October 1, 2012

September was drier than average across Wyoming, western Colorado, and much of Utah. Wetter-than-average conditions prevailed in central Colorado, far western Utah, and other parts of Utah. Over the just-completed 2012 water year, nearly all of the region was drier than average, with about half the region receiving less than 70% of average precipitation. The latest US Drought Monitor reflects the widespread long-term dryness, with nearly all of the region mired in severe (D2) or worse drought conditions, including small areas of D4 in far northeastern and southeastern Colorado.

The very first snowpack accumulations of the season are being reported by the SNOTEL network. The majority of stream gages reporting across the three states have flows in the normal range, but with many gages at below-normal and much-below normal flows also scattered throughout the region.

The latest monthly and seasonal Climate Outlooks from NOAA CPC show equal chances (EQ) for above-normal or below-normal precipitation for the October through January period, and enhanced odds for above-normal temperatures during that period, consistent with the long-term trend towards warmer conditions. The latest CPC Seasonal Drought Outlook projects that the drought conditions across our region will persist through at least December. The latest experimental precipitation forecast guidance from NOAA ESRL PSD shows enhanced chances for wetter-than-average conditions in eastern Colorado for the October-December period.

This summer, conditions in the tropical Pacific appeared to be in a rapid transition to El Nino, but that transition has slowed in the past month, and NOAA has not yet announced an El Nino. The most recent ensemble of ENSO prediction models forecasts that conditions will either remain on the warm side of ENSO-neutral, or transition to weak El Niño conditions through the winter season.