Extended Streamflow Guidance
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FGUS65 KSTR 152048

National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah

                        SPRING FLOOD POTENTIAL OUTLOOK
     February 15, 2017

The 2017 spring runoff flood potential due to snowmelt is high for Weber, Provo,
Duchesne and Bear River basins of Utah at this time. This potential is due to
the much above median snow conditions in all of these areas. It should also be
emphasized that snow typically accumulates into mid April and even May and that
the threat of spring flooding will largely be determined by hydrometeorologic events
that occur during the next several months. Conditions in the Virgin and Sevier River
basin are near normal. Conditions in the Six Creeks basin near Salt Lake City are
above average but not as high as in the Provo, Weber, Bear or Duchesne and Green
River Basins.

Specific forecast procedures and flood flow levels do not exist for all streams,
however the CBRFC hydrologic model is forecasting above average peak flows across
north central Utah during the snowmelt runoff period. 90% exceedance forecasts for
many sites are projected to be above defined bankfull levels, with 50% and 10%
exceedance forecasts above the defined flood flow at quite a few of those

February month to date precipitation is much above average in central and northern
Utah. The snow water equivalent in the Weber, Provo, Duchesne and Bear River basins
are much above normal with many of our snow gaging locations already exceeding the
annual peak snowpack which typically occur in mid April or early May. The current
snow water equivalent is 165% of median in the Weber River drainage, 197% of median
in the Provo River drainage, 191% of median in the Duchesne and 160% of median in
the Bear River headwaters. Many of Utah`s SNOTEL`s are currently ranked in the top
3 highest years for the period of record.  Additionally several are ranked as the
highest in the period of record at near 200% of median as of February 15.

Current volumetric forecasts for the April through July runoff period are much
above average for all of the above mentioned basins with the exception of those
in south central and southern Utah.

Although spring temperatures affect the pattern of snowmelt runoff and consequently
the magnitude of peak flows, peak flows may roughly correspond to volumetric flows
in their magnitude. 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 during any year.

The spring runoff flood potential will be re-evaluated in March and an updated
product will be issued at that time.

CBRFC/B.Bernard, A.Nielson, T. Cox


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