485
FGUS75 KBOI 052135
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-
067-069-071-073-075-077-079-081-083-085-087-070600-
WATER SUPPLY OUTLOOK
NATIONAL WEATHER SERVICE BOISE ID
235 PM MST THU MAR 5 2026
..IDAHO SPRING FLOOD AND WATER RESOURCES OUTLOOK
SPRING FLOOD POTENTIAL...
THE OVERALL RISK FOR SPRING FLOODING DUE TO SNOWMELT IS LOW ACROSS
IDAHO. ABOVE NORMAL TEMPERATURES CAUSED MUCH OF OUR WINTER
PRECIPITATION TO FALL AS RAIN INSTEAD OF SNOW, RESULTING IN A SNOW
DROUGHT. THE LACK OF LOW AND MID ELEVATION SNOW HAS SIGNIFICANTLY
REDUCED THE THREAT OF SPRING SNOWMELT FLOODING. HOWEVER, SOME AREAS
IN EASTERN IDAHO SUCH AS THE WOOD RIVER BASINS AND BIG LOST RIVER
BASIN ARE HOLDING A GOOD MID AND HIGH ELEVATION SNOWPACK AND THE
SPRING FLOOD RISK FOR THESE AREAS IS ABOUT AVERAGE.
IDAHO'S SNOWPACK AS A WHOLE TYPICALLY CONTINUES BUILDING THROUGH
MARCH AND PEAKS IN EARLY APRIL, LEAVING SEVERAL WEEKS AHEAD OF US
FOR ADDITIONAL SNOW ACCUMULATION AND POTENTIAL CHANGES TO THE SPRING
FLOOD 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 IF MAINSTEM RIVERS DO NOT REACH FLOOD
STAGE, SMALLER CREEKS AND STREAMS CAN STILL OVERFLOW THEIR BANKS.
UNDER THE RIGHT SCENARIO, SPRING FLOODING IS POSSIBLE EVEN FOR AREAS
THAT HAVE LOW SNOWPACK. ADDITIONALLY, WILDFIRE BURN SCARS CAN HAVE A
SIGNIFICANT IMPACT ON LOCAL FLOOD POTENTIAL DURING SPRING SNOWMELT.
TEMPERATURE AND PRECIPITATION SUMMARY...
AVERAGE TEMPERATURES FOR THE 2026 WATER YEAR HAVE BEEN ABOVE NORMAL
ACROSS THE ENTIRE STATE. THE WATER YEAR KICKED OFF WITH NEAR NORMAL
TEMPERATURES IN OCTOBER BUT THE FOLLOWING MONTHS OF NOVEMBER AND
DECEMBER SAW TEMPERATURE ANOMALIES OF 5-10 DEGREES (F) ABOVE NORMAL.
THE WARM TEMPERATURES IN NOVEMBER AND DECEMBER WERE CRITICAL FOR OUR
MOUNTAIN SNOWPACK AS MUCH OF THE PRECIPITATION FELL AS RAIN INSTEAD
OF SNOW. TEMPERATURE ANOMALIES IN JANUARY AND FEBRUARY WEREN'T QUITE
AS EXTREME AS THE PREVIOUS TWO MONTHS BUT STILL AVERAGED AROUND 5
DEGREES ABOVE NORMAL FOR THE MAJORITY OF THE STATE. PRELIMINARY DATA
INDICATES THAT SOME LOCATIONS IN IDAHO ARE ON TRACK FOR THEIR
WARMEST WINTER ON RECORD.
WATER YEAR PRECIPITATION THROUGH THE END OF FEBRUARY HAS BEEN NORMAL
TO ABOVE NORMAL FOR THE MAJORITY OF IDAHO. THE EXCEPTION IS FAR
SOUTHWEST IDAHO, PARTICULARLY THE OWYHEE MOUNTAINS WHERE
PRECIPITATION HAS ONLY BEEN 60-80 PERCENT OF NORMAL. OCTOBER
PRECIPITATION WAS WELL ABOVE NORMAL ACROSS SOUTHERN IDAHO WITH
NORMAL TO BELOW NORMAL PRECIPITATION FALLING ACROSS NORTHERN IDAHO.
MUCH OF THE IDAHO PANHANDLE SAW WELL ABOVE NORMAL PRECIPITATION IN
NOVEMBER WHILE SOUTHERN IDAHO WAS QUITE DRY. DECEMBER BROUGHT
ABUNDANT PRECIPITATION TO THE ENTIRE STATE AS A NUMBER OF VERY WARM
ATMOSPHERIC RIVERS IMPACTED THE REGION. JANUARY WAS VERY DRY
THROUGHOUT THE STATE. A MORE ACTIVE WEATHER PATTERN IN FEBRUARY
RESULTED IN WELL ABOVE NORMAL PRECIPITATION ACROSS FAR SOUTHERN
IDAHO WITH A MIX OF NORMAL TO BELOW NORMAL PRECIPITATION FOR OTHER
REGIONS OF IDAHO.
SNOWPACK...
SNOWPACK PERCENTAGES AS OF MARCH 2ND WERE WELL BELOW AVERAGE FOR
ALMOST ALL BASINS IN IDAHO, GENERALLY RANGING FROM 60 TO 85 PERCENT
OF AVERAGE. THE EXCEPTIONS WERE ACROSS EASTERN IDAHO IN THE LITTLE
WOOD BASIN, BIG LOST AND LITTLE LOST BASINS, AND THE SNAKE RIVER
ABOVE HEISE WHERE SNOWPACK WAS 90 TO 120 PERCENT OF AVERAGE. THE
LOWEST SNOWPACK PERCENTAGES WERE IN SOUTHERN IDAHO NEAR THE NEVADA
BORDER RANGING FROM 20 TO 55 PERCENT WITH THE OWYHEE BASIN BEING THE
LOWEST. THE LOW AND MID ELEVATION SNOWPACK IS EXTREMELY POOR ACROSS
MUCH OF THE STATE RESULTING IN A SNOW DROUGHT. THIS IS DUE TO ABOVE
NORMAL TEMPERATURES THAT CAUSED MUCH OF OUR WINTER PRECIPITATION TO
FALL AS RAIN INSTEAD OF SNOW. SNOW LEVELS DURING ATMOSPHERIC RIVER
EVENTS IN DECEMBER RANGED FROM 7 TO 9 THOUSAND FEET AT TIMES. IDAHO
SNOWPACK AS A WHOLE TYPICALLY BUILDS THROUGH MARCH AND PEAKS IN
EARLY APRIL.
RESERVOIRS...
THE 2026 WATER YEAR BEGAN WITH ABOVE AVERAGE STORAGE IN SW IDAHO AND
SE OREGON, THOUGH THE UPPER SNAKE RIVER LAGGED BEHIND. UNUSUAL
DECEMBER RAINFALL SIGNIFICANTLY BOOSTED STORAGE IN THE BOISE AND
PAYETTE RIVER SYSTEMS. SMALLER NON-FEDERAL RESERVOIRS IN SOUTHERN
IDAHO WERE GENERALLY HOLDING WELL BELOW NORMAL STORAGE AS OF EARLY
MARCH. WEATHER PATTERNS, IRRIGATION DEMAND, AND FLOOD RISK
MANAGEMENT WILL DRIVE RESERVOIR OPERATIONS OVER THE NEXT SEVERAL
MONTHS. WET SPRING WEATHER OR EXTENDED PERIODS OF ABOVE NORMAL
TEMPERATURES RESULTING IN RAPID SNOWMELT AND LARGE RESERVOIR INFLOWS
COULD RESULT IN SIGNIFICANT FLUCTUATIONS IN RESERVOIR DISCHARGE AND
DOWNSTREAM RIVER LEVELS.
OBSERVED STREAMFLOWS...
USGS STREAMFLOW CONDITIONS AS OF EARLY MARCH ARE A MIX ACROSS THE
STATE. MANY STREAM GAUGE SITES HAVE BEEN RUNNING MUCH ABOVE NORMAL
DUE TO RAINFALL RUNOFF OVER THE WINTER. MEANWHILE, THERE ARE SOME
GAUGING STATIONS SHOWING WELL BELOW NORMAL STREAMFLOWS, ESPECIALLY
ALONG THE MAINSTEM SNAKE RIVER IN SOUTHERN IDAHO.
DROUGHT...
DROUGHT CONDITIONS HAVE IMPROVED OVERALL SINCE THE START OF THE 2026
WATER YEAR. HOWEVER, SNOW DROUGHT HAS BECOME A SIGNIFICANT CONCERN
ACROSS THE STATE AND WATER SUPPLY FORECASTS CONTINUE TO TREND DOWN.
SNOW DROUGHT HAS HIT THE OWYHEE BASIN IN FAR SOUTHWEST IDAHO
PARTICULARLY HARD WHERE LITTLE TO NO SNOW EXISTS, EVEN AT THE HIGH
ELEVATIONS. TEMPERATURE AND PRECIPITATION PATTERNS THROUGH THE
SPRING WILL DETERMINE WHETHER OR NOT DROUGHT CONDITIONS IMPROVE OR
DETERIORATE.
WATER SUPPLY...
NATIONAL WEATHER SERVICE WATER SUPPLY FORECASTS FOR APRIL THROUGH
SEPTEMBER, 2026 INDICATE WELL BELOW NORMAL RUNOFF VOLUMES (50-80
PERCENT) FOR THE MAJORITY OF FORECAST LOCATIONS IN IDAHO. EXCEPTIONS
ARE IN PORTIONS OF THE PANHANDLE WHERE THE KOOTENAI RIVER AND CLARK
FORK AT CABINET GORGE ARE CLOSE TO 100 PERCENT OF NORMAL. IN CENTRAL
AND SOUTHERN IDAHO THE SALMON RIVER AT SALMON, THE BIG WOOD AT
HAILEY, AND LITTLE WOOD RIVER NEAR CAREY ARE CLOSE TO 100 PERCENT OF
NORMAL AS WELL. THE HIGHEST PERCENTAGES ARE ON THE BIG LOST RIVER
WITH FORECASTS INDICATING AROUND 130-140 PERCENT OF NORMAL.
SEASONAL OUTLOOK...
THE OUTLOOK FOR THE MONTH OF MARCH INDICATES EQUAL CHANCES FOR
EITHER BELOW NORMAL, NORMAL, OR ABOVE NORMAL TEMPERATURES FOR THE
NORTHERN HALF OF IDAHO WHILE ABOVE NORMAL TEMPERATURES ARE SLIGHTLY
FAVORED ACROSS SOUTHERN IDAHO. THE PRECIPITATION OUTLOOK FOR MARCH
INDICATES EQUAL CHANCES OF EITHER CATEGORY THROUGHOUT THE STATE.
THE OUTLOOK FOR APRIL THROUGH JUNE, 2026 FAVORS ABOVE NORMAL
TEMPERATURES ACROSS ALL BUT FAR NORTHERN IDAHO WHERE EQUAL CHANCES
OF EITHER BELOW NORMAL, NORMAL, OR ABOVE NORMAL TEMPERATURES EXISTS.
ODDS FAVOR BELOW NORMAL PRECIPITATION ACROSS ALL OF IDAHO DURING THE
PERIOD.
ON-LINE RESOURCES...
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.NRCS.USDA.GOV/WPS/PORTAL/NRCS/MAIN/ID/SNOW
DROUGHT CONDITIONS
U.S. DROUGHT PORTAL WWW.DROUGHT.GOV
PEAK FLOW FORECASTS
NORTHWEST RIVER FORECAST CENTER WWW.NWRFC.NOAA.GOV/PEAK/
COLORADO BASIN RIVER FORECAST CENTER
WWW.CBRFC.NOAA.GOV/LMAP/LMAP.PHP?INTERFACE=PEAKFP
TEMPERATURE AND PRECIPITATION OUTLOOK
CLIMATE PREDICTION CENTER WWW.CPC.NCEP.NOAA.GOV/
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