381  
FGUS73 KFSD 131749  
ESFFSD  
SDC005-011-027-035-061-067-079-083-087-099-101-111-125-127-135-  
MNC033-063-081-083-101-105-117-133-NEC043-051-  
IAC021-035-041-059-093-119-141-143-149-167-193-261800-  
 
PROBABILISTIC HYDROLOGIC OUTLOOK  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
1145 PM CST THU FEB 13 2020  
   
..SPRING FLOOD OUTLOOK
 
 
THIS SPRING FLOOD OUTLOOK IS FOR THE RIVERS AND STREAMS IN SOUTHEAST  
SOUTH DAKOTA, SOUTHWEST MINNESOTA, NORTHWEST IOWA, AND EXTREME  
NORTHEAST NEBRASKA.  
 
DUE TO THE VERY WET CONDITIONS ACROSS THE AREA LAST SPRING AND  
SUMMER, ALONG WITH A VERY WET PREVIOUS YEAR IN 2018, THE CHANCES FOR  
MINOR, MODERATE, OR MAJOR FLOODING ARE ABOVE NORMAL THIS SPRING.  
 
THE FLOOD THREAT THROUGH THIS SPRING, BOTH IN LOCATION AND SEVERITY,  
WILL LARGELY BE DETERMINED BY FUTURE RAIN, FUTURE SNOWFALL, AND HOW  
FAST THE MELTING OF THE SNOWPACK OCCURS.  
 
THE OUTLOOK FOR THE NEXT 2 WEEKS SHOWS THAT THERE IS A HIGHER CHANCE  
FOR BELOW NORMAL PRECIPITATION ALONG WITH A HIGHER CHANCE FOR ABOVE  
NORMAL TEMPERATURES. THE 30 DAY OUTLOOK INTO MARCH SHOWS EQUAL  
CHANCES FOR ABOVE NORMAL, NORMAL, OR BELOW NORMAL PRECIPITATION AND  
TEMPERATURES. THE 90 DAY OUTLOOK THROUGH APRIL SHOWS A HIGHER CHANCE  
FOR ABOVE NORMAL PRECIPITATION ALONG WITH A HIGHER CHANCE FOR BELOW  
NORMAL TEMPERATURES.  
 
FOR MANY OF THE RIVERS IN THE AREA, THE CHANCES FOR MINOR, MODERATE,  
OR MAJOR FLOODING ARE ABOVE NORMAL. THE AREAS WITH THE GREATEST RISK  
OF MODERATE OR MAJOR FLOODING ARE THE JAMES RIVER, THE VERMILLION  
RIVER, THE BIG SIOUX RIVER, AND SPLIT ROCK CREEK.  
   
..CURRENT SNOW CONDITIONS
 
 
THE CURRENT SNOW PACK IS WIDESPREAD FOR ALL AREAS ALONG AND NORTH OF  
INTERSTATE 90. DEPTHS ARE GENERALLY 10 TO 20 INCHES IN THAT AREA,  
WITH SOME LOCATIONS BETWEEN HIGHWAY 14 AND HIGHWAY 212 HAVING 20 TO  
30 INCHES OF SNOW ON THE GROUND. THE WATER CONTENT OF THE SNOW PACK  
IN THIS AREA IS GENERALLY 2 TO 4 INCHES. AREAS BETWEEN I-90 AND  
HIGHWAY 18 GENERALLY HAVE 5 TO 10 INCHES OF SNOW ON THE GROUND, WITH  
A WATER CONTENT OF 1 TO 2 INCHES. AREAS SOUTH OF HIGHWAY 18  
GENERALLY HAVE LESS THAN 5 INCHES OF SNOW ON THE GROUND, WITH A  
WATER CONTENT OF 1 INCH OR LESS.  
   
..CURRENT SOIL CONDITIONS
 
 
SOILS IN THE AREA ARE GENERALLY FROZEN TO 1 TO 2 FEET DEEP. WITH THE  
WET CONDITIONS BOTH LAST YEAR AND IN 2018, SOILS ARE MUCH MORE  
SATURATED THAN NORMAL, WHICH WILL PREVENT THEM FROM SOAKING UP AS  
MUCH OF THE SNOW MELT WHEN IT OCCURS.  
   
..CURRENT RIVER CONDITIONS
 
 
RIVER LEVELS AND FLOWS ARE ABOVE NORMAL ACROSS THE REGION. MOST  
RIVERS ARE ICE COVERED, WITH THE EXCEPTION OF PORTIONS OF THE  
MISSOURI RIVER. ICE JAMS ARE POSSIBLE FOR ICE COVERED RIVERS AS WE  
HEAD INTO THE SPRING SINCE INCREASED FLOWS MAY RAISE AND BREAK UP  
THE RIVER ICE BEFORE IT MELTS.  
   
..PROBABILISTIC OUTLOOKS
 
 
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: 02/15/2020 - 05/15/2020  
 
: 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  
-------- ----- ----- ----- : --- --- --- --- --- ---  
:FLOYD RIVER  
SHELDON 12.0 14.0 16.0 : 23 29 7 10 <5 <5  
ALTON 12.0 16.0 18.0 : 66 39 27 15 <5 <5  
LE MARS 20.0 21.0 24.0 : 34 23 30 19 8 14  
:WEST BRANCH FLOYD RIVER  
STRUBLE 14.0 15.0 16.0 : 12 18 5 8 <5 <5  
:FLOYD RIVER  
MERRILL 12.0 14.0 16.0 : 8 15 5 9 <5 <5  
JAMES 26.0 30.0 34.0 : <5 <5 <5 <5 <5 <5  
:LITTLE SIOUX RIVER  
MILFORD 12.0 14.0 16.0 : >98 78 >98 73 79 62  
SPENCER 10.0 14.0 16.0 : >98 65 32 24 <5 5  
:OCHEYEDAN RIVER  
SPENCER 8.0 9.5 10.5 : 77 37 35 32 16 18  
:LITTLE SIOUX RIVER  
LINN GROVE 18.0 19.5 21.0 : 61 43 34 24 10 6  
CHEROKEE 17.0 21.0 24.0 : 63 44 24 18 <5 5  
CORRECTIONVILLE 19.0 21.0 23.0 : 32 19 14 15 10 8  
:WEST FORK DITCH  
HORNICK 20.0 22.0 26.5 : 33 26 22 21 7 6  
:PERRY CREEK  
SIOUX CITY 24.0 26.0 28.0 : <5 <5 <5 <5 <5 <5  
:BIG SIOUX RIVER  
BROOKINGS 9.0 10.5 12.0 : >98 51 >98 45 >98 32  
DELL RAPIDS 12.0 14.0 15.0 : >98 46 >98 40 77 31  
SIOUX FALLS I-90 12.0 15.0 17.0 : >98 58 >98 37 47 24  
:SKUNK CREEK  
SIOUX FALLS 11.5 15.0 17.0 : 52 20 12 7 5 <5  
:BIG SIOUX RIVER  
SIOUX FALLS N CLIFF 16.0 18.0 31.0 : >98 45 >98 42 <5 <5  
:SPLIT ROCK CREEK  
CORSON 8.5 11.0 14.0 : 87 35 51 27 27 16  
:ROCK RIVER  
LUVERNE 10.0 12.0 14.0 : 24 23 11 13 7 <5  
ROCK RAPIDS 13.0 16.0 19.0 : 87 48 36 24 19 18  
ROCK VALLEY 16.0 17.0 19.0 : 33 24 27 21 14 10  
:BIG SIOUX RIVER  
HAWARDEN 20.5 24.0 27.0 : >98 51 92 44 57 36  
AKRON 16.0 18.0 20.0 : >98 51 95 44 57 36  
SIOUX CITY 32.0 38.0 41.0 : 24 15 5 <5 <5 <5  
:JAMES RIVER  
HURON 11.0 13.0 15.0 : >98 45 >98 31 >98 27  
FORESTBURG 12.0 14.0 16.0 : >98 37 >98 32 >98 21  
MITCHELL 17.0 20.0 22.0 : >98 49 >98 35 >98 26  
:FIRESTEEL CREEK  
MOUNT VERNON 8.0 13.0 15.0 : >98 35 19 16 11 11  
:JAMES RIVER  
SCOTLAND 13.0 14.0 16.0 : >98 38 >98 32 >98 27  
YANKTON 12.0 14.0 16.0 : >98 32 >98 30 >98 28  
:WEST FORK VERMILLION RIVER  
PARKER 9.0 10.0 11.0 : 20 8 12 6 <5 <5  
:EAST FORK VERMILLION RIVER  
PARKER 12.0 14.0 16.0 : >98 41 >98 33 77 20  
:VERMILLION RIVER  
DAVIS 11.0 13.0 15.0 : >98 47 >98 34 36 11  
WAKONDA 14.0 15.5 17.0 : >98 43 >98 39 94 34  
VERMILLION 21.0 22.0 30.0 : 74 29 65 25 <5 <5  
:REDWOOD RIVER  
MARSHALL 14.0 15.0 16.5 : 42 16 28 11 13 8  
:WEST FORK DES MOINES RIVER  
JACKSON 12.0 12.5 14.0 : 33 9 13 <5 <5 <5  
:MISSOURI RIVER  
SOUTH SIOUX CITY 30.0 33.0 36.0 : 22 5 16 <5 8 <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: 02/15/2020 - 05/15/2020  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
:FLOYD RIVER  
SHELDON 7.7 8.4 9.2 10.1 11.6 13.6 14.5  
ALTON 8.8 9.4 11.4 13.5 16.2 16.7 17.3  
LE MARS 13.1 13.5 15.3 17.3 21.2 23.5 24.4  
:WEST BRANCH FLOYD RIVER  
STRUBLE 6.4 7.0 9.1 10.5 13.2 14.2 15.0  
:FLOYD RIVER  
MERRILL 2.6 2.9 4.5 6.2 8.9 11.9 14.0  
JAMES 10.9 11.3 12.7 14.5 17.0 20.1 22.9  
:LITTLE SIOUX RIVER  
MILFORD 15.3 15.6 16.2 17.4 20.0 23.0 23.9  
SPENCER 11.1 11.4 11.8 13.0 14.3 15.3 15.8  
:OCHEYEDAN RIVER  
SPENCER 6.8 7.4 8.0 8.9 10.0 10.7 11.3  
:LITTLE SIOUX RIVER  
LINN GROVE 15.0 15.8 16.8 18.7 20.0 21.0 21.4  
CHEROKEE 14.1 14.7 16.0 18.5 21.0 22.2 23.7  
CORRECTIONVILLE 11.6 12.2 13.5 16.8 19.3 23.1 24.4  
:WEST FORK DITCH  
HORNICK 11.3 12.6 14.1 17.7 21.4 24.7 28.1  
:PERRY CREEK  
SIOUX CITY 8.1 8.2 8.7 9.4 10.7 15.0 16.1  
:BIG SIOUX RIVER  
BROOKINGS 12.6 12.7 12.9 13.2 13.5 13.8 13.9  
DELL RAPIDS 14.3 14.4 15.1 15.5 16.3 16.6 17.8  
SIOUX FALLS I-90 15.0 15.1 16.3 16.9 18.5 18.9 19.6  
:SKUNK CREEK  
SIOUX FALLS 8.8 9.6 10.1 11.8 13.2 15.6 17.1  
:BIG SIOUX RIVER  
SIOUX FALLS N CLIFF 18.3 18.9 21.1 23.2 24.5 25.4 27.6  
:SPLIT ROCK CREEK  
CORSON 6.9 7.7 9.6 11.2 14.1 16.5 18.4  
:ROCK RIVER  
LUVERNE 6.5 6.7 7.2 7.9 9.7 12.8 14.1  
ROCK RAPIDS 12.5 12.7 13.5 14.4 17.4 22.4 24.7  
ROCK VALLEY 11.5 12.0 12.5 14.3 17.6 19.3 20.2  
:BIG SIOUX RIVER  
HAWARDEN 23.3 24.3 25.2 28.1 32.0 34.8 36.2  
AKRON 17.9 18.4 19.0 20.5 22.1 22.9 23.4  
SIOUX CITY 23.8 24.5 25.3 27.8 31.9 35.4 37.6  
:JAMES RIVER  
HURON 17.2 17.6 19.2 20.3 22.4 22.6 23.6  
FORESTBURG 16.5 17.2 18.3 19.1 21.6 22.6 23.3  
MITCHELL 23.6 23.8 24.5 24.9 25.9 26.8 27.4  
:FIRESTEEL CREEK  
MOUNT VERNON 8.8 9.1 10.0 11.3 12.1 15.7 16.9  
:JAMES RIVER  
SCOTLAND 17.3 17.6 18.5 19.1 20.7 22.1 22.5  
YANKTON 18.4 18.9 20.5 21.3 24.1 26.5 27.2  
:WEST FORK VERMILLION RIVER  
PARKER 3.1 3.2 4.3 6.1 7.7 10.1 10.6  
:EAST FORK VERMILLION RIVER  
PARKER 14.9 15.5 16.2 17.5 18.9 19.8 20.4  
:VERMILLION RIVER  
DAVIS 13.5 13.7 14.2 14.8 15.3 15.6 15.8  
WAKONDA 17.0 17.0 17.1 17.2 17.4 17.5 17.5  
VERMILLION 17.2 18.1 20.8 24.0 27.6 29.1 29.6  
:REDWOOD RIVER  
MARSHALL 12.3 12.4 13.0 13.6 15.2 16.9 17.8  
:WEST FORK DES MOINES RIVER  
JACKSON 10.9 11.0 11.1 11.6 12.2 12.6 13.8  
:MISSOURI RIVER  
SOUTH SIOUX CITY 18.8 18.9 20.7 23.0 28.7 35.0 38.9  
 
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: 02/15/2020 - 05/15/2020  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
:FLOYD RIVER  
SHELDON 4.0 4.0 4.0 4.0 4.0 4.0 4.0  
ALTON 5.8 5.8 5.8 5.8 5.7 5.7 5.7  
LE MARS 8.6 8.6 8.6 8.6 8.3 8.1 8.1  
:WEST BRANCH FLOYD RIVER  
STRUBLE 4.9 4.9 4.9 4.9 4.8 4.8 4.8  
:FLOYD RIVER  
MERRILL 0.3 0.3 0.3 0.3 0.2 0.0 0.0  
JAMES 9.1 9.1 9.1 9.1 9.1 8.9 8.8  
:LITTLE SIOUX RIVER  
MILFORD 7.8 7.8 7.8 7.7 7.5 7.5 7.4  
SPENCER 5.1 5.1 5.0 4.8 4.6 4.5 4.4  
:OCHEYEDAN RIVER  
SPENCER 2.6 2.6 2.6 2.5 2.4 2.4 2.3  
:LITTLE SIOUX RIVER  
LINN GROVE 6.8 6.7 6.7 6.7 6.5 6.4 6.4  
CHEROKEE 5.9 5.9 5.9 5.9 5.9 5.8 5.7  
CORRECTIONVILLE 5.3 5.3 5.2 5.2 5.2 5.2 5.1  
:WEST FORK DITCH  
HORNICK 6.2 6.2 6.2 6.1 6.0 5.9 5.8  
:PERRY CREEK  
SIOUX CITY 7.1 7.1 7.1 7.1 7.1 7.1 7.1  
:BIG SIOUX RIVER  
BROOKINGS 4.0 4.0 4.0 3.9 3.9 3.8 3.8  
DELL RAPIDS 4.9 4.9 4.9 4.9 4.8 4.7 4.7  
SIOUX FALLS I-90 10.2 10.2 10.2 10.1 10.1 10.1 10.1  
:SKUNK CREEK  
SIOUX FALLS 3.9 3.9 3.9 3.9 3.8 3.8 3.7  
:BIG SIOUX RIVER  
SIOUX FALLS N CLIFF 7.8 7.8 7.8 7.8 7.6 7.6 7.5  
:SPLIT ROCK CREEK  
CORSON 2.5 2.5 2.5 2.5 2.4 2.3 2.2  
:ROCK RIVER  
LUVERNE 4.5 4.5 4.5 4.4 4.4 4.4 4.4  
ROCK RAPIDS 7.9 7.9 7.9 7.9 7.9 7.9 7.8  
ROCK VALLEY 3.3 3.3 3.3 3.3 3.2 3.1 3.0  
:BIG SIOUX RIVER  
HAWARDEN 13.5 13.5 13.5 13.5 13.4 13.2 13.1  
AKRON 7.7 7.7 7.6 7.6 7.5 7.3 7.1  
SIOUX CITY 14.9 14.8 14.8 14.7 14.7 14.5 14.4  
:JAMES RIVER  
HURON 10.1 10.0 10.0 10.0 10.0 10.0 10.0  
FORESTBURG 8.4 8.3 8.3 8.3 8.1 7.9 7.9  
MITCHELL 14.5 14.5 14.5 14.5 14.4 14.1 13.9  
:FIRESTEEL CREEK  
MOUNT VERNON 2.0 2.0 2.0 2.0 2.0 2.0 2.0  
:JAMES RIVER  
SCOTLAND 9.0 9.0 9.0 8.9 8.9 7.7 7.2  
YANKTON 5.4 5.3 5.3 5.2 5.2 5.2 5.2  
:WEST FORK VERMILLION RIVER  
PARKER 0.1 0.1 0.1 0.1 0.1 0.0 0.0  
:EAST FORK VERMILLION RIVER  
PARKER 4.0 4.0 4.0 4.0 4.0 4.0 4.0  
:VERMILLION RIVER  
DAVIS 3.3 3.2 3.2 3.2 3.2 3.2 3.2  
WAKONDA 4.4 4.4 4.4 4.4 4.4 4.3 4.3  
VERMILLION 3.1 3.1 3.1 3.1 3.1 3.0 2.9  
:REDWOOD RIVER  
MARSHALL 6.8 6.8 6.8 6.8 6.8 6.8 6.7  
:WEST FORK DES MOINES RIVER  
JACKSON 8.0 8.0 8.0 8.0 7.9 7.8 7.8  
:MISSOURI RIVER  
SOUTH SIOUX CITY 12.3 12.3 12.3 12.3 12.2 12.1 12.0  
 
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/FSD FOR MORE WEATHER AND WATER  
INFORMATION.  
 
THE NEXT OUTLOOK WILL BE ISSUED THURSDAY FEBRUARY 27, 2020.  
 

 
 
VANDENBOOGART  
 
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