Synopsis…The Climate Prediction Center is forecasting near normal ocean temperatures across the central Pacific Ocean this upcoming winter. This means that El Nino and La Nina conditions are not expected through the spring of 2006. This forecast was compared with past winter seasons that produced similar ocean temperatures across the central Pacific Ocean. These years were then looked at to find years with similar conditions as forecast for this winter…as well as similar weather patterns of the summer and early fall months of 2005. All of these data were used to predict the overall weather pattern we can expect for this upcoming winter.
We expect the general weather pattern to produce more systems moving out of the northwest. These systems generally produce light precipitation…with heavier amounts possible in the upslope areas of the northern Black Hills and Bear Lodge mountains.
At this time it appears that temperatures across northeastern Wyoming and western South Dakota will be above normal from October through March. The warmest areas are expected to be in northeastern Wyoming…the Black Hills and southwestern South Dakota. Despite the forecast for warmer than normal temperatures…arctic intrusions will occur at times across the region. The most likely area for these intrusions is expected to be across central and south central South Dakota.
At this time is appears precipitation will likely be below normal on the plains of northeastern Wyoming and western South Dakota…with above normal precipitation across the Bear Lodge mountains…northern Black Hills and northern foothills.
It should be noted that precipitation on the plains of northeastern Wyoming and western South Dakota for November through February averages only 1.6 to 2.5 inches…which is only about fifteen percent of the annual average. Thus…even if the precipitation is 20 percent below normal for this time period…it would only be a 0.3 to 0.5 inch deficit over the four month period on the plains.
In the upslope areas of the northern Black Hills and Bear Lodge mountains average precipitation for this time period is 4.5 to 6 inches. Thus…if the precipitation is 20 percent above normal for this time period…it would be 0.90 to 1.2 inches of additional precipitation over the time period. Therefore…the net effect is that the drought conditions across northeastern Wyoming and the Black Hills are likely to persist over the winter months.