The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-December precipitation ranged from 110 to 130 percent of average in the Salt River Basin and 100 to 120 percent of average in the Verde River Basin.

December precipitation was 165 percent of average in the Salt River Basin, and near 200 percent in the Verde River Basin.

Streamflow:
December streamflow was near 80 percent of median on the Salt River and 120% of median on the Verde River.

Snow:
January 1st snowpack conditions were 130 percent of average in the Verde River Basin and 135 percent of average in the Salt River Basin.

Salt River Basin Snow Plot.
Verde River Basin Snow Plot.

Soil Moisture:
Modeled soil moisture states are near average at this time.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
Despite above average seasonal precipitation, and above average January 1st snowpack, La Nina climate conditions suggest below average precipitation over the next few months. Forecast volumes are near 83 percent of median in the Tonto, 89 percent of median in the Verde River Basin and 81 percent of median in the Salt River Basin.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-December precipitation was 90 percent of average in the southern portions and up to 130 percent of average in the headwaters.

December precipitation ranged from 75 percent of average in the southern portions to greater than 150 percent of average in the headwaters.

Streamflow:
Minimal streamflow observations exist for December. December volume on the Gila River into San Carlos Reservoir was near 70 percent of median.

Snow:
Basin snowpack conditions were near 280 percent of average in San Francisco Basin and 185 percent of average in the upper Gila Basin. The overall Basin average was 165 percent of average.

Upper Gila Basin Snow Plot.
San Francisco Basin Snow Plot

Soil Moisture:
Modeled soil moisture states are near average at this time.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
Although snowpack was above average for January 1st, the presence of La Nina climate conditions suggest below average precipitation into the spring. Forecast volumes range from 83 to 89 percent of median.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-December precipitation varied from near 90 percent of average over the eastern portions to 125 percent of average over the Mogollon Rim.

December precipitation ranged from 85 percent of average over the east to greater than 150 percent of average in the headwaters.

Streamflow:
Minimal streamflow observations exist for December. December volume on the Little Colorado near Lyman was near 40 percent of median.

Snow:
Basin snowpack conditions were near 160 percent of average in the southern Headwaters.

Little Colorado River Snow Plot
Central Mogollon Rim Snow Plot

Soil Moisture: Modeled soil moisture states are near average at this time.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
Although snowpack was above average for January 1st, the presence of La Nina climate conditions suggest below average precipitation into the spring. Forecast volumes range from 70 to 74 percent of median.

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 1981-2010 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