Flood Potential Outlook
Issued by NWS Portland, OR

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Water Supply Outlook
National Weather Service Portland OR
145 PM PDT Friday May 5 2017

...OREGON WATER SUPPLY OUTLOOK AS OF MAY 5TH 2017...

The water supply forecast for the spring and summer of 2017 is above-
average across the state.  April through September runoff-volume
forecasts range from 90 to 170 percent of average, with above-
average forecasts for most rivers basins in Oregon, except near-
average forecasts for a few basins in coastal western Oregon and
northeast Oregon.

Snowpack as of May 4th remains above-average in higher elevations
statewide. Snow has melted from lower and mid elevations, but
significant snow remains at elevations above 5000 feet north and
6000 feet south. April precipitation was above-average, continuing
the trend of wet months that started in February.

The May 2017 outlook by the Climate Prediction Center calls for
increased likelihood of below-average precipitation in western
Oregon, with equal chances of near, above, or below-average
precipitation for central and eastern Oregon. The outlook for May
temperatures is equal chances statewide. For June through August,
there is a slightly-enhanced chance of above-average temperatures
for Oregon, with equal chances of near, above, or below-average
precipitation across the state. For more details, visit
www.cpc.ncep.noaa.gov.

Refer to the sections below and links provided for details regarding
snowpack, precipitation, reservoir conditions, and water supply
forecasts for individual basins.

The Oregon water supply outlook will be updated early each month
through June. Look for the next update by June 5th.

============================================================
Snowpack across Oregon

Oregon snowpack ranges from 110 to 160 percent of average as of May
4th. There is still significant snowpack above 5000 feet north and
6000 feet south in the Cascades and eastern Oregon mountains.
Snowmelt in late March and much of April was a major contribution to
recent high streamflow, especially for rivers east of the Cascades.

Additional snowpack information:

NOAA National Weather Service - Northwest River Forecast Center
www.nwrfc.noaa.gov/snow/

USDA Natural Resources Conservation Service
www.nrcs.usda.gov/wps/portal/nrcs/main/or/snow/

============================================================
Precipitation and Temperatures across Oregon

Precipitation for the 2017 water year thus far (Oct 1, 2016 through
April 30, 2017) ranges from 120 to 150 percent of average in Oregon.
Adding to what has already been a wet winter, combined February-
March-April precipitation was much-above average, with record
amounts in parts of western Oregon. April temperatures were 1 to 3
degrees below-average across the state.

Details on precipitation and temperatures:

NOAA National Weather Service - Northwest River Forecast Center
www.nwrfc.noaa.gov/water_supply/wy_summary/wy_summary.php

NOAA NWS - California-Nevada River Forecast Center (Klamath basin)
www.cnrfc.noaa.gov/water_resources_update.php

============================================================
Reservoirs

Reservoir storage increased in April, adding to the major increases
in March. As of early May, most irrigation reservoirs around the
state are 85 to 100 percent full, and nearly all reservoirs are
expected to fill to summer full-pool levels by late May. Note that
Owyhee Reservoir, Oregon`s largest irrigation reservoir, is filled
to 100 percent of capacity.

Reservoir data is provided by the Natural Resources Conservation
Service, the Bureau of Reclamation, and the US Army Corps of
Engineers.

Additional reservoir information:

www.wcc.nrcs.usda.gov/basin.html
www.usbr.gov/pn/hydromet/select.html
www.nwd-wc.usace.army.mil/nwp/teacup/willamette/

============================================================
Observed Streamflow

Observed streamflow in April 2017 was above-average for nearly all
Oregon rivers, except near-average in south-central Oregon.

Visit waterwatch.usgs.gov for details on observed streamflow. Water
year and monthly runoff data is available at www.nwrfc.noaa.gov for
several locations in Oregon.

============================================================
Forecast Streamflow and Seasonal Runoff Volumes

Forecasts for April-September runoff volume range from 90 to 170
percent of average, with the highest values generally in
southwestern and eastern Oregon and the lowest values in northwest
Oregon. Seasonal forecasts have trended upward over the past three
months.

The May 4th forecast for the Columbia River at The Dalles, which is
a good index of conditions across the Columbia Basin, is 129 percent
of average for April-September, an increase of 9 percent from the
forecast on April 4th.

Details on basin-scale water supply forecasts:

NOAA National Weather Service - Northwest River Forecast Center
www.nwrfc.noaa.gov/ws/

USDA Natural Resources Conservation Service
www.wcc.nrcs.usda.gov/wsf/

Bryant
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