November modeled soil moisture indicated much below and below average conditions for most of Green River Basin. (Click for November 1st image) This signal is incorporated in the ESP model guidance utilized by the CBRFC in generating our forecasts. At the time of this publication, seasonal precipitation is near normal for most of the region. Snowpack ranges from above average to below average in the major tributaries of the Green River.

February precipitation was below average in the Upper Colorado Basin and near average in the Gunnison and Dolores basins. The March 1st snow water equivalent was above average in all of the basins, but down just a bit from the February 1st percent of averages. Forecasts generally held steady in the Upper Colorado Basin and dropped around 5% in the Gunnison and Dolores basins compared to last month.

-Model Soil Moisture/Observed Streamflow...Soil moisture for most of the upper basins in the San Juan were below average last fall. This was most likely due to limited monsoonal precipitation over the summer months. Observed streamflow for the month of February was mostly below average for the San Juan.

-Snowpack/Precipitation...Snow water equivalents for the entire San Juan Basin on March 1st was 105 percent of average. Precipitation over the San Juan Basin for February was below average with 75 percent. Seasonal precipitation for the San Juan Basin remained at 105 percent of average.

-Short Term Precipitation Forecast...The forecast models through March 10th suggest near average precipitation for the San Juan Basin.

-General Discussion...The CPC guidance has the possibility of below average precipitation for March through May. Due to the below average soil moiture in the upper basin this fall and the combination of current snowpack conditions and the CPC forecast, the median April-July forecast for the San Juan Basin is 100 percent of average. This is a 10 percent drop from last month's forecast due to the decrease in percent of average snowpack.

-Model Soil Moisture/Observed Streamflow...The November soil moisture conditions were much below average in the Upper Green Basin. Observed streamflow for the month of February was 75 percent of average.

-Snowpack/Precipitation...In the Upper Green Basin, February precipitation was 75 percent of average. The basinwide to date snowpack condition is 85 percent of average with individual Snotel stations ranging from 48 to 102 percent of average.

-General Discussion...National Weather Service models suggest near to slightly above normal precipitation for the next 7-10 days. Beyond that the 30 Day CPC guidance shows equal chances for above, normal, or below precipitation. The 90 Day CPC guidance is for below normal precipitation. The antecedent soil moisture conditions will not change prior to runoff. April through July forecast indicate below average to average runoff volumes.

-Model Soil Moisture/Observed Streamflow...While soil moisture indicate drier than average Fall conditions in portions of this region, headwater basins had near average conditions. Therefore, soil moisture deficits are not adversely effecting model guidance as much as in other regions. Observed streamflow for the month of February was above average.

-Snowpack/Precipitation...Currently, the Yampa and White River basin has the highest snowpack conditions within the Green, with 75 percent of the Snotel stations having values greater than 110 percent of average on March 1st. February precipitation was only 85 percent of average.

-General Discussion...National Weather Service models suggest near to slightly above normal precipitation for the next 7-10 days. Beyond that the 30 Day CPC guidance shows equal chances for above, normal, or below precipitation. The 90 Day CPC guidance is for below normal precipitation. April through July forecast runoff volumes for the Yampa and White Basins ranged from average to above average.

-Model Soil Moisture/Observed Streamflow...Fall soil conditions in the Duchesne were similar to the Upper Green with many basins indicating much below average conditions. Observed streamflow for the month of February was below average.

-Snowpack/Precipitation...The snowpack condition in the Duchesne Basin on March 1st is same as on the 1st of the last two months (January and February) at 85 percent of average, with 78 percent of the Snotel stations located in in the basin reporting below average conditions. February precipitation was 95 percent of average.

-General Discussion...National Weather Service models suggest near to slightly above normal precipitation for the next 7-10 days. Beyond that the 30 Day CPC guidance shows equal chances for above, normal, or below precipitation. The 90 Day CPC guidance is for below normal precipitation. Forecasts range below average on the headwaters of the basin to much below average at downstream locations.

-Model Soil Moisture/Observed Streamflow...The November soil moisture conditions were much below average in the Lower Green Basin. Observed streamflow for the month of February was below average.

-Snowpack/Precipitation...The Lower Green Basin snowpack condition was 80 percent of average on March 1st. February precipitation was 95 percent of average.

-General Discussion...National Weather Service models suggest near to slightly above normal precipitation for the next 7-10 days. Beyond that the 30 Day CPC guidance shows equal chances for above, normal, or below precipitation. The 90 Day CPC guidance is for below normal precipitation. Forecasts at this time, are now all below average.

-Model Soil Moisture/Observed Streamflow... Soil moisture was near to above normal in the Upper Colorado heading into the winter. February streamflow was near normal.

-Snowpack/Precipitation... Although February precipitation was below average in the Upper Colorado River Basin at 80%, the water year precipitation is still slightly above average at 105%. Snow water equivalent as of March 1st was 115% of average basin wide. The Roaring Fork basin continues to have the highest snowpack with near 125% of average, which is a drop of about 10 percentage points from February 1st. Most other basins had decreases closer to 5% in the snow water equivalent percent of average from last month.

-General Discussion... Few changes were made to the April through July streamflow volume forecasts from last month because even though there was below average precipitation during February, the snow water equivalent remains above average. The April through July streamflow volume forecasts now range between 96% and 114% of average, with a median value of 110%.

-Model Soil Moisture/Observed Streamflow...Soil moisture for most of the upper basins in the Gunnison was near to slightly below average in the fall. Observed streamflow for the month of February was near to slightly below average for the Gunnison.

-Snowpack/Precipitation...Precipitation over the Gunnison Basin for February was near average at 90 percent. The March 1st snow water equivalent percent of average was 110 percent, which dropped about 5 percent from February 1st. Seasonal precipitation for the Gunnison is 105 percent of average.

-Short Term Precipitation Forecast...The forecast models through March 10th suggest that the Gunnison Basin will see near average precipitation with below average temperatures.

-General Discussion...The CPC guidance shows the possibility of below average precipitation and above normal temperatures March through May. Due to the average soil moiture in the upper basin this fall and the combination of current snowpack conditions and the CPC forecast, the median April-July forecast for the Gunnison Basin is 105 percent of average. This is down 5 percent from last month's forecast due to the February precipitation and the 5 percent drop in percent of average snowpack.

-Model Soil Moisture/Observed Streamflow...Soil moisture for most of the upper basins in the Dolores was below average in the fall. This was most likely due to limited monsoonal precipitation during the summer months. Observed streamflow for the month of February was mostly average for the Dolores.

-Snowpack/Precipitation...As of March 1st, snow water equivalents across the Dolores were 115 percent of average, which was a 5 percent drop from February 1st. Precipitation over the Dolores Basin for February was near average with 90 percent. Seasonal precipitation for the Dolores Basin remained near average with 95 percent.

-Short Term Precipitation Forecast...The forecast models through March 10th suggest near average precipitation with below average temperatures.

-General Discussion...The CPC guidance shows the possibility of below average precipitation and above normal temperatures for March through May for the Dolores Basin. Due to the below average soil moiture in the upper basin this fall and the combination of current snowpack conditions and the CPC forecast, the median April-July forecast for the Dolores Basin is 100 percent of average. This is down 5 percent from last month's forecast due to the February precipitation and the 5 percent drop in percent of average snowpack.

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 1971-2000 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