Hydrologic Outlook
Issued by NWS Portland, OR
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000 FGUS76 KPQR 062301 ESFPQR Water Supply Outlook National Weather Service Portland OR 400 PM PST Tuesday June 6 2023 ...OREGON WATER SUPPLY SUMMARY AS OF JUNE 6TH 2023... The water supply forecast for the summer of 2023 is above average for almost all Oregon watersheds. Spring precipitation resulted in major increases in streamflow and reservoir storage statewide, especially for central and eastern Oregon, areas previously impacted by multi-year drought. Precipitation so far this water year (Oct 2022 - May 2023) is slightly below average for the Cascades, along with most of western and north-central Oregon. Water year precipitation is above average for eastern, central, and portions of southwest Oregon. Spring precipitation, March through May, was notably above average for most of Oregon, helping to boost mountain snowpack and spring and summer water supply volumes. Despite recent improvements, drought impacts remain for portions of the state. Drought declarations from the Oregon Governor`s Office are in effect for Crook, Deschutes, Grant, Harney, Jefferson, Lake, Sherman and Wasco counties. Refer to the sections below and links provided for details regarding precipitation, temperatures, seasonal climate outlooks, reservoirs, streamflow, and water supply forecasts. This is the final water supply summary of the season. Updates will resume in January 2024. PRECIPITATION AND TEMPERATURES ACROSS OREGON Precipitation for the 2023 water year thus far (Oct 2022 - May 2023) ranges from 70 to 110 percent of average in Oregon, with most of the state being below average. However, spring precipitation, March through May, was above average for most of the state and resulted in major increases in streamflow, reservoir storage, and summer water supply forecasts. Temperatures through most of the winter and spring were below average. May precipitation was above average for central and eastern Oregon and below average for western and northern Oregon. May temperatures were 1 to 3 degrees above average, with periods of hot weather in mid and late May. Details on precipitation and temperatures: NOAA NWS - 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 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 June outlook shows an enhanced likelihood of above-average temperatures, especially for the northern half of Oregon. The outlook also shows a slightly enhanced likelihood of above-average precipitation for most of the state, especially for eastern Oregon. The big message for the July through September outlook is an enhanced likelihood of above-average temperatures. Precipitation amounts during this time are typically not significant in terms of water year totals and are likely to be a little below average. Visit www.cpc.ncep.noaa.gov for more about seasonal outlooks. RESERVOIRS Reservoir storage increased greatly in April and May for most irrigation reservoirs across the state. Several reservoirs that were at or near record low storage in late winter are now full or near full. Owyhee Reservoir, the largest irrigation project in the state, had observed storage on June 5th of about 571,000 acre-feet, an increase of about 60,000 acre-feet from a month ago. This represents 80 percent of capacity and is 107 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 southeast and central Oregon, near average for northeast Oregon basins and western Oregon coastal watersheds, and below average elsewhere. Runoff in May was above average for most of the state but near- average for much of western Oregon. Several rivers in central and eastern Oregon had flooding due to rapid snowmelt along with periods of rain. Visit waterwatch.usgs.gov for details on observed streamflow. Runoff data is also 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 above average for most Oregon watersheds, with only a smattering of near or below average forecasts around the state. Forecasts are notably high for central and east-central Oregon, ranging from 150 to 300 percent of average, and even higher for a few small watersheds. The forecast for the Columbia River at The Dalles, which is a good index of conditions across the Columbia Basin, is 90 percent of average for April-September, an decrease of 3 percent from a month ago. 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/ $$

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Portland Weather Forecast Office
5241 NE 122nd Avenue
Portland, OR 97230-1089
(503) 261-9246
Page last modified: 6-Jun-2023 11:01 PM
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