The Northern Great Basin started the water year with average October precipitation, a dry and warm November, a wet, cold and snowy December, followed by a wet and snowy January. January monthly precipitation was 143% and seasonal precipitation totals are 109% of average. The indexed Great Basin snow is currently 119% of average. Conditions in the Bear River Drainage are mostly average, except in the northeastern corner where snows were still much below average on February 1. Short term weather model guidance for northern Utah is predicting a moderately intense and fast hitting system with storm total precipitation of approximately 1 inch ending February 8th. This storm will have little affect on the overall forecast numbers, except possibly in the Bear River Basin. The 8-14 day model guidance suggest the probability of a shift to above average temperatures. It also suggest a shift in probability to wet conditions in the northern most Bear River Basin. All volumetric forecasts are currently in the average to above average category, except in the northeastern Bear River where forecast are in the much below to below average category 60% to 89%. The remaining forecasts ranged from 90% to 115% of average.

Conditions in the Bear River Basin improved during January and now are generally in the range of average in terms of snow and seasonal precipitation. Monthly precipitation was 138% of average and seasonal precipitation is now 97% of average. Snow water equivalent improved from 80% of average to 97% of average on February 1, however on February 5th it increased to 104% of average. Currently, forecast range from 62% at Bear below Stewart Dam to 106% at Bear near Utah-Wyoming State Line. Snow conditions in the northeast corner of the basin are still below average at 68% near the Smith Fork Drainage.

A wet January has greatly improved the outlook for the entire Weber River Basin as of February 1, 2008. Monthly precipitation numbers were 150% of average and seasonal totals improved to 108% of average. Snow water equivalents improved from 83% of average on January 1st to 119% of average on February 5th. April through July volume forecasts ranged from 101% to 116% of average.

The Six Creeks basin continues to be the big winner in the northern Great Basin drainages in terms of snow and precipitation. After a December with an impressive 183% of average monthly precipitation, January came in with 148% of average monthly precipitation. Seasonal precipitation for the Six Creek area improved to 121% of average. The biggest increase was in snow water equivalent which increased from 85% of average to 135% of average as of February 5th. The recording station at Alta broke the 1949 precipitation record of 14.09 inches, with a new record 16.4 inches (275% of average) and 170 inches of snow. The normal monthly precipitation is 5.99 inches and the normal monthly snow average is 93 inches. Forecasts for the basin range from 111% to 116% of average.

The Utah Lake Basin which includes the Provo river, Spanish Fork and American Fork drainages had a very cold and snowy January. Monthly precipitation was recorded at 147% of average and seasonal numbers increased to 114% of average. Snow water eqivalent conditions were the big winner improving from 83% of average on January 1st to 117% of average on February 5th. April through July water supply forecast now range from 110% to 116% 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