The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation ranged from near 110 to 125 percent of average across the Salt and Verde River Basins.

February precipitation was near average in the Verde Basin and ranged from 70 to 115 percent of average in the Salt Basin. Higher elevations of the Salt River Basin received precipitation amounts closer to average.

Streamflow:
Precipitation combined with low elevation snow melt resulted in above median streamflow in February. Streamflow volumes were near 180 percent of median on the Salt River, 200 percent on the Tonto River, and 250 percent of median on the Verde River.

Snow:
Record or near record snowpack conditions existed on March 1st at higher elevation in the Salt and Verde River Basins. March 1st snowpack conditions were near 270 percent of average in the Verde Basin and 150 to 400 percent of average in the upper Salt River Basin.

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

Soil Moisture:
Significant rainfall in January, and additional precipitation during February maintained moist soil conditions throughout the Salt and Verde Basins with the exception of higher elevations. Higher elevations that have been under persistent snowpack through the winter season have modeled soil moisture states that are drier compared to this time last season.

Climate Forecasts:
El Nino climate conditions suggest increased chances for precipitation in this area this spring. The El Nino influence was accounted for in generation of these forecasts.

Forecast Summary:
A significant snowpack exists in the Salt and Verde Basins for this time of year with extensive snow cover extending down to the 6000 foot elevation level. Although dry soils under the snowpack could act to reduce snow melt runoff, snow melt is still expected to provide a significant contribution to March through May streamflow volumes this year. Above average precipitation is anticipated into the spring months due to the El Nino climate condition. March through May streamflow volumes from 150 to 225 percent of median are expected. Significant rainfall combined with snow melt would result in larger volumes.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation is near 110 percent of average in upper Gila River Basin.
February precipitation ranged from 100 to 115 percent of average in the upper Gila River Basin.

Streamflow:
February streamflow volumes were 160 to 200 percent of median in the San Francisco and upper Gila River Basin.

Snow:
Upper Gila Basin snowpack conditions ranged between 170 to 250 percent of average on March 1st. Record to near record snow pack exists in high elevations of the San Francisco drainage. March 1st snowpack in the San Francisco drainage ranged from 170 to 400 percent of average.

Upper Gila Basin Snow Plot.
San Francisco Basin Snow Plot

Soil Moisture:
Modeled soil moisture conditions in the upper Gila and and San Francisco drainage are wetter than this time ast year due to rainfall in January and February. The exception are higher elevations where snowpack has persisted through the winter. In these areas modeled soil states are drier and they have changed little since the beginning of the season.

Climate Forecasts:
El Nino climate conditions suggest increased chances for precipitation in this area. The El Nino influence was accounted for in generation of these forecasts.

Forecast Summary:
Above average snowpack exists in the upper Gila Basin with near record snopwack for this time of year in the San Francisco drainage. Above average rainfall is anticipated this spring due to the El Nino climate condition. Additional rainfall and runoff from snow melt are expected to yield March through May streamflow volumes between 150 and 250 percent of median. Significant rainfall combined with snow melt would result in larger volumes.

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation is near average throughout the Little Colorado Basin.
February precipitation ranged from 60 to 110 percent of average. Headwater locations were near 90 percent of average. This followed a very wet January that observed monthly totals ranging from 240 to 380 percent of average.

Streamflow:
February streamflow volumes in the Little Colorado were below median in the higher elevations. This was due to below average precipitation and below average temperatures for the month that retained the snowpack preventing much snow melt.

Snow:
Basin snowpack conditions ranged frome 160 to 370 percent of average on March 1st in the Southern Headwaters of the Little Colorado Basin.

Little Colorado Southern Headwaters Snow Plot
Central Mogollon Rim Snow Plot

Soil Moisture: Modeled soil moisture remains slightly drier than this time last year under areas of continous snowpack. At lower elevations below the snow line soil moisture states have become much wetter since early in the season.

Climate Forecasts:
El Nino climate conditions suggest increased chances for precipitation in this area. The El Nino influence was accounted for in generation of these forecasts.

Forecast Summary:
A significant snowpack exists in higher elevations of the Little Colorado drainage. Although dry soils under the snowpack could act to reduce snow melt runoff, snow melt is still expected to provide a significant contribution to March through May streamflow volumes this year. This is most likely in smaller high elevation tributaries in close proximity to the snowpack. Above average precpitation is anticipated this spring due to El Nino climate conditions. March through May streamflow volumes from near 150 to 560 percent of median are expected. Significant rainfall combined with snow melt would result in larger volumes.

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