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WATER SUPPLY OUTLOOK
NATIONAL WEATHER SERVICE BOISE IDAHO
355 PM MDT TUE APR 15 2014

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

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

AS OF MID APRIL...THE RISK OF SPRING FLOODING DUE TO SNOWMELT IS
ABOVE AVERAGE ACROSS THE UPPER SNAKE AND BEAR RIVER REGIONS OF
EASTERN IDAHO. FOR NORTH CENTRAL IDAHO AND THE PANHANDLE REGION...
THE RISK OF SPRING SNOWMELT FLOODING IS NEAR AVERAGE...WHILE
SOUTHWEST AND MOST OF SOUTH CENTRAL IDAHO HAS A BELOW AVERAGE RISK.

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. FLOWS WILL BE INCREASED OUT OF SOME RESERVOIRS THIS SPRING
TO ALLOW SPACE FOR SNOWMELT RUNOFF. THIS IS ESPECIALLY TRUE IN THE
UPPER SNAKE BASIN...WHERE RESERVOIR OPERATIONS MAY PUSH THE MAIN
STEM SNAKE RIVER TO NEAR BANKFULL FOR A FEW WEEKS FROM HEISE
DOWNSTREAM TO AMERICAN FALLS. WATER STORAGE IS NOT AS PROMISING FOR
MUCH OF SOUTHERN IDAHO THOUGH...AS BEAR LAKE...OWYHEE RESERVOIR...
AND MOST RESERVOIRS IN SOUTH CENTRAL IDAHO ARE NOT EXPECTED TO FILL.

THE PRIMARY FACTORS IN THE DEVELOPMENT OF SPRING RIVER 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.

IT IS NOT ALWAYS POSSIBLE TO FORECAST SPECIFIC RAIN STORMS...RAIN
ON SNOW EVENTS...OR EXTREME TEMPERATURE EVENTS MORE THAN 4 TO 7
DAYS INTO THE FUTURE. THEREFORE...SHORT RANGE RIVER FORECASTS
SHOULD BE MONITORED CLOSELY. DETAILS REGARDING POSSIBLE OR
RESULTING FLOODING WILL BE AVAILABLE IN SHORT TERM OUTLOOKS...FLOOD
WATCHES AND FLOOD WARNINGS ISSUED BY THE NATIONAL WEATHER SERVICE.

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...AND
PAYETTE RIVER AREAS...AS WELL AS THE UPPER SNAKE RIVER. ELSEWHERE...
THE OUTLOOK IS NOT AS PROMISING...WITH BELOW AVERAGE RUNOFF VOLUMES
EXPECTED. PORTIONS OF THE MAGIC VALLEY...AND SOUTH CENTRAL AND
SOUTHWEST IDAHO BASINS NEAR THE NEVADA BORDER HAVE BEEN THE
DRIEST...WITH WATER SUPPLY FORECASTS INDICATING AROUND 50 PERCENT OR
LESS OF NORMAL RUNOFF. FORECASTS ON THE SNAKE RIVER BELOW AMERICAN
FALLS DAM INDICATE ABOUT 60 TO 70 PERCENT OF NORMAL RUNOFF VOLUMES.

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.

THE FIRST HALF OF APRIL WAS RATHER DRY ACROSS IDAHO. MUCH OF SOUTH
CENTRAL AND SOUTHWEST IDAHO STILL SUFFER FROM LONG TERM DRYNESS AND
ARE FACING WATER SUPPLY SHORTAGES DURING THE GROWING SEASON. THUS...
COOL AND WET CONDITIONS THE REST OF SPRING WOULD BE VERY BENEFICIAL
AND EASE DROUGHT AND WATER SUPPLY CONCERNS IN THESE AREAS.

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 APRIL 15...BASIN SNOWPACK VARIED CONSIDERABLY ACROSS IDAHO.
THE LOWEST PERCENTAGES WERE ACROSS FAR SOUTHWEST IDAHO...WITH THE
OWYHEE BASIN AT ONLY 45 PERCENT OF NORMAL. MEANWHILE...THE
CLEARWATER...UPPER SNAKE...AND BEAR RIVER BASIS WERE THE HIGHEST...
RANGING FROM 130 TO 150 PERCENT OF NORMAL. THE BULK OF THE SNOWPACK
RESIDES AT THE HIGH ELEVATIONS...AS LOW ELEVATION...AND MUCH OF THE
MID ELEVATION SNOW HAS ALREADY MELTED.

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 APRIL 8...MODERATE TO
EXTREME DROUGHT CONDITIONS EXIST ACROSS MOST OF SOUTHERN IDAHO.
PROLONGED DROUGHT CONDITIONS LAST YEAR...AND THROUGH THE FIRST
SEVERAL 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 A POSSIBLE
REMOVAL OR RELAXATION OF THE DROUGHT INTENSITY IN ALL OF EASTERN
IDAHO AND THE CENTRAL MOUNTAINS.

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 MAY THROUGH JULY FAVORS ABOVE NORMAL TEMPERATURES ACROSS
SOUTHWEST IDAHO...AND EQUAL CHANCES OF BELOW AVERAGE...AVERAGE OR
ABOVE AVERAGE TEMPERATURES ACROSS NORTHERN AND EASTERN IDAHO. FOR
PRECIPITATION DURING THE MAY THROUGH JULY PERIOD...THERE ARE EQUAL
CHANCES OF BELOW AVERAGE...AVERAGE...OR ABOVE AVERAGE PRECIPITATION
ACROSS THE STATE.

THE NATIONAL WEATHER SERVICE CLIMATE PREDICTION CENTER HAS ISSUED AN
EL NINO WATCH...INDICATING ABOUT A 50 PERCENT CHANCE OF EL NINO
DEVELOPING DURING THE SUMMER OR FALL OF 2014. 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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