Flood Potential Outlook
Issued by NWS Boise, ID

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WATER SUPPLY OUTLOOK
NATIONAL WEATHER SERVICE BOISE IDAHO
100 PM MDT FRI MAY 16 2014

...IDAHO SPRING FLOOD AND WATER SUPPLY OUTLOOK AS OF MAY 2014...

...ABOVE AVERAGE SPRING FLOOD RISK IN THE BEAR RIVER BASIN AND
PORTIONS OF THE UPPER SNAKE BASIN IN EASTERN IDAHO...
...AVERAGE SPRING FLOOD RISK FOR NORTH CENTRAL AND NORTHERN IDAHO...
...BELOW AVERAGE SPRING FLOOD RISK FOR SOUTH CENTRAL AND SOUTHWEST
IDAHO...

...NORMAL TO ABOVE NORMAL RUNOFF VOLUMES EXPECTED ACROSS MOST OF
EASTERN...NORTH CENTRAL...AND NORTHERN IDAHO...
...BELOW NORMAL RUNOFF VOLUMES EXPECTED ACROSS SOUTH CENTRAL AND
SOUTHWEST IDAHO...

AS OF MID MAY...THE RISK OF SPRING FLOODING IS ABOVE AVERAGE ACROSS
THE UPPER SNAKE RIVER AND BEAR RIVER REGIONS OF EASTERN IDAHO...
PRIMARILY FOR CREEKS AND TRIBUTARIES TO MAIN STEM RIVERS.  FOR NORTH
CENTRAL IDAHO AND THE PANHANDLE REGION... THE RISK OF SPRING
FLOODING IS NEAR AVERAGE...WHILE SOUTHWEST AND SOUTH CENTRAL IDAHO
HAS A BELOW AVERAGE RISK.

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.

RESERVOIRS IN THE UPPER SNAKE BASIN...AND CENTRAL AND NORTHERN IDAHO
ARE GENERALLY IN GOOD SHAPE WITH ADEQUATE SNOWPACK TO EITHER FILL OR
COME CLOSE TO FILLING...DEPENDING ON RUNOFF TIMING AND IRRIGATION
DEMAND. WATER STORAGE IS NOT AS PROMISING FOR MUCH OF SOUTHERN IDAHO
THOUGH...AS MOST RESERVOIRS IN SOUTH CENTRAL IDAHO AND THE OWYHEE
BASIN WILL NOT FILL. SPRING WEATHER PATTERNS WILL DRIVE RESERVOIR
OPERATIONS THROUGH MAY AND JUNE. THIS IS ESPECIALLY TRUE FOR THE
UPPER SNAKE RIVER...WHERE WET SPRING WEATHER OR EXTENDED PERIODS OF
WARMTH COULD RESULT IN FLOWS ON MAIN STEM RIVERS NEAR BANKFULL FOR A
PERIOD.

THE NATIONAL WEATHER SERVICE WATER SUPPLY OUTLOOK FOR IDAHO FOR THE
2014 WATER YEAR PROJECTS NEAR AVERAGE TO ABOVE AVERAGE RUNOFF
VOLUMES FOR THE PANHANDLE REGION...THE CLEARWATER...SALMON...
PAYETTE...AND BOISE RIVER BASINS...AS WELL AS THE UPPER SNAKE RIVER.
EXPECTATIONS FOR THE BEAR RIVE BASIN ARE MIXED...BUT NEAR NORMAL
RUNOFF VOLUMES ARE FORECAST FOR THE MAJORITY OF THE BASIN.
ELSEWHERE...THE OUTLOOK IS NOT AS PROMISING...WITH BELOW AVERAGE
RUNOFF VOLUMES EXPECTED. MOST WATER SUPPLY FORECASTS FOR LOCATIONS
IN THE LOST AND WOOD RIVER BASINS...AND SOUTH SIDE SNAKE RIVER
BASINS INDICATE AROUND 50 PERCENT OR LESS OF NORMAL RUNOFF.
FORECASTS ON THE SNAKE RIVER DOWNSTREAM OF MILNER INDICATE ABOUT 60
TO 70 PERCENT OF NORMAL RUNOFF VOLUME.

SUMMARY OF 2014 WATER YEAR...

THE 2014 WATER YEAR STARTED OFF VERY DRY ACROSS IDAHO. JANUARY
MARKED THE FOURTH CONSECUTIVE MONTH THAT BELOW NORMAL PRECIPITATION
OCCURRED ACROSS ALMOST THE ENTIRE STATE. AT THE END OF JANUARY...
WITH EXCEPTION OF THE CLEARWATER BASIN AND EXTREME SOUTHEAST IDAHO
...WATER YEAR PRECIPITATION WAS LESS THAN LESS THAN 75 PERCENT OF
NORMAL ACROSS THE STATE...AND MUCH OF SOUTH CENTRAL AND SOUTHWEST
IDAHO HAD ONLY RECEIVED ABOUT 50 PERCENT OF NORMAL. THE WEATHER
PATTERN RESPONSIBLE FOR THE PERSISTENT DRYNESS FINALLY GAVE WAY TO A
MOIST WESTERLY FLOW OFF THE PACIFIC OCEAN...WHICH DOMINATED THROUGH
FEBRUARY AND MARCH. THE RESULT WAS BACK TO BACK MONTHS OF WELL ABOVE
NORMAL PRECIPITATION FOR MOST OF THE STATE. FEBRUARY PRECIPITATION
WAS OVER 130 PERCENT OF NORMAL FOR MOST AREAS...AND MUCH OF THE
MOUNTAINS RECEIVED 200 TO 300 PERCENT OF NORMAL. MARCH PRECIPITATION
WAS NEARLY AS IMPRESSIVE...EXCEPT FOR PORTIONS OF THE LOST AND WOOD
RIVER BASINS IN SOUTHERN IDAHO WHICH RECEIVED BELOW NORMAL
PRECIPITATION.

APRIL BROUGHT A PATCH-WORK OF ABOVE NORMAL AND BELOW NORMAL
PRECIPITATION TO THE STATE. UNFORTUNATELY...AREAS OF SOUTHERN IDAHO
THAT HAVE BEEN THE DRIEST EXPERIENCED ANOTHER MONTH OF BELOW NORMAL
PRECIPITATION. THE FIRST HALF OF MAY HAS BEEN QUITE DRY FOR MUCH OF
THE SALMON RIVER...WOOD RIVER...AND LOST RIVER BASINS...AND FOR THE
MAJORITY OF SOUTHERN IDAHO...EXCEPT NEAR THE NEVADA BORDER.

REFER TO SECTIONS BELOW AND LINKS PROVIDED FOR THE LATEST DETAILS
REGARDING WATER SUPPLY FORECASTS FOR SPECIFIC LOCATIONS...SNOWPACK
...PRECIPITATION...RESERVOIR CONDITIONS AND LONG TERM WEATHER
OUTLOOKS.

WATER SUPPLY VOLUME FORECASTS...

WATER SUPPLY FORECASTS ISSUED BY THE NORTHWEST AND COLORADO BASIN
RIVER FORECAST CENTERS ARE ISSUED FREQUENTLY...ON EITHER A WEEKLY
OR DAILY BASIS. FOR THE LATEST WATER SUPPLY FORECASTS FOR IDAHO
PLEASE REFER TO THE FOLLOWING WEB SITES.

NATIONAL WEATHER SERVICE-NORTHWEST RIVER FORECAST CENTER
WWW.NWRFC.NOAA.GOV/WS/

NATIONAL WEATHER SERVICE-COLORADO BASIN RIVER FORECAST CENTER
(BEAR RIVER BASIN)
HTTP://WWW.CBRFC.NOAA.GOV/

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

SNOWPACK INFORMATION...

AS OF MAY 16...BASIN SNOWPACK VARIED CONSIDERABLY ACROSS IDAHO. THE
LOWEST PERCENTAGES WERE ACROSS THE OWYHEE...BRUNEAU...AND SALMON
FALLS BASINS...AS WELL AS THE LITTLE WOOD...BIG LOST...WILLOW...
BLACKFOOT...AND PORTNUEF BASINS...WHICH WERE ALL AROUND 60 PERCENT
OR LESS PERCENT OF MEDIAN. IN FACT...A NUMBER OF SNOTEL SITES IN
THESE BASINS ALREADY HAVE...OR ARE ON PACE TO MELT OUT A MONTH
EARLIER THAN NORMAL. ELSEWHERE...THE BEAR RIVER AND SNAKE HEADWATERS
REGIONS ARE STILL HOLDING ABUNDANT HIGH ELEVATION SNOWPACK...AS IS
THE PANHANDLE REGION...SOUTH ACROSS THE CLEARWATER...SALMON...
PAYETTE...AND BOISE RIVER BASINS. THE CLEARWATER AND SNAKE RIVER
ABOVE PALISADES WERE CARRYING THE HIGHEST PERCENTAGES AT AROUND 170
PERCENT OF MEDIAN.

CURRENT DAY SNOW WATER EQUIVALENT AND PERCENT OF NORMAL SNOWPACK
INFORMATION CAN BE FOUND AT THE FOLLOWING LINKS.

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

NATIONAL WEATHER SERVICE-NATIONAL OPERATIONAL HYDROLOGIC REMOTE
SENSING CENTER
HTTP://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/CGIBIN/RESV-GRAPH.PL?STATE=ID

DROUGHT CONDITIONS

ACCORDING TO THE U.S. DROUGHT MONITOR...AS OF MAY 13...MODERATE TO
EXTREME DROUGHT CONDITIONS EXIST ACROSS MOST OF SOUTHERN IDAHO.
PROLONGED DROUGHT CONDITIONS LAST YEAR...AND THROUGH THE FIRST SIX
MONTHS OF THE CURRENT WATER YEAR...HAVE HAD LONG TERM IMPACTS ON
RESERVOIR STORAGE AND WATER SUPPLY FOR SOUTHERN IDAHO. THE 90 DAY
U.S. SEASONAL DROUGHT OUTLOOK INDICATES THAT DROUGHT WILL LIKELY
PERSIST IN AREAS CURRENTLY PLAGUED BY LONG-TERM DRYNESS.

FOR THE LATEST DROUGHT CONDITIONS ACROSS THE REGION PLEASE REFER TO
THE FOLLOWING WEB SITES.

U.S. DROUGHT PORTAL
HTTP://WWW.DROUGHT.GOV

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

NATIONAL DROUGHT MITIGATION CENTER
HTTP://DROUGHT.UNL.EDU/

PEAK FLOW FORECASTS...

FOR PEAK FLOW FORECASTS PLEASE REFER TO THE FOLLOWING WEB SITES.

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

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

TEMPERATURE AND PRECIPITATION OUTLOOK...

ACCORDING TO THE CLIMATE PREDICTION CENTER...THE LONG RANGE OUTLOOK
FOR JUNE THROUGH AUGUST FAVORS ABOVE NORMAL TEMPERATURES FOR THE
WESTERN HALF OF IDAHO...AND EQUAL CHANCES OF BELOW AVERAGE...AVERAGE
OR ABOVE AVERAGE TEMPERATURES ACROSS THE EASTERN HALF OF IDAHO. FOR
PRECIPITATION DURING THE JUNE THROUGH AUGUST PERIOD...PROBABILITIES
FAVOR ABOVE AVERAGE PRECIPITATION FOR THE EASTERN HALF OF
IDAHO...AND THERE ARE EQUAL CHANCES OF BELOW AVERAGE...AVERAGE...OR
ABOVE AVERAGE PRECIPITATION ELSEWHERE ACROSS THE STATE.

THE NATIONAL WEATHER SERVICE CLIMATE PREDICTION CENTER HAS ISSUED AN
EL NINO WATCH...WITH THE CHANCE OF EL NINO INCREASING DURING THE
REMAINDER OF THE YEAR...EXCEEDING 65 PERCENT BY SUMMER. TYPICAL
WINTER TIME IMPACTS OF EL NINO ON IDAHO WEATHER ARE FOR WARMER THAN
NORMAL TEMPERATURES AND BELOW NORMAL SNOWPACK.

FOR EL NINO INFORMATION AND LONG RANGE AND SEASONAL OUTLOOKS ISSUED
BY THE NATIONAL WEATHER SERVICE CLIMATE PREDICTION CENTER PLEASE
REFER TO THE FOLLOWING WEBSITE.
WWW.CPC.NCEP.NOAA.GOV/

$$



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