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Virgin Water Supply Outlook, February 1, 2011

Prepared by G. Smith
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah


Virgin Summary

*Median of forecasts within each basin.

Virgin Basin Conditions

The following conditions influenced this month's forecasts:

Seasonal October-January precipitation was near 255 percent of average in the Virgin Basin headwaters, and 130 to 280 percent of average basin wide.

January precipitation was near 10 percent of average in the Virgin Basin headwaters, and 5 to 35 percent of average throughout the remainder of the basin.

February 1st snowpack in the Virgin River Basin ranged from 150 to 215 percent of average at elevations above 7500 feet. Above average temperatures and dry conditions in January allowed most lower elevation snow to melt off.

Virgin River Basin Snow Plot.

January streamflow volumes were near the 1971-2000 median on the Virgin Basin headwaters.

Soil Moisture:
Above average soil moisture conditions exist throughout the Virgin River Basin.

Climate Forecasts:
La Nina climate conditions suggest slightly decreased chances of precipitation in this area. The La Nina influence was considered in generation of these forecasts.

Forecast Summary:
Significant precipitation in October and December resulted in above average soil moisture conditions and a high elevation snowpack that has exceeded the seasonal peak, which typically occurs in late March or early April. Dry conditions in January, more typical of existing La Nina climate conditions, resulted in decreased April-July runoff forecasts. Above median volumes are still anticipated at this time, however continued dry conditions may result in further decreases to forecast volumes. As of Februay 1st April-July runoff volumes are forecasted to range between 245 to 260 percent of median, or 145 to 160 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: G. Smith