Extended Streamflow Guidance
Issued by NWS
FGUS65 KSTR 151925
NATIONAL WEATHER SERVICE
COLORADO BASIN RIVER FORECAST CENTER
SALT LAKE CITY, UT
SPRING FLOOD POTENTIAL
FOR THE COLORADO RIVER BASIN WITHIN COLORADO
FEBRUARY 15, 2017
The 2017 spring runoff flood potential due to snowmelt is higher than usual
at this time for the Yampa/White, Upper Colorado mainstem, Gunnison, Dolores
and San Juan basins. It should be emphasized that it is still early in the
snow accumulation season and conditions could change before the runoff begins.
Specific forecast procedures and flood flow levels do not exist for all streams.
However, the CBRFC hydrologic model is currently forecasting above average peak
flows across western Colorado during the snowmelt runoff period. 50% exceedance
forecasts for many sites are projected to be above defined bankfull levels,
with 10% exceedance forecasts above defined flood flow at quite a few of those
Areas prone to flooding in the past may experience issues again this year.
The area with the highest threat of flooding at this time is the Gunnison River
February 15th month to date precipitation is below average, but February 15th
snow water equivalent remains much above median across western Colorado.
Individual SNOTEL sites are generally between 130 and 200 percent of median in
the Upper Colorado mainstem, Gunnison, Dolores and San Juan basins and between
110 and 130 percent of median in the Yampa/White basin. Values at many sites
have already exceeded the normal peak snow water equivalent levels that
typically occur in April. In addition, several sites in the Gunnison River
headwaters have record amounts of snow water equivalent for this time of year.
FEBRUARY 3, 2017
January precipitation exceeded 200 percent of average across most of western
Colorado; the exception was the Yampa/White basin which had 185 percent of
average for the month. The Gunnsion, Dolores and San Juan basins ranged
between 245 and 260 percent of average, while the Upper Colorado mainstem had
225 percent of average. Many SNOTEL sites recorded their highest January
precipitation on record, with most others in the top three on record. October
through January seasonal precipitation totals now range between 120 and 140
percent of average in these basins.
February 1st snow water equivalent was much above median with the Yampa/White
basin at 130 percent, the Upper Colorado mainstem at 145 percent and the
Gunnison, Dolores, and San Juan basins ranging between 160 and 175 percent
of median. Some individual SNOTEL sites outside of the Gunnison and Dolores
basins have also exceeded normal peak snow water equivalent levels at this time.
The current volume forecasts for the April through July runoff period are
generally above to much above average for the basins in western Colorado.
Highest forecasts, as a percent of average, are in the Gunnison and Dolores
basins which range between 125 and 150 percent of average. The Upper Colorado
mainstem and San Juan River Basin forecasts generally range between 110 and
125 percent of average, while the Yampa/White basin forecasts range from 100
to 115 percent of average.
Although spring temperatures affect the pattern of snowmelt runoff and
consequently the magnitude of peak flows, peak flows also roughly correspond
to volumetric flows. 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.