Flood Potential Outlook
Issued by NWS Portland, OR

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Water Supply Outlook
National Weather Service Portland OR
145 PM PDT Friday February 3 2017

...OREGON WATER SUPPLY OUTLOOK AS OF FEBRUARY 3RD 2017...

The water supply forecast for the spring and summer of 2017 is
generally average to above-average across the state.  April-
September runoff volume forecasts range from about 80 to 150 percent
of average, with above-average runoff volume for central, southeast,
and extreme southwest Oregon, and near-average runoff volume for
most of western, north-central, and northeast Oregon.

The above-average snowpack through the end of January is the big
driver for the water supply forecasts this time of year. Significant
changes in basin forecasts are possible for the next few months
since significant seasonal snow accumulation and rainfall continues
into April.

Precipitation thus far this water year, starting October 1, 2016,
has been much above-average in Oregon. The amount of area in the
state under drought designation has thus been greatly reduced, with
only a small area of D1 Moderate Drought remaining in eastern
Oregon. Visit drought.gov for the latest assessment and outlook
regarding drought conditions.

Note that the current Oregon snowpack is actually pretty similar to
this same time last year. Spring 2016 proved to be an illustration
of the significance of spring temperatures and precipitation.
Relatively warm and dry conditions in March and April resulted in
rapid and earlier-than-usual snowmelt and subsequent low streamflow
in June and July. That said, the outlook by the Climate Prediction
Center calls for increased likelihood of above-average precipitation
and temperatures for February, with equal chances of near, above, or
below normal temperatures and precipitation for March through May.
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 March 6th.

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

Seasonal snowpack through early February ranges from about 100 to
160 percent of average and is notably high in much of east-central
and southeast Oregon, even at valley elevations. Peak seasonal
snowpack, in terms of water content, typically occurs between mid
March and mid April.

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
Jan 31, 2017) ranges from 100 to 150 percent of average in Oregon.
October was notably wet across all of Oregon, with December and
January notably wet across the southern half of Oregon.

Temperatures were near-average in October, above-average in
November, and dramatically below-average in December and January.

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 is highly variable, as is typical for this time of
year, and ranges from about 10 to 70 percent of capacity. Reservoir
storage is typically low this time of year due to a couple factors:
1) Most irrigation reservoirs in central and eastern Oregon draw
down through the summer and fall to provide water for downstream
users and then refill with spring snowmelt and rainfall, and 2) most
reservoirs in western Oregon operate primarily for flood control and
are purposely kept near minimum pool through the winter.

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 and Forecast Streamflow

Observed streamflow in December 2016 and January 2017 was generally
near-average, with above-average streamflow in southwestern Oregon.
Water year runoff is also running near average for most basins.

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.

Forecasts for April-September runoff volume range from 80 to 150
percent of average, with the highest values generally in southeast
and south-central Oregon and the lowest values in northwest Oregon.
Seasonal forecasts may change significantly based on what happens
with temperatures and precipitation February through April.

The forecast for the Columbia River at The Dalles, which is a good
index of conditions across the Columbia Basin, is 97 percent of
average for April-September.

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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