Flood Potential Outlook
Issued by NWS Aberdeen, SD

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3
930
FGUS73 KABR 021515
ESFABR
MNC011-155-SDC013-017-021-025-029-031-037-039-041-045-049-051-057-
059-065-069-075-085-089-091-107-109-115-117-119-129-291200-

Probabilistic Hydrologic Outlook
National Weather Service Aberdeen SD
915 AM CST Thu Mar 02 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.

With very little snow cover remaining across the area, the flood
threat through this spring will be determined by future rain or
snowfall. The outlook for the next two weeks indicates the best
chances are for near to above normal precipitation and above normal
temperatures. The 30 day outlook for the month of March shows equal
chances for above normal, normal or below normal precipitation and
above 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 near to 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 west of the James River Valley.
East of that line, snow depths generally range from 1 to 4 inches.
The water equivalent of the snow pack is less than one inch. All of
this snow should be melting off over the next several days with the
forecasted much above normal temperatures.

...Current soil conditions...

Most areas still have some frost in the ground in the top 10 to 20
inches, but the top 2 to 6 inches of soil are starting to thaw with
the recent warm temperatures and snow melt, and will continue to thaw
over the next 1 to 2 weeks with above normal temperatures expected.

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 anomolies are 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. Most of the thicker ice on the rivers has
already melted or been flushed downstream, but cooler temperatures in
the past several days has allowed for the redevelopment of some slush
ice on the surface of the rivers and streams, mainly in the overnight
and morning hours. This type of ice will generally not cause any
issues with ice jams. With above normal temperatures again expected
for the next 2 weeks, the formation of thicker ice that could lead to
jams is unlikely.


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:  03/04/2017  - 06/02/2017

                                       :    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 :   8   12    7   10   <5    8
:James River
Columbia            13.0   16.0   18.0 : >98   42   39   28   12   16
Stratford           14.0   17.0   18.5 : >98   48   39   30   15   16
Ashton              13.0   14.0   16.0 :  33   30   32   28   20   24
:Turtle Creek
Redfield             7.0   10.0   15.0 :  19   44    7   20   <5    9
:James River
Redfield            20.0   22.0   25.0 :  17   20   13   17   11   15
:Big Sioux River
Watertown           10.0   11.0   12.0 :  <5   28   <5   13   <5   <5
Watertown            8.0   10.0   12.0 :  24   55   <5   28   <5   <5
Watertown - Broad   11.0   14.0   16.0 :  23   44   <5   <5   <5   <5
Castlewood           9.0   11.0   16.0 :  36   51   14   29   <5   <5
:Grand River
Little Eagle        15.0   17.0   21.0 :   5    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 :   9   18   <5   <5   <5   <5
:Little Minnesota River
Peever              17.0   22.0   24.0 :  10   24   <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: 03/04/2017  - 06/02/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Elm River
Westport              6.6    6.6    6.6    7.3   10.5   12.5   17.1
:James River
Columbia             15.3   15.3   15.3   15.4   17.3   18.6   19.8
Stratford            16.9   16.9   16.9   16.9   17.7   19.1   20.7
Ashton               11.9   11.9   11.9   11.9   14.8   19.9   24.7
:Turtle Creek
Redfield              3.1    3.1    3.1    3.6    5.7    9.6   11.0
:James River
Redfield             11.1   11.1   11.1   11.1   14.2   25.1   27.4
:Big Sioux River
Watertown             4.4    4.6    5.3    6.4    7.7    9.3    9.6
Watertown             4.0    4.2    4.7    5.4    7.3    9.1    9.4
Watertown - Broad     5.6    5.9    6.9    8.0   10.5   11.6   12.3
Castlewood            5.1    5.8    6.5    8.4   10.7   11.4   11.6
:Grand River
Little Eagle          4.5    4.7    6.5    9.1   11.8   13.4   15.2
:Moreau River
Whitehorse            4.8    4.9    6.3    9.1   16.1   18.1   19.4
:Bad River
Fort Pierre           3.5    4.0    6.8    9.6   14.5   20.8   22.2
:Little Minnesota River
Peever               11.4   11.7   12.4   13.8   15.4   17.1   19.8
:Minnesota River
Big Stone Lake      968.0  968.0  968.0  968.0  968.1  969.4  971.0

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: 03/04/2017  - 06/02/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Elm River
Westport              5.3    5.2    5.1    4.9    4.8    4.8    4.8
:James River
Columbia             11.5   11.4    9.8    8.8    8.5    8.4    8.2
Stratford            14.0   13.4   11.9   10.8   10.2   10.1    9.9
Ashton                7.9    7.9    7.5    6.0    5.4    5.1    5.0
:Turtle Creek
Redfield              3.1    3.1    3.1    3.1    3.1    3.0    3.0
:James River
Redfield              6.8    6.8    6.8    6.5    6.1    5.9    5.8
:Big Sioux River
Watertown             4.0    4.0    3.9    3.9    3.7    3.6    3.6
Watertown             3.6    3.6    3.6    3.5    3.1    3.1    3.0
Watertown - Broad     5.1    5.0    5.0    5.0    4.9    4.9    4.8
Castlewood            4.8    4.8    4.7    4.6    4.5    4.5    4.5
:Grand River
Little Eagle          3.3    3.3    3.2    3.1    3.0    2.9    2.8
:Moreau River
Whitehorse            2.8    2.8    2.8    2.6    2.6    2.6    2.6
:Bad River
Fort Pierre           2.7    2.7    2.7    2.7    2.7    2.7    2.7
:Little Minnesota River
Peever               10.4   10.4    9.8    9.7    9.7    9.7    9.7
:Minnesota River
Big Stone Lake      967.8  967.8  967.8  967.8  967.8  967.8  967.8

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/abr for more weather and water
information.

The next outlook will be issued later this month.

$$

Parkin





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.