Flood Potential Outlook
Issued by NWS Des Moines, IA

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Probabilistic Hydrologic Outlook
National Weather Service Des Moines IA
1112 AM CST Thu Feb 25 2021

...Spring Flood and Water Resources Outlook...

This flood outlook is for the NWS Des Moines service area. It covers
the time period for early March through late May 2001. It includes
the following rivers and their tributaries in north central, central
and south central Iowa...

Iowa, Cedar, Skunk, Des Moines, Raccoon, Nishnabotna, 102, Thompson
and Chariton Rivers


This outlook is the second in a series of three outlooks for the
spring flood season. The next outlook will be issued on March 11th.
Regular monthly long-range Probabilistic Hydrologic Outlooks will
resume on April 1st. You may also refer to the NWS Des Moines Website
for more information at... http://www.weather.gov/desmoines .

...Flood Outlook Highlights...

* The risk of minor flooding is near normal at all locations. The
  risk of moderate flooding is near normal at all locations. The risk
  of major flooding is near normal at all locations.

* It is important to continue monitoring weather and river
  conditions--as well as future outlooks--for any changes to the
  flood threat. Any future precipitation--as well as changes to
  river or other weather conditions--may increase or decrease the
  risk of flooding.

* Maps and graphics concerning the risk of flooding are available on
  the NWS Des Moines Advanced Hydrologic Prediction Service Web page
  at http://water.weather.gov/ahps2/index.php?wfo=dmx . On that page
  click on the tab above the map labeled Experimental Long-Range
  Flood Risk.

* You may also refer to our web site for more information at
  http://www.weather.gov/desmoines .

This outlook provides long-range probabilistic river outlooks for
river basins in the NWS Des Moines service area. This outlook is
divided into three parts--the first part for the probabilities of
minor, moderate and major flooding, the second part for high water
and the final part for low water.

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:  03/01/2021 - 05/30/2021

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Cedar River
Janesville          13.0   15.0   18.0 :  <5    9   <5   <5   <5   <5
:West Fork Cedar River
Finchford           17.0   18.0   20.0 :  <5   <5   <5   <5   <5   <5
:Winnebago River
Mason City          10.0   14.5   15.5 :  <5   <5   <5   <5   <5   <5
:Shell Rock River
Shell Rock          13.5   18.0   20.0 :   9   12   <5   <5   <5   <5
:Beaver Creek
New Hartford        12.5   14.0   15.0 :   7    9   <5   <5   <5   <5
:Cedar River
Cedar Falls         89.0   92.0   94.0 :  31   48   13   20   <5   10
:Black Hawk Creek
Hudson              14.0   15.0   19.0 :  41   39   26   24   <5   <5
:Cedar River
Waterloo            13.0   19.0   21.0 :  18   32   <5    5   <5   <5
:Iowa River
Rowan               12.5   15.0   17.0 :   9   16   <5   <5   <5   <5
Marshalltown        19.0   23.0   26.0 :  <5    9   <5   <5   <5   <5
Tama Hwy E49        12.5   13.0   14.0 :  18   21    8   17   <5   <5
:South Skunk River
Ames W Riverside    12.5   16.0   16.5 :  <5   <5   <5   <5   <5   <5
:Squaw Creek
Ames Lincoln Way    10.0   14.0   15.5 :  <5   <5   <5   <5   <5   <5
:South Skunk River
Ames US 30          21.5   23.5   24.5 :   6    9   <5   <5   <5   <5
Colfax              18.0   19.0   21.0 :   8    7   <5   <5   <5   <5
Oskaloosa           24.5   28.5   30.0 :  <5   <5   <5   <5   <5   <5
:East Fork Des Moines River
Algona              17.0   18.0   22.0 :  <5   16   <5   12   <5   <5
Dakota City         20.0   24.0   28.0 :  <5    6   <5   <5   <5   <5
:Boone River
Webster City        14.0   17.0   19.0 :  <5   <5   <5   <5   <5   <5
:Beaver Creek
Grimes              14.0   16.0   17.0 :  <5   <5   <5   <5   <5   <5
:North Raccoon River
Jefferson           19.0   21.0   23.0 :  <5    7   <5   <5   <5   <5
Perry               15.0   18.0   20.0 :  28   50   11   30    5   18
:South Raccoon River
Redfield            20.0   24.0   27.0 :  <5   <5   <5   <5   <5   <5
:Raccoon River
Van Meter           17.0   22.0   23.0 :   9   20   <5   <5   <5   <5
Des Moines IA 28    36.0   38.0   40.0 :   6   10   <5   <5   <5   <5
Des Moines Fleur    12.0   16.0   25.0 :  59   66    9   21   <5   <5
:North River
Norwalk             22.0   25.0   26.0 :  12   19   <5   <5   <5   <5
:Middle River
Indianola           23.0   26.0   28.0 :   9   16   <5   <5   <5   <5
:South River
Ackworth            29.0   30.0   32.0 :   6    5   <5   <5   <5   <5
:Cedar Creek
Bussey              25.0   30.0   32.0 :  <5   <5   <5   <5   <5   <5
:West Fork Des Moines River
Estherville         10.0   13.0   14.5 :  <5   21   <5    8   <5   <5
Emmetsburg          11.0   13.0   15.0 :  <5   18   <5   <5   <5   <5
Humboldt            10.0   13.0   14.0 :  10   30   <5   <5   <5   <5
:Des Moines River
Fort Dodge          10.5   16.0   17.0 :   9   25   <5   <5   <5   <5
Stratford           19.0   25.0   27.0 :   6   18   <5   <5   <5   <5
Des Moines 2nd Av   23.0   26.0   30.0 :  <5   <5   <5   <5   <5   <5
Des Moines SE 6th   24.0   26.0   30.0 :  24   46    6   15   <5   <5
Eddyville           63.0   68.0   70.0 :   6   10   <5   <5   <5   <5
Ottumwa             11.5   15.0   19.0 :  25   28   <5   <5   <5   <5
:Thompson River
Davis City          12.0   20.0   24.0 :  11   21   <5   <5   <5   <5
:South Fork Chariton River
Promise City        25.0   28.0   31.0 :  <5   <5   <5   <5   <5   <5
:Chariton River
Chariton            19.5   26.0   29.0 :  <5   <5   <5   <5   <5   <5
Moulton             36.0   37.0   38.0 :  <5   <5   <5   <5   <5   <5
:East Nishnabotna River
Atlantic            19.0   23.0   24.0 :  12   16   <5   <5   <5   <5
:East Fork 102 River
Bedford             24.0   25.0   26.0 :  <5   <5   <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: 03/01/2021 - 05/30/2021
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Cedar River
Janesville            3.5    3.8    4.8    6.1    7.5   11.1   12.1
:West Fork Cedar River
Finchford             8.9    9.1   10.0   11.3   12.5   15.0   15.4
:Winnebago River
Mason City            4.5    4.6    5.2    6.2    7.3    7.9    9.0
:Shell Rock River
Shell Rock            9.2    9.3   10.0   10.7   11.7   13.3   13.8
:Beaver Creek
New Hartford          4.3    4.8    5.6    7.4   10.3   11.9   13.3
:Cedar River
Cedar Falls          82.2   82.8   84.9   87.4   89.3   92.9   93.9
:Black Hawk Creek
Hudson                9.9   10.3   12.1   13.7   15.1   15.7   16.3
:Cedar River
Waterloo              7.4    7.7    8.7   10.0   11.5   15.2   17.5
:Iowa River
Rowan                 5.5    5.7    6.5    8.9   10.7   12.2   13.5
Marshalltown         11.3   11.5   12.5   14.4   16.0   17.7   18.8
Tama Hwy E49          4.9    5.3    7.1    9.9   11.3   12.9   13.3
:South Skunk River
Ames W Riverside      4.5    5.3    6.8    7.5    9.3   10.5   11.1
:Squaw Creek
Ames Lincoln Way      2.9    3.4    4.2    5.0    6.1    7.2    9.3
:South Skunk River
Ames US 30           12.6   13.5   15.5   16.9   18.6   20.5   21.6
Colfax                9.0    9.5   12.0   14.0   16.6   17.7   18.4
Oskaloosa            10.7   11.2   14.5   17.0   19.9   22.4   23.5
:East Fork Des Moines River
Algona                8.4    8.6    9.9   12.5   14.3   16.2   16.9
Dakota City           9.2    9.4   10.2   12.2   13.4   15.5   17.0
:Boone River
Webster City          4.5    4.6    5.8    7.2    9.1   10.1   11.4
:Beaver Creek
Grimes                4.5    5.1    7.2    8.6   11.0   12.2   12.9
:North Raccoon River
Jefferson             6.6    7.2    8.6   11.5   13.3   15.6   17.1
Perry                 6.5    7.3   10.3   13.9   15.4   18.2   20.3
:South Raccoon River
Redfield              3.8    4.0    6.5    7.6    9.4   13.6   17.8
:Raccoon River
Van Meter             4.9    5.5    9.3   11.7   13.1   16.5   20.3
Des Moines IA 28     22.7   23.4   28.0   30.4   31.7   34.5   36.7
Des Moines Fleur      5.6    6.4   10.6   12.3   13.2   15.7   18.1
:North River
Norwalk               8.0    9.6   13.6   17.1   20.3   22.1   22.3
:Middle River
Indianola            10.4   11.3   14.6   15.7   17.8   22.7   24.1
:South River
Ackworth              8.5    9.3   11.5   13.1   19.4   24.8   29.4
:Cedar Creek
Bussey                8.0    9.4   10.9   13.7   15.8   19.1   20.7
:West Fork Des Moines River
Estherville           3.5    3.6    3.8    4.8    7.5    9.3    9.9
Emmetsburg            2.8    2.9    3.4    4.7    7.4    8.9    9.9
Humboldt              5.3    5.5    6.0    7.2    8.7   10.0   10.3
:Des Moines River
Fort Dodge            5.1    5.4    5.9    7.6    9.1   10.2   10.9
Stratford             7.9    8.4   10.3   13.4   15.4   17.7   19.5
Des Moines 2nd Av    16.7   16.9   18.2   20.6   21.1   22.0   22.2
Des Moines SE 6th    13.3   13.8   18.9   22.1   23.8   25.2   26.3
Eddyville            53.3   53.9   58.8   60.8   61.5   62.2   63.3
Ottumwa               4.4    4.7    8.3    9.9   11.6   12.6   13.8
:Thompson River
Davis City            1.7    1.9    5.5    7.3    9.7   12.2   14.5
:South Fork Chariton River
Promise City          6.4    6.7   13.8   18.7   21.2   22.0   22.5
:Chariton River
Chariton              9.0   11.8   14.7   16.3   17.0   17.6   18.7
Moulton              25.8   25.8   27.4   30.0   33.1   33.9   34.3
:East Nishnabotna River
Atlantic              5.4    6.0    7.4   12.0   15.8   19.5   20.1
:East Fork 102 River
Bedford              12.0   13.0   15.3   16.4   18.1   19.3   20.6


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--Non-Exceedance Probabilities...

                            Chance of Falling Below Stages
                                 at Specific Locations
                          Valid Period: 03/01/2021 - 05/30/2021
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Cedar River
Janesville            1.1    1.1    1.1    1.1    1.1    1.1    1.1
:West Fork Cedar River
Finchford             5.7    5.7    5.6    5.6    5.6    5.6    5.6
:Winnebago River
Mason City            3.1    3.1    3.1    3.1    3.1    3.1    3.0
:Shell Rock River
Shell Rock            7.5    7.5    7.5    7.5    7.5    7.5    7.5
:Beaver Creek
New Hartford          1.7    1.7    1.7    1.7    1.7    1.7    1.7
:Cedar River
Cedar Falls          78.4   78.4   78.4   78.4   78.4   78.4   78.4
:Black Hawk Creek
Hudson                5.1    5.1    5.0    5.0    5.0    5.0    5.0
:Cedar River
Waterloo              5.3    5.3    5.3    5.3    5.3    5.3    5.3
:Iowa River
Rowan                 3.3    3.2    3.2    3.1    3.1    3.1    3.1
Marshalltown          9.1    9.0    9.0    9.0    8.9    8.9    8.9
Tama Hwy E49          1.3    1.3    1.3    1.2    1.2    1.2    1.2
:South Skunk River
Ames W Riverside      2.8    2.8    2.8    2.8    2.8    2.8    2.4
:Squaw Creek
Ames Lincoln Way      0.8    0.8    0.8    0.8    0.8    0.8    0.7
:South Skunk River
Ames US 30            9.6    9.6    9.6    9.6    9.6    9.5    9.2
Colfax                6.7    6.7    6.7    6.7    6.7    6.7    6.5
Oskaloosa             8.4    8.3    8.2    8.2    8.0    7.8    7.7
:East Fork Des Moines River
Algona                6.8    6.7    6.7    6.7    6.5    5.9    5.7
Dakota City           7.4    7.3    7.3    7.3    7.2    7.2    7.2
:Boone River
Webster City          2.0    2.0    1.9    1.9    1.8    1.8    1.7
:Beaver Creek
Grimes                3.5    3.5    3.2    3.0    2.7    2.2    2.2
:North Raccoon River
Jefferson             5.4    5.3    5.3    5.2    5.0    4.9    4.8
Perry                 4.3    4.3    4.2    4.1    3.8    3.5    3.4
:South Raccoon River
Redfield              2.7    2.7    2.6    2.4    2.3    2.1    2.0
:Raccoon River
Van Meter             3.3    3.2    3.1    2.8    2.6    2.3    2.1
Des Moines IA 28     21.0   20.9   20.8   20.5   20.2   20.0   19.8
Des Moines Fleur      3.9    3.9    3.7    3.4    3.2    2.9    2.8
:North River
Norwalk               5.8    5.8    5.7    5.5    5.1    4.9    4.8
:Middle River
Indianola             7.8    7.7    7.5    7.2    7.0    7.0    6.9
:South River
Ackworth              5.9    5.9    5.9    5.8    5.8    5.7    5.7
:Cedar Creek
Bussey                5.8    5.7    5.4    5.3    5.1    4.9    4.9
:West Fork Des Moines River
Estherville           2.2    2.2    2.2    2.2    2.2    2.0    2.0
Emmetsburg            0.4    0.4    0.4    0.3    0.3    0.3    0.3
Humboldt              3.4    3.4    3.3    3.3    3.2    3.1    2.9
:Des Moines River
Fort Dodge            3.7    3.7    3.7    3.6    3.5    3.4    3.3
Stratford             5.6    5.6    5.5    5.4    5.3    5.1    4.9
Des Moines 2nd Av    15.5   15.5   15.4   15.3   15.2   15.0   14.9
Des Moines SE 6th    10.8   10.6   10.5   10.3    9.8    9.5    9.3
Eddyville            50.8   50.6   50.1   49.7   48.8   48.3   48.1
Ottumwa               3.0    2.8    2.5    2.2    1.8    1.4    1.3
:Thompson River
Davis City            0.6    0.6    0.6    0.6    0.6    0.6    0.6
:South Fork Chariton River
Promise City          3.5    3.4    3.4    3.3    3.1    3.0    3.0
:Chariton River
Chariton              4.7    4.5    4.1    3.8    3.4    2.0    1.8
Moulton              19.1   19.0   18.7   18.6   18.5   18.5   18.4
:East Nishnabotna River
Atlantic              2.9    2.9    2.9    2.6    2.4    2.2    2.2
:East Fork 102 River
Bedford              10.7   10.7   10.7   10.7   10.7    9.7    9.2


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.


...Current Conditions as of February 25th 2021...

* Snow Pack...the snow pack is above normal across the NWS Des Moines
  service area. Water equivalent of the snow pack is generally around
  1 to 2 inches, however it is 2 or more inches some areas especially
  eastern parts of the service area.

* Soil Moisture...soil moisture is generally below normal across the
  western service area, near normal across the central service area
  and below normal across the far eastern service area.

* Frost Depth...ground frost ranges from around 10 inches across the
  southern service area to 10 to 15 inches across the central and
  northern service area.

* Streamflows...streamflows are generally near normal across the
  service area, with some places reporting slightly above normal and
  some places reporting slightly below normal streamflows.

* Drought Conditions...drought conditions exist across the western
  service area. They are as extreme as D2 drought across the
  northwestern service area.

$$

Zogg



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