The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was 84 percent of average in the upper Bear Basin. December precipitation was 36 percent of average.

Streamflow:
The Bear River at the Utah-Wyoming Stateline was 189 percent of average. The Logan River above State Dam recorded 160 percent of average streamflow.

Snowpack:
This years snow is much below average. A wet October and an average November gave way to one of the driest Decembers on record. The current snow water equivalent for the Bear Basin is 54% of average. Several of the current snow stations in the Bear have values in the top 3 lowest amounts ever recorded for January 1st.


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. Modeled soil moisture states indicate above average mositure conditions as of December 1st. This is a contributor to the above average baseflows in the Bear River Basin.

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

Forecast Summary:
The current Bear River volume forecast range from below average to much below average. April through July seasonal volume forecast range from 66% to 79% of average with a median volume of 76 percent of average. The above average soil moisture and higher than average current baseflow conditions are resulting in higher forecast than one might expect due to current snow only conditions.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was 67 percent of average in the Weber Basin. December precipitation was 19 percent of average.

Streamflow:
The Weber at Oakley gage is currently frozen. The inflow to Rockport Reservoir was 119% percent of average.

Snowpack:
This year's snow is much below average. A wet October and an average November gave way to one of the driest Decembers on record. Current snow water equivalent are 49 percent of average. Several of the current snow stations in the Weber Basin have values in the top 3 lowest amounts ever recorded for January 1st.

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

Soil Moisture:
Modeled Soil Moisture, click on map to zoom. Modeled soil moisture states indicate above average mositure conditions as of December 1st. This is a contributor to the above average baseflows in the Weber River Basin.

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

Forecast Summary:
April though July volume forecast are currently much below average. April through July seasonal volume forecasts range between 63 and 72 percent of average with a median forecast volume of 71 percent of average. The above average soil moisture and higher than average current baseflow conditions are resulting in higher forecast than one might expect due to current snow only conditions.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was near 67 percent of average. December precipitation was 19 percent of average.

Streamflow:
December streamflow for Big Cottonwood Creek was 99 percent of average.

Snowpack:
This year's snow is currently below to much below average. A wet October and an average November gave way to one of the driest Decembers on record. The current Six Creeks snow water equivalent is 49 percent of average. Several of the current snow stations in the Six Creeks basin have values in the top 3 lowest amounts ever recorded for January 1st.

Six Creeks Headwaters Basins Snow Plot.

Big and Little Cottonwood Canyons Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom. Modeled soil moisture states indicate above mostly average mositure conditions as of December 1st. Although flows are dropping in the Six Creeks basin, above average soil moistures have been influencing baseflows through the fall and December was the first month that they dropped to near average.

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

Forecast Summary:
Current Six Creeks streamflow volume forecast are below to much below average. April through July seasonal volume forecasts range between 61 and 73 percent of average with a median forecast of 65 percent of average. The above average soil moisture and higher than average current baseflow conditions are resulting in higher forecast than one might expect due to current snow only conditions.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October thought December seasonal precipitation was 63 percent of average. December precipitation was 17 percent of average.

Streamflow:
Streamflow conditions for the Provo at Woodland were 113 percent of average. Inflow to Utah Lake was recorded at 94 percent of average.

Snowpack:
This year's snow is much below average. A wet October and an average November gave way to one of the driest Decembers on record. Current snow water equivalents are 45 percent of average. Several of the current snow stations in the Utah Lake drainage have values in the top 3 lowest amounts ever recorded for January 1st.

Provo River, Utah Lake Drainage Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom. Modeled soil moisture states indicate mostly average with some above average conditions as of December 1st. This is a contributor to the current baseflows conditions in the Provo and Utah Lake forecast.

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

Forecast Summary:
Despite the cool and wet weather during December there was little change in the median April through July forecast median volume. April through July seasonal volume forecasts range between 53 and 72 percent of average with a median forecast volume of 67 percent of average. The above average soil moisture and higher than average current baseflow conditions are resulting in higher forecast than one might expect due to current snow only conditions.

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