The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation was near 80 percent of average in the upper Salt River Basin and 75 percent of average in the Verde River Basin.

February precipitation was 40 percent of average in the upper Salt Basin and 35 percent of average in the Verde Basin.

Streamflow:
February streamflow was near 45 percent of median on the Salt River, 10 percent of median on the Tonto, and 40 percent of median on the Verde River.

Snow:
March 1st snowpack was 40 percent of average in the Verde River Basin. Snowpack in the upper Salt River Basin was 75 percent of average.

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

Soil Moisture:
Modeled soil moisture states are below 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:
Dry conditions over the past several months are somewhat consistent with La Nina climate conditions that currently exist. Below average precipitation and below median runoff are observed more frequently during La Nina events. March-May forecast volumes are for 40 percent of median in the Salt River Basin, near 35 percent of median in the Tonto Basin, and near 40 percent of median in the Verde Basin.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation was 85 percent of average.

February precipitation was 35 percent of average.

Streamflow:
February streamflow was near 45 percent of median.

Snow:
March 1st snowpack conditions were near 70 percent of average in the upper Gila Basin.

Upper Gila Basin Snow Plot.
San Francisco Basin Snow Plot

Soil Moisture:
Below average precipitation resulted in below average modeled soil moisture states.

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:
Several conditions exist that support much below median March-May streamflow volumes in the Gila River Basin. These include below average seasonal precipitation and soil moisture, and below average snowpack. The presence of La Nina climate conditions suggest drier than average conditions have a better chance of occuring through the forecast period. March-May forecast volumes range from 32 to 56 percent of median.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation was 80 percent of average.

February precipitation was 45 percent of average throughout the Little Colorado Basin.

Streamflow:
February streamflow on the Little Colorado at Lyman was near 15 percent of median.

Snow:
Basin snowpack conditions on February 1st were near 60 percent of average in the southern Headwaters.

Little Colorado Snow Plot
Central Mogollon Rim Snow Plot

Soil Moisture: Below average precipitation resulted in below average modeled soil moisture states.

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:
The presence of La Nina climate conditions suggest below average precipitation into the spring. Below average seasonal precipitation exists over the Little Colorado Basin, with below average soil moisture conditions in the headwaters. Snowpack conditions dropped from February 1st to March 1st, and remain well below average. March-May streamflow volumes are forecast around 45 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