600
FGUS75 KPIH 151802 CCA
ESFPIH
HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE POCATELLO IDAHO
1200 PM MDT THU MAY 15 2008
..EASTERN IDAHO WEEKLY HYDROLOGIC UPDATE
SYNOPSIS
A MILD WEEK ALLOWED FOR SOME GENTLE SNOWMELT, WHICH HELD SNOW WATER
EQUIVALENT (SWE) VALUES IN CHECK AT 110% OF NORMAL FOR THE REGION,
ACCORDING TO NRCS SNOTEL DATA. THE HENRY'S AND TETON BASINS MARKED
A 14% INCREASE TO 140%. THIS TIME OF YEAR, HOWEVER, IT IS IMPORTANT
TO REALIZE AS AVERAGE SNOW PACK LEVELS ARE DECREASING, ANY
ADDITIONAL SNOW MAY RESULT IN LARGE PERCENTAGE INCREASES. THE
BLACKFOOT/PORTNEUF AND OAKLEY BASINS TOOK THE GREATEST SWE LOSSES AT
15% AND 11%, RESPECTIVELY. THE BASIN AVERAGE PRECIPITATION TOOK
ANOTHER ONE-POINT DECLINE OVER THE WEEK TO 98%.
7-DAY FORECAST
A RIDGE OF HIGH PRESSURE IS BUILDING ACROSS EASTERN IDAHO BRINGING A
WARMING TREND WITH WEEKEND AFTERNOON HIGHS CLIMBING WELL INTO THE
80S AND LOWS IN THE MID 40S. THE RIDGE WILL WEAKEN TUESDAY, AS
WESTERLY FLOW WILL PREVAIL WITH SOME CHANCES OF PRECIPITATION ACROSS
THE FORECAST AREA CONTINUING INTO THURSDAY.
AREAS OF IMMEDIATE CONCERN
THE COMING WARMING TREND WILL INCREASE RIVER AND STREAM FLOWS ACROSS
THE REGION THIS WEEKEND.
THE MAIN AREA OF CONCERN IS THE HENRY'S FORK NEAR REXBURG WITH A
PEAK FORECAST OF 9.35 FEET (7400 CFS) IN THE AFTERNOON OF THURSDAY
MAY 22. FLOOD STAGE FOR THE HENRY'S FORK IS 9.5 FEET (7810
CFS).
MANY SMALL STREAMS ARE CURRENTLY APPROACHING BANKFULL, HOWEVER, NO
OTHER MAJOR RIVERS ARE EXPECTED TO REACH BANKFULL. THOSE NEAR
RIVERS AND STREAMS SHOULD BE AWARE OF THE CHANGING RIVER LEVELS.
SHOULD YOU SEE WATER CROSSING A ROAD, DO NOT DRIVE THROUGH IT. TAKE
AN ALTERNATE ROUTE.
RIVER FORECASTS WILL BE UPDATED ONCE A DAY AND AS CONDITIONS WARRANT
THROUGH THE WARMING TREND.
LONG-RANGE FORECAST
THE NATIONAL WEATHER SERVICE CLIMATE PREDICTION CENTERS (CPC)
JUNE-JULY-AUGUST FORECAST IS CALLING FOR BELOW-NORMAL TEMPERATURES
AND PRECIPITATION.
LONG-RANGE FORECAST VALID MAY 15, 2008.
LONG RANGE FORECAST PRODUCTS ARE RELEASED THE THIRD THURSDAY OF
EVERY MONTH.
DATA ROUND-UP
EASTERN IDAHO SNOWPACK
5/8/2008 5/14/2008 WEEKLY CHG
SWE PRECIP SWE PRECIP
BASIN % AVG % AVG % AVG % AVG SWE PRECIP
SALMON 121 102 124 101 3 -1
BIG WOOD 98 95 94 93 -4 -2
LITTLE WOOD 99 97 91 96 -8 -1
BIG LOST 83 94 83 92 0 -2
LITTLE LOST 99 94 94 93 -5 -1
HENRY'S/TETON 126 107 140 108 14 1
SNAKE ABV PALISADES 114 103 123 103 9 0
BLACKFOOT/PORTNEUF 138 96 123 96 -15 0
OAKLEY 121 109 110 108 -11 -1
BEAR 104 92 115 93 11 1
EASTERN IDAHO AVG 110 99 110 98 0 -1
RESERVOIR STATUS
THE UPPER SNAKE RIVER RESERVOIR SYSTEM IS CURRENTLY AT 61% OF
CAPACITY. SELECT RESERVOIR STORAGE AMOUNT ARE BELOW. ALL VALUES
ARE A PERCENT OF RESERVOIR CAPACITY.
JACKSON 48
PALISADES 44
AMERICAN FALLS 74
HENRY'S LAKE 95
ISLAND PARK 94
LITTLE WOOD 63
EASTERN IDAHO RIVER LEVELS
RIVERS ACROSS EASTERN IDAHO ARE APPROACHING NORMAL LEVELS FOR THIS
TIME OF YEAR.
FOR MORE HYDROLOGIC AND WEATHER INFORMATION, PLEASE VISIT THE
POCATELLO WEATHER FORECAST OFFICE WEBSITE AT
WWW.WEATHER.GOV/POCATELLO.
HEBERT
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