Extended Streamflow Guidance
Issued by NWS
FGUS65 KSTR 171403
COLORADO BASIN RIVER FORECAST CENTER
NATIONAL WEATHER SERVICE SALT LAKE CITY UTAH
SPRING FLOOD POTENTIAL
FOR THE GREEN AND BEAR RIVER BASINS IN WYOMING
March 16, 2015
The 2015 spring runoff flood potential due to snowmelt is
is not high this time for the Upper Green and Bear River
basins. However, it should be emphasized that snow typically
accumulates into April, therefore conditions may change before
the runoff begins.
Currently, the following sites are forecast to peak at or above
the bankfull or flood flow at the given exceedance level
(for example, there is a 25% chance the Green River near LaBarge
will exceed bankfull):
No points are forecast to exceed flood flow
Green River near LaBarge 25%
Green River at Green River, Wyoming 25%
Below average peak flows are expected for southwest
Wyoming based on the current snow conditions. However, it is
important to note that specific forecast procedures and flood
flow levels do not exist for every stream.
February precipitation was below average in all basins across
southwest Wyoming with values ranging from 65 to 70 percent of average.
Seasonal precipitation was slightly below average in early March
in both the Upper Green above Flaming Gorge and Bear River basins.
However, seasonal precipitation was near normal in headwater
areas above Fontenelle reservoir as of March 1st.
March month to date precipitation is below average near 60%.
The March 16 snow water equivalent is 110% of median
above Fontenelle reservoir, 97% of median above Flaming Gorge reservoir,
and 60% of median in the headwaters of the Bear River. However, there is much
variation between individual SNOTEL sites within each basin due
to the generally warm winter which has seen precipitation
falling as rain instead of snow as well as some early snow
melt that occurred during February and the first half of March at
relatively high elevations.
Although spring temperatures affect the pattern of snowmelt runoff and
consequently the magnitude of peak flows, peak flows also roughly correspond
to volumetric flows. The current volume forecasts for the April through
July runoff period are near average in the Upper Green above Fontenelle reservoir
and below average in all other basins.
It is also important to keep in mind that an extended period of
much above normal temperatures or heavy rainfall during the melt
period can cause or exacerbate flooding problems in any
year, regardless of snowpack conditions.
A list of specific spring peak flow forecasts are available at:
A map of the current spring peak flow forecasts is available at: