Flood Potential Outlook
Issued by NWS Seattle/Tacoma, WA

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WATER SUPPLY OUTLOOK
NATIONAL WEATHER SERVICE SEATTLE WA
120 PM PDT FRI JUN 12 2015

...WESTERN WASHINGTON WATER SUPPLY AND SPRING SNOW MELT
FLOOD POTENTIAL...

OVERVIEW: THE FORECASTS OF WATER SUPPLY FOR THE SUMMER WERE FOR
MUCH BELOW NORMAL TO RECORD LOWS FOR WESTERN WASHINGTON RIVERS. ALL
RIVERS NOW HAVE FORECASTS THAT AT BELOW OR WELL BELOW 60 PERCENT OF
NORMAL. THIS IS MOSTLY DUE TO VERY LOW TO NEAR RECORD LOW SNOW PACK
IN THE OLYMPIC AND CASCADE MOUNTAINS. IN ADDITION...APRIL...MAY AND
THE FIRST PART OF JUNE HAVE BEEN DRIER THAN NORMAL. THE U.S. DROUGHT
MONITOR FOR JUNE 11 HAS EXPANDED THE MODERATE DROUGHT CONDITIONS FOR
THE OLYMPIC PENINSULA AND WASHINGTON COAST AND CONTINUES IT FOR THE
WASHINGTON CASCADES. THE REMAINDER OF WESTERN WASHINGTON IS IN THE
ABNORMALLY DRY CATEGORY. THE GOVERNOR HAS DECLARED A DROUGHT ACROSS
THE ENTIRE STATE OF WASHINGTON. DROUGHT IMPACTS ARE EXPECTED IN
VARIOUS LOCATIONS THROUGHOUT THE STATE. HOWEVER...NOT EVERYWHERE
WILL EXPERIENCE IMPACTS...PARTICULARLY IN THE METROPOLITAN CORRIDOR
OF SNOHOMISH...KING...AND PIERCE COUNTIES.

SPRING AND SUMMER SNOW MELT FLOODING WILL NOT OCCUR THIS YEAR. THE
CURRENT SNOW PACK IS LARGELY MELTED OFF AND RIVER HAVE ALREADY HAD
THEIR PEAK FLOWS FOR THIS MELT SEASON.

PRECIPITATION SUMMARY
---------------------
MAY BROUGHT MUCH BELOW NORMAL PRECIPITATION TO WESTERN WASHINGTON
WITH BELOW TO ABOVE NORMAL PRECIPITATION TO EASTERN WASHINGTON. MOST
OF THE REGIONS CONTINUE AT NEAR NORMAL PRECIPITATION FOR THE WATER
YEAR THUS FAR EXCEPT FOR THE SOUTHWEST INTERIOR IS IN NOW BELOW
NORMAL. WITH LITTLE PRECIPITATION DURING THE DRY SEASON...THESE
PERCENTAGES WILL NOT LIKELY CHANGE MUCH THE REST OF THE WATER YEAR.

THE MONTHLY PERCENTAGE OF NORMAL FOR PRECIPITATION RANGED FROM 12
PERCENT FOR THE COAST TO 36 PERCENT OF NORMAL IN THE SOUTHWEST
INTERIOR. THE GREATEST AMOUNT OF PRECIPITATION AT THE CLIMATE
STATIONS FOR THE MOUNTAINS...COAST...AND INTERIOR LOWLANDS WAS 3.37
INCHES AT PACKWOOD IN THE CASCADE FOOTHILLS...2.55 INCHES AT
LONGMIRE...AND 1.88 INCHES AT THE MAYFIELD POWER PLANT IN THE
SOUTHWEST INTERIOR.

THE TABLE BELOW GIVES PRECIPITATION FIGURES AS A PERCENT OF NORMAL
FOR REGIONS OF WASHINGTON.  THE CURRENT WATER YEAR BEGAN 1 OCTOBER
2014 AND ENDS 30 SEPTEMBER 2015.

                          MAY      WATER YEAR      PAST3      PAST12
                         2015       TO DATE      MONTHS       MONTHS
 WESTERN WASHINGTON
  COAST                    12           97           80            95
  OLYMPICS                 24           96           74            93
  NORTHWEST INTERIOR       28          108           81           107
  PUGET SOUND LOWLANDS     29           94           71            97
  SOUTHWEST INTERIOR       36           86           67            87
  WEST FOOTHILLS CASCADES  35           95           74            97
  CASCADES WEST            34           97           75            98


SNOWPACK CONDITIONS
-------------------

THE SNOWPACK WAS VIRTUALLY GONE FOR WESTERN WASHINGTON AS OF JUNE 12
WITH ALL REPORTING STATIONS COMPLETELY MELTED OUT AT ZERO SNOW.



STREAMFLOWS SUMMARY
-------------------

STREAMFLOWS FOR OF WESTERN WASHINGTON RIVERS FOR LAST MONTH WERE
MOSTLY MUCH BELOW NORMAL. CURRENT FLOWS ON MANY RIVERS AS OF JUNE 12
WERE AT RECORD LOW DAILY FLOWS.


RESERVOIR STORAGE SUMMARY
-------------------------

STORAGE FOR ROSS RESERVOIR FOR JUNE 1 WAS AT 86% OF AVERAGE...DOWN
FROM 94% LAST MONTH. OTHER RESERVOIRS:
ROSS LAKE           86%
HOWARD HANSEN      185%
UPPER BAKER        108%


WEATHER OUTLOOK
---------------

THE OUTLOOK FOR WESTERN WASHINGTON FOR JUNE AND BEYOND...OVER THE
NEXT 7 DAYS THE PRECIPITATION FORECAST IS FOR VERY LITTLE
PRECIPITATION...GENERALLY LESS THAN A QUARTER INCH IN THE MOUNTAINS
AND MAINLY IN THE NORTHERN HALF OF THE STATE. FOR THE NEXT TWO WEEKS
THE OUTLOOK IS FOR BELOW NORMAL PRECIPITATION WITH NORMAL TO ABOVE
NORMAL TEMPERATURES. THE MONTHLY OUTLOOK FOR JUNE IS FOR GREATER
CHANCES OF BELOW NORMAL PRECIPITATION AND ABOVE NORMAL TEMPERATURES.
THE THREE MONTH OUTLOOK FOR THE SUMMER FROM  JUNE THROUGH AUGUST HAS
GREATER ODDS OF DRIER THAN NORMAL AND WARMER THAN NORMAL CONDITIONS.
FOR THE FALL FOR SEPTEMBER THROUGH NOVEMBER THERE ARE GREATER
CHANCES THAT IT WILL BE DRIER THAN NORMAL AND WARMER THAN NORMAL. IF
THAT PANS OUT IT WOULD NOT BE HELPFUL IN ENDING THE DROUGHT AT THE
END OF THIS SUMMER.


WATER SUPPLY OUTLOOK
--------------------

FORECASTS TRENDED SIGNIFICANTLY DOWNWARD FOR MOST RIVERS FROM A FEW
PERCENT UP TO 17 PERCENT LOWER FROM A MONTH AGO. LONG RANGE
HYDROLOGIC MODELS ARE FORECASTING MUCH BELOW NORMAL AND RECORD LOW
RIVER FLOWS AND WATER SUPPLY FOR MOST RIVERS THROUGH THIS SPRING AND
SUMMER. WATER SUPPLY FORECASTS FOR WESTERN WASHINGTON RANGE FROM A
LOW OF 15 PERCENT FOR THE INFLOW TO TOLT RESERVOIR TO 60 PERCENT FOR
THE CHEHALIS RIVER AT GRAND MOUND. THE FORECASTS FOR ALMOST ALL OF
THE RIVERS RANK AS THE LOWEST VOLUMES FOR THE PERIOD OF RECORD WHICH
ARE AS LONG AS 64 YEARS.

WATER SUPPLY FORECASTS THAT INCLUDE REGULATION ARE USED FOR
LOCATIONS WHERE FORECASTS ARE LISTED BELOW AS REGULATED...FOR ALL
OTHER LOCATIONS FORECASTS ARE FOR NATURAL VOLUMES. HERE ARE THE
STREAM FLOW VOLUME FORECASTS FOR SPECIFIC RIVERS AND SITES AS OF
JUNE 12.

                           WATER SUPPLY FORECASTS
                  NATURAL FLOW UNLESS OTHERWISE SPECIFIED
                        (IN THOUSANDS OF ACRE FEET)

RIVER AND GAUGING SITE            PERIOD   FORECAST   NORMAL  PERCENT

NOOKSACK RIVER
   AT NORTH CEDARVILLE            APR-SEP      495      1195      42

SKAGIT RIVER
   NEAR CONCRETE (REGULATED)      APR-SEP      3534     5934      59

BAKER RIVER
   UPPER BAKER RESERVOIR INFLOW   APR-SEP       457      805      57

SULTAN RIVER
   SPADA LAKE INFLOW              APR-SEP        69      191      37

TOLT RIVER
   TOLT RESERVOIR INFLOW          APR-SEP         8       51      15

CEDAR RIVER
   CHESTER MORSE LAKE INFLOW      APR-SEP        44      154      29

GREEN RIVER
   HOWARD HANSON DAM INFLOW       APR-SEP       101      260      39

NISQUALLY RIVER
   ALDER RESERVOIR INFLOW         APR-JUL       224      376      59

COWLITZ RIVER
   MAYFIELD RESERVOIR (REGULATED) APR-SEP       888     1835      49

CHEHALIS RIVER
   NEAR GRAND MOUND               APR-SEP       232      398      60

ELWHA RIVER
   MCDONALD BRIDGE                APR-SEP       185      472      39

DUNGENESS RIVER
   NEAR SEQUIM                    APR-SEP        55      145      38

WYNOOCHEE RIVER
   WYNOOCHEE DAM INFLOW           APR-SEP        49       99      50

SKOKOMISH RIVER
   NF SKOKOMISH RIVER
   BELOW STAIRCASE RAPIDS         APR-SEP        31      135      23



SNOW MELT

WITH THE RECORD LOW SNOW PACK VIRTUALLY GONE IN MOST AREAS...RIVERS
HAVE ALREADY EXPERIENCED THEIR SPRING/SUMMER SNOW MELT PEAK FLOWS.

CLIMATOLOGY:

RIVERS WEST OF THE CASCADES CREST USUALLY REACH THEIR HIGHEST PEAK
FLOWS DURING THE WINTER SEASON. THE VAST MAJORITY OF RIVER FLOODING
IN WESTERN WASHINGTON...AND ALMOST ALL MAJOR FLOODS...OCCUR BETWEEN
OCTOBER AND MARCH. HEAVY RAINFALL...RATHER THAN SNOW MELT...IS THE
PRIMARY CAUSE OF THESE EVENTS.

THE HISTORICAL RECORD DOES NOT SHOW MAJOR FLOODING IN WESTERN
WASHINGTON DURING THE PERIOD WHEN THE MOUNTAIN SNOWPACK RUNS OFF.
THE RUNOFF FROM SNOW MELT...EVEN DURING UNUSUALLY HOT WEATHER...IS
SMALL COMPARED TO THE RUNOFF DURING HEAVY WINTER RAINS. THIS IS TRUE
REGARDLESS OF THE SIZE OF THE MOUNTAIN SNOWPACK. RARELY...UNDER JUST
THE RIGHT CONDITIONS OF GREATER THAN NORMAL SNOW PACK...GREATER
COVERAGE TO LOWER ELEVATIONS...AND NEAR RECORD WARM TEMPERATURES...
RIVER FLOWS MIGHT RISE TO NEAR MINOR FLOOD STAGE.

WHILE FLOOD PRODUCING RAINFALL IS RARE AFTER MARCH...MODERATE TO
HEAVY RAIN IN SPRING OR SUMMER...WHILE RIVERS ARE SWOLLEN WITH SNOW
MELT RUNOFF...OCCASIONALLY DRIVE THE MOST FLOOD PRONE RIVERS ABOVE
FLOOD STAGE. TYPICALLY THESE ARE RIVERS SUCH AS THE SKOKOMISH AND
SNOQUALMIE. HEAVY RAIN IN THE SPRING OR SUMMER...WHEN ROSS LAKE IS
FULL...CAN ALSO CAUSE THE SKAGIT RIVER TO FLOOD. WHILE THESE FLOODS
ARE TYPICALLY MINOR COMPARED TO THE WINTER EVENTS...THEY SOMETIMES
CAUSE SUBSTANTIAL DAMAGE TO FARM CROPS.


SPRING AND SUMMER SNOW MELT PEAK FLOW FORECASTS: RIVERS HAVE ALREADY
HAD THEIR SNOW MELT PEAK FLOWS AND FORECASTS INDICATE THE BEST
CHANCE FOR HIGHER PEAK FLOWS IS NOT UNTIL THE RAINS BEGIN IN THE
FALL.

FORECASTS ARE SELECTED FROM THOSE PREPARED BY THE NWRFC.
FOR FURTHER DETAILS...GRAPHICS...AND STATISTICS REGARDING THE WATER
SUPPLY FORECASTS VISIT:
HTTP://WWW.NWRFC.NOAA.GOV/WS (LOWER CASE)
HTTP://WWW.NWRFC.NOAA.GOV/ESPNATURAL (LOWER CASE)

FOR FURTHER DETAILS...GRAPHICS...AND STATISTICS REGARDING THE PEAK
FLOW FORECASTS VISIT:
HTTP://WWW.NWRFC.NOAA.GOV/PEAK (LOWER CASE)

THIS IS THE LAST  SPRING FLOOD OUTLOOK FOR THE SEASON UNTIL NEXT
SPRING. THE NEXT WATER SUPPLY FOR WESTERN WASHINGTON WILL BE ISSUED
AROUND THE WEEK OF JULY 15.

$$

WEATHER.GOV/SEATTLE
JBB






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