Extended Streamflow Guidance
Issued by NWS
FGUS65 KSTR 062050
National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
May 6, 2013
FLOOD POTENTIAL OUTLOOK
Eastern Great Basins:
The 2013 spring runoff flood potential due solely to snowmelt runoff as of
May 6, remains low however the potential for a rain on snow event is always
present in May and early June.
Peak flow forecast in the Eastern Great Basin for the spring of 2013 continue
to indicate less than a 10% chance of reaching their average mean daily
peak flows. None of these points are currently forecast to reach flood flow
however ample snow exist in the headwaters of the Weber, Provo, Bear and Little
Cottonwood Canyon areas so that if conditions rapidly changed or a rain
on snow event occurred we could potentially encounter significant flows.
Please refer to the link at the bottom of the page for access our peak flow
webpage which is updated as necessary when we feel a significant change in
conditions is about to occur. Also feel free to call anytime at 801 524-3570.
Duchesne, Price and San Rafael River Basins:
The 2013 spring runoff flood potential due to snowmelt is not high at
this time for the Duchesne, Price and San Rafael basins. Currently, there
are no sites in the Duchesne, Price and San Rafael basins
forecast to peak at or above the flood flow levels. All forecast
peak flows are below average. However, it is important to
emphasize that flood flows and forecast procedures do not
exist for all streams and rivers.
April precipitation was much above average at 145 and 130
percent of average in the Duchesne and Price/San Rafael
basins. Despite a wet month, seasonal precipitation is still below average
near 80 percent of average in both basins. Temperatures were below normal
in April delaying significant snow melt. As a result cold and
wet conditions in April snowpack condition had improved especially in
the Duchesne. However, snow water equicalent on May 1 was still
below average at 75 and 50 percent of average in the Duchesne and
Lower Green river basins.
Virgin and Sevier River Basins:
The 2013 spring runoff flood potential due to snowmelt is low as of May 1 for
the Virgin and Sevier River Basins. The snowpack in these basins is 50-55% of
average as of May 1, and the snowpack has been depleted from areas outside the
high elevations. Southern Utah received less precipitation in April than
northern Utah; April precipitation in the Sevier and Virgin River Basins was
55-70% of average.
As of May 1, the peak of snowmelt-driven flow has already occurred in the
Sevier River Basin. There is an outside chance that flows in the Virgin
River Basin could exceed the peak flows that occurred last week. However,
the chance is small, and any peak flows due to snowmelt-driven flow would
be below the average peak flow.
Spring weather is probably the single most important factor contributing to
peak flows in any given year. Even with a below average snow pack,given the
right temperature pattern it is possible to reach flood flows as was the case
in 2010. Conditions can and do change rapidly and we will continue to monitor
those conditions and provide updates as necessary.
The current forecast are availabe through the following link:
CBRFC/B.Bernard, A.Nielson, S.Bender