975  
FGUS75 KBOI 132230  
ESFBOI  
IDC001-003-005-007-009-011-013-015-017-019-021-023-025-027-029-031-  
033-035-037-039-041-043-045-047-049-051-053-055-057-059-061-063-065-  
067-069-071-073-075-077-079-081-083-085-087-140700-  
 
WATER SUPPLY OUTLOOK  
NATIONAL WEATHER SERVICE BOISE ID  
330 PM MST TUE FEB 13 2018  
   
..IDAHO SPRING FLOOD AND WATER RESOURCES OUTLOOK
 
 
THE POTENTIAL FOR SPRING FLOODING DUE TO SNOWMELT IS SLIGHTLY  
ELEVATED FOR PORTIONS OF EASTERN AND NORTH CENTRAL IDAHO. THE SPRING  
FLOOD RISK FOR THE REST OF THE STATE IS AVERAGE TO BELOW AVERAGE.  
 
GOOD SOIL MOISTURE RECHARGE FROM AUTUMN RAINS AND WELL ABOVE AVERAGE  
RESERVOIR STORAGE HAS RESULTED IN A SLIGHTLY ELEVATED THREAT OF  
SPRING FLOODING ALONG THE MAINSTEM SNAKE RIVER IN EASTERN IDAHO, AND  
ALONG SMALLER TRIBUTARIES ABOVE IDAHO FALLS. SPRING FLOOD RISK IS  
ALSO SLIGHTLY ELEVATED IN THE CLEARWATER BASIN WHICH IS CURRENTLY  
HOLDING ONE OF THE GREATEST SNOWPACK PERCENTAGES IN THE STATE.  
ELSEWHERE, THE ABSENCE OF LOW ELEVATION SNOW AND AREAS OF BELOW  
AVERAGE MID ELEVATION SNOW SUGGEST AN AVERAGE OR BELOW AVERAGE  
SPRING FLOOD THREAT.  
 
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 THAT HAVE LOW SNOWPACK, SPRING  
FLOODING IS POSSIBLE UNDER THE RIGHT SCENARIO. ADDITIONALLY,  
WILDFIRE BURN SCARS CAN HAVE A SIGNIFICANT IMPACT ON LOCAL FLOOD  
POTENTIAL DURING SPRING SNOWMELT.  
 
WATER SUPPLY  
 
NATIONAL WEATHER SERVICE APRIL THROUGH SEPTEMBER WATER SUPPLY VOLUME  
FORECASTS VARY FROM 90 TO 135 PERCENT OF AVERAGE FOR MOST OF THE  
CENTRAL MOUNTAINS NORTH ACROSS THE CLEARWATER AND PANHANDLE REGIONS.  
IN SOUTHERN IDAHO, FORECASTS FOR THE BIG LOST BASIN, THE MAINSTEM  
SNAKE RIVER AND TRIBUTARIES ABOVE AMERICAN FALLS RANGE FROM 80 TO  
125 PERCENT OF AVERAGE, WITH THE EXCEPTION OF WILLOW CREEK NEAR  
RIRIE WITH A FORECAST OF 38 PERCENT OF AVERAGE. FORECASTS FOR THE  
REST OF SOUTHERN IDAHO RANGE FROM 39 TO 73 PERCENT OF AVERAGE WITH  
THE LOWEST PERCENTAGES IN SOUTHWEST IDAHO. THESE FORECASTS MAY  
CHANGE CONSIDERABLY OVER THE NEXT COUPLE OF MONTHS SINCE SEASONAL  
SNOW ACCUMULATION AND RAINFALL TYPICALLY OCCUR DURING FEBRUARY,  
MARCH, AND APRIL.  
 
PRECIPITATION  
 
AS OF FEBRUARY 12, WATER YEAR PRECIPITATION WAS NEAR NORMAL OR ABOVE  
NORMAL FOR THE PANHANDLE, SPOKANE, CLEARWATER, AND SALMON BASINS, AS  
WELL AS THE UPPER SNAKE BASIN NEAR THE WYOMING BORDER. THE  
CLEARWATER BASIN HAD THE GREATEST ANOMALIES AT 130 TO 150 PERCENT OF  
AVERAGE. ASIDE FROM THE SNAKE RIVER HEADWATERS REGION, WATER YEAR  
PRECIPITATION ACROSS SOUTHERN IDAHO STOOD AT 60 TO 80 PERCENT OF  
AVERAGE WITH SOUTH SIDE SNAKE RIVER BASINS HAVING THE LOWEST  
PERCENTAGES.  
 
SNOWPACK  
 
AS OF FEBRUARY 13, THE HIGHEST SNOWPACK PERCENTAGES IN THE STATE  
WERE 113 AND 115 PERCENT OF MEDIAN IN THE CLEARWATER BASIN AND THE  
UPPER SNAKE ABOVE PALISADES. PERCENTAGES WERE 89 TO 105 PERCENT OF  
MEDIAN FOR BASINS ALONG THE MONTANA BORDER IN EASTERN IDAHO, AND THE  
SALMON, SPOKANE, AND PANHANDLE BASINS. ELSEWHERE IN SOUTH CENTRAL  
AND SOUTHEAST IDAHO THE SNOWPACK WAS 56 TO 80 PERCENT OF MEDIAN,  
DROPPING TO 35 TO 48 PERCENT OF MEDIAN IN THE OWYHEE AND BRUNEAU  
BASINS IN SOUTHWEST IDAHO. DAILY SNOWPACK READINGS INDICATE RECORD  
LOW LEVELS FOR A HANDFUL OF SNOTEL LOCATIONS IN SOUTHERN IDAHO.  
MOUNTAIN SNOWPACK IN IDAHO TYPICALLY BUILDS THROUGH MARCH, SO EARLY  
APRIL SNOW CONDITIONS WILL BE PIVOTAL TO WATER SUPPLY CONDITIONS  
THROUGH THE SUMMER.  
 
RESERVOIRS  
 
RESERVOIR STORAGE ACROSS IDAHO IS IN GOOD SHAPE. MAJOR RESERVOIR  
SYSTEMS ACROSS THE NORTHERN HALF OF THE STATE WERE HOLDING NEAR  
AVERAGE OR ABOVE AVERAGE STORAGE AS OF FEBRUARY 1. ACROSS THE  
SOUTHERN HALF OF THE STATE, WITH THE EXCEPTION OF BROWNLEE AT 85  
PERCENT AND MANN CREEK AT 45 PERCENT OF AVERAGE, MOST MAJOR PROJECTS  
HAD WELL ABOVE AVERAGE STORAGE WHICH IS GREAT NEWS CONSIDERING THE  
BELOW AVERAGE SNOWPACK IN MANY BASINS. WEATHER PATTERNS, IRRIGATION  
DEMAND, AND FLOOD CONTROL NEEDS WILL DRIVE RESERVOIR OPERATIONS OVER  
THE NEXT SEVERAL MONTHS. WET SPRING WEATHER OR EXTENDED PERIODS OF  
ABOVE NORMAL TEMPERATURES RESULTING IN RAPID SNOWMELT COULD RESULT  
IN SIGNIFICANT INCREASES IN RESERVOIR OUTFLOWS AND RIVER LEVELS.  
 
DROUGHT  
 
AFTER RECORD SETTING PRECIPITATION AND SNOWPACK LAST YEAR,  
ABNORMALLY DRY CONDITIONS HAVE RETURNED TO PORTIONS OF WEST CENTRAL  
AND SOUTHERN IDAHO. WEATHER AND PRECIPITATION FOR THE REMAINDER OF  
WINTER AND THIS SPRING WILL DETERMINE WHETHER OR NOT CONDITIONS  
IMPROVE OR DETERIORATE FOR AREAS EXPERIENCING SHORT TERM DRYNESS.  
GOOD RESERVOIR CARRYOVER WILL HELP EASE DROUGHT CONCERNS FOR THOSE  
SERVED BY MAJOR STORAGE PROJECTS.  
 
LONG RANGE OUTLOOK  
 
THE OUTLOOK THROUGH THE END OF FEBRUARY FAVORS BELOW NORMAL  
TEMPERATURES, AND NORMAL OR BELOW NORMAL PRECIPITATION FOR THE  
STATE. THE OUTLOOK FOR MARCH, APRIL, AND MAY SUGGESTS BELOW NORMAL  
TEMPERATURES FOR THE PANHANDLE, AND NORMAL OR ABOVE NORMAL  
TEMPERATURES FOR THE CENTRAL AND SOUTHERN PARTS OF THE STATE. THE  
PRECIPITATION OUTLOOK FOR MARCH, APRIL, AND MAY SLIGHTLY FAVORS  
WETTER THAN NORMAL CONDITIONS FOR THE PANHANDLE, BUT DOES NOT SHIFT  
THE PROBABILITIES ONE WAY OR ANOTHER FOR THE REST OF THE STATE.  
 
REFER TO THE LINKS PROVIDED BELOW FOR THE LATEST INFORMATION ON  
WATER RESOURCES.  
 
WATER SUPPLY VOLUME FORECASTS NATIONAL WEATHER SERVICE-NORTHWEST  
RIVER FORECAST CENTER WWW.NWRFC.NOAA.GOV/WS/  
 
NATIONAL WEATHER SERVICE-COLORADO BASIN RIVER FORECAST CENTER  
WWW.CBRFC.NOAA.GOV/  
 
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.NRCS.USDA.GOV/WPS/PORTAL/NRCS/MAIN/ID/SNOW/  
 
RESERVOIR STORAGE BUREAU OF RECLAMATION  
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  
 
NATIONAL DROUGHT MITIGATION CENTER WWW.DROUGHT.UNL.EDU/  
 
PEAK FLOW FORECASTS NORTHWEST RIVER FORECAST CENTER  
WWW.NWRFC.NOAA.GOV/PEAK/  
 
COLORADO BASIN RIVER FORECAST CENTER  
WWW.CBRFC.NOAA.GOV/RMAP/PEAK/PEAKLIST.PHP  
 
TEMPERATURE AND PRECIPITATION OUTLOOK CLIMATE PREDICTION CENTER  
WWW.CPC.NCEP.NOAA.GOV/  
 

 
 
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