Flood Potential Outlook
Issued by NWS Sioux Falls, SD

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Probabilistic Hydrologic Outlook
National Weather Service Sioux Falls SD
810 AM CST Thu Feb 16 2017


...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.

With very little snow cover remaining across the area, the flood
threat through this spring will be determined by future rain
or snow fall. The outlook for the next 2 weeks indicates the best
chances are for above normal precipitation. The 30 day outlook for
the entire month of March shows increased chances for above normal
precipitation from the James River west, with near normal
precipitation east of there. The 90 day outlook for March through
May shows equal chances of above normal, normal, or below normal
precipitation.

For the James and Vermillion river basins, the chances for minor,
moderate, or major flooding are near normal. For the Big Sioux
River, chances for minor, moderate or major flooding are near normal
for the middle and upper portions of the basin, while the lower Big
Sioux has above normal chances for minor flooding and normal chances
for moderate or major flooding. For the Rock, Floyd, Des Moines, and
Redwood river basins, chances for minor, moderate, or major flooding
are near normal. For the Little Sioux river basin, there are above
normal chances for minor flooding, and normal chances for moderate
or major flooding.

...Current Snow Conditions...

There is very little remaining snow cover across the entire area.
There are still areas that have snow in ditches, shelterbelts, and
other shaded areas, but this should be melting off over the next
several days with the forecasted much above normal temperatures.

...Current Soil Conditions...

There are still 10 to 20 inches of frozen soil for most of the area,
but the top several inches of soil are starting to thaw with the
recent warm temperatures and snow melt.

Soil moisture is above normal for the entire region following much
above normal rainfall last fall and the melting of the snow that fell
earlier this winter. Modeled soil moisture anomalies range from
around 1 inch above normal in the western portions of the region to
3 to 4 inches above normal in northwestern Iowa and southwestern
Minnesota.

...Current River Conditions...

River levels and flows continue to run above normal to much above
normal due to recent melting of snow and ice. There are also still
many rivers and streams that have some ice cover that needs to melt
or be flushed downstream.

...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:  02/18/2017  - 05/19/2017

                                       :    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 :  46   35   24   23   <5   <5
Alton               12.0   16.0   18.0 :  49   38   15   22   <5    5
Le Mars             20.0   21.0   24.0 :  23   22   12   18   <5   <5
:West Branch Floyd River
Struble             14.0   15.0   16.0 :  10   14   <5    9   <5   <5
:Floyd River
Merrill             12.0   14.0   16.0 :  11   12    8   10   <5    5
James               26.0   30.0   34.0 :  <5    5   <5   <5   <5   <5
:Little Sioux River
above Spencer       10.0   13.0   15.0 :  47   56   13   21   <5    9
at Spencer          10.0   14.0   16.0 :  81   65   17   20   <5    9
:Ocheyedan River
Spencer              8.0    9.5   10.5 :  49   49   33   24   12   14
:Little Sioux River
Linn Grove          18.0   19.5   21.0 :  76   63   39   36   21   17
Cherokee            17.0   21.0   24.0 :  50   42   20   22   <5    6
Correctionville     19.0   21.0   23.0 :  23   25   17   20   12   15
:West Fork Ditch
Hornick             20.0   22.0   27.0 :  19   28   15   19   <5    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 :  58   48   34   37   17   26
Dell Rapids         12.0   14.0   15.0 :  33   36   19   25   13   17
Sioux Falls I-90    12.0   14.0   16.0 :  29   35   15   23   <5   10
:Skunk Creek
Sioux Falls         11.5   15.0   17.0 :   8   11   <5    5   <5   <5
:Big Sioux River
Sioux Falls N Cliff 16.0   18.0   31.0 :  33   35   24   31   <5   <5
:Split Rock Creek
Corson               8.5   11.0   14.0 :  36   36   18   21    8    9
:Rock River
Luverne             10.0   12.0   14.0 :  15   18    5    9   <5   <5
Rock Rapids         13.0   16.0   19.0 :  51   42   25   25   11   13
Rock Valley         16.0   17.0   19.0 :  25   28   18   19    7   11
:Big Sioux River
Hawarden            19.0   24.0   27.0 :  87   58   35   35   16   15
Akron               16.0   18.0   20.0 :  80   50   59   40   29   30
Sioux City          32.0   38.0   41.0 :  <5   <5   <5   <5   <5   <5
:James River
Huron               11.0   13.0   15.0 :  52   42   31   32   23   19
Forestburg          12.0   14.0   16.0 :  39   39   28   28   10   16
Mitchell            17.0   20.0   22.0 :  47   48   22   27   10   15
:Firesteel Creek
Mount Vernon         8.0   13.0   15.0 :  18   35   <5    7   <5   <5
:James River
Scotland            13.0   14.0   16.0 :  34   42   26   33   14   21
Yankton             12.0   14.0   16.0 :  22   33   18   25   10   21
:West Fork Vermillion River
Parker               9.0   10.0   11.0 :   8   11   <5    8   <5   <5
:East Fork Vermillion River
Parker              12.0   14.0   16.0 :  10   24   <5   14   <5   <5
:Vermillion River
Davis               11.0   13.0   15.0 :  41   40   18   33   <5    8
Wakonda             14.0   15.5   17.0 :  48   41   41   36   33   34
Vermillion          21.0   22.0   30.0 :  26   30   18   27   <5   <5
:Redwood River
Marshall            14.0   15.0   16.5 :  16   17   12   15    9   10
:West Fork Des Moines River
Jackson             12.0   14.0   16.0 :  23   24    6   16   <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: 02/18/2017  - 05/19/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Floyd River
Sheldon               7.3    7.6    8.4   10.5   13.7   15.0   15.2
Alton                 8.1    8.8    9.7   11.9   14.4   16.8   17.4
Le Mars              12.9   13.1   13.8   15.7   19.2   21.3   22.3
:West Branch Floyd River
Struble               6.7    6.7    7.3    8.7   10.5   14.0   15.0
:Floyd River
Merrill               2.7    2.8    3.3    5.0    8.9   12.5   15.2
James                11.4   11.4   11.9   14.0   16.7   20.9   23.6
:Little Sioux River
above Spencer         7.5    7.8    8.5    9.6   12.1   13.3   14.0
at Spencer            9.6    9.7   10.2   11.5   13.6   14.5   15.2
:Ocheyedan River
Spencer               5.7    5.7    6.1    7.8    9.8   11.2   11.4
:Little Sioux River
Linn Grove           17.8   17.8   18.0   19.0   20.8   22.1   23.4
Cherokee             14.2   14.2   14.2   17.0   20.4   22.1   22.9
Correctionville      11.7   11.7   11.7   14.6   18.9   21.9   22.7
:West Fork Ditch
Hornick               9.5   10.1   11.8   14.3   18.6   24.2   25.7
:Perry Creek
Sioux City            7.3    7.5    7.7    8.3    9.4   11.6   12.9
:Big Sioux River
Brookings             4.9    5.1    7.7    9.4   11.2   12.6   12.8
Dell Rapids           6.1    6.6    8.3   10.1   13.2   15.2   15.7
Sioux Falls I-90      4.5    4.8    6.7    8.7   12.6   14.9   15.6
:Skunk Creek
Sioux Falls           4.9    5.5    7.0    8.0    9.4   11.0   14.1
:Big Sioux River
Sioux Falls N Cliff   8.1    8.8   10.9   13.2   17.7   22.5   24.6
:Split Rock Creek
Corson                4.7    6.0    6.4    8.0    9.5   13.4   15.3
:Rock River
Luverne               5.1    5.8    6.3    7.1    8.6   10.7   12.0
Rock Rapids          10.5   10.9   12.0   13.1   16.0   19.2   20.7
Rock Valley           8.5    9.4   10.8   13.0   16.1   18.1   19.3
:Big Sioux River
Hawarden             17.7   18.6   21.3   23.2   25.4   28.4   29.3
Akron                12.9   13.9   16.6   18.5   20.8   22.8   23.4
Sioux City           14.2   15.0   17.4   19.9   23.9   31.5   34.1
:James River
Huron                10.2   10.3   10.5   11.1   14.9   17.1   18.0
Forestburg            7.4    8.3    9.0   10.9   14.5   16.0   16.9
Mitchell             12.7   13.5   14.2   16.6   19.5   22.1   23.2
:Firesteel Creek
Mount Vernon          2.3    2.3    2.8    3.8    7.1   10.4   12.3
:James River
Scotland              5.8    6.2    7.2   11.3   14.2   16.6   18.2
Yankton               3.4    3.9    4.7    7.3   11.4   16.2   19.7
:West Fork Vermillion River
Parker                1.4    1.4    1.7    2.7    4.6    8.4    9.7
:East Fork Vermillion River
Parker                4.4    4.4    5.0    7.1    9.8   12.1   13.9
:Vermillion River
Davis                 5.8    5.8    6.2    9.0   12.1   14.2   14.8
Wakonda               9.7    9.7    9.7   13.4   17.4   17.5   17.7
Vermillion            8.8    8.8    8.8   12.4   21.1   24.9   26.8
:Redwood River
Marshall              9.9   10.0   10.2   11.2   13.0   16.0   18.1
:West Fork Des Moines River
Jackson               9.2    9.3    9.5   10.0   11.8   13.5   14.2

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: 02/18/2017  - 05/19/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Floyd River
Sheldon               4.6    4.4    4.1    4.0    4.0    4.0    4.0
Alton                 6.4    6.3    6.1    6.0    5.9    5.9    5.9
Le Mars              10.2    9.7    9.2    8.7    8.4    8.2    8.2
:West Branch Floyd River
Struble               4.3    4.2    4.1    4.0    3.9    3.9    3.9
:Floyd River
Merrill               1.1    0.8    0.6    0.3    0.1    0.0    0.0
James                10.1    9.9    9.8    9.6    9.5    9.5    9.4
:Little Sioux River
above Spencer         6.4    6.1    5.9    5.7    5.5    5.4    5.3
at Spencer            7.7    7.3    6.8    6.3    5.8    5.4    5.3
:Ocheyedan River
Spencer               3.8    3.5    3.2    3.0    2.8    2.7    2.7
:Little Sioux River
Linn Grove           16.7   16.6   16.4   16.2   16.1   16.1   16.0
Cherokee             10.8   10.2    9.2    8.7    8.3    7.9    7.8
Correctionville       8.5    7.9    7.2    6.8    6.3    6.0    5.9
:West Fork Ditch
Hornick               6.4    6.3    5.9    5.6    5.3    5.2    5.2
:Perry Creek
Sioux City            7.1    7.0    7.0    6.8    6.5    6.3    6.2
:Big Sioux River
Brookings             3.4    3.3    3.1    2.9    2.8    2.6    2.5
Dell Rapids           4.9    4.8    4.5    4.4    4.3    4.2    4.1
Sioux Falls I-90      2.9    2.7    2.5    2.3    2.2    2.1    1.9
:Skunk Creek
Sioux Falls           4.4    4.2    4.0    3.9    3.8    3.7    3.6
:Big Sioux River
Sioux Falls N Cliff   6.6    6.4    6.2    6.1    6.0    5.9    5.7
:Split Rock Creek
Corson                2.6    2.5    2.5    2.4    2.3    2.3    2.2
:Rock River
Luverne               3.8    3.8    3.7    3.7    3.7    3.6    3.6
Rock Rapids           8.5    8.4    8.3    8.2    8.2    8.1    8.1
Rock Valley           5.8    5.5    5.2    5.1    4.9    4.8    4.7
:Big Sioux River
Hawarden             14.5   14.0   13.6   13.2   13.0   12.7   12.4
Akron                 8.5    7.8    7.2    6.7    6.5    6.1    5.7
Sioux City           11.2   10.6   10.3    9.9    9.7    9.5    9.3
:James River
Huron                 9.3    9.3    9.3    9.3    9.3    9.3    9.2
Forestburg            5.2    5.1    5.0    5.0    5.0    4.9    4.9
Mitchell             11.0   11.0   10.8   10.7   10.7   10.6   10.6
:Firesteel Creek
Mount Vernon          2.3    2.3    2.2    2.2    1.9    1.9    1.9
:James River
Scotland              5.1    5.1    4.9    4.8    4.8    4.8    4.7
Yankton               2.6    2.5    2.2    2.1    2.1    2.1    2.0
:West Fork Vermillion River
Parker                0.8    0.7    0.6    0.5    0.3    0.1    0.1
:East Fork Vermillion River
Parker                3.8    3.7    3.7    3.6    3.4    3.3    3.2
:Vermillion River
Davis                 3.2    3.1    2.9    2.7    2.5    2.4    2.4
Wakonda               4.5    4.4    4.2    3.9    3.7    3.7    3.7
Vermillion            3.3    3.3    2.9    2.6    2.3    2.2    2.2
:Redwood River
Marshall              7.9    7.9    7.6    7.2    6.9    6.8    6.8
:West Fork Des Moines River
Jackson               8.5    8.4    8.2    8.1    8.0    7.9    7.8

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 at weather.gov/fsd for more weather and water
information.

The next outlook will be issued on Thursday March 2.

$$

Gillispie



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