Flood Potential Outlook
Issued by NWS Aberdeen, SD

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FGUS73 KABR 291659
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Probabilistic Hydrologic Outlook
National Weather Service Aberdeen SD
1059 AM CST Thu Feb 29 2024

...Spring Flood Outlook...

This spring flood outlook is for the rivers and streams in northeast
South Dakota, portions of central South Dakota, and portions of west
central Minnesota.

A current lack of snow cover, areas of thawed ground, and decreasing
river ice currently point toward a below normal flood risk over the
area over the next 90 days. With this said, additional
heavy precipitation events or cold outbreaks could change the flood
risk going forward. Changes to the flood risk factors will continue
to be monitored and updates provided in future outlooks.

The outlook for the next two weeks is for increased chances for
above normal temperatures and above normal precipitation. The 90 day
outlook for March through May indicates increased chances for above
normal temperatures, and equal chances for below, near or above
normal precipitation.

...Current snow conditions...
Current snow depth ranges from a trace to less than 1 inch across
parts of Corson, Campbell and Walworth counties, as well as a small
area north of Webster to the North Dakota border. The remainder of
the area is currently snow free. The liquid water equivalent with
any remaining snow pack is generally less than one tenth of an inch.

...Current soil conditions...
Soil moisture is near to above normal across the entire area. Frost
depths are generally around or below one foot. The areas currently
in drought at this time are all of Codington, Deuel, Hamlin, Brown,
McPherson, Campbell and Corson counties, and portions of Roberts,
Marshall, Day, Edmunds, Walworth, Dewey, Grant, and Clark counties
in South Dakota and Big Stone and Traverse counties in Minnesota.

...Current river conditions...
Most of the rivers are at least partially iced over, but reports
indicate that there are areas of open water.  River levels and flows
are generally running near to below normal across the region. The
threat for break-up ice jams appears low at this time.

...Probabalistic 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:
                    Valid  Period: 03/04/2024 - 06/02/2024
                                       :    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   28   <5   22   <5    9
:James River
Columbia            13.0   16.0   18.0 :  15   55    6   41    5   29
Stratford           14.0   17.0   18.5 :  23   58    6   43    5   29
Ashton              13.0   14.0   16.0 :   7   54    6   45    6   43
Redfield            20.0   22.0   25.0 :   9   42    6   41    6   39
:Snake Creek
Ashton              11.5   13.0   16.0 :   8   49    6   39    5   34
:Turtle Creek
Redfield             7.0   10.0   15.0 :  26   54   16   42    8   30
:Big Sioux River
Watertown 10NW      10.0   11.0   12.0 :  <5   19   <5   <5   <5   <5
Watertown Conifer    9.0   10.0   12.0 :  <5   35   <5   29   <5   <5
Watertown Broadwy   10.5   11.0   13.5 :  <5   34   <5   33   <5   <5
Castlewood           9.0   11.0   16.0 :  11   37   <5   28   <5   <5
:Grand River
Little Eagle        15.0   17.0   21.0 :  <5   27   <5   17   <5    6
:Moreau River
White Horse         21.0   23.0   25.0 :  <5   22   <5   17   <5   11
:Bad River
Fort Pierre         21.0   25.0   27.0 :  10   12    5    5   <5   <5
:Little Minnesota
Peever              17.0   22.0   24.0 :  15   26   <5   <5   <5   <5
:Minnesota River
Big Stone Lake     971.5  973.0  975.0 :  <5    6   <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:
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Elm River
Westport              4.6    4.6    4.6    5.0    8.7   11.5   12.5
:James River
Columbia              7.2    7.2    7.2    8.1   11.9   15.0   17.8
Stratford             8.8    8.8    8.8    8.9   13.0   15.8   18.5
Ashton                6.0    6.0    6.0    6.0    8.3   11.3   21.1
Redfield              6.6    6.6    6.6    6.6   10.6   19.3   26.9
:Snake Creek
Ashton                2.5    2.5    2.5    3.1    6.4   10.9   17.2
:Turtle Creek
Redfield              3.5    3.5    3.5    4.1    7.3   14.2   16.5
:Big Sioux River
Watertown 10NW        4.1    4.1    4.5    5.4    6.7    8.2    9.1
Watertown Conifer     3.7    3.8    3.9    4.5    5.2    6.8    8.4
Watertown Broadwy     5.2    5.2    5.3    5.8    6.8    8.7   10.3
Castlewood            5.2    5.2    5.3    5.8    7.0    9.1   10.2
:Grand River
Little Eagle          2.9    2.9    3.7    5.5    8.1    9.2   10.0
:Moreau River
White Horse           2.5    3.5    5.5    6.7   10.3   12.7   14.1
:Bad River
Fort Pierre           3.4    4.5    6.4    9.6   13.4   20.5   24.2
:Little Minnesota
Peever               11.1   11.8   12.8   14.3   15.9   17.8   20.0
:Minnesota River
Big Stone Lake      968.0  968.0  968.0  968.0  968.0  969.2  970.3

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:
LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Elm River
Westport              4.1    4.0    4.0    3.9    3.9    3.9    3.9
:James River
Columbia              6.3    6.0    5.9    5.9    5.9    5.9    5.8
Stratford             7.1    6.8    6.6    6.5    6.5    6.5    6.5
Ashton                4.5    4.4    4.0    3.9    3.9    3.8    3.8
Redfield              5.4    5.2    4.8    4.8    4.8    4.7    4.7
:Snake Creek
Ashton                2.5    2.5    2.5    2.5    2.5    2.5    2.5
:Turtle Creek
Redfield              3.3    3.2    3.1    3.1    3.1    3.1    3.1
:Big Sioux River
Watertown 10NW        4.0    4.0    3.8    3.8    3.8    3.8    3.8
Watertown Conifer     3.7    3.7    3.7    3.6    3.6    3.6    3.6
Watertown Broadwy     5.1    5.1    5.0    5.0    4.9    4.9    4.9
Castlewood            5.0    4.9    4.7    4.6    4.6    4.5    4.4
:Grand River
Little Eagle          2.6    2.6    2.6    2.5    2.5    2.4    2.4
:Moreau River
White Horse           2.3    2.3    2.3    2.3    2.2    2.2    2.2
:Bad River
Fort Pierre           0.8    0.8    0.7    0.7    0.7    0.6    0.6
:Little Minnesota
Peever               10.6   10.5    9.9    9.7    9.7    9.7    9.7
:Minnesota River
Big Stone Lake      967.6  967.6  967.6  967.6  967.6  967.6  967.6

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 on March 14th.


$$

Parkin


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