Flood Potential Outlook
Issued by NWS Sioux Falls, SD

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FGUS73 KFSD 231317
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-
IAC021-035-041-059-093-119-141-143-149-167-193-221800-

Probabilistic Hydrologic Outlook
National Weather Service Sioux Falls SD
814 AM CDT Thu Apr 23 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:  04/25/2020  - 07/24/2020

                                       :    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 :  22   33   20   15   <5    5
Alton               12.0   16.0   18.0 :  55   32   24   11    5   <5
Le Mars             20.0   21.0   24.0 :  22   19   15   15   <5   <5
:West Branch Floyd River
Struble             14.0   15.0   16.0 :  21    5   13   <5   <5   <5
:Floyd River
Merrill             12.0   14.0   16.0 :  12    8    6    5   <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 :  89   90   74   75   61   58
Spencer             10.0   14.0   16.0 :  79   71   20   26    8    8
:Ocheyedan River
Spencer              8.0    9.5   10.5 :  45   45   19   28   14   11
:Little Sioux River
Linn Grove          18.0   19.5   21.0 :  20   33    8   11    6    7
Cherokee            17.0   21.0   24.0 :  48   55   11   21   <5    6
Correctionville     19.0   21.0   23.0 :  29   23   20   20   11   13
:West Fork Ditch
Hornick             20.0   22.0   26.5 :  42   43   30   26    8    5
: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 :  77   52   67   37   44   26
Dell Rapids         12.0   14.0   15.0 :  69   45   42   22   30   16
Sioux Falls I-90    12.0   15.0   17.0 :  69   46   34   18   14    8
:Skunk Creek
Sioux Falls         11.5   15.0   17.0 :  13    6   <5   <5   <5   <5
:Big Sioux River
Sioux Falls N Cliff 16.0   18.0   31.0 :  52   32   38   19   <5   <5
:Split Rock Creek
Corson               8.5   11.0   14.0 :  33   24   19   13   11    6
:Rock River
Luverne             10.0   12.0   14.0 :  14   12    8    5   <5   <5
Rock Rapids         13.0   16.0   19.0 :  44   38   20   16    8    5
Rock Valley         16.0   17.0   19.0 :  23   20   10   12   <5   <5
:Big Sioux River
Hawarden            20.5   24.0   27.0 :  76   54   47   31   30   21
Akron               16.0   18.0   20.0 :  76   54   47   33   22   20
Sioux City          32.0   38.0   41.0 :   7    7   <5   <5   <5   <5
:James River
Huron               11.0   13.0   15.0 : >98   47  >98   36   39   29
Forestburg          12.0   14.0   16.0 : >98   39  >98   33   17   21
Mitchell            17.0   20.0   22.0 : >98   40   61   35   35   23
:Firesteel Creek
Mount Vernon         8.0   13.0   15.0 :  66   40   14   11    7    8
:James River
Scotland            13.0   14.0   16.0 : >98   36   59   35   38   25
Yankton             12.0   14.0   16.0 :  58   35   42   29   33   24
:West Fork Vermillion River
Parker               9.0   10.0   11.0 :   9    7   <5    6   <5   <5
:East Fork Vermillion River
Parker              12.0   14.0   16.0 :  35   19   22   16   13    8
:Vermillion River
Davis               11.0   13.0   15.0 :  44   32   29   20    6    7
Wakonda             14.0   15.5   17.0 :  50   36   49   31   31   23
Vermillion          21.0   22.0   30.0 :  11   13   10   12   <5   <5
:Redwood River
Marshall            14.0   15.0   16.5 :  16    8   10    6    7    5
:West Fork Des Moines River
Jackson             12.0   12.5   14.0 :   7    6    6   <5   <5   <5
:Missouri River
South Sioux City    30.0   33.0   36.0 :   5    7   <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: 04/25/2020  - 07/24/2020
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Floyd River
Sheldon               5.1    5.5    7.9    8.9   11.0   14.6   15.6
Alton                 7.7    9.2   10.3   12.6   15.8   17.2   18.0
Le Mars              12.8   13.6   14.4   16.4   19.8   21.4   22.2
:West Branch Floyd River
Struble               6.0    7.7    8.7   10.5   13.0   15.2   15.4
:Floyd River
Merrill               2.3    3.1    4.4    6.0    9.4   12.8   14.6
James                10.9   11.5   12.8   14.2   17.3   21.7   23.6
:Little Sioux River
Milford              10.6   11.6   13.8   16.4   18.1   23.9   29.1
Spencer               8.9    9.3   10.7   12.2   13.2   15.3   17.1
:Ocheyedan River
Spencer               4.7    5.6    6.4    7.8    9.1   11.1   12.6
:Little Sioux River
Linn Grove           10.9   12.0   13.5   16.7   17.7   19.1   21.6
Cherokee             11.6   12.3   13.6   16.9   18.4   22.0   23.9
Correctionville       9.1   10.0   12.3   15.3   19.9   23.6   24.7
:West Fork Ditch
Hornick              10.0   11.9   13.7   18.3   22.8   25.4   27.7
:Perry Creek
Sioux City            7.2    7.9    8.2    8.6    9.1   10.8   19.5
:Big Sioux River
Brookings             7.0    7.3    9.4   11.4   12.9   13.3   14.1
Dell Rapids           8.8    9.2   10.7   13.3   15.1   16.5   17.3
Sioux Falls I-90     10.4   10.4   11.2   13.0   15.6   18.6   19.2
:Skunk Creek
Sioux Falls           5.1    5.6    6.7    8.4    9.5   12.5   13.7
:Big Sioux River
Sioux Falls N Cliff  10.4   10.6   13.2   16.2   20.4   24.7   26.1
:Split Rock Creek
Corson                4.5    4.9    6.0    7.4    9.3   14.8   17.8
:Rock River
Luverne               4.9    5.2    6.0    6.9    8.2   11.4   13.4
Rock Rapids          10.0   10.0   11.8   12.6   15.3   18.4   21.7
Rock Valley           7.5    8.2   10.4   12.6   15.8   17.2   18.2
:Big Sioux River
Hawarden             17.1   18.4   20.6   22.9   27.3   31.7   34.1
Akron                12.6   14.1   16.2   17.6   20.0   22.3   23.2
Sioux City           16.3   17.1   19.2   21.3   25.1   30.9   33.6
:James River
Huron                14.2   14.2   14.2   14.2   16.3   18.2   21.8
Forestburg           14.3   14.3   14.3   14.5   15.6   17.5   21.2
Mitchell             19.8   19.8   19.8   21.1   22.6   24.3   25.6
:Firesteel Creek
Mount Vernon          3.2    3.2    3.6   11.0   11.8   13.5   15.8
:James River
Scotland             13.5   13.5   13.5   14.8   17.1   18.9   20.0
Yankton              10.9   10.9   10.9   12.8   17.7   20.9   22.7
:West Fork Vermillion River
Parker                1.9    1.9    2.0    3.5    5.4    8.7    9.4
:East Fork Vermillion River
Parker                6.7    6.7    6.8    8.9   13.1   17.2   18.4
:Vermillion River
Davis                 7.5    7.5    7.5   10.3   13.3   14.6   15.2
Wakonda               9.1    9.1    9.1   14.4   17.0   17.2   17.3
Vermillion            7.8    7.8    7.8   12.5   18.2   22.7   26.4
:Redwood River
Marshall              8.3    8.3    8.9   10.5   12.6   15.2   17.2
:West Fork Des Moines River
Jackson               9.1    9.1    9.3   10.2   10.8   11.4   12.8
:Missouri River
South Sioux City     15.0   15.0   16.0   18.4   24.3   28.0   29.6

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: 04/25/2020  - 07/24/2020
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Floyd River
Sheldon               4.5    4.5    4.5    4.4    4.4    4.3    4.3
Alton                 6.2    6.1    6.0    5.9    5.8    5.8    5.8
Le Mars              10.3    9.8    9.6    9.1    8.8    8.7    8.6
:West Branch Floyd River
Struble               4.7    4.6    4.5    4.4    4.3    4.3    4.3
:Floyd River
Merrill               1.2    1.1    1.0    0.7    0.5    0.4    0.4
James                 9.6    9.4    9.4    9.2    9.1    9.1    9.1
:Little Sioux River
Milford               9.0    8.9    8.7    8.3    7.9    7.8    7.7
Spencer               7.0    6.3    5.9    5.2    4.7    4.5    4.3
:Ocheyedan River
Spencer               3.3    3.1    2.9    2.7    2.5    2.4    2.3
:Little Sioux River
Linn Grove            8.6    7.7    6.6    5.9    5.4    5.1    5.0
Cherokee              8.5    6.5    4.6    2.9    2.0    2.0    2.0
Correctionville       6.7    6.5    6.1    5.6    5.2    4.9    4.9
:West Fork Ditch
Hornick               6.8    6.7    6.5    6.4    6.1    6.0    6.0
:Perry Creek
Sioux City            7.1    7.1    7.1    7.0    6.9    6.7    6.6
:Big Sioux River
Brookings             4.4    4.3    4.0    3.9    3.7    3.6    3.6
Dell Rapids           5.8    5.7    5.3    5.1    4.9    4.7    4.7
Sioux Falls I-90      7.4    7.3    6.8    6.5    6.2    6.0    5.9
:Skunk Creek
Sioux Falls           4.4    4.3    4.1    4.1    4.0    4.0    4.0
:Big Sioux River
Sioux Falls N Cliff   8.0    7.9    7.5    7.3    7.1    7.0    6.9
:Split Rock Creek
Corson                2.5    2.4    2.2    2.2    2.1    2.1    2.1
:Rock River
Luverne               4.6    4.6    4.5    4.5    4.5    4.5    4.4
Rock Rapids           8.6    8.3    8.1    8.1    7.9    7.8    7.8
Rock Valley           5.8    5.5    5.0    4.8    4.6    4.5    4.5
:Big Sioux River
Hawarden             15.0   14.3   13.7   13.4   13.1   12.8   12.8
Akron                 9.3    8.3    7.4    7.0    6.6    6.2    6.1
Sioux City           13.8   13.2   12.5   12.2   12.0   11.7   11.6
:James River
Huron                10.9   10.7   10.2    9.9    9.9    9.9    9.9
Forestburg           11.8   11.0    9.1    7.0    6.9    6.7    6.7
Mitchell             14.9   14.5   12.4   11.5   11.5   11.5   11.5
:Firesteel Creek
Mount Vernon          2.0    2.0    2.0    2.0    2.0    2.0    2.0
:James River
Scotland              8.5    7.8    5.9    3.0    3.0    3.0    3.0
Yankton               5.2    5.1    2.9    2.0    2.0    2.0    2.0
:West Fork Vermillion River
Parker                1.3    1.2    1.1    1.1    1.1    1.1    1.1
:East Fork Vermillion River
Parker                3.4    3.1    2.9    2.9    2.9    2.9    2.9
:Vermillion River
Davis                 3.8    3.6    3.1    3.0    2.9    2.8    2.8
Wakonda               5.0    4.7    4.3    4.2    4.0    3.9    3.9
Vermillion            1.2    1.2    1.2    1.2    1.2    1.2    1.2
:Redwood River
Marshall              7.6    7.3    7.0    6.9    6.8    6.7    6.7
:West Fork Des Moines River
Jackson               8.7    8.6    8.4    8.2    8.0    7.9    7.8
:Missouri River
South Sioux City     14.4   13.8   13.3   12.4   11.8   11.4   11.2

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 toward the end of May.

$$






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