The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was near 170 percent of average in the upper Bear Basin.December precipitation was 185 percent of average.

Streamflow:
Streamflows for the Little Bear River above Hyrum Reservoir were 88 percent of average for December. Streamflow for the Logan River above State Dam were 93 percent of average for December. Streamflow gages in the upper Bear River Basin are all frozen at this time and no averages can be calculated until they thaw.

Snowpack:
This year's snow pack is much above average. As of January 1, the Bear Basin was 180 percent of average.


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

Soil Moisture:
Modeled Soil Moisture states were near average to above average for the northern Uinta Mountains heading into the winter.

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

Forecast Summary:
Monthly precipitation this fall was much above average and seasonal precipitation is nearly double average. Soil moisture conditions are wet. However it is early in the snow accumulation period (January 1st snow water equivalent is 67 percent of the average seasonal peak) and our models assume near normal precipitation into the future. Therefore, current April through July seasonal volume forecasts are above to much above average and range between 126 and 148 percent of average with a median value of 136 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was 175 percent of average in the Weber Basin. December precipitation was 325 percent of average.

Streamflow:
December streamflow above Rockport Reservoir on the Weber River was 167 percent of average and the Weber at Coalville was 154 percent of average.

Snowpack:
Snowpacks in the Weber Basin are currently much above average at 180 percent of average.

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

Soil Moisture:
Modeled Soil Moisture states were mostly above normal in the western Uinta Mountains near the headwaters of the Weber heading into winter.

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:
Monthly precipitation this fall was much above average and seasonal precipitation is nearly double average. Soil moisture conditions are wet. However it is early in the snow accumulation period (January 1st snow water equivalent is 77 percent of the average seasonal peak) and our models assume near normal precipitation into the future. Therefore, current April through July seasonal volume forecasts are much above average and range between 130 and 152 percent of average with a median value of 141 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was near 190 percent of average. December precipitation was 265 percent of average.

Streamflow:
Streamflows for City Creek near Salt Lake City in December were 105 percent of average.

Snowpack:
Snowpacks in the Six Creeks basin are currently much above average at 185 percent of average.

Six Creeks River Basin Snow Plot.

Big and Little Cottonwood Canyons Snow Plot.

Soil Moisture:
Modeled Soil Moisture states were near average in the Six Creeks Basin heading into winter.

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:
Monthly precipitation this fall was much above average and seasonal precipitation is nearly double average. Soil moisture conditions are wet. However it is early in the snow accumulation period (January 1st snow water equivalent is 72 percent of the average seasonal peak) and our models assume near normal precipitation into the future. Therefore, current April through July seasonal volume forecasts are above average to much above average, and range between 118 and 156 percent of average with a median value of 121 percent of average.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October thought December seasonal precipitation was 215 percent of average. December precipitation was 325 percent of average.

Streamflow:
Calculated inflow to Utah Lake for December was 127 percent of average.

Snowpack:
Snowpacks in the Provo and Utah Lake basin areas are currently much above average at 204 percent of average. This is 80% of the seasonal peak value.

Provo River, Utah Lake Basin Snow Plot.

Soil Moisture:
Modeled Soil Moisture states were average to above average heading into the winter.

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:
Monthly precipitation this fall was much above average and seasonal precipitation is nearly double average. Soil moisture conditions are wet. However it is early in the snow accumulation period (January 1st snow water equivalent is 80 percent of the average seasonal peak) and our models assume near normal precipitation into the future. Therefore, current April through July seasonal volume forecasts are much above average and range between 113 and 161 percent of average with a median value of 142 percent.

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