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Sevier Water Supply Outlook, May 1, 2010

Prepared by Brent Bernard
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah


Sevier Summary

*Median of forecasts within each basin.

Sevier Basin Conditions

The following conditions influenced this month's forecasts:

Seasonal, October through April precipitation was 97 percent of average in the Sevier River Basin. April precipitation was 125 percent of average.

April streamflow estimates were 85 percent of average for the Sevier River at Hatch.

May 1st, indexed snow water equivalent was 104 percent of average. In the headwater region, indexed snow totals were 144 percent of average. In the lower Sevier Basin, indexed snow totals were 68 percent of average.

Upper Sevier River Basin Snow Plot.
Sevier River Basin Snow Plot.
Lower Sevier River Basin Snow Plot.

Soil Moisture:
Modeled Soil Moisture, states were below average heading into this winter and tend to lower seasonal volume forecasts.

Climate Forecasts:
The 30 day outlook suggest a shift in probabilities to above average temperature and above average precipitation for the Sevier River Basin. El Nino conditions weakened during April however anomolies remain near +0.5 degrees C across most of the Pacific Ocean. The El Nino influence was not directly accounted for in the generation of these forecasts.

Forecast Summary:
The Sevier Basin seasonal precipitation remains much above average. The southern headwaters have much above average snow and precipitation numbers, where as the northern portions of the basin are much below average. This situation presents a challenge when describing the overall condition of the basin, hence the wide range of forecasts. April through July Seasonal volume forecast for the Sevier River Basin for May 1st range between 60 and 155 percent of average. The median April through July forecast this month was 107 percent of average compared to 105 percent last month. Residual May through July forecasts range from 55 to 163 percent of average with a median forecast volume of 112 percent of average.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Differences between the full period forecasts and the residual forecasts may not exactly equal the actual observed volumes due to rounding conventions (see Definitions section).

Precipitation Maps

Hydrologist: Brent Bernard