The outlook for November through February calls for near to slightly above average precipitation for most of northeast Wyoming and western South Dakota. Temperatures are expected to be near or slightly below average. Based on the present La Nina conditions…the overall weather pattern this winter will likely produce more storm systems originating over the Pacific Northwest. These systems will produce more frequent upslope conditions over the northern Black Hills and Bear Lodge Mountains…where above normal precipitation is expected. Elsewhere…near normal precipitation is expected.
Moderate to possibly strong La Nina conditions are expected through the spring of 2011. Previous winter seasons with similar La Nina conditions have been reviewed …as well as years with weather patterns like those of the summer and early fall months of 2010. These were used to predict the overall weather pattern for this winter.
Winter temperatures will likely be near average across northeastern Wyoming with slightly below average temperatures expected across western South Dakota. The coldest temperatures are expected across central South Dakota where occasional strong arctic intrusions are expected.
Precipitation will likely be near average on the plains of northeastern Wyoming and western South Dakota. Above average precipitation is expected across the Bear Lodge Mountains…the northern Black Hills…the northern Foothills and northwestern South Dakota where more frequent upslope snowfall events may occur.
Precipitation on the plains of northeastern Wyoming and western South Dakota for November through February averages about 1.5 to 2.5 inches…which is only around 10 percent of the annual average. In the upslope areas of the northern Black Hills and Bear Lodge Mountains average precipitation for the winter season is 4 to 6 inches.