Although the January percent of average monthly precipitation was not quite as high as December, it was still much above average across the Upper Colorado Basin. As a result, the February 1 snow water equivalent percent of average values rose 15% in the Upper Colorado mainstem and 30% in the Gunnison and Dolores basins from the January 1 values. Forecasts of the April through July runoff volumes rose 10% to 40% from those issued January 1.

January was another wet month in the Upper Colorado mainstem with 165% of the basin average precipitation. This brought the seasonal precipitation to 130% of average and the snow water equivalent to 120% of average as of February 1st. However, the snowpack is not uniform across the basin. The Roaring Fork and Plateau Creek basins represent the high end of the spectrum with close to 150% of average snow water equivalent, while the basins above Kremmling generally have between 100% and 115% of average snow water equivalent. Because of the great gains in the snowpack all forecasts increased from last month, with the Roaring Fork and Plateau Creek points changing the most. The April through July streamflow forecasts now range between 100% and 130% of average.

Above average precipitation continued in the Gunnison Basin for the month of January with the basin receiving 215% of the monthly average. The basin is now at 155% of the seasonal average as of February 1st. All SNOTEL gages in the basin are now above 70% of their average seasonal maximum snowpack accumulation. Three SNOTELs, Overland Res. (127%), Park Cone (111%), and Columbine Pass (111%), have already accumulated over 100% of their average seasonal maximum snowpack. Even though precipitation was above normal for January, streamflow remains around average since most precipitation fell as snow. April through July volume forecasts have increased because of the above average snow fall. Volume forecasts now range from 131% of average at Taylor Park Reservoir to 152% of average at Paonia Reservoir.

Monthly precipitation in the Dolores Basin for January was above normal. The precipitation total was not as impressive as December but still much above average at 155% of the monthly average. Seasonal precipitation is now at 125% as of February 1st. All SNOTEL gages in the Dolores are above 80% of their average seasonal maximum snowpack accumulation. Scotch Creek (105%) and Lizard Head Pass (105%) are already above 100% of their average seasonal maximum snowpack accumulation. Even though precipitation was above normal for January, streamflow remains around average since most precipitation fell as snow. April through July volume forecasts have increased because of the above average snow fall. Volume forecasts now range from 136% of average on the San Miguel River at Placerville to 159% of average on the Dolores River at Cisco.

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