Flood Potential Outlook
Issued by NWS Portland, OR

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Water Supply Outlook
National Weather Service Portland OR
300 PM PST Monday February 5 2018


The water supply forecast for the spring and summer of 2018 is below-
average for most Oregon watersheds, especially so for the southern
half of the state. April through September runoff-volume forecasts
range from 25 to 90 percent of average, lowest in south-central
Oregon and highest in northwest and far-northeast Oregon.

Snowpack is notably low in the Cascades and all mountain ranges in
eastern Oregon. The major causes for this winter`s low snowpack are
a relatively-dry December and a relatively-warm January.

The February 2018 outlook by the Climate Prediction Center calls for
a high likelihood of below-average precipitation and above-average
temperatures in Oregon. Looking at March through May, the
temperature outlook calls for an enhanced possibility of below-
average temperatures, especially for western Oregon, and 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 next update will be issued by March 5, 2018.

Snowpack across Oregon

As of early February, basin snowpack ranges from 30 to 60 percent of
average, in terms of the water content of the snow. Values are
lowest across the southern third of the state.

Weather conditions the past 2 months have not been favorable for
building snowpack. In December 2017, precipitation was below-average
and temperatures in the mountains were above-average. In January,
precipitation was near to below-average, but temperatures were 3 to
8 degrees above average. The February weather outlook indicates
similar trends will probably continue, with generally dry and
relatively-warm conditions expected through much of the month.

Additional snowpack information:

NOAA National Weather Service - Northwest River Forecast Center

USDA Natural Resources Conservation Service

Precipitation and Temperatures across Oregon

Precipitation for the 2018 water year thus far (Oct 1, 2017 through
February 4, 2018) ranges from 60 to 100 percent of average in
Oregon, highest in northwest and far-northeast Oregon and lowest in
south-central Oregon. Temperatures in December and January were
above-average, especially at higher elevations.

Details on precipitation and temperatures:

NOAA National Weather Service - Northwest River Forecast Center

NOAA NWS - California-Nevada River Forecast Center (Klamath basin)


Reservoir storage as of early February is generally average to a
little above-average for this time of year and 40 to 80 percent of
storage capacity. Many reservoirs around the state have carry-over
storage from last year.

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

Additional reservoir information:


Observed Streamflow

Observed streamflow in January 2018 was near-average for the
northern half of Oregon and portions of southeast Oregon, while it
was below-average for southwest Oregon and notably below-average
for 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 25 to 90
percent of average. The highest values are in northwest and far-
northeast Oregon. The lowest are in central and south-central
Oregon. The forecasts are updated daily and have generally been
trending downward the past 2 months.

The forecast for the Columbia River at The Dalles, which is a good
index of conditions across the Columbia Basin, is 107 percent of
average for April-September, reflecting above-average snowpack in
northern Washington and the Rocky Mountain portion of the Columbia
River basin.

Details on basin-scale water supply forecasts:

NOAA National Weather Service - Northwest River Forecast Center

USDA Natural Resources Conservation Service


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