Flood Potential Outlook
Issued by NWS Pueblo, CO

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Water Supply Outlook
National Weather Service Pueblo CO
300 PM MDT Tue May 8, 2018

...Water Supply Outlook for South Central and Southeast Colorado as
of May 1, 2018...

April continued the dry conditions of March but the warm conditions
moderated considerably with climate stations reporting near average
temperatures. Precipitation was only 43 percent of average in the
mountains of the upper Rio Grande basin. It was only 64 percent of
average in the Arkansas basin.

Snowpack in the mountains reflects the limited precipitation seen
this water year. Snow-water equivalents (SWE) in the Arkansas basin
are at 52 percent of median.  An early melt in the Rio Grande has
diminished the snowpack to 12 percent of median for this time of the
season. Below-average runoff is forecast across southeast and south
central Colorado.

As of May 1, snowpack in the Upper Rio Grande basin of south central
Colorado was at 12 percent of median.  Snow pack values for the sub-
basins of the Rio Grande are uniformly very low. Stations in the
Culebra and Trinchera basins are reporting no snow and the upper Rio
Grande stations are only reporting 20 percent of median snowpack.

The April 1 snowpack in the Arkansas River basin was at 52 percent
of median overall.  The greatest snowpack percentages favored the
extreme headwaters of the Arkansas mainstem.  There, in the upper
Arkansas, snowpack is 73% of median. Tributary basins farther south
are showing extremely poor snowpack compared to the median value. In
the middle portion of the basin, the combined Cucharas and Huerfano
basins reported 6 percent of median snowpack. Stations in the
Purgatoire River basin are showing no remaining snowpack.

There is some good news to report with regard to water supply. At
the end of April, overall reservoir storage was well-above average
in the Arkansas and Rio Grande drainages.  Storage in the Rio Grande
basin was at 115 percent of average overall compared to 99 percent
of average last year at the same time.  Overall storage in the
Arkansas basin was at 129 percent of average, compared to 106
percent of average at the same time last year.

For the Rio Grande basin, streamflow volumes for the upcoming runoff
season are forecast to be near historic lows across the basin.
Following are the latest available streamflow forecasts for selected
locations in the Rio Grande basin assuming normal precipitation for
the remainder of the snow season:

Location                   % of Average     Runoff Period

Rio Grande River
  Thirty Mile Bridge             42            Apr-Jul
  Wagon Wheel Gap                51            Apr-Sep
Rio Grande River
  Near Del Norte                 33            Apr-Sep
South Fork Rio Grande River
  South Fork                     37            Apr-Sep
Saguache Creek
  Near Saguache                  36            Apr-Sep
Alamosa Creek
  Terrace Reservoir Inflow       40            Apr-Sep
La Jara Creek
  Near Capulin                   35            Mar-Jul
Trinchera Creek
  Above Turners Ranch            24            Apr-Sep
Conejos River
  Platoro Reservoir Inflow       44            Apr-Sep
  Near Mogote                    40            Apr-Sep
Culebra Creek
  San Luis                       20            Apr-Sep
San Antonia River
  Ortiz                          19            Apr-Sep
Los Pinos
  Ortiz                          37            Apr-Sep

For the Arkansas basin, streamflow volumes for the upcoming runoff
season are generally forecast to be well-below average. Following
are the latest available streamflow forecasts for selected
locations in the Arkansas basin assuming normal precipitation for
the remainder of the snow season:

Location                   % of Average     Runoff Period

Arkansas River
  Granite                        69            Apr-Sep
  Salida                         68            Apr-Sep
  Canon City                     65            Apr-Sep
  Above Pueblo                   59            Apr-Sep
Chalk Creek
  Near Nathrop                   62            Apr-Sep
Grape Creek
  Near Westcliffe                12            Apr-Sep
Huerfano River
  Near Redwing                   30            Apr-Sep
Cucharas River
  Near La Veta                   25            Apr-Sep
Purgatoire River
  Trinidad                       15            Apr-Sep

These forecasts reflect natural flow only.  Actual observed flow
will likely be affected by upstream water management.

The forecasts below are for 2 locations on the southeast Colorado
plains in the lower part of the Arkansas basin.  These forecasts
include projected upstream water management expected to impact
flows.

Arkansas River
  Las Animas                     61            Apr-Sep
Purgatoire River
  Las Animas                     21            Apr-Sep

This outlook is based on recent observations of snowpack and assumes
normal precipitation for the remainder of the snow season.  If the
actual observed precipitation deviates from normal, then the actual
observed runoff will likely be different than the forecast in this
outlook.  This is the fifth of six scheduled outlooks for the 2018
runoff season. The next outlook will be issued during the first part
of June.

Users of this product are encouraged to contact the National Weather
Service in Pueblo for continued updates on the water supply
situation.  Meteorological conditions could develop that would have
a significant impact on water supply forecasts.

For additional hydrologic products available on the world wide
web, visit the Pueblo National Weather Service web site at
weather.gov/pub.

Or visit the NRCS or the NWS River Forecast Centers that provide
our water supply forecasts at:

weather.gov/abrfc/water_supply

www.wcc.nrcs.usda.gov/wsf/index.html

This message is the result of collaboration between the National
Weather Service and the Natural Resources Conservation Service.

AJA


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