141
FGUS73 KFSD 271611
ESFFSD
IAC021-035-041-059-093-119-141-143-149-167-193-MNC033-063-081-083-
101-105-117-133-NEC043-051-SDC003-005-009-011-015-023-027-035-043-
053-061-067-073-077-079-083-087-097-099-101-111-125-127-135-011600-
PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1011 AM CST THU FEB 27 2025
..SPRING FLOOD AND WATER RESOURCE OUTLOOK
THIS SPRING FLOOD AND WATER RESOURCE OUTLOOK IS FOR THE SIOUX FALLS
HYDROLOGIC SERVICE AREA (HSA), WHICH COVERS PORTIONS OF CENTRAL AND
SOUTHEASTERN SOUTH DAKOTA, SOUTHWESTERN MINNESOTA, NORTHWESTERN IOWA
AND FAR NORTHEAST NEBRASKA. THE MAIN RIVER BASINS INCLUDE THE
MISSOURI, JAMES, BIG SIOUX, VERMILLION, REDWOOD, WEST FORK OF THE
DES MOINES, LITTLE SIOUX, ROCK, FLOYD RIVERS.
FLOOD OUTLOOK SUMMARY
A LACK OF EXISTING SNOW COVER, COMBINED WITH DRIER ANTECEDENT SOILS,
POINT TOWARD A BELOW NORMAL FLOOD RISK THIS SPRING. WITH THIS SAID,
SUBSTANTIAL FROST DEPTHS ACROSS THE REGION WOULD BRING CONCERN FOR
INCREASED RUNOFF SHOULD A HEAVY SPRING RAIN EVENT OCCUR PRIOR TO
REMOVAL OF FROST FROM THE GROUND. SOME THAWING OF THE TOP LAYER HAS
RECENTLY OCCURRED. PRECIPITATION TRENDS INTO EARLY SPRING WILL
CONTINUE TO BE MONITORED AND WILL LIKELY BE THE PRIMARY DRIVER FOR
FUTURE FLOOD OUTLOOKS.
TEMPERATURE AND PRECIPITATION
PRECIPITATION OVER THE PAST 90 DAYS HAS GENERALLY BEEN BELOW NORMAL
OVER MUCH OF THE REGION WITH EVEN LARGER PRECIPITATION DEFICITS
EXIST WHEN LOOKING ACROSS THE ENTIRE WATER YEAR. MANY LOCATIONS
SINCE OCT 1ST ARE 1TO 2 INCHES BELOW NORMAL IN TERMS OF
PRECIPITATION. TEMPERATURES OVER THE PAST 90 DAYS HAVE TRENDED ON
THE COOL SIDE OF NORMAL.
THE NEXT CHANCE FOR MEANINGFUL PRECIPITATION ARRIVES MARCH 4TH AND
5TH. UNCERTAINTY REMAINS ON THE TRACK, AMOUNTS, AND PRECIPITATION
TYPE WITH THIS SYSTEM AND WILL CONTINUE TO BE MONITORED. AT THIS
TIME, THIS PRECIPITATION IS NOT EXPECTED TO RESULT IN RIVER FLOODING.
MEDIUM RANGE OUTLOOKS INTO MID TO LATE MARCH FAVOR A SLIGHTLY
INCREASED ODDS OF ABOVE NORMAL TEMPERATURES WITH NO CLEAR SIGNAL IN
TERMS OF PRECIPITATION.
SNOW COVER AND LIQUID WATER CONTENT
RECENT WARMTH HAS MELTED THE SNOWPACK ACROSS THE BROADER REGION
WITH ALL IMMEDIATE DRAINAGE BASINS NOW SNOW-FREE.
MOUNTAIN SNOWPACK AND ASSOCIATED SNOW WATER EQUIVALENT (SWE) ABOVE
FORT PECK ON THE MISSOURI RIVER IS ROUGHLY 93% OF AVERAGE ACCORDING
TO THE USACE. SIMILARLY, MOUNTAIN SWE IN THE FORT PECK TO GARRISON
REACH IS ROUGHLY 97% OF AVERAGE.
SOIL CONDITIONS AND FROST DEPTH
A COUPLE OF RAIN EVENTS IN NOVEMBER AND DECEMBER THAT LARGELY FELL
ON UNFROZEN GROUND ALLOWED FOR SOME BENEFICIAL MOISTURE TO BE
TRAPPED IN THE SOILS. WITH THIS SAID, SOIL MOISTURE DEFICITS WERE
ALREADY IN PLACE WITH SOIL MOISTURE ANOMALIES STILL REFLECTING DRIER
THAN NORMAL SOILS.
RIVER AND LAKE CONDITIONS
ENTERING THE WINTER FREEZE-UP MONTHS, RIVER LEVELS AND STREAMFLOW
WERE GENERALLY RUNNING NEAR NORMAL IN MOST LOCATIONS. MOST AREA
STREAMS AND RIVERS STILL CONTAIN SUBSTANTIAL RIVER ICE ALTHOUGH
RECENT WARMTH HAS BEGUN THE PROCESS OF ICE ROTTING IN PLACE.
PROBABILISTIC OUTLOOKS
IN TABLE 1 BELOW, THE CURRENT (CS) AND HISTORICAL (HS) OR NORMAL
PROBABILITIES OF EXCEEDING MINOR...MODERATE...AND MAJOR FLOOD STAGE
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 GREATER 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: 03/03/2025 - 05/30/2025
: 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 : <5 36 <5 23 <5 <5
ALTON 12.0 16.0 22.0 : 5 42 <5 23 <5 <5
LE MARS 20.0 21.0 26.0 : <5 20 <5 12 <5 <5
:WEST BRANCH FLOYD RIVER
STRUBLE 14.0 15.0 18.0 : <5 8 <5 5 <5 <5
:FLOYD RIVER
MERRILL 12.0 14.0 16.0 : <5 10 <5 8 <5 7
JAMES 26.0 30.0 34.0 : <5 6 <5 <5 <5 <5
:LITTLE SIOUX RIVER
MILFORD 13.0 16.0 20.0 : 13 75 <5 53 <5 6
SPENCER 10.0 14.0 16.0 : 12 69 <5 8 <5 <5
:OCHEYEDAN RIVER
SPENCER 8.0 9.5 10.5 : <5 43 <5 13 <5 6
:LITTLE SIOUX RIVER
LINN GROVE 16.5 20.0 22.5 : <5 43 <5 <5 <5 <5
CHEROKEE 17.0 21.0 24.0 : <5 50 <5 6 <5 <5
CORRECTIONVILLE 19.0 21.0 23.0 : <5 10 <5 7 <5 <5
:WEST FORK DITCH
:PERRY CREEK
SIOUX CITY 24.0 26.0 28.0 : <5 <5 <5 <5 <5 <5
:BIG SIOUX RIVER
BROOKINGS 9.0 10.5 15.0 : 10 46 <5 34 <5 <5
DELL RAPIDS 12.0 14.0 15.0 : 7 43 <5 18 <5 16
SIOUX FALLS I-90 12.0 15.0 17.0 : 6 43 <5 17 <5 8
:SKUNK CREEK
SIOUX FALLS 12.0 15.0 17.0 : 6 43 <5 17 <5 8
:BIG SIOUX RIVER
SIOUX FALLS N CLIFF 16.0 18.0 31.0 : <5 22 <5 18 <5
<5
:SPLIT ROCK CREEK
CORSON 8.5 11.0 14.0 : <5 16 <5 10 <5 <5
:ROCK RIVER
LUVERNE 10.0 12.0 14.0 : <5 15 <5 10 <5 <5
ROCK RAPIDS 13.0 16.0 19.0 : 9 36 <5 20 <5 9
ROCK VALLEY 16.0 17.0 19.0 : <5 17 <5 12 <5 <5
:BIG SIOUX RIVER
HAWARDEN 20.5 24.0 30.0 : 17 51 5 31 <5 8
AKRON 16.0 18.0 20.0 : 12 51 <5 29 <5 17
SIOUX CITY 32.0 38.0 41.0 : <5 <5 <5 <5 <5 <5
:JAMES RIVER
HURON 11.5 15.0 19.0 : 14 55 10 41 5 30
FORESTBURG 12.0 14.5 18.0 : 18 56 12 43 5 29
MITCHELL 17.0 21.5 24.0 : 19 58 8 39 <5 28
:FIRESTEEL CREEK
MOUNT VERNON 8.0 13.0 15.0 : 14 38 5 24 <5 20
:JAMES RIVER
SCOTLAND 13.0 16.0 18.0 : 13 51 10 39 5 32
YANKTON 12.0 16.0 21.0 : 11 41 7 37 <5 27
:WEST FORK VERMILLION RIVER
PARKER 9.0 10.0 12.0 : <5 12 <5 10 <5 <5
:EAST FORK VERMILLION RIVER
PARKER 12.0 14.0 16.5 : 11 48 10 41 <5 31
:VERMILLION RIVER
DAVIS 11.0 13.0 15.0 : 15 49 12 41 <5 16
WAKONDA 14.0 15.5 17.0 : 14 48 13 46 10 40
VERMILLION 21.0 22.0 30.0 : <5 36 <5 26 <5 <5
:REDWOOD RIVER
MARSHALL 14.0 17.0 18.5 : 6 14 <5 7 <5 <5
:WEST FORK DES MOINES RIVER
AVOCA 1425.0 1426.0 1428.0 : <5 13 <5 10 <5 <5
WINDOM 19.0 21.0 25.0 : <5 11 <5 7 <5 <5
JACKSON 12.0 12.5 14.0 : <5 9 <5 7 <5 <5
:MISSOURI RIVER
SOUTH SIOUX CITY 30.0 33.0 36.0 : <5 9 <5 8 <5 6
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: 03/03/2025 - 05/30/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:FLOYD RIVER
SHELDON 5.4 5.5 6.1 6.7 8.2 9.8 11.4
ALTON 6.3 6.4 6.7 7.3 8.4 9.8 12.3
LE MARS 10.6 10.7 11.3 13.5 14.8 16.3 18.7
:WEST BRANCH FLOYD RIVER
STRUBLE 3.8 4.0 4.3 5.4 6.2 8.0 10.2
:FLOYD RIVER
MERRILL 0.4 0.4 0.9 2.3 3.5 4.7 7.7
JAMES 8.9 9.0 9.2 10.2 11.3 12.4 15.6
:LITTLE SIOUX RIVER
MILFORD 7.1 7.3 7.6 9.9 11.0 14.4 15.5
SPENCER 4.3 4.4 5.3 7.8 8.7 10.8 11.5
:OCHEYEDAN RIVER
SPENCER 2.5 2.6 3.1 3.9 4.6 6.2 7.6
:LITTLE SIOUX RIVER
LINN GROVE 5.7 5.8 6.4 7.8 8.9 11.7 13.1
CHEROKEE 8.0 8.2 9.1 10.5 12.2 13.6 15.1
CORRECTIONVILLE 5.2 5.4 6.2 7.1 9.3 10.7 14.2
:WEST FORK DITCH
:PERRY CREEK
SIOUX CITY 7.2 7.3 7.6 7.8 8.4 8.9 9.5
:BIG SIOUX RIVER
BROOKINGS 2.6 2.6 3.0 4.1 5.8 8.9 9.8
DELL RAPIDS 3.5 3.7 4.1 5.1 8.0 10.9 12.6
SIOUX FALLS I-90 4.3 4.8 5.5 6.6 9.8 11.2 12.2
:SKUNK CREEK
SIOUX FALLS 4.3 4.8 5.5 6.6 9.8 11.2 12.2
:BIG SIOUX RIVER
SIOUX FALLS N CLIFF 6.1 6.4 6.9 7.5 9.9 13.1 15.1
:SPLIT ROCK CREEK
CORSON 2.0 2.1 2.3 3.1 4.8 6.6 7.1
:ROCK RIVER
LUVERNE 3.4 3.4 3.7 4.2 5.4 7.7 8.4
ROCK RAPIDS 7.2 7.4 8.2 8.6 10.2 12.7 13.7
ROCK VALLEY 4.6 4.7 5.0 6.0 8.9 11.0 12.9
:BIG SIOUX RIVER
HAWARDEN 12.4 12.9 13.6 14.5 19.5 20.9 23.6
AKRON 5.2 5.9 6.9 8.6 15.2 16.3 17.5
SIOUX CITY 8.6 9.1 9.8 11.2 15.9 17.8 18.8
:JAMES RIVER
HURON 9.1 9.1 9.1 9.6 10.4 14.8 18.3
FORESTBURG 4.4 4.4 4.4 6.0 10.2 15.0 17.5
MITCHELL 10.3 10.3 10.3 11.9 14.7 20.4 23.5
:FIRESTEEL CREEK
MOUNT VERNON 2.1 2.1 2.1 2.8 5.2 11.0 13.5
:JAMES RIVER
SCOTLAND 4.2 4.2 4.4 5.3 8.1 16.0 18.3
YANKTON 2.7 2.7 2.8 3.5 4.7 13.9 19.0
:WEST FORK VERMILLION RIVER
PARKER 1.0 1.0 1.0 1.7 2.6 4.6 5.9
:EAST FORK VERMILLION RIVER
PARKER 3.2 3.2 3.2 4.0 7.3 13.6 14.7
:VERMILLION RIVER
DAVIS 2.3 2.3 2.3 3.5 7.2 13.4 13.8
WAKONDA 2.0 2.0 2.6 5.1 7.9 16.9 17.2
VERMILLION 2.0 2.0 2.1 3.1 6.7 17.3 19.6
:REDWOOD RIVER
MARSHALL 7.3 7.7 8.0 8.7 10.2 12.9 14.7
:WEST FORK DES MOINES RIVER
AVOCA 1419.0 1419.3 1419.5 1420.0 1420.4 1421.8 1423.0
WINDOM 11.4 11.6 11.8 12.3 13.1 15.6 16.0
JACKSON 8.2 8.3 8.5 8.8 9.4 10.2 10.4
:MISSOURI RIVER
SOUTH SIOUX CITY 10.9 11.0 11.8 12.6 12.9 18.7 25.3
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: 03/03/2025 - 05/30/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:FLOYD RIVER
SHELDON 4.2 4.2 4.2 4.2 4.1 4.1 4.1
ALTON 5.1 5.1 5.1 5.1 5.1 5.1 5.1
LE MARS 9.7 9.7 9.7 9.7 9.6 9.6 9.6
:WEST BRANCH FLOYD RIVER
STRUBLE 3.4 3.4 3.3 3.3 3.3 3.3 3.3
:FLOYD RIVER
MERRILL 0.0 0.0 0.0 0.0 0.0 0.0 0.0
JAMES 8.4 8.4 8.4 8.3 8.3 8.2 8.2
:LITTLE SIOUX RIVER
MILFORD 5.8 5.8 5.7 5.5 5.5 5.5 5.5
SPENCER 3.3 3.3 3.2 3.1 3.1 3.0 3.0
:OCHEYEDAN RIVER
SPENCER 1.9 1.9 1.8 1.7 1.6 1.2 1.1
:LITTLE SIOUX RIVER
LINN GROVE 5.1 5.1 5.1 5.0 5.0 4.9 4.9
CHEROKEE 5.6 5.6 5.5 5.3 5.1 4.5 3.7
CORRECTIONVILLE 4.9 4.9 4.9 4.9 4.8 4.8 4.8
:WEST FORK DITCH
:PERRY CREEK
SIOUX CITY 5.4 5.4 5.4 5.2 5.0 5.0 5.0
:BIG SIOUX RIVER
BROOKINGS 1.6 1.5 1.5 1.4 1.4 1.4 1.4
DELL RAPIDS 3.0 3.0 3.0 3.0 3.0 3.0 3.0
SIOUX FALLS I-90 3.2 3.2 3.1 3.1 3.0 3.0 3.0
:SKUNK CREEK
SIOUX FALLS 3.2 3.2 3.1 3.1 3.0 3.0 3.0
:BIG SIOUX RIVER
SIOUX FALLS N CLIFF 5.3 5.2 5.1 4.9 4.7 4.7 4.7
:SPLIT ROCK CREEK
CORSON 1.9 1.9 1.9 1.9 1.9 1.9 1.9
:ROCK RIVER
LUVERNE 3.4 3.4 3.4 3.4 3.4 3.4 3.4
ROCK RAPIDS 6.8 6.8 6.8 6.8 6.8 6.8 6.8
ROCK VALLEY 4.2 3.4 3.2 3.1 3.0 3.0 3.0
:BIG SIOUX RIVER
HAWARDEN 11.5 11.5 11.4 11.3 11.2 11.1 11.1
AKRON 4.0 4.0 3.9 3.8 3.6 3.5 3.5
SIOUX CITY 7.5 7.5 7.4 7.4 7.4 7.4 7.4
:JAMES RIVER
HURON 9.1 9.1 9.1 9.1 9.1 9.1 9.1
FORESTBURG 4.4 4.3 4.3 4.3 4.3 4.2 4.2
MITCHELL 10.2 10.2 10.2 10.2 10.1 9.9 9.9
:FIRESTEEL CREEK
MOUNT VERNON 2.1 2.1 2.1 2.1 2.1 2.1 2.1
:JAMES RIVER
SCOTLAND 4.2 4.2 4.2 4.2 4.1 4.1 4.1
YANKTON 2.7 2.7 2.7 2.7 2.7 2.6 2.6
:WEST FORK VERMILLION RIVER
PARKER 1.0 1.0 0.9 0.8 0.8 0.8 0.8
:EAST FORK VERMILLION RIVER
PARKER 3.2 3.2 3.2 3.1 3.1 3.1 3.1
:VERMILLION RIVER
DAVIS 2.3 2.3 2.3 2.3 2.2 2.2 2.2
WAKONDA 2.0 2.0 1.9 1.8 1.8 1.8 1.8
VERMILLION 2.0 2.0 2.0 2.0 2.0 2.0 2.0
:REDWOOD RIVER
MARSHALL 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:WEST FORK DES MOINES RIVER
AVOCA 0.1 0.1 0.1 0.0 0.0 0.0 0.0
WINDOM 0.1 0.1 0.1 0.1 0.1 0.0 0.0
JACKSON 0.1 0.1 0.1 0.1 0.1 0.0 0.0
:MISSOURI RIVER
SOUTH SIOUX CITY 5.2 5.0 4.9 4.9 4.8 4.8 3.8
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 BY MARCH 13TH.
KALIN
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