Snow Water Equivalent & Precipitation - February precipitation in the Great Basin was average at 98%. Snow accumulation was average this past month and remains slightly below average for the season. Indexed snow totals were 97% of average in the Weber and Ogden basins, 92% in the Provo basin, 90% in the Bear River basin and 102% in the Six Creeks basin. Seasonal precipitation for the Great Basin Salt Lake Basin was 102% of average and overall snow water equivalents are 96% of average.

Soil Moisture & Streamflow - Soil moisture grids from the ESP model remain below to much below average in all headwater regions, which tends to lower April through July volume forecasts. Streamflow for selected points in each of the four main drainages were 98% of average.

Short Term Precipitation Forecasts - Weather guidance from National Weather Service Meteorological Models show cool and wet conditions during the first 6-10 days of the month. Longer range guidance shows a trend toward above average temperatures and below normal precipitation.

General Discussion - Longer range predictions from NOAA's Climate Prediction Center are now factoring in a weak La Nina episode, predicted to last through the spring of 2009. Please reference the web link above for further details and effects within the Great Basin. Volumetric forecasts were largely unchanged in the Bear River Basin with the median forecast being 85% of average. In the Weber, Provo and Six Creeks drainages, forecasts remained at their February 1st values or were lowered slightly.

This month we begin forecasting the max summer elevation of the Great Basin. Current ESP estimates are for a final maximum elevation of 4194.66 ft. above mean sea level by early to mid May, 2009. The lake is currently at 4194.01 ft. above mean sea level

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Bear River drainage improved slightly during February. Monthly precipitation was 109% of average and snow water equivalent increased to 92% of average. Seasonal precipitation is currently 101% of average.

Soil Moisture & Streamflow - Observed streamflows for January were estimated for Bear at the UT/WY State line at 86% of average. Observed flows on the Logan River nr Logan above State Dam were 86% of average.

Short Term Precipitation Forecasts - Short term National Weather Service Models are indicating a period of cool and wet weather during the first 6-10 days of the month. Short term CPC guidance shows the possibility of below average precipitation and above normal temperatures for the middle of March.

General Discussion - Volumetric forecast for April through July were largely unchanged this month and range from 60% at Bear nr Montpelier to 87% of average at the Utah, Wyoming State line.

Snow Water Equivalent and Precipitation - Conditions in the Weber and Ogden River River basins remain largely unchanged for February 2009. Monthly precipiation totalled 94% of average, while snow water equivalent numbers remainded steady at 97% of average. The explaination is that high elevation stations were favored during February and received more water than valley locations. This trend is apparent in the monthly maps at the end of this report. Seasonal precipitation decreased slightly to 97% of average.

Soil Moisture & Streamflow - Soil moisture conditions remain dry in the upper basin, varying from 70% to 89% of average. Observed streamflows for the month were 102% of average for the Weber at Oakley.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period cool and wet weather during the first 6-10 days of the month. Short term CPC guidance shows the possibility of below average precipitation and normal temperatures during the middle of March.

General Discussion - Volumetric forecasts in the Weber Basin were all lowered and weighted more towards ESP models results than SWS equations results, which weight low soil moistures condition, the trend in warmer than average temperatures for the last 7 years and the slightly below average monthly precipitation numbers for February. The forecasts now range from 78% at Echo Reservoir to 90% of average at Wheeler Creek near Pineview Reservoir.

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Six Creeks basins remained largely unchanged during February. Monthly precipitation was 86% of average and snow water equivalent was 102% of average. Seasonal precipitation now totals 108% of average.

Soil Moisture & Streamflow - Streamflows in Big and Little Cottonwood Canyons were 96% of average. Soil moisture grids currently range from 50%-90% of average.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period of cool and wet weather during the next 6-10 days in the Six Creeks region. Short term CPC guidance shows the possibility of below average precipitation for the middle of March.

General Discussion - Volumetric forecasts remained steady for most points in the Six Creeks basin. Forecast now range from 84% at Parleys Creek near Salt Lake City to 98% at Little Cottonwood Canyon near Salt Lake City.

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Utah Lake drainages showed below average accumulations for the month of February . Monthly precipitation totalled 82% and snow water equivalent numbers are 92% of average. Seasonal precipitation now totals 103% of average. There were problems with the Timanogos Divide SNOTEL and calculations with out it show 85% SWE but we have include ground truth measurements and NRCS indicate 92% of average snow water equivalent.

Soil Moisture & Streamflow - Streamflows for Spanish Fork near Castilla and Provo at Woodland combined were 100% of average. Soil moisture grids along the Provo River range from 50-90% of average. The Spanish Fork drainage ranges from 70% to 99% of average.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period of cool and wet weather during the first 6-10 days of the month. Short term CPC guidance shows the possibility of below average precipitation and above average temperatures during the middle of March.

General Discussion - Volumetric forecast for Utah Lake and its associated rivers were lowered this month in responsed to below average precipiation and continued dry soil moisture conditions from last summer and fall. The forecast now range from 85% at Utah Lake to 94% at American Fork near the UP Power Plant.

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