During February the Great Basin continued its run of good water supply conditions and as of early March is heading into the critical part of the water supply season with above average snow and precipitition numbers in all but a few localities. Monthly precipitation from NWS Cooperative Observer Stations totalled 126% of average while seasonal precipitation (the cumulative total) finished the October through February period with 109% of average. Indexed snow over the Great Basin Salt Lake Basin is currently 112% of average. Short term guidance from National Weather Service Models indicates mostly average conditions with no large storms forecast in the next 10 days. Climate models from the Climate Predition Center currently show no signal of wet or dry, warm or cold instead showing equal probabalistic chances over our area. Volumetric forecast for the Great Basin ranged 68% to 120% of average with an average forecast of 108%.

Conditions in the Bear River Basin improved during the month of February. There exist pockets of below average conditions in the northeast corner but overall February was a near normal to slightly above normal month. Monthly precipitation was 120% of average and seasonal precipitation now totals 100% of average. Snow water equivalent improved from 97% of average to 104%, except north of Evanston to Soda Springs were conditions are below average. Forecasts remain mostly unchanged from February now ranging form 68% of average near Montpelier to 111% at the Utah/Wyoming border.

The Weber River basin had another above average month improving conditions to above average. Monthly precipitation was recorded at 123% of average and season precipitaiton totalled 111% of average. Snow water equivalents numbers decreased from 119% of average to 114% of average. Overall the April through July volumetric forecasts increased slightly downstream of Oakley and range from 100% to 116% of average.

The Six Creeks basin had another wet and snowy month with the first hint of warming at lower elevations which diminished some of those low elevation snow packs. Monthly precipitation finished off at 131% and seasonal precipitation now totals 121% of average. Indexed snow numbers for the basin are 131% of average. April through July volume forecasts range from 112% to 120% of average.

The Utah Lake Basin experienced another wet and snowy month with several warm days to help start melting low elevation snows. Monthly precipitation was 130% of average and seasonal has now risen to 117% of average. Snow water eqivalent conditions continued to improve over average and in the Provo basin proper is 139% of average. Currently the indexed snow for the Utah Lake Basin is 120% of average. April through July water supply forecast increased by 5% from February 1st levels and range from 107% to 114% of average.

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