Flood Potential Outlook
Issued by NWS Aberdeen, SD

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FGUS73 KABR 162021
ESFABR
MNC011-155-SDC013-017-021-025-029-031-037-039-041-045-049-051-057-
059-065-069-075-085-089-091-107-109-115-117-119-129-221200-

Probabilistic Hydrologic Outlook
National Weather Service Aberdeen SD
220 PM CST Thu Feb 16 2017

...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 fairly deep snow pack remains over portions of north central South
Dakota, with little to no snow cover over the remainder of the area.
The outlook for the next 2 weeks indciates the best chances are for
above normal precipitation. The 30 day outlook for the month of March
shows increased chances for above normal precipitation and near to
below normal temperatures. The 90 day outlook for March through May
shows increased chances for above normal precipitation and near to
above normal temperatures.

For the James river basin, the chances for minor to moderate flooding
are above normal. For the remainder of the river basins in the area,
the chances for flooding are below normal.

...Current snow conditions...

Snow depths are nearly non-existent south and east of a line from
Murdo to Leola. North and west of that line, snow depths generally
range from 2 to 10 inches, with depths of 10 to 20 inches over
portions of Corson county. The water equivalent of the snow pack is 2
to 4 inches, and 4 to 8 inches with the deeper snow pack over Corson
county. There are still areas that have additional snow in ditches,
shelterbelts, and other shaded areas left over from snowfall earlier
this winter.

...Current soil conditions...

Frost depths remain fairly deep across the area, generally around 10
to 20 inches, but the top several inches of soil in areas with no
snow cover are starting to thaw with the recent warm temperatures and
snow melt. Soil moisture is above normal across the area. Modeled
soil moisture anomolies are generally around one inch or so above
normal.

...Current river conditions...

River levels and flows continue to run above normal due to recent
melting of snow and ice. There are also still some rivers and streams
that have 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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Elm River
Westport            14.0   16.0   19.0 :  13   12   <5   10   <5    8
:James River
Columbia            13.0   16.0   18.0 : >98   37   53   26   23   16
Stratford           14.0   17.0   18.5 : >98   45   50   26   24   15
Ashton              13.0   14.0   16.0 :  51   30   48   28   34   24
:Turtle Creek
Redfield             7.0   10.0   15.0 :  22   40    8   16   <5    9
:James River
Redfield            20.0   22.0   25.0 :  22   20   19   16   15   15
:Big Sioux River
Watertown           10.0   11.0   12.0 :  <5   28   <5   13   <5   <5
Watertown            8.0   10.0   12.0 :  33   55   <5   28   <5   <5
Watertown - Broad   11.0   14.0   16.0 :  30   44   <5   <5   <5   <5
Castlewood           9.0   11.0   16.0 :  41   49   20   29   <5   <5
:Grand River
Little Eagle        15.0   17.0   21.0 :  10    7   <5    6   <5   <5
:Moreau River
Whitehorse          21.0   23.0   25.0 :  <5    7   <5    6   <5   <5
:Bad River
Fort Pierre         21.0   25.0   27.0 :  14   15    6   <5   <5   <5
:Little Minnesota River
Peever              17.0   22.0   24.0 :   9   22   <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: 02/18/2017  - 05/19/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Elm River
Westport              5.4    5.4    5.8    7.7   11.2   14.2   15.4
:James River
Columbia             13.9   14.2   15.0   16.6   17.7   19.3   20.0
Stratford            15.2   15.4   16.1   16.9   18.4   19.7   20.9
Ashton               10.7   10.8   11.8   13.2   17.5   22.6   25.4
:Turtle Creek
Redfield              3.1    3.1    3.3    4.9    6.5    9.3   12.1
:James River
Redfield              9.3    9.5   10.4   11.9   17.5   26.6   28.3
:Big Sioux River
Watertown             4.5    4.6    5.5    6.8    8.3    9.8    9.9
Watertown             3.9    4.1    5.0    5.6    8.8    9.5    9.7
Watertown - Broad     5.4    5.9    7.1    8.4   11.3   12.4   12.5
Castlewood            5.8    5.9    6.7    8.2   10.6   11.5   12.0
:Grand River
Little Eagle          9.3    9.3    9.5   10.8   14.2   15.0   15.4
:Moreau River
Whitehorse           12.2   12.2   12.2   12.3   16.5   18.8   19.2
:Bad River
Fort Pierre           7.3    7.3    7.6   10.6   16.7   24.0   25.3
:Little Minnesota River
Peever               11.8   11.9   12.7   13.9   15.3   16.7   18.9
:Minnesota River
Big Stone Lake      968.0  968.0  968.0  968.0  968.2  969.4  970.8

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%
--------            ------ ------ ------ ------ ------ ------ ------
:Elm River
Westport              4.7    4.7    4.7    4.7    4.6    4.5    4.4
:James River
Columbia              5.6    5.6    5.6    5.6    5.6    5.6    5.6
Stratford             6.8    6.8    6.8    6.8    6.8    6.8    6.8
Ashton                4.0    4.0    4.0    4.0    4.0    4.0    4.0
:Turtle Creek
Redfield              3.1    3.1    3.1    3.1    3.1    3.0    3.0
:James River
Redfield              3.9    3.9    3.9    3.9    3.9    3.9    3.9
:Big Sioux River
Watertown             4.0    4.0    3.9    3.9    3.8    3.7    3.6
Watertown             3.6    3.6    3.6    3.6    3.5    3.1    3.0
Watertown - Broad     5.1    5.0    5.0    5.0    4.9    4.9    4.8
Castlewood            4.7    4.7    4.7    4.6    4.5    4.5    4.4
:Grand River
Little Eagle          3.4    3.4    3.3    3.3    3.2    3.1    3.0
:Moreau River
Whitehorse            2.9    2.9    2.9    2.7    2.7    2.6    2.6
:Bad River
Fort Pierre           2.8    2.8    2.8    2.7    2.7    2.7    2.7
:Little Minnesota River
Peever               10.4   10.4   10.2    9.7    9.6    9.6    9.6
:Minnesota River
Big Stone Lake      967.5  967.5  967.5  967.5  967.5  967.5  967.5

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 Thursday, March 2nd.

$$

Parkin





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