Flood Potential Outlook
Issued by NWS Portland, OR

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Water Supply Outlook
National Weather Service Portland OR
350 PM PST Wednesday June 5 2019


The water supply forecast for the spring and summer of 2019 is above-
average for most Oregon watersheds, with the exception of some
watersheds in far-northwest Oregon, especially rivers draining the
Coast Range in Clatsop, Columbia, and Tillamook counties, where
below-average water supply is forecast. Major snowpack increases in
February and heavy rain in early April caused most reservoirs to
fill to summer full-pool levels and boosted spring streamflows,
especially for central, eastern, and far-southwest Oregon rivers.

The June 2019 outlook by the Climate Prediction Center calls for
enhanced likelihood of above-average temperatures statewide and
below-average precipitation in northwest Oregon, with equal chances
of below, above, or near-average precipitation for the rest of the
state. The outlook for the rest of the summer calls for enhance
probability of above-average temperatures statewide.

Refer to the sections below and links provided for details regarding
snowpack, precipitation, seasonal climate outlooks, reservoirs,
streamflow, water supply forecasts, and spring flood potential.

Most of Oregon has been affected by drought for the past year, with
very low streamflow seen statewide since summer 2018, but drought
conditions have improved significantly since February. However, with
extended dry periods this spring in northwest Oregon, some drought
concerns have returned for far-northwest Oregon rivers. For
information about drought declarations and impacts around the state,
visit the Oregon Water Resources Department drought page at

This is the last scheduled outlook for this water year. Refer to the
links provided below for conditions through the summer and fall.

Precipitation and Temperatures across Oregon

Precipitation for the 2019 water year thus far (Oct 1, 2018 through
June 4, 2019) ranges from 75 to 100 percent of average in Oregon,
highest in eastern, south-central, and southwest Oregon and lowest
in northwest Oregon.

May precipitation was 50 to 60 percent of average for most of
western Oregon, except 80 to 90 percent of average in far-southwest
Oregon. Central and eastern Oregon monthly totals were 100 to 150
percent of average, higheast in far-southeast Oregon.

Temperatures this winter prior to February were mostly above-
average, but February and March temperatures were below-average
statewide. April and May temperatues were near-average to 2 degrees
above average statewide.

Details on precipitation and temperatures:

NOAA National Weather Service - Northwest River Forecast Center

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

Snowpack across Oregon

As of early June, mountain snowpack has melted, except for typical
late-spring snow on the highest peaks. Peak seasonal snowpack
occurred in mid-March to early-April and ranged from 100 to 160
percent of average.

Additional snowpack information:

NOAA National Weather Service - Northwest River Forecast Center

USDA Natural Resources Conservation Service

Precipitation and Temperature Outlook

The Climate Prediction Center produces monthly and seasonal
outlooks, in which there is a weighing of the odds of near-normal,
above-normal, or below-normal temperatures and precipitation.

The big message for June through September is a high likelihood of
above-average temperatures. There is also some enhanced likelihood
this summer for above-average precipitation in far-eastern Oregon.

Visit www.cpc.ncep.noaa.gov for more about seasonal outlooks.


Reservoir storage as of early June is near average. Storage
increased dramatically in early and mid April due to heavy rain and
rapid snowmelt. Most reservoirs are full, although there are some
exceptions, including Hyatt, Howard Prairie, Fish Lake and Fourmile
Lake in southwest Oregon, all around 60 percent full; Wickiup and
Cresent Lake around 70 percent full in central Oregon; and Phillips
Reservoir just above 60 percent full in eastern Oregon.

Owyhee Reservoir, the largest irrigation project in the state,
increased to 710,000 acre-feet, which is 100 percent of capacity, as
of early June.

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

Additional reservoir information:


Observed Streamflow

Observed runoff so far this water year is below-average for
northwest Oregon rivers, near average for southwest and central
Oregon rivers, and above-average for eastern Oregon rivers. May
runoff was below average in northwest Oregon and near-average for
the rest of the state.

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

Water supply forecasts for April-September runoff volume are
generally above-average statewide except for some watersheds in far-
northwest Oregon with below-average forecasts, as low as 70 percent
of average for rivers draining the Coast Range in Clatsop, Columbia,
and Tillamook counties. Values for the rest of the state range from
about 100 to 200 percent of average.

The forecast for the Columbia River at The Dalles, which is a good
index of conditions across the Columbia Basin, is 94 percent of
average for April-September, reflecting near to below-average
snowpack across much of the Columbia basin. This forecast value is
an increase of 2 percent from a month ago and 27 percent lower than
this same time last year.

Details on basin-scale water supply forecasts:

NOAA National Weather Service - Northwest River Forecast Center

USDA Natural Resources Conservation Service


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