HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE POCATELLO IDAHO
500 PM MDT TUE APR 11 2006
...EASTERN AND CENTRAL IDAHO APRIL 1 WATER SUPPLY AND FLOOD
POTENTIAL OUTLOOK...
WITH ABUNDANT SNOW PACK IN THE MOUNTAINS FOR THE FIRST TIME SINCE
...1997 AND THE SPRING SNOWMELT SEASON UPON EASTERN IDAHO THE TIME
IS NOW TO PREPARE FOR POTENTIAL FLOODING IN MANY AREAS.
...PRECIPITATION...
MARCH PRECIPITATION WAS 121% OF NORMAL FOR FIVE AUTOMATED SURFACE
OBSERVING SYSTEMS (ASOS) IN EASTERN IDAHO AND 133% OF NORMAL FOR THE
2006 WATER YEAR. THE REPRESENTATIVE STATIONS FOLLOW...
MARCH WATER YEAR
PERCENT OF PERCENT OF
STATION NORMAL NORMAL
BURLEY 143.5 131.9
CHALLIS 56.9 102.0
IDAHO FALLS 117.9 108.9
POCATELLO 123.9 126.2
STANLEY 132.8 163.7
REGIONAL AVERAGE 121.4 133.3
AS OF THE END OF MARCH...MOUNTAIN SNOW WATER EQUIVALENT (SWE) IS
AVERAGING 126% OF NORMAL FOR THE 2006 WATER YEAR FOR EASTERN IDAHO
BASINS. THE BASIN SUMMARY FOLLOWS...
SNOW WATER
EQUIVALENT
BASIN PERCENT NORMAL
BIG WOOD 131
LITTLE WOOD 142
BIG LOST 134
LITTLE LOST 114
HENRY'S TETON 119
SNAKE ABOVE PALISADES 108
BLACKFOOT, PORTNEUF 121
OAKLEY 145
BEAR 119
REGIONAL AVERAGE 126
...WATER SUPPLY...
ACCORDING TO THE APRIL 1 2006 WATER SUPPLY OUTLOOK BY THE NATURAL
RESOURCES CONSERVATION SERVICE (NRCS)...MUCH OF EASTERN IDAHO'S
STREAMFLOW FORECASTS LOOK THE BEST SINCE 1997. THE UPPER SNAKE AND
BEAR RIVER BASINS ARE FORECAST AT 113% AND 119% OF NORMAL
RESPECTIVELY...WHILE THE BIG WOOD AND SOUTHSIDE SNAKE RIVER BASINS
ARE FORECAST NEAR THE HIGHEST IN THE STATE AT 148% AND 188% OF
NORMAL RESPECTIVELY.
THE MOST PROBABLE...MAXIMUM AND MINIMUM APRIL THROUGH SEPTEMBER
FORECAST SUMMARIES FOR EACH OF THE BASINS FOLLOW...
NOTE...
ONLY THE MINIMUM FORECAST FOR THE UPPER SNAKE AND THE BEAR RIVER
BASINS ARE SLIGHTLY BELOW NORMAL FLOWS WITH ALL OTHER FORECASTS
ABOVE NORMAL...INDICATING THE LIKELIHOOD FOR FLOODING.
MOST 30-YEAR
PROBABLE PERCENT AVERAGE
BASIN (KAF) AVERAGE MAXIMUM MINIMUM (KAF)
WOOD AND
LOST RIVER 250 148 179 119 165
UPPER SNAKE 1843 113 129 97 16455
SOUTHSIDE
SNAKE RIVER 314 188 234 148 167
BEAR RIVER 193 119 144 94 163
KAF = 1000 ACRE-FEET
FOR MORE INFORMATION REGARDING THE APRIL 1 NRCS WATER SUPPLY
OUTLOOK PLEASE VISIT THEIR WEB SITE AT...
http://www.id.nrcs.usda.gov/snow/watersupply/
...LONG-RANGE FORECAST...
ACCORDING TO THE NATIONAL WEATHER SERVICE CLIMATE PREDICTION CENTER
(CPC) OUTLOOK FOR MAY JUNE AND JULY...TEMPERATURES ARE EXPECTED TO
BE ABOVE NORMAL FOR EASTERN IDAHO. THE CPC PRECIPITATION FORECAST
CALLS FOR AN EQUAL CHANCE TO BE AT...ABOVE...OR BELOW NORMAL FOR
SAME PERIOD.
...RESERVOIR STATUS FROM THE BUREAU OF RECLAMATION...
THE UPPER SNAKE RIVER...WHICH INCLUDES JACKSON LAKE...PALISADES...
GRASSY LAKE...ISLAND PARK...RIRIE...AMERICAN FALLS AND LAKE WALCOTT...
IS AT 72% OF CAPACITY. THE TOTAL SPACE AVAILABLE IS 1,136,190 ACRE-FEET
AND THE TOTAL STORAGE CAPACITY IS 4,045,695 ACRE-FEET.
...FLOOD POTENTIAL OUTLOOK...
ACCORDING TO THE APRIL 8 2006 PEAK FLOW FORECAST BY THE NATIONAL
WEATHER SERVICE NORTHWEST RIVER FORECAST CENTER...THE HENRYS FORK
NEAR REXBURG AND THE PORTNEUF RIVERS ARE FORECAST TO RISE ABOVE
FLOOD STAGE AND CAUSE MINOR FLOODING.
THE MOST PROBABLE DISCHARGE AND PEAK FLOWS AND REPRESENTATIVE FLOOD
STAGES FOR EIGHT OF TEN RIVER FORECAST POINTS IN EASTERN IDAHO
FOLLOW...
FORECAST POINT DISCHARGE PEAK STAGE FLOOD STAGE
(CFS) (FEET) (FEET)
HENRY'S FORK
AT ST. ANTHONY 8200 6.6 7.0
TETON NEAR DRIGGS 1576 3.6 5.0
BIG WOOD
AT HAILEY 3400 5.4 6.0
SNAKE NEAR HEISE 22600 7.3 8.0
PORTNEUF AT
POCATELLO 1200 8.9 8.5
HENRY'S FORK
NEAR REXBURG 8800 9.8 9.5
SNAKE
NEAR SHELLEY 22700 11.3 12.0
TETON NEAR
ST. ANTHONY 4300 5.6 6.0
CFS = CUBIC FEET PER SECOND
...SPRING CLIMATE...
THE WILD CARD DURING SPRING SNOWMELT IS THE WEATHER. A RAPID
WARMING IN TEMPERATURES WILL CAUSE SUDDEN SNOWMELT AND RIVERS TO
RISE QUICKLY. A WARM AND WET SPRING IS THE WORST CASE....THIS
SCENARIO WILL HAVE THE SAME INFLUENCE ON RIVERS WITH THE ADDITIONAL
PRECIPITATION ADDING TO THE MIX CAUSING A FURTHER INCREASE IN RIVER
LEVELS AND THE POTENTIAL FOR FLOODING. THE IDEAL SCENARIO IS A COOL
SPRING WITH OCCASIONAL PRECIPITATION TO KEEP THE RIVERS FLOWING AND
THE RESERVOIRS FILLING.
...FLOOD SAFETY...
PLANNING AND PREPARATION ARE THE BEST DEFENSES AGAINST FLOODING.
MAKE SURE FLOOD PLANS ARE CURRENT AND READY TO EMPLOY AND KNOW YOUR
COMMUNITY FLOOD PLANS.
AND REMEMBER WHEN NEAR ANY RIVERS OR STREAMS AND WATER LEVELS ARE
HIGH OR ANTICIPATED TO RISE...BE ALERT AND NEVER DRIVE THROUGH
MOVING WATER. TURN AROUND DON'T DROWN.
FOR COMPLETE WEATHER AND HYDROLOGIC INFORMATION VISIT
THE NATIONAL WEATHER SERVICE WEB PAGE AT
http://www.weather.gov/pocatello/
HEBERT