a link just above the maps that allows you to switch to temperature composite maps instead. Each group of maps has a map based on historical weak events, a map based on moderate to strong events, and a map that combines all La Ninas on record.