Flood Potential Outlook
Issued by NWS Boise, ID

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WATER SUPPLY OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE BOISE IDAHO
1155 AM MST THU MAR 5 2015

...IDAHO SPRING FLOOD AND WATER RESOURCES OUTLOOK...

...SPRING FLOOD RISK IS AVERAGE FOR THE SNAKE RIVER HEADWATERS
REGION...AND BELOW AVERAGE ELSEWHERE IN IDAHO...

...AVERAGE TO BELOW AVERAGE RUNOFF VOLUMES EXPECTED ACROSS IDAHO...

ABOVE NORMAL TEMPERATURES HAVE DOMINATED ACROSS IDAHO THROUGH THE
WINTER MONTHS. MUCH OF THE WINTER PRECIPITATION HAS FALLEN AS RAIN
INSTEAD OF SNOW...ESPECIALLY AT MID AND LOW ELEVATIONS. THE
RELATIVELY WARM WEATHER HAS ALSO CAUSED MUCH OF THE MID AND LOW
ELEVATION SNOWPACK TO ALREADY MELT. AS A RESULT...BELOW AVERAGE
SNOWPACK EXISTS ACROSS MOST OF IDAHO. AT THIS TIME...THE THREAT OF
SPRING FLOODING DUE TO SNOWMELT IN IDAHO IS NEAR AVERAGE FOR THE
SNAKE RIVER HEADWATERS AREA...AND BELOW AVERAGE ELSEWHERE ACROSS THE
STATE.

ONE THING TO REMEMBER IS THAT OUR MOUNTAIN SNOWPACK TYPICALLY PEAKS
IN EARLY APRIL...LEAVING SEVERAL WEEKS TO POTENTIALLY BOOST OUR
SNOWPACK AND CHANGE THE FLOOD POTENTIAL.

THE PRIMARY FACTORS IN THE DEVELOPMENT OF SPRING FLOODING ARE THE
OCCURRENCE OF PERSISTENT ABOVE NORMAL TEMPERATURES...AND RAIN ON
SNOW PRECIPITATION EVENTS. EVEN FOR AREAS WHERE DROUGHT CONDITIONS
EXIST...OR THAT HAVE LOW SNOWPACK...SPRING FLOODING IS POSSIBLE
UNDER THE RIGHT SCENARIO. ADDITIONALLY...BURN SCARS CAN HAVE A
SIGNIFICANT IMPACT ON LOCAL FLOOD POTENTIAL DURING SPRING SNOWMELT.

WATER SUPPLY...

NATIONAL WEATHER SERVICE WATER SUPPLY FORECASTS FOR THE THE 2015
WATER YEAR VARY CONSIDERABLY FROM REGION TO REGION ACROSS IDAHO. FOR
PORTIONS OF EASTERN AND CENTRAL IDAHO WHERE THE BETTER SNOWPACK
EXISTS...FORECASTS INDICATE AVERAGE OR A LITTLE BELOW AVERAGE RUNOFF
VOLUMES FOR THE APRIL THROUGH SEPTEMBER PERIOD. ELSEWHERE...
FORECASTS GENERALLY SHOW BELOW OR WELL BELOW AVERAGE RUNOFF VOLUMES.
SOUTHWEST IDAHO SOUTHSIDE SNAKE RIVER BASINS HAVE THE LOWEST
FORECAST PERCENTAGES...NEAR 50 PERCENT OF AVERAGE OR LESS.

SNOWPACK...

AS OF MARCH 5...SNOWPACK VARIED CONSIDERABLY ACROSS IDAHO. THE
LOWEST SNOWPACK PERCENTAGES WERE ACROSS SOUTHWEST AND WEST CENTRAL
IDAHO IN THE OWYHEE AND WEISER BASINS...AT 28 AND 43 PERCENT OF
MEDIAN. THE PANHANDLE AND SPOKANE BASINS IN NORTHERN IDAHO HAVE NOT
FARED MUCH BETTER...SITTING NEAR 50 PERCENT OF MEDIAN. THE HIGHEST
PERCENTAGES WERE AROUND 85 TO 100 PERCENT OF MEDIAN IN THE SNAKE
RIVER HEADWATERS REGION...SALMON BASIN...LITTLE LOST AND BIRCH
BASINS...GOOSE CREEK AND OAKLEY BASINS. THE REMAINDER OF IDAHO
BASINS WERE ABOUT 65 TO 80 PERCENT OF MEDIAN.

RESERVOIRS...

MAJOR RESERVOIR SYSTEMS ACROSS IDAHO WERE GENERALLY HOLDING NEAR OR
ABOVE AVERAGE STORAGE. A FEW OF THE SMALLER RESERVOIRS IN SOUTHERN
IDAHO WERE ONLY HOLDING ABOUT 60 TO 80 PERCENT OF AVERAGE. MOST OF
THE LARGE RESERVOIR SYSTEMS ARE LIKELY TO FILL OR COME CLOSE TO
FILLING. HOWEVER...THE OWYHEE BASIN CONTINUES TO SUFFER FROM
CONSECUTIVE YEARS OF DROUGHT AND OWYHEE RESERVOIR STORAGE WILL
LIKELY REMAIN FAR BELOW AVERAGE. WEATHER PATTERNS AND IRRIGATION
DEMAND WILL DRIVE RESERVOIR OPERATIONS OVER THE NEXT SEVERAL MONTHS.
WET SPRING WEATHER OR EXTENDED PERIODS OF WARMTH RESULTING IN RAPID
SNOWMELT COULD RESULT IN SIGNIFICANT INCREASES IN RESERVOIR OUTFLOWS
AND RIVER LEVELS.

DROUGHT...

ACCORDING TO THE U.S. DROUGHT MONITOR AS OF MARCH 3...IN SOUTHERN
IDAHO MODERATE TO SEVERE DROUGHT EXISTS ACROSS MUCH OF THE UPPER
SNAKE PLAIN...THE WOOD RIVER AND LOST RIVER BASINS...ACROSS SOUTH
CENTRAL IDAHO AND OWYHEE COUNTY...EXTENDING NORTH NEAR THE OREGON
BORDER ACROSS WESTERN WASHINGTON AND WESTERN ADAMS COUNTIES. EXTREME
DROUGHT EXISTS ACROSS FAR WESTERN OWYHEE COUNTY AND FAR SOUTHWEST
WASHINGTON COUNTY. PROLONGED DROUGHT CONDITIONS IN THESE AREAS HAVE
LEFT LONG TERM IMPACTS ON GROUND WATER...STREAMFLOWS...AND STORAGE
IN SOME RESERVOIRS. THE 90 DAY U.S. SEASONAL DROUGHT OUTLOOK
INDICATES DROUGHT CONDITIONS ARE LIKELY TO PERSIST IN THESE AREAS
THROUGH SPRING.

LONG RANGE OUTLOOK...

THE OUTLOOK FOR MARCH FAVORS ABOVE NORMAL TEMPERATURES ACROSS
IDAHO...AND EQUAL CHANCES OF EITHER BELOW AVERAGE...AVERAGE...OR
ABOVE AVERAGE PRECIPITATION. FOR THE APRIL THROUGH JUNE
PERIOD...ABOVE NORMAL TEMPERATURES ARE ONCE AGAIN FAVORED...WITH
EQUAL CHANCES OF BELOW AVERAGE...AVERAGE...OR ABOVE AVERAGE
PRECIPITATION.

REFER TO THE LINKS PROVIDED BELOW FOR THE LATEST INFORMATION ON
WATER RESOURCES.

WATER SUPPLY VOLUME FORECASTS...
NATIONAL WEATHER SERVICE-NORTHWEST
RIVER FORECAST CENTER HTTP://WWW.NWRFC.NOAA.GOV/WS/

NATIONAL WEATHER SERVICE-COLORADO BASIN RIVER FORECAST CENTER
WWW.CBRFC.NOAA.GOV/

USDA-NATURAL RESOURCES CONSERVATION SERVICE
WWW.NRCS.USDA.GOV/WPS/PORTAL/NRCS/MAIN/ID/SNOW/

SNOWPACK INFORMATION...
NATIONAL WEATHER SERVICE-NORTHWEST RIVER
FORECAST CENTER WWW.NWRFC.NOAA.GOV/SNOW/

NATIONAL WEATHER SERVICE-NATIONAL OPERATIONAL HYDROLOGIC REMOTE
SENSING CENTER
WWW.NOHRSC.NOAA.GOV/

USDA-NATURAL RESOURCES CONSERVATION SERVICE
WWW.ID.NRCS.USDA.GOV/SNOW/DATA/CURRENT.HTML

RESERVOIR STORAGE...
BUREAU OF RECLAMATION RESERVOIR STORAGE
WWW.USBR.GOV/PN/HYDROMET/SELECT.HTML

USDA-NATURAL RESOURCES CONSERVATION SERVICE
WWW.WCC.NRCS.USDA.GOV/BASIN.HTML

DROUGHT CONDITIONS...
U.S. DROUGHT PORTAL WWW.DROUGHT.GOV

U.S. DROUGHT MONITOR
WWW.DROUGHTMONITOR.UNL.EDU/

PEAK FLOW FORECASTS...
NORTHWEST RIVER FORECAST CENTER PEAK FLOW
WWW.NWRFC.NOAA.GOV/PEAK/

COLORADO BASIN RIVER FORECAST CENTER PEAK FLOW
WWW.CBRFC.NOAA.GOV/RMAP/PEAK/PEAKLIST.PHP

TEMPERATURE AND PRECIPITATION OUTLOOK...
CLIMATE PREDICTION CENTER WWW.CPC.NCEP.NOAA.GOV/

$$

LINDQUIST



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