521  
FGUS73 KABR 251244  
ESFABR  
MNC011-155-SDC013-017-021-025-029-031-037-039-041-045-049-051-057-  
059-065-069-075-085-089-091-107-109-115-117-119-129-221200-  
 
PROBABILISTIC HYDROLOGIC OUTLOOK  
NATIONAL WEATHER SERVICE ABERDEEN SD  
744 AM CDT FRI SEP 25 2020  
 
IN TABLE 1 BELOW...THE CURRENT (CS) AND HISTORICAL (HS) OR NORMAL  
PROBABILITIES OF EXCEEDING MINOR...MODERATE...AND MAJOR FLOOD STAGES  
ARE LISTED FOR THE VALID TIME PERIOD.  
 
CS VALUES INDICATE THE PROBABILITY OF REACHING A FLOOD CATEGORY  
BASED ON CURRENT CONDITIONS.  
 
HS VALUES INDICATE THE PROBABILITY OF REACHING A FLOOD CATEGORY  
BASED ON HISTORICAL OR NORMAL CONDITIONS.  
 
WHEN THE VALUE OF CS IS MORE THAN HS...THE PROBABILITY OF  
EXCEEDING THAT LEVEL IS HIGHER THAN NORMAL. WHEN THE VALUE OF CS IS  
LESS THAN HS...THE PROBABILITY OF EXCEEDING THAT LEVEL IS LOWER  
THAN NORMAL.  
 
   
..TABLE 1--PROBABILITIES FOR MINOR...MODERATE AND MAJOR FLOODING
 
 
VALID PERIOD: 09/26/2020 - 12/25/2020  
 
: CURRENT AND HISTORICAL  
: CHANCES OF EXCEEDING  
: FLOOD CATEGORIES  
: AS A PERCENTAGE (%)  
CATEGORICAL :  
FLOOD STAGES (FT) : MINOR MODERATE MAJOR  
LOCATION MINOR MOD MAJOR : CS HS CS HS CS HS  
-------- ----- ----- ----- : --- --- --- --- --- ---  
:ELM RIVER  
WESTPORT 14.0 16.0 19.0 : <5 <5 <5 <5 <5 <5  
:JAMES RIVER  
COLUMBIA 13.0 16.0 18.0 : 10 6 7 <5 <5 <5  
STRATFORD 14.0 17.0 18.5 : 14 9 9 <5 <5 <5  
:SNAKE CREEK  
ASHTON 11.5 13.0 16.0 : <5 <5 <5 <5 <5 <5  
:JAMES RIVER  
ASHTON 13.0 14.0 16.0 : 8 6 7 <5 6 <5  
:TURTLE CREEK  
REDFIELD 7.0 10.0 15.0 : 8 8 5 <5 <5 <5  
:JAMES RIVER  
REDFIELD 20.0 22.0 25.0 : <5 <5 <5 <5 <5 <5  
:BIG SIOUX RIVER  
WATERTOWN 10.0 11.0 12.0 : <5 <5 <5 <5 <5 <5  
WATERTOWN SIOUX C 9.0 10.0 12.0 : 10 <5 <5 <5 <5 <5  
WATERTOWN BROADWA 10.5 11.0 13.5 : 13 10 9 8 <5 <5  
CASTLEWOOD 9.0 11.0 16.0 : 14 11 <5 <5 <5 <5  
:GRAND RIVER  
LITTLE EAGLE 15.0 17.0 21.0 : <5 <5 <5 <5 <5 <5  
:MOREAU RIVER  
WHITEHORSE 21.0 23.0 25.0 : <5 <5 <5 <5 <5 <5  
:BAD RIVER  
FORT PIERRE 21.0 25.0 27.0 : <5 <5 <5 <5 <5 <5  
:LITTLE MINNESOTA RIVER  
PEEVER 17.0 22.0 24.0 : <5 <5 <5 <5 <5 <5  
:MINNESOTA RIVER  
BIG STONE LAKE 971.5 973.0 975.0 : <5 <5 <5 <5 <5 <5  
 
LEGEND  
CS = CONDITIONAL SIMULATION (CURRENT OUTLOOK)  
HS = HISTORICAL SIMULATION  
FT = FEET  
 
IN TABLE 2 BELOW...THE 95 THROUGH 5 PERCENT COLUMNS INDICATE THE  
PROBABILITY OF EXCEEDING THE LISTED STAGE LEVELS (FT) FOR THE VALID  
TIME PERIOD.  
   
..TABLE 2--EXCEEDANCE PROBABILITIES
 
 
CHANCE OF EXCEEDING STAGES  
AT SPECIFIC LOCATIONS  
VALID PERIOD: 09/26/2020 - 12/25/2020  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
:ELM RIVER  
WESTPORT 3.0 3.0 3.0 3.0 4.6 9.3 12.0  
:JAMES RIVER  
COLUMBIA 8.0 8.0 8.0 8.0 8.0 12.7 17.4  
STRATFORD 12.8 12.8 12.8 12.8 12.8 16.2 18.1  
:SNAKE CREEK  
ASHTON 2.5 2.5 2.5 2.5 2.6 4.7 9.3  
:JAMES RIVER  
ASHTON 9.9 9.9 9.9 9.9 9.9 10.9 16.8  
:TURTLE CREEK  
REDFIELD 3.4 3.4 3.4 3.5 3.6 5.3 9.5  
:JAMES RIVER  
REDFIELD 9.5 9.5 9.5 9.5 9.5 10.5 16.5  
:BIG SIOUX RIVER  
WATERTOWN 4.3 4.3 4.3 4.3 7.3 9.1 9.7  
WATERTOWN SIOUX C 3.9 3.9 3.9 3.9 6.1 9.0 9.5  
WATERTOWN BROADWA 5.4 5.4 5.4 5.4 7.6 11.0 11.5  
CASTLEWOOD 4.6 4.6 4.7 4.7 6.9 9.6 10.6  
:GRAND RIVER  
LITTLE EAGLE 3.5 3.5 3.5 3.8 5.0 7.2 8.9  
:MOREAU RIVER  
WHITEHORSE 2.3 2.4 2.4 2.9 5.1 7.1 9.3  
:BAD RIVER  
FORT PIERRE 1.0 1.0 1.0 1.0 4.4 7.4 8.2  
:LITTLE MINNESOTA RIVER  
PEEVER 10.2 10.2 10.2 10.3 10.8 12.4 13.9  
:MINNESOTA RIVER  
BIG STONE LAKE 968.1 968.1 968.1 968.1 968.1 968.1 968.1  
 
IN TABLE 3 BELOW...THE 95 THROUGH 5 PERCENT COLUMNS INDICATE THE  
PROBABILITY OF FALLING BELOW THE LISTED STAGE LEVELS (FT) FOR THE  
VALID TIME PERIOD.  
   
..TABLE 3--NONEXCEEDANCE PROBABILITIES
 
 
CHANCE OF FALLING BELOW STAGES  
AT SPECIFIC LOCATIONS  
VALID PERIOD: 09/26/2020 - 12/25/2020  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
:ELM RIVER  
WESTPORT 3.0 3.0 3.0 3.0 3.0 3.0 3.0  
:JAMES RIVER  
COLUMBIA 7.1 6.0 5.8 5.7 5.7 5.7 5.6  
STRATFORD 10.2 9.6 9.2 9.2 9.2 9.2 9.2  
:SNAKE CREEK  
ASHTON 2.5 2.5 2.5 2.5 2.5 2.5 2.5  
:JAMES RIVER  
ASHTON 5.6 4.6 4.3 4.2 4.2 4.2 4.2  
:TURTLE CREEK  
REDFIELD 3.3 3.3 3.3 3.3 3.3 3.3 3.3  
:JAMES RIVER  
REDFIELD 7.1 6.2 6.0 6.0 6.0 5.9 5.9  
:BIG SIOUX RIVER  
WATERTOWN 4.3 4.3 4.3 4.2 4.2 4.2 4.2  
WATERTOWN SIOUX C 3.8 3.8 3.8 3.8 3.8 3.8 3.8  
WATERTOWN BROADWA 5.3 5.3 5.3 5.3 5.3 5.3 5.3  
CASTLEWOOD 4.6 4.6 4.6 4.6 4.6 4.6 4.6  
:GRAND RIVER  
LITTLE EAGLE 2.7 2.7 2.7 2.7 2.7 2.7 2.7  
:MOREAU RIVER  
WHITEHORSE 2.2 2.2 2.2 2.2 2.2 2.2 2.2  
:BAD RIVER  
FORT PIERRE 1.0 1.0 1.0 1.0 1.0 1.0 1.0  
:LITTLE MINNESOTA RIVER  
PEEVER 9.7 9.7 9.7 9.7 9.7 9.7 9.7  
:MINNESOTA RIVER  
BIG STONE LAKE 967.1 967.1 967.1 967.1 967.1 967.1 967.1  
 
THESE LONG-RANGE PROBABILISTIC OUTLOOKS CONTAIN FORECAST VALUES THAT  
ARE CALCULATED USING MULTIPLE SEASON SCENARIOS FROM 30 OR MORE YEARS  
OF CLIMATOLOGICAL DATA...INCLUDING CURRENT CONDITIONS OF THE  
RIVER...SOIL MOISTURE...SNOW COVER...AND 30 TO 90 DAY LONG-RANGE  
OUTLOOKS OF TEMPERATURE AND PRECIPITATION. BY PROVIDING A RANGE OF  
PROBABILITIES...THE LEVEL OF RISK ASSOCIATED WITH LONG-RANGE PLANNING  
DECISIONS CAN BE DETERMINED. THESE PROBABILISTIC FORECASTS ARE PART  
OF THE NATIONAL WEATHER SERVICE'S ADVANCED HYDROLOGIC PREDICTION  
SERVICE.  
 
VISIT OUR WEB SITE WEATHER.GOV/ABR FOR MORE WEATHER AND WATER  
INFORMATION.  
 
THE NEXT OUTLOOK WILL BE ISSUED LATE NEXT MONTH.  
 

 
 
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