...17 May through 31 August 2011 Summer Outlook...

Synopsis...  
As of early May 2011...La Nina conditions continued to weaken across the Equatorial Pacific. The climate prediction center forecasts that La Nina conditions will continue to weaken this spring...with a return to ENSO-neutral conditions for late May through August. These oceanic conditions...along with recent weather patterns associated with winter La Nina conditions trending to ENSO-neutral conditions in the summer...were used to develop our prediction of the general
weather pattern across the northern high plains for mid May through August.

Outlook...
Precipitation is expected to be above long term averages through June...with near to slightly below average precipitation in July and August. Temperatures are expected to be below long term averages through the summer...with the best chances of near to slightly above average temperatures in July and August.

Impacts...
Across northeastern Wyoming and the Bear Lodge Mountains...rainfall is expected to be 120 to 150 percent of average. Rainfall for May through August averages 7 to 9 inches on the plains of northeastern Wyoming and 9 to 11 inches in the Bear Lodge Mountains. Based on our outlook...this could result in a 1.40 to 4.50 inch rainfall surplus on the plains...and a 1.80 to 5.50 inch surplus in the Bear Lodge Mountains.

In western South Dakota...rainfall is expected to be 120 to 150 percent of average. Rainfall for May through August averages 9 to 11 inches on the plains and 11 to 14 inches in the Black Hills. Based on our outlook...this could result in a 2.20 to 7.00 inch rainfall surplus in the Black Hills...and a 1.80 to 5.50 inch surplus on the plains.

Snowfall and rain from this past winter and spring have filled reservoirs and stock ponds across western South Dakota. If the anticipated rainfall for May into July occurs...then above average stream and river flows will continue into mid-summer.

 

 


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