The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through March precipitation was near 66 percent of average in the upper Bear Basin as a whole. March precipitation was 61 percent of average.

Streamflow:
Bear River Streamflow at Stewart Dam was 36 percent of average for March. The Logan River above State Dam was 66 percent of average for March.

Snowpack:
April 1st snow water equivalent was 58 percent of average for the Bear Basin as a whole.


Upper Bear River Basin Snow Plot.
Bear River Below Woodruff Narrows Reservoir Snow Plot.
Bear River Basin Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom.

Climate Forecasts:
Climate forecasts were not factored into the northern Utah forecasts because there is not a strong correlation between El Nino conditions and winter precipitation.

Forecast Summary:
April 1st snow water equivalent values are below average. As a result, the April through July streamflow volume forecasts remain much below average with little change from last months numbers. These forecasts now range between 17 and 58 percent of average with a median value of 40 percent of average.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through March precipitation was near 64 percent of average in the Weber Basin. March precipitation was 60 percent of average.

Streamflow:
Rockport Reservoir inflow recorded 77 percent of average.

Snowpack:
April 1st snow water equivalent was near 65 percent of average in the basin as a whole.

Weber River Basin Snow Plot.
Upper Weber River Basin Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom.

Climate Forecasts:
Climate forecasts were not a factored into the northern Utah forecasts because there is not a strong correlation between El Nino conditions and winter precipitation.

Forecast Summary:
Due to continued much below average seasonal precipitation and still below average April 1st snow water equivalent values, the April through July streamflow volume forecasts were lowered to much below average. However, a week of very wet weather since April 1st may result in a moderate rise in Weber Basin forecasts in subsequent updates. These forecasts now range between 24 and 57 percent of average with a median value of 41 percent of average.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through March precipitation was near 73 percent of average. March precipitation was 60 percent of average.

Streamflow:
Big Cottonwood Creek streamflow was 77 percent of average during March.

Snowpack:
April 1st snow water equivalent was near 75 percent of average in the basin as a whole.

Six Creeks River Basin Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom.

Climate Forecasts:
Climate forecasts were not factored into the northern Utah forecasts because there is not a strong correlation between El Nino conditions and winter precipitation.

Forecast Summary:
As of April 1st, seasonal precipitation remains much below normal. As a result, April through July streamflow forecasts remain similar to last month. However, a week of very wet weather since April 1st may result in a moderate rise in Six Creeks Basin forecasts in subsequent updates. Currently, the forecasts range between 31 and 68 percent of average with a median value of 54 percent of average.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October thought March precipitation was 68 percent of average. March precipitation was 77 percent of average.

Streamflow:
March streamflow was 61 percent of average for the Provo at Woodland.

Snowpack:
April 1st snow water equivalent for Utah Lake was near 68 percent of average in the basin as a whole.

Provo River, Utah Lake Basin Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom.

Climate Forecasts:
Climate forecasts were not factored into the northern Utah forecasts because there is not a strong correlation between El Nino conditions and winter precipitation here.

Forecast Summary:
Due to below average April 1st snow water equivalent values the April through July streamflow volume forecasts remained much below average. The forecasts now range between 38 and 64 percent of average with a median value of 50 percent of average.

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 1971-2000 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