Extended Streamflow Guidance
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FGUS65 KSTR 042055
ESGNM
TTAA00 KSLR DDHHMM
NATIONAL WEATHER SERVICE
COLORADO BASIN RIVER FORECAST CENTER
SALT LAKE CITY UT
Apr 4, 2019

 SAN JUAN RIVER BASIN SPRING FLOOD POTENTIAL OUTLOOK


Peak flows due to snowmelt are expected to be above average
this spring. Highest peaks in the San Juan Basin are more
frequently associated with summer monsoon rain events than with
snowmelt. The latest hydrologic model guidance does not indicate
flood levels being reached even at the 10% exceedance probability
level. However flood levels and peak flow procedures do not
exist for all stream sites.

Streamflow peaks are expected to run in the top 25-30 percent of
the historical record throughout the San Juan Basin. Areas that
have experienced high water issues during heavy snowpack years will
be at risk again this year.

The primary flood threat may be if heavy rainfall occurs during
the peak runoff period when channel capacities are reduced.

As of early April snowpack conditions in the San Juan Basin are 150
percent of normal above Navajo Reservoir and 160 percent of average
in the Animas River Basin. Many SNOTEL sites are well above the
seasonal peak snow, although lower elevation snow has slowly been
melting off.

Seasonl runoff volumes (April-July) are expected to range from near
115 to 130 percent of average.

The spring runoff peak flow outlook will continue to evolve with a
and possibly change over the next 2-4 weeks depending on the snowmelt
pattern and future weather.

The most recent snowmelt peaks can be accessed on the CBRFC website
at:

https://www.cbrfc.noaa.gov/lmap/lmap.php?interface=peak

G. Smith/ CBRFC

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