The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through February precipitation was 130 percent of average in the Upper Green basin. February precipitation was 115 percent of average in the basin as a whole; however, portions of the basin such as the headwaters of the Blacks Fork River received near 130 percent of avearge precipitation in February.

Snow:
March 1st snow water equivalent was 115 percent of average in the basin.
--- Upper Green basin snow water equivalent plot.

Streamflow:
February streamflow was near 80 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:
With the addition of above average precipitation for February, the seasonal precipitation and snow water equivalent still remain much above average and above average, respectively. As a result of the current conditions, the April through July streamflow volume forecasts are the same as the February forecasts or have increased slightly. Current forecasts range between 100 and 124 percent of average with a median value of 102 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through February precipitation was 135 percent of average in the Yampa/White basin. February precipitation was 115 percent of average in the basin as a whole.

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

Streamflow:
February streamflow was near 80 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:
With the addition of above average precipitation in February, the seasonal precipitation and current snow water equivalent remain much above average and above average, respectively. It is also important to note that many of the snotel locations have already surpassed the average seasonal peak. As a result of the current conditions, the April through July streamflow volume forecasts are similar to the February forecasts or have increased by approximately 5 to 8 percent. Current forecasts range between 108 and 138 percent of average with a median value of 127 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through February precipitation was 170 percent of average in the Duchesne basin. February precipitation was 140 percent of average.

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

Streamflow:
February streamflow was 90 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:
With the addition of much above average precipitation in February, the seasonal precipitation and current snow water equivalent remain much above average. It is also important to note that the majority of snotel locations in the basin have already surpassed the average seasonal peak. As a result of the current conditions, the April through July streamflow volume forecasts are similar to the February forecasts or have increased by approximately 5 to 10 percent. Current forecasts range between 115 and 182 percent of average with a median value of 145 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through February precipitation was 180 percent of average in the Lower Green basin. February precipitation was 120 percent of average.

Snow:
March 1st snow water equivalent was 120 percent of average in the basin as a whole.
--- Lower Green basin snow water equivalent plot.

Streamflow:
February streamflow was near 95 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:
With the addition of above average precipitation in February, the seasonal precipitation and current snow water equivalent remain much above average and above average, respectively. As a result of the current conditions, the April through July streamflow volume forecasts are similar to the February forecasts. Current forecasts range between 121 and 151 percent of average with a median value of 129 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through February precipitation was near 135 percent of average in the Upper Colorado mainstem basin. February precipitation was near 120 percent of average in the basin as a whole.

Snow:
March 1st snow water equivalent was near 130 percent of average in the basin as a whole; this is near 100% of the average 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:
As of March 1st the percent of average of both the seasonal precipitation and snow water equivalent were much above average in the basin as a whole. Almost all forecast volumes were raised from last month due to yet another month of above average precipitation. Current April through July streamflow volume forecasts range between 115 and 139 percent of average with a median value of 125 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through February precipitation was 120 percent of average in the Gunnison basin. February precipitation was 105 percent of average.

Snow:
March 1st snow water equivalent was near 120 percent of average in the Gunnison basin; this is 95% of the seasonal peak.
--- Gunnison basin snow water equivalent plot

Streamflow:
February streamflow was 85 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:
February precipitation throughout the Gunnison basin was average at 105%. Seasonal precipitation for the Gunnison basin dropped a little from last month to 120% of average. March 1st seasonal snow water equivalent for the Gunnison was above average with 120%; whereas the snow water equivalent is 95% of the average seasonal peak. The percent of average for both seasonal snow water equivalent and seasonal precipitation decreased little from last month over the entire basin. Since there were slight increases in both the seasonal snow water equivalent and seasonal precipitation in the northern portions of the Gunnison basin, the current April through July streamflow volume forecasts remained the same from last month's forecast. Current April through July streamflow volume forecasts range between 99 and 126 percent of average with a median value of 110 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through February precipitation was 105 percent of average in the entire Dolores basin. February precipitation was just 65 percent of average.

Snow:
March 1st snow water equivalent was 95 percent of average in the Dolores basin as a whole; this is 75% of the seasonal peak.
--- Dolores basin snow water equivalent plot

Streamflow:
February streamflow was 75 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:
February precipitation throughout the Dolores basin was much below average at 65%. Seasonal precipitation for the Dolores basin dropped from last month to 105% of average. March 1st seasonal snow water equivalent for the Dolores was average with 95%; 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 Dolores Basin from last month's forecast. Current April through July streamflow volume forecasts range between 83 and 88 percent of average, with a median value of 85 percent.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through February precipitation was 100 percent of average, which dropped 5 percent from February 1st. February precipitation was 75 percent of average, which was below average.

Snow:
Current snow water equivalent for the entire basin is 100%, which is average. The Animas basin is similar with 100%, while above Navajo snow water equivalent was 95 percent of average. All three dropped slightly or remained the same since February 1st.
--- Animas River Basin Snow Plot.
--- Above Navajo Basin Snow Plot.

Streamflow:
Streamflow for the entire San Juan Basin was much below average for February at 50%. Seasonal streamflow since October continued to be much below average at 60%, 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 March forecast process.

Forecast Summary:
Since February precipitation was below to much below average in the San Juan Basin, the March Water Supply April-July volume dropped 10 percent. The April-July forecast were down compared to last month with a range from 83 to 95 percent of average. The median value of 85 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