Flood Potential Outlook
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3
000
FGUS76 KPQR 072146
ESFPQR

Water Supply Outlook
National Weather Service Portland OR
145 PM PST Thursday March 7 2024

...OREGON WATER SUPPLY SUMMARY AND SPRING FLOOD OUTLOOK AS OF
MARCH 7TH 2024...

The water supply forecast for the spring and summer of 2024 is near
to slightly-above average for most watersheds in Oregon. The primary
exception is below average forecasts for several watersheds in south-
central Oregon. Seasonal water supply forecasts generally increased
5 to 20 percent from early February. Water supply forecasts may
evolve significantly through March and April. The potential for
spring snowmelt flooding is low, generally 5 to 25 percent, for
watersheds east of the Cascades. Recent increases in snowpack have
increased flooding chances slightly, but some watersheds still have
multi-year soil moisture and precipitation deficits. Spring snowmelt
flooding has historically not occurred along rivers west of the
Cascades and is not expected this year.

Precipitation so far this water year (Oct 2023 - Feb 2024) is
variable statewide, with above average precipitation for coastal
portions of western Oregon and most of eastern Oregon, below average
for most of the Oregon Cascades, south-central Oregon, and far-
northeast Oregon, and near average elsewhere.

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

The next update to this outlook will be issued by April 3 2024.


PRECIPITATION AND TEMPERATURES ACROSS OREGON

Precipitation for the 2024 water year thus far (Oct 2023 - Jan 2024)
ranges from 75 to 120 percent of average in Oregon, with the lowest
percent of average in south-central and interior southwest Oregon
and the highest in coastal southwest Oregon and portions of eastern
Oregon.

February precipitation was above average for most of the state,
ranging from 85 to 150 percent of average. Coastal southwest Oregon
and most of central and eastern Oregon were above average. Portions
of interior southwest Oregon and north-central Oregon were below
normal. All remaining areas were near normal.

Winter temperatures were above average for all of Oregon, except the
Columbia basin portion of north-central Oregon. February
temperatures were generally above average statewide and notably much
above average for the mountains of northeast Oregon.

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

Westwide Drought Tracker Precipitation & Temperature graphics
wrcc.dri.edu/wwdt/index.php?region=or


SNOWPACK ACROSS OREGON

As of March 5, mountain snowpack was above average for most of
Oregon, with basin snowpack ranging from 85 to 130 percent of
average. The highest totals relative to average are in the north
Oregon Coast Range and the mountains of east-central Oregon.
Snowpack in the Cascades is generally a little above average,
ranging from 90 to 120 percent of average. Basin totals for the
Cascades range from 70 to 85 percent. In recent weeks, snowpack
increased gradually from mid February onward and more sharply in
late February and early March.

Additional mountain snow is forecast through mid March. Seasonally,
significant snow accumulation is possible through March for southern
Oregon and April for northern Oregon.

Additional snowpack information:

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

USDA Natural Resources Conservation Service
nwcc-apps.sc.egov.usda.gov/imap/


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.

Strong El Nino conditions in the tropical Pacific have been the
driving factor for seasonal outlooks through the winter, but El Nino
conditions are expected to moderate through the spring and early
summer. Historically, the primary impact of El Nino on Oregon
conditions is above-average temperatures.

Based on the continued influence of El Nino and long-term
temperature trends, the outlook for March through May is for an
enhanced likelihood of above-average temperatures. The precipitation
outlook also indicates a slightly-enhanced likelihood for below-
average precipitation, albeit less confident than the temperature
outlook. The outlook for the likelihood of above-average
temperatures and below-average precipitation continues through the
summer.

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


RESERVOIRS

Reservoir storage for most irrigation reservoirs across the state is
generally above average, with the exception of southwest Oregon.
Reservoir storage ranges from about 50 to 90 percent of capacity,
much of that being carry-over storage from last year. Flood control
reservoirs are dependent on spring precipitation and snowmelt to
refill March through May.

Owyhee Reservoir, the largest irrigation project in the state, has
observed storage of about 536,000 acre-feet, an increase of 77,000
acre-feet from a month ago. This is 75 percent of capacity and 133
percent of average for this time of year.

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


OBSERVED STREAMFLOW

Observed runoff so far this water year has been above average for
most watersheds statewide, particularly so for watersheds in central
Oregon. The only area with below-average runoff is south-central and
interior southwest Oregon.

Runoff in February was generally near to above average statewide,
again with the exception of below average for watersheds in the
Klamath basin.

Visit waterwatch.usgs.gov for details on observed streamflow. Runoff
data is available at www.nwrfc.noaa.gov/natural/index.html at water
year and monthly time scales for several locations in Oregon.


WATER SUPPLY SEASONAL FORECASTS

Water supply forecasts for April-September runoff volume are near to
above average for most of the state, except for below-average
forecasts for watersheds within the Klamath basin. The highest
forecasts, relative to average, are in central and east-central
Oregon. Forecasts for the April-September period may change
significantly through March and April.

The forecast for the Columbia River at The Dalles, which is a good
index of conditions across the Columbia Basin, is 82 percent of
average for April-September.

Details on basin-scale water supply forecasts:

NOAA NWS - Northwest River Forecast Center
www.nwrfc.noaa.gov/ws/

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

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

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.