Extended Streamflow Guidance
Issued by NWS

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FGUS65 KSTR 051257
ESGWY
COLORADO BASIN RIVER FORECAST CENTER
NATIONAL WEATHER SERVICE SALT LAKE CITY UTAH


                     SPRING FLOOD POTENTIAL
          FOR THE GREEN AND BEAR RIVER BASINS IN WYOMING

                       May 4, 2017


The 2017 spring runoff flood potential due to snowmelt is
high for Upper Green and Bear River basins in southwest
Wyoming at this time due to much above normal snow conditions
in these areas. The magnitude and timing of peak flows will largely
be determined by hydrometeorologic events that occur over the next
4-6 weeks.

Specific forecast procedures and flood flow levels do not exist
for all streams.Above average peaks, bankfull, and flooding
conditions are possible on several streams and small tributaries
due to a significant snowpack and delayed melt.

Currently the following sites are forecast to peak at flood flow
at the given exceedance level (for example, there is a 25% chance the New Fork
River nr Big Piney will exceed flood flow):

Flood Flow:
New Fork River nr Big Piney          25%
Green River nr LaBarge               90%
Green River nr Green River           25%
Hams Fork River nr Pole Creek        10%
Bear River nr Evanston               10%
Bear River nr Border                 90%

April precipitation was much above average for the fifth month
in a row in southwest Wyoming.Water year precipitation in
southwest Wyoming is currently 170%. The snow water equivalent
in the Upper Green and Bear River basins is much above normal.
The current snow water equivalent is 205% of median above
Fontenelle Reservoir in the Upper Green and 150% of normal in the
Bear River headwaters.

Current volume forecasts for the April through July runoff period
are much above average for both the Upper Green and Bear River basins.
May 1st forecasted volumes are near or above record for Fontenelle
and Flaming Gorge reservoir inflows.

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.

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


A list of specific spring peak flow forecasts are available at:
http://www.cbrfc.noaa.gov/rmap/peak/peaklist.php

A map of the current spring peak flow forecasts is available at:
http://www.cbrfc.noaa.gov/lmap/lmap.php?interface=peak



CBRFC/A.Nielson

$$








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