Flood Potential Outlook
Issued by NWS Portland, OR

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WATER SUPPLY OUTLOOK
NATIONAL WEATHER SERVICE PORTLAND OR
300 PM PDT TUESDAY APRIL 5 2016

...OREGON WATER SUPPLY OUTLOOK AND SPRING FLOOD POTENTIAL AS OF
APRIL 5TH 2016...

THE WATER SUPPLY FORECAST FOR THE SPRING AND SUMMER OF 2016 IS NEAR-
AVERAGE FOR MOST OF OREGON...ALTHOUGH SOME BASINS IN NORTHWESTERN
OREGON ARE PREDICTED TO BE A LITTLE BELOW-AVERAGE...AND SOME BASINS
IN SOUTH-CENTRAL OREGON ARE PREDICTED TO BE ABOVE-AVERAGE. NOTE THAT
SIGNIFICANT CHANGES IN BASIN FORECASTS ARE STILL POSSIBLE...SINCE
THE WET SEASON FOR OREGON TYPICALLY EXTENDS INTO APRIL OR MAY. MAJOR
DEPARTURES FROM AVERAGE FOR PRECIPITATION OR TEMPERATURES DURING THE
SPRING WOULD SIGNIFICANTLY AFFECT THE SEASONAL WATER SUPPLY
FORECASTS. THE POTENTIAL FOR SPRING FLOODING IS NEAR-AVERAGE FOR
CENTRAL AND EASTERN OREGON...WITH AN ENHANCED RISK IN THE CANYON
CREEK DRAINAGE NEAR JOHN DAY DUE TO THE SUMMER 2015 WILDFIRE.

APRIL-SEPTEMBER RUNOFF VOLUME FORECASTS FOR OREGON RANGE FROM ABOUT
70 TO 115 PERCENT OF AVERAGE. THE LOWEST VALUES ARE FOR BASINS IN
NORTHWESTERN OREGON. THE HIGHEST VALUES ARE FOR SOUTH-CENTRAL AND
SOUTHWEST OREGON BASINS...WHICH ARE ALSO WHERE DROUGHT IMPACTS THE
LAST THREE YEARS HAVE BEEN MOST PRONOUNCED.

THE WATER CONTENT OF THE OREGON SNOWPACK AS OF EARLY APRIL 2016 IS
MUCH HIGHER THAN SEEN IN APRIL 2015...WHEN MOUNTAIN SNOW WAS ALMOST
NON-EXISTENT. BASIN SNOWPACK AROUND THE STATE RANGES FROM 80 TO 105
PERCENT OF AVERAGE.

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 THE REST OF APRIL AND CONTINUING THROUGH THE SPRING.
PRECIPITATION DURING APRIL IS LIKELY TO BE ABOVE-AVERAGE FOR
SOUTHERN OREGON AND NEAR-AVERAGE FOR NORTHERN OREGON. BEYOND
APRIL...THERE IS NOT A STRONG SIGNAL FOR PRECIPITATION EITHER ABOVE
OR BELOW AVERAGE. THE INFLUENCE OF THE ONGOING EL NINO IS EXPECTED
TO CONTINUE THROUGH THE SPRING...AND THEN CONDITIONS WILL GRADUALLY
TREND TO ENSO-NEUTRAL THIS SUMMER. FOR MORE INFORMATION ON SEASONAL
OUTLOOKS AND EL NINO CONDITIONS...VISIT THE CLIMATE PREDICTION
CENTER WEB PAGE AT WWW.CPC.NCEP.NOAA.GOV.

PRECIPITATION THUS FAR THIS WINTER HAS ALLEVIATED DROUGHT CONDITIONS
FOR MUCH OF OREGON...ESPECIALLY IN SOUTHERN OREGON...WHERE MULTI-
YEAR DROUGHT HAD PERSISTED. NOTE THAT SEVERAL COUNTIES IN CENTRAL
AND EASTERN OREGON...STILL HAVE MINOR 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 MAY 6TH.

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SNOWPACK ACROSS OREGON

AS OF EARLY APRIL...BASIN SNOWPACK RANGES FROM 80 TO 105 PERCENT OF
AVERAGE. MOST OF THE SNOWPACK BELOW 4000 FEET IN THE NORTH AND 5000
FEET IN THE SOUTH HAS MELTED... WHILE MUCH SNOW REMAINS IN HIGHER
ELEVATIONS. HOWEVER...ALL SNOTEL STATIONS ARE SHOWING DECLINING SNOW-
WATER EQUIVALENT...WHICH INDICATES SNOWMELT...AND THE PEAK SEASONAL
SNOWPACK IS LIKELY NOW PAST.  THE LOWEST VALUES RELATIVE TO AVERAGE
ARE IN THE NORTH OREGON CASCADES. THE HIGHEST VALUES ARE IN PORTIONS
OF THE BLUE MOUNTAINS...THE SOUTHERN OREGON CASCADES...AND SOUTHEAST
OREGON MOUNTAINS.

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 OREGON. PRECIPITATION TOTALS...
OCTOBER 1 THROUGH APRIL 1...RANGE FROM 90 TO 140 PERCENT OF AVERAGE.
SEASONAL TOTALS WERE BOLSTERED BY ABOVE-AVERAGE PRECIPITATION IN
MARCH...AS MUCH AS 150 PERCENT OF AVERAGE IN WESTERN OREGON AND 100
TO 120 PERCENT IN CENTRAL AND EASTERN OREGON.

SEASONAL TEMPERATURES FOR OREGON ARE A LITTLE ABOVE-AVERAGE SO FAR
THIS WINTER. MARCH TEMPERATURES WERE GENERALLY 1 TO 3 DEGREES ABOVE
AVERAGE.

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 30 TO 100 PERCENT OF CAPACITY IN CENTRAL AND EASTERN
OREGON. CONDITIONS ARE HIGHLY VARIABLE AND DEPENDENT ON RECENT
SNOWMELT AND RAINFALL RUNOFF...ALONG WITH LONG-TERM STORAGE DEFICITS
DUE TO MULTI-YEAR DROUGHT. OWYHEE IS THE LARGEST IRRIGATION
RESERVOIR IN OREGON...AND STORAGE HAS INCREASED SHARPLY IN RECENT
WEEKS UP FROM 32 PERCENT OF CAPACITY IN EARLY MARCH TO 58 PERCENT IN
EARLY APRIL. OTHER RESERVOIRS IN CENTRAL AND EASTERN OREGON SAW
SIMILAR INCREASES IN MARCH. FLOOD CONTROL RESERVOIRS IN WESTERN
OREGON ARE ON PACE TO FILL TO SUMMER FULL-POOL LEVELS IN MAY.

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

VISIT THE FOLLOWING LINKS FOR MORE 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 MARCH WAS ABOVE-AVERAGE IN WESTERN OREGON AND
PORTIONS OF NORTHEASTERN OREGON AND NEAR-AVERAGE ELSEWHERE.
STREAMFLOW WAS BOLSTERED BY ABOVE-AVERAGE PRECIPITATION AND MELTING
OF LOWER-ELEVATION SNOWPACK.

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

FORECAST STREAMFLOW VOLUMES FOR THE SPRING AND SUMMER /APRIL THROUGH
SEPTEMBER/ RANGE FROM 70 TO 115 PERCENT OF AVERAGE FOR OREGON
BASINS...WITH THE HIGHEST VALUES IN SOUTHWEST OREGON BASINS AND THE
LOWEST IN NORTHWEST OREGON BASINS.

THE FORECAST FOR THE COLUMBIA RIVER AT THE DALLES...WHICH IS A GOOD
INDEX OF CONDITIONS ACROSS THE COLUMBIA BASIN...IS 102% OF AVERAGE
FOR THE APRIL-SEPTEMBER PERIOD...AN INCREASE OF 2% FROM THE FORECAST
IN EARLY MARCH.

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/

=============================================================
SPRING FLOOD POTENTIAL

THE POTENTIAL FOR SPRING SNOWMELT FLOODING IS NEAR-AVERAGE...BASED
ON EARLY-APRIL SNOWPACK CONDITIONS. HISTORICALLY...THE FREQUENCY OF
SPRING-SNOWMELT FLOODING IS LOW FOR CENTRAL AND EASTERN OREGON.
SPRINGTIME /MAY-JUNE/ FLOODING IS TYPICALLY LIMITED TO BASINS EAST
OF THE CASCADE CREST AND IS USUALLY CAUSED BY A COMBINATION OF
SNOWMELT AND RAINFALL. THE RECENT MELTING OF LOWER-ELEVATION
SNOWPACK WILL LIKELY REDUCE THE THREAT OF LATE-SPRING FLOODING.

THIS YEAR...THERE IS PARTICULAR CONCERN ABOUT FLOODING IN THE CANYON
CREEK DRAINAGE OF THE JOHN DAY RIVER BASIN. THIS AREA EXPERIENCED A
DEVASTATING WILDFIRE IN THE SUMMER OF 2015...AND THE BURNED AREA IS
SUSCEPTIBLE TO HIGHER RUNOFF DUE TO DAMAGED SOILS AND THE LOSS OF
VEGETATION. SNOWPACK IN THIS AREA IS A LITTLE ABOVE-AVERAGE. NWS
PENDLETON IS WORKING WITH THE NATURAL RESOURCES CONSERVATION SERVICE
AND STATE AND LOCAL PARTNERS TO MONITOR CONDITIONS AND PROVIDE
FORECASTS REGARDING THE POTENTIAL FOR SPRING-TIME FLOODING.

FOR INFORMATION REGARDING THE CANYON CREEK BURN AREA VISIT:
WWW.WRH.NOAA.GOV/PDT/FORECAST/CANYON_CREEK_DSS/INDEX.PHP

BRYANT
$$



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