The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation was 90 percent of average.

January precipitation was 80 percent of average in the Sevier River basin.

Streamflow:
Streamflow for the Sevier River at Hatch was 155 percent of average for January.

Snowpack:
February 1st snow water equivalent was 70 percent of average for the overall Sevier River Basin. For the Sevier River headwaters, the February 1st snow water equivalent was 60 percent of average.

Sevier River Drainage Snow Plot.
Sevier River Basin Headwaters Snow Plot.
Lower Sevier River Basin Below Piute Snow Plot.

Soil Moisture:
Modeled soil moisture content was above average in the Sevier River headwater areas going into the winter.

Climate Forecasts:
Generally climate scenarios like El Nino and La Nina have a weak to moderate effect in the Sevier River Basin. However, because we lack a good statistical correlation, these events are not specifically factored into our water supply forecasts.

Forecast Summary:
February 1st snow water equivalent was 70 percent of average for the overall Sevier River Basin, while it was lower in the Sevier River headwaters at 60 percent of average. Higher than average baseflows, due to elevated soil moisture content, continue to occur in the Sevier River basin. Current April through July Seasonal volume forecasts range between 58 to 83 percent of average. The median April through July forecast was 65 percent of average.

The forecasts for the Sevier River at Hatch, the Sevier River near Kingston, the East Fork of the Sevier River, Piute Reservoir, and the Sevier River near Gunnison are 'Regulated or Observed' flow forecasts rather than 'Natural or Unregulated' forecasts, which are corrected for all upstream diversions.

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).

10% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 10% chance of being exceeded. Previously referred to as "Reasonable Maximum Forecast".

50% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 50% chance of being exceeded. Previously referred to as "Most Probable Forecast".

90% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 90% chance of being exceeded. Previously referred to as "Reasonable Minimum Forecast".

Acre-Foot (af): The volume equal to one acre covered one foot deep (43,560 cubic feet). See kaf below.

Average: The arithmetic mean. The sum of the values divided by the number of values. Values from 1981-2010 are used for this publication.

Categories: Much Above Average=Greater than 130%, Above Average=111-130%, Near Average=90-110%, Below Average=70-89%, Much Below Average=Less than 70%.

CBRFC: Colorado Basin River Forecast Center.

Forecast Period: The period from April 1 through July 31, unless otherwise noted.

kaf: Thousand Acre-Feet. See Acre-Foot above.

Inflow: The volume of water that flows into a reservoir or lake.

Median: The middle value of an ordered set of values. Half of the values are higher and half of the values are lower. When the set contains an even number of values the median is the average of the two middle numbers.

NOAA: National Oceanic and Atomospheric Administration.

NWS: National Weather Service.

Water supply forecasts take into consideration present hydrometeorological conditions and use average basin temperatures and precipitation for the forecast period. As the forecast season progresses, a greater portion of the future hydrologic and climatic uncertainty becomes known and monthly forecasts become more accurate. For more information on the tools we use, consult Water Supply Forecasting Tools.

Volume forecasts represent adjusted flows; that is, observed flows with upstream water use taken into account. Adjusted flows will closely approximate natural or unimpaired flows. However, not all upstream diversions or impoundments are measured or quantifiable. For specific adjustments used with each forecast point, consult the Guide to Water Supply Forecasting.

The Water Supply Outlook is issued monthly January through May by the Colorado Basin River Forecast Center. It represents a coordinated effort between the National Weather Service, Natural Resources Conservation Service, Bureau of Reclamation, U.S. Geological Survey and local water district managers.

Note: Data used in this report are provisional and are subject to revision.

For more information, or to be included on the mailing list, please contact:

Colorado Basin River Forecast Center
2242 W North Temple
Salt Lake City, UT 84116
(801) 524-5130
www.cbrfc.noaa.gov