The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was 150 percent of average in the Upper Green basin. December precipitation was 215 percent of average.

Snow:
January 1st snow water equivalent was 130 percent of average in the basin.
--- Upper Green basin snow water equivalent plot.

Streamflow:
December streamflow was near 110 percent of average.

Soil Moisture:
Modeled soil moisture states were below average heading into the winter.

Climate Forecasts:
Climate forecasts were not a factor because there is not a strong correlation between La Nina conditions and winter precipitation in the Upper Green basin.

Forecast Summary:
The Upper Green has received much above average monthly precipitation since October. As of January 1st, both seasonal precipitation and snow water equivalent are much above average. Despite the much above average conditions, it is early in the snow accumulation period and snow water equivalent is currently 55% of the average seasonal peak. It is also important to note that our models assume near normal precipitation into the future. As a result, current April through July streamflow volume forecasts range between 100 and 118 percent of average with a median value of 100 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was 165 percent of average in the Yampa/White basin. December precipitation was 230 percent of average.

Snow:
January 1st snow water equivalent was 150 percent of average in the basin.
--- Yampa basin snow water equivalent plot.

Streamflow:
December streamflow was near 110 percent of average.

Soil Moisture:
Modeled soil moisture states were near average heading into the winter for the Yampa, Little Snake,and White River basins.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Yampa/White basin.

Forecast Summary:
The Yampa and White river basins have received much above average monthly precipitation since October. As of January 1st, both seasonal precipitation and snow water equivalent are much above average. Despite the much above average conditions, it is early in the snow accumulation period and snow water equivalent is currently near 60% of the average seasonal peak. It is also important to note that our models assume near normal precipitation into the future. As a result, current April through July streamflow volume forecasts range between 108 and 134 percent of average with a median value of 120 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was 230 percent of average in the Duchesne basin. December precipitation was 330 percent of average.

Snow:
January 1st snow water equivalent was 210 percent of average in the basin as a whole.
--- Duchesne basin snow water equivalent plot.

Streamflow:
December streamflow was 100 percent of average.

Soil Moisture:
Modeled soil moisture states were much below average to below average heading into the winter.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Duchesne basin.

Forecast Summary:
The Duchesne river basin has received much above average monthly precipitation since October. As of January 1st, both seasonal precipitation and snow water equivalent are much above average. However,it is important to note that it is still early in the snow accumlation period and that our models assume near normal precipitation into the future. As a result, current April through July streamflow volume forecasts range between 115 and 174 percent of average with a median value of 145 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was 240 percent of average in the Lower Green basin. December precipitation was 350 percent of average.

Snow:
January 1st snow water equivalent was 205 percent of average in the basin as a whole.
--- Lower Green basin snow water equivalent plot.

Streamflow:
December streamflow was near 150 percent of average.

Soil Moisture:
Modeled soil moisture states were much below to near average heading into the winter.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Lower Green basin.

Forecast Summary:
The Lower Green has received above to much above average monthly precipitation since October. As of January 1st, both seasonal precipitation and snow water equivalent are much above average. However, it is important to note that it is still early in the snow accumlation period and that our models assume near normal precipitation into the future. As a result, current April through July streamflow volume forecasts range between 141 and 176 percent of average with a median value of 140 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation was near 155 percent of average in the Upper Colorado mainstem basin. December precipitation was near 195 percent of average.

Snow:
January 1st snow water equivalent was near 145 percent of average in the basin as a whole; this is 60% of the seasonal peak.
--- Upper Colorado basin snow water equivalent plot

Streamflow:
December streamflow was near 120 percent of average.

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

Climate Forecasts:
Climate forecasts were not a factor because there is not a strong correlation between La Nina conditions and winter precipitation in the Upper Colorado mainstem basin.

Forecast Summary:
Monthly precipitation has been above to much above average in the Upper Colorado mainstem each month of the water year so far, with December being the highest yet. As of January 1st both the seasonal precipitation and snow water equivalent are near 150% of average. However, it is early in the snow accumulation period (January 1st snow water equivalent is 60% of the average seasonal peak) and our models assume near normal precipitation into the future. Therefore, current April through July streamflow volume forecasts range between 113 and 139 percent of average with a median value of 120 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation was 150 percent of average in the Gunnison basin. December precipitation was 210 percent of average.

Snow:
January 1st snow water equivalent was 160 percent of average in the Gunnison basin.
--- Gunnison basin snow water equivalent plot

Streamflow:
December streamflow was 115 percent of average.

Soil Moisture:
Modeled soil moisture states were below to near average heading into the winter.

Climate Forecasts:
Climate forecasts were not a factor because there is not a strong correlation between La Nina conditions and winter precipitation in the Gunnison basin.

Forecast Summary:
January precipitation throughout the Gunnison basin was 210% of average. January 1st snow water equivalent for the Gunnison was much above average with 160%. However, it is early in the snow accumulation period (January 1st snow water equivalent is 65% of the average seasonal peak) and our models assume near normal precipitation into the future. Therefore, current April through July streamflow volume forecasts range between 103 and 146 percent of average with a median value of 115 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation was 140 percent of average in the entire Dolores basin. December precipitation was 220 percent of average.

Snow:
January 1st snow water equivalent was 125 percent of average in the Dolores basin.
--- Dolores basin snow water equivalent plot

Streamflow:
December streamflow was 115 percent of average.

Soil Moisture:
Modeled soil moisture states were average to slightly below average heading into the winter.

Climate Forecasts:
The correlation of El Nino and April through July water volumes in the Dolores basin is small that it did not influence the forecast process.

Forecast Summary:
January precipitation throughout the Dolores Basin was 220% of average. Seasonal October through January precipitation in the Dolores basin was much above average with 140%. However, it is early in the snow accumulation period (January 1st snow water equivalent is 50% of the average seasonal peak) and our models assume near normal precipitation into the future. Therefore, current April through July streamflow volume forecasts range between 106 and 109 percent of average, with a median value of 105 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through December precipitation amounts rose from last month to above average, 125%, due to the very heavy precipitation during the last part of December.
December precipitation was much above average with 210%

Snow:
Current snow water equivalent for the entire basin is 135%, which is much above average. The Animas basin is similar with 135%, while above Navajo snow water equivalent was 125 percent of average.
--- Animas River Basin Snow Plot.
--- Above Navajo Basin Snow Plot.

Streamflow:
Streamflow for the entire San Juan Basin was below average for December with 85%. Seasonal streamflow since October continued to be below average with 65%, due to the much below average fall precipitation.

Soil Moisture:
Modeled soil moisture as of November 1st, 2010 was average to below average across the entire San Juan Basin.

Climate Forecasts:
The correlation of La Nina and April through July water volumes in the San Juan basin does suggest slightly drier than average December through May precipitation, but it did not influence the February forecast process.

Forecast Summary:
Seasonal precipitation and current snowpack are above to much above average. Also, soil moisture conditions before the winter season were near average in the upper basin. This drove the San Juan Water Supply April-July forecast to a median value of 110 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