The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation was 130 percent of average in the Upper Green basin. January precipitation was 75 percent of average in the basin as a whole; however, portions of the basin such as the Ham's Fork river basin received near average precipitation.

Snow:
February 1st snow water equivalent was 120 percent of average in the basin.
--- Upper Green basin snow water equivalent plot.

Streamflow:
December streamflow was near 95 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 majority of Upper Green received below average precipitation for January. As a result of the January precipitation, the percent of average for both snow water equivalent and seasonal precipitation decreased from last month. However, due to the above to much above average monthly precipitation prior to January, the seasonal precipitation and February 1st snow water equivalent still remain above average. As a result, April through July streamflow volumes are similar to January or have decreased slightly. Current forecasts range between 100 and 124 percent of average with a median value of 100 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation was 140 percent of average in the Yampa/White basin. January precipitation was 70 percent of average in the basin as a whole; however, portions of the basin such as the Yampa and Elk river basins received near average precipitation.

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

Streamflow:
January streamflow was near 95 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 majority of the Yampa basin received below average precipitation for January. As a result of the January precipitation, the percent of average for both snow water equivalent and seasonal precipitation decreased from last month. However, due to the much above average monthly precipitation prior to January, the seasonal precipitation and February 1st snow water equivalent still remain much above average. As a result, April through July streamflow volumes did not change. Current 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 January precipitation was 180 percent of average in the Duchesne basin. January precipitation was 40 percent of average.

Snow:
February 1st snow water equivalent was 160 percent of average in the basin as a whole.
--- Duchesne basin snow water equivalent plot.

Streamflow:
January streamflow was 95 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 basin received much below average precipitation for January. As a result of the January precipitation, the percent of average for both snow water equivalent and seasonal precipitation decreased from last month. However, due to the much above average monthly precipitation prior to January, the seasonal precipitation and February 1st snow water equivalent still remain much above average. As a result, April through July streamflow volumes did not change. Current forecasts range between 115 and 174 percent of average with a median value of 143 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation was 190 percent of average in the Lower Green basin. February precipitation was 30 percent of average.

Snow:
February 1st snow water equivalent was 130 percent of average in the basin as a whole.
--- Lower Green basin snow water equivalent plot.

Streamflow:
January streamflow was near 130 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 river basin received much below average precipitation in January. As a result of the January precipitation, the percent of average for both snow water equivalent and seasonal precipitation decreased from last month. However,due to the much above average monthly precipitation prior to January, the seasonal precipitation and February 1st snow water equivalent still remain much above average. April through July streamflow volumes did not change or decreased slightly. Current forecasts range between 121 and 162 percent of average with a median value of 129 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation was near 135 percent of average in the Upper Colorado mainstem basin. January precipitation was near 85 percent of average in the basin as a whole, however upper portions of the basin, such as the Blue and Eagle river basins and the mainstem headwaters, received near to above average precipitation.

Snow:
February 1st snow water equivalent was near 130 percent of average in the basin as a whole; this is 75% of the seasonal peak.
--- Upper Colorado basin snow water equivalent plot

Streamflow:
February streamflow was near 95 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:
January was the first month of this water year with below average precipitation in the Upper Colorado mainstem basin; monthly precipitation had been above to much above average each month of the water year prior to January. As of February 1st the percent of average of both the seasonal precipitation and snow water equivalent are lower than they were at the start of last month, but still much above average in the basin as a whole. Most forecast volumes are the same as last month. Decreases at the Colorado River near Cisco and Lake Powell inflow were due to changes in other contributing basins. 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 125 percent of average in the Gunnison basin. January precipitation was 55 percent of average.

Snow:
February 1st snow water equivalent was near 130 percent of average in the Gunnison basin; this is 75% of the seasonal peak.
--- Gunnison basin snow water equivalent plot

Streamflow:
January streamflow was 95 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 much below average at 55%. Seasonal precipitation for the Gunnison basin dropped from last month to 125% of average. February 1st seasonal snow water equivalent for the Gunnison was above average with 130%; whereas the snow water equivalent is 75% of the average seasonal peak. Since the percent of average for both seasonal snow water equivalent and seasonal precipitation decreased from last month, the current April through July streamflow volume forecasts dropped in the Gunnison Basin from last month's forecast. Current April through July streamflow volume forecasts range between 93 and 126 percent of average with a median value of 110 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation was 110 percent of average in the entire Dolores basin. January precipitation was just 25 percent of average.

Snow:
February 1st snow water equivalent was 100 percent of average in the Dolores basin as a whole; this is 60% of the seasonal peak.
--- Dolores basin snow water equivalent plot

Streamflow:
January streamflow was 95 percent of average.

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

Climate Forecasts:
The correlation of La Nina 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 much below average at 25%. Seasonal precipitation for the Dolores basin dropped from last month to 110% of average. February 1st seasonal snow water equivalent for the Dolores was average with 110%; whereas the snow water equivalent is 60% of the average seasonal peak. Since the percent of average for both seasonal snow water equivalent and seasonal precipitation decreased from last month, the current April through July streamflow volume forecasts dropped in the Dolores Basin from last month's forecast. Current April through July streamflow volume forecasts range between 87 and 93 percent of average, with a median value of 90 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through January precipitation amounts dropped from last month to near average, 105%, due to the very dry month of January.
January precipitation was 20 percent of average, which was much below average.

Snow:
Current snow water equivalent for the entire basin is 105%, which is near average. The Animas basin is similar with 110%, while above Navajo snow water equivalent was 95 percent of average. All three dropped significantly since January 1st.
--- Animas River Basin Snow Plot.
--- Above Navajo Basin Snow Plot.

Streamflow:
Streamflow for the entire San Juan Basin was below average for January at 65%. Seasonal streamflow since October continued to be below average at 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 have dropped to average values compared to last month. 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 down to a median value of 95 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