Flood Potential Outlook
Issued by NWS Portland, OR

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WATER SUPPLY OUTLOOK
NATIONAL WEATHER SERVICE PORTLAND OR
330 PM PDT FRIDAY MAY 6 2016

...OREGON WATER SUPPLY OUTLOOK AS OF MAY 6TH 2016...

THE WATER SUPPLY FORECAST FOR THE SPRING AND SUMMER OF 2016 IS BELOW-
AVERAGE FOR MUCH OF OREGON...ALTHOUGH SOME BASINS IN SOUTHWESTERN...
NORTH-CENTRAL...AND FAR-EASTERN OREGON ARE FORECAST TO BE NEAR
AVERAGE. WATER SUPPLY VOLUME FORECASTS FOR APRIL-SEPTEMBER HAVE
DROPPED SIGNIFICANTLY DUE TO RAPID MELT OF MOUNTAIN SNOWPACK SINCE
LATE MARCH. DRY AND WARM CONDITIONS ARE EXPECTED THROUGH THE FIRST
HALF OF MAY ACROSS THE STATE. HOWEVER...THE POTENTIAL FOR ADDITIONAL
SPRING SNOWMELT FLOODING IN MAY AND JUNE IS GREATLY REDUCED NOW THAT
MOST OF THE SNOWPACK HAS MELTED.

REFER TO THE SECTIONS BELOW AND THE LINKS PROVIDED FOR DETAILS
REGARDING SNOWPACK...PRECIPITATION...RESERVOIR CONDITIONS AND WATER
SUPPLY FORECASTS FOR INDIVIDUAL BASINS.

NOAA`S CLIMATE OUTLOOKS INDICATE ABOVE-AVERAGE TEMPERATURES ARE
LIKELY THROUGH MAY AND THE REST OF SPRING AND SUMMER. PRECIPITATION
DURING THE FIRST HALF OF MAY IS LIKELY TO BE BELOW-AVERAGE...WITH AN
ENHANCED POSSIBILITY OF ABOVE-AVERAGE PRECIPITATION DURING THE
LATTER HALF OF MAY. BEYOND MAY...THERE IS NOT A STRONG SIGNAL FOR
PRECIPITATION EITHER ABOVE OR BELOW AVERAGE...AND THE SUMMER MONTHS
ARE TYPICALLY THE DRIEST OF THE YEAR FOR MOST OF THE STATE. EL NINO
CONDITIONS ARE RAPIDLY TRANSITIONING TO ENSO-NEUTRAL...AND LA NINA
CONDITIONS ARE LIKELY STARTING IN THE FALL. FOR MORE INFORMATION ON
SEASONAL OUTLOOKS...VISIT THE CLIMATE PREDICTION CENTER AT
WWW.CPC.NCEP.NOAA.GOV.

PRECIPITATION THIS WINTER HAS ALLEVIATED DROUGHT CONDITIONS FOR MUCH
OF OREGON...ESPECIALLY IN SOUTHERN OREGON...WHERE MULTI-YEAR DROUGHT
HAD PERSISTED THROUGH 2015. NOTE THAT SEVERAL COUNTIES IN CENTRAL
AND EASTERN OREGON STILL SOME DROUGHT ISSUES DUE TO DRY CONDITIONS
THE THREE YEARS PRIOR TO THIS WINTER. VISIT DROUGHT.GOV AND
WWW.OREGON.GOV/OWRD/PAGES/WR/DROUGHT.ASPX FOR MORE INFORMATION.

THIS PRODUCT WILL BE ISSUED ON A MONTHLY BASIS THROUGH JUNE 2016.
THE NEXT UPDATE WILL BE ISSUED BY JUNE 6TH.

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SNOWPACK ACROSS OREGON

SEASONAL SNOWPACK PEAKED NEAR AVERAGE IN MARCH...BUT AS OF EARLY
MAY...THE WATER CONTENT OF THE OREGON SNOWPACK RANGES FROM ABOUT 10
TO 80 PERCENT OF AVERAGE. THE SNOW-WATER CONTENT AND THE OVERALL
AREA OF SNOW COVER HAS DECREASED DRAMATICALLY SINCE EARLY APRIL DUE
TO MONTHLY TEMPERATURES 4 TO 6 DEGREES ABOVEAVERAGE. THE SNOWPACK
BELOW 5000 FEET IN THE NORTH AND 6000 FEET IN THE SOUTH HAS MOSTLY
MELTED... WHILE SOME SNOW REMAINS IN HIGHER ELEVATIONS. SNOWMELT
OCCURRED VERY RAPIDLY FROM LATE MARCH THROUGH EARLY MAY...AND SOME
BASINS...INCLUDING THE JOHN DAY AND MALHEUR...HAVE NO SNOW
REMAINING.

REFER TO THE FOLLOWING LINKS FOR MORE INFORMATION.

NOAA`S 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

2016 WATER YEAR PRECIPITATION IS ABOVE-AVERAGE ACROSS THE STATE...
ESPECIALLY SO IN WESTERN AND SOUTHEAST OREGON. PRECIPITATION
TOTALS...OCTOBER 1 THROUGH MAY 1...RANGE FROM 90 TO 125 PERCENT OF
AVERAGE. MONTHLY TOTALS FOR APRIL WERE MUCH-BELOW-AVERAGE...40 TO 80
PERCENT.

FOR THE WATER YEAR...TEMPERATURES HAVE BEEN ABOVE-AVERAGE EVERY
MONTH...EXCEPT NOVEMBER AND DECEMBER...AND HAVE BEEN NOTABLY WARM
SINCE FEBRUARY.

VISIT THE FOLLOWING LINKS FOR MORE DETAILS ON PRECIPITATION AND
TEMPERATURES.

NOAA`S NATIONAL WEATHER SERVICE - NORTHWEST RIVER FORECAST CENTER
WWW.NWRFC.NOAA.GOV/WATER_SUPPLY/WY_SUMMARY/WY_SUMMARY.PHP

NOAA`S NATIONAL WEATHER SERVICE - CALIFORNIA NEVADA RFC
(KLAMATH BASIN ONLY) WWW.CNRFC.NOAA.GOV/WATER_RESOURCES_UPDATE.PHP

============================================================
RESERVOIRS

RESERVOIR STORAGE HAS INCREASED SIGNIFICANTLY THE PAST SEVERAL WEEKS
AND RANGES FROM 50 TO 100 PERCENT OF CAPACITY. CONDITIONS ARE
VARIABLE AND DEPENDENT ON RECENT SNOWMELT AND RAINFALL
RUNOFF...ALONG WITH LONG-TERM STORAGE DEFICITS DUE TO MULTI-YEAR
DROUGHT. OWYHEE...THE LARGEST IRRIGATION RESERVOIR IN OREGON...HAS
INCREASED SHARPLY IN RECENT WEEKS UP FROM 32 PERCENT OF CAPACITY IN
EARLY MARCH TO 62 PERCENT IN EARLY APRIL. OTHER RESERVOIRS IN
CENTRAL AND EASTERN OREGON SAW SIMILAR INCREASES IN MARCH AND APRIL.
RECENT DRY CONDITIONS HAVE REDUCED THE LIKELIHOOD THAT FLOOD CONTROL
RESERVOIRS IN WESTERN OREGON WILL COMPLETELY FILL TO SUMMER FULL-
POOL LEVELS.

RESERVOIR DATA IS PROVIDED BY THE NATURAL RESOURCES CONSERVATION
SERVICE...THE BUREAU OF RECLAMATION...AND THE US ARMY CORPS OF
ENGINEERS.

VISIT THE FOLLOWING LINKS FOR 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/

============================================================
CURRENT AND FORECAST STREAMFLOW

OBSERVED STREAMFLOW IN APRIL WAS BELOW-AVERAGE IN NORTHWEST...WEST-
CENTRAL...AND NORTHEAST OREGON...AND NEAR-AVERAGE ELSEWHERE IN THE
STATE. STREAMFLOW IN CENTRAL OREGON WAS BOLSTERED BY SNOWMELT.

VISIT WATERWATCH.USGS.GOV FOR MORE DETAILS ON OBSERVED STREAMFLOW.

APRIL-SEPTEMBER RUNOFF VOLUME FORECASTS FOR OREGON RANGE FROM 40 TO
105 PERCENT OF AVERAGE...WITH THE HIGHEST VALUES IN SOUTHWEST OREGON
BASINS AND THE LOWEST IN NORTHWEST OREGON BASINS. MANY BASINS HAVE
SEEN FORECAST DECREASES ON THE ORDER OF 20 PERCENT OR MORE DUE TO
DRY AND WARM CONDITIONS IN APRIL. PARTICULAR AREAS OF CONCERN FOR
LOW SEASONAL STREAMFLOW VOLUME INCLUDE NORTH COASTAL RIVERS..THE
WILLAMETTE BASIN...AND SOME RIVERS IN NORTHEAST OREGON. SEASONAL
FORECAST VOLUMES NEAR AVERAGE ARE STILL FORECAST FOR MOST BASINS IN
FAR-SOUTHWESTERN AND SOUTH-CENTRAL OREGON...AREAS WHERE DROUGHT
IMPACTS THE LAST THREE YEARS HAVE BEEN MOST PRONOUNCED.

THE FORECAST FOR THE COLUMBIA RIVER AT THE DALLES...WHICH IS A GOOD
INDEX OF CONDITIONS ACROSS THE COLUMBIA BASIN...IS 99% OF AVERAGE
FOR THE APRIL-SEPTEMBER PERIOD...A DECREASE OF 3% FROM THE FORECAST
IN EARLY APRIL.

VISIT THE FOLLOWING LINKS FOR MORE DETAILS ON BASIN-SCALE WATER
SUPPLY FORECASTS:

NOAA`S 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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