Forecasts for Hams Fork, Blacks Fork, and Flaming Gorge inflow are in the top five historical observed volumes.
The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 140 percent of average in the Upper Green basin. May precipitation was 200 percent of average in the basin as a whole.

Snow:
June 1st snow water equivalent was 360 percent of average in the basin; please note that this time of year the percent of average may not provide a valid measure of current conditions. The seasonal peak occurred near mid April and was near 135 percent of average. However, it should be noted that there are no snotel locations above 10,000 ft making it difficult to determine the current snowpack conditions.
--- Upper Green basin snow water equivalent plot.

Streamflow:
May streamflow was near 95 percent of average.

Soil Moisture:
Modeled soil moisture states were below average heading into the winter.

Climate Forecasts:
Climate forecasts were not a factor because there is not a strong correlation between La Nina conditions and winter precipitation in the Upper Green basin.

Forecast Summary:
Most forecast volumes increased from last month due to the much above average precipitation in May and cold temperatures which have delayed the snow melt. Snowpack and seasonal precipitation were still both much above average on June 1st. As a result of the current conditions, the April through July streamflow volume forecasts increased by approximately 5 to 10 percent from the May 1 forecasts. Current forecasts range between 115 and 181 percent of average with a median value of 145 percent. Forecasts for Hams Fork, Blacks Fork, and Flaming Gorge inflow are in the top five historical observed volumes.

All of these forecast volumes are at or above the record volume with the exception of the White River.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through May precipitation was 140 percent of average in the Yampa/White basin. May precipitation was 155 percent of average in the basin as a whole.

Snow:
June 1st snow water equivalent was 274 percent of average in the basin; please note that this time of year the percent of average may not provide a valid measure of current conditions. A wet and cold May has delayed snow melt and on June 1st there was still 135% of the seasonal peak, which typically occurs in mid April, at snotels above above 9,500ft. Many of the snotels in the basin have record snow water equivalent.
--- Yampa basin snow water equivalent plot.

Streamflow:
May streamflow was near 115 percent of average.

Soil Moisture:
Modeled soil moisture states were near average heading into the winter for the Yampa, Little Snake,and White River basins.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Yampa/White basin.

Forecast Summary:
Most forecast volumes increased from last month due to the much above average precipitation in May and cold temperatures which have delayed the snow melt. Snowpack and seasonal precipitation were still both much above average on June 1st. It is also important to note that many of the snotel locations have record snow water equivalent for June 1. As a result of the current conditions, the April through July streamflow volume forecasts have increased by approximately 5 to 10 percent. Current forecasts range between 161 and 242 percent of average with a median value of 200 percent. All of these forecast volumes are at or above the record volume with the exception of the White River.

Many of these forecast volumes are in the top five historical observed volumes.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through May precipitation was 165 percent of average in the Duchesne basin. May precipitation was 200 percent of average the basin as a whole.

Snow:
June 1st snow water equivalent was 385 percent of average in the basin; please note that this time of year the percent of average may not provide a valid measure of current conditions. A wet and cold May has delayed snow melt and on June 1st there was still 100% of the seasonal peak, which typically occurs in mid April. However, the majority of the snow exists in areas above 10,000ft.
--- Duchesne basin snow water equivalent plot.

Streamflow:
May streamflow was 80 percent of average.

Soil Moisture:
Modeled soil moisture states were much below average to below average heading into the winter.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Duchesne basin.

Forecast Summary:
Most forecast volumes increased from last month due to the much above average precipitation in May and cold temperatures which have delayed the snow melt. Snowpack and seasonal precipitation were still both much above average on June 1st. As a result of the current conditions, the majority of the April through July streamflow volume forecasts increased by approximately 5 to 10 percent. Current forecasts range between 108 and 275 percent of average with a median value of 188 percent. Many of these forecast volumes are in the top five historical observed volumes.

Many of these forecast volumes are in the top five historical observed volumes.
The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 165 percent of average in the Lower Green basin. May precipitation was 190 percent of average.

Snow:
June 1st snow water equivalent was 445 percent of average in the basin; please note that this time of year the percent of average may not provide a valid measure of current conditions. Typically, the snow has melted out in this basin by June 1. However, currenlty there is still a small amount of snow located only at the highest elevations.
--- Lower Green basin snow water equivalent plot.

Streamflow:
May streamflow was near 115 percent of average.

Soil Moisture:
Modeled soil moisture states were much below to near average heading into the winter.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Lower Green basin.

Forecast Summary:
Most forecast volumes increased slightly from last month due to the much above average precipitation in May and cold temperatures which have delayed the snow melt. As a result of the current conditions, the majority of the April through July streamflow volume forecasts increased, by approximately 5 to 10 percent. Current forecasts range between 163 and 212 percent of average with a median value of 190 percent.

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