Flood Potential Outlook
Issued by NWS St. Louis, MO

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FGUS73 KLSX 271919
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Probabilistic Hydrologic Outlook
National Weather Service ST. LOUIS MO
217 PM CDT THU AUG 27 2020

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:  08/31/2020 - 11/29/2020

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Mississippi River
Canton              15.0   20.0   25.0 :  10    9   <5   <5   <5   <5
LaGrange            17.0   23.0   25.0 :   6    9   <5   <5   <5   <5
Quincy              19.0   22.0   26.0 :   7    9   <5    7   <5   <5
Lock & Dam 21       18.0   21.0   25.0 :   6    9   <5    7   <5   <5
Hannibal            17.0   22.0   24.0 :  12   10   <5   <5   <5   <5
Saverton            16.0   20.0   24.0 :  15   13   <5    8   <5   <5
Louisiana           15.0   20.0   25.0 :  20   21   <5    7   <5   <5
Clarksville         25.0   31.0   33.0 :  20   21   <5    6   <5   <5
Winfield            26.0   30.0   34.0 :  18   18   <5    8   <5   <5
Grafton             20.0   24.0   29.0 :  15   20    9    8   <5   <5
Mel Price LD        21.0   29.0   34.0 :  22   23    8   11    5    6
St. Louis           30.0   35.0   40.0 :  21   18   12   13    6    9
Chester             27.0   35.0   40.0 :  33   31   19   16   12   13
:North Fabius River
Ewing               11.0   17.0   20.0 :  24   28   <5    9   <5   <5
:Middle Fabius River
Ewing               12.0   17.0   20.0 :  27   27   14   12   <5    7
:South Fabius River
Taylor              10.0   14.0   19.0 :  31   26   20   16    7    5
:North River
Palmyra             13.0   16.0   22.0 :  21   16   13   13   <5   <5
:Mid Fork Salt River
Holliday            17.0   22.0   26.0 :  28   22    8    6   <5   <5
:Salt River
New London          19.0   25.0   27.0 :  <5   <5   <5   <5   <5   <5
:Cuivre River
Troy                21.0   25.0   29.0 :  43   27   21   12    5    5
Old Monroe          24.0   27.0   30.0 :  18   19   11   12   <5   <5
:Dardenne Creek
St. Peters          18.0   20.0   23.0 :  26   16   14   11   <5   <5
:Meramec River
Steelville          12.0   20.0   25.0 :  20   15   <5   <5   <5   <5
Sullivan            11.0   20.0   29.0 :  36   18   10   <5   <5   <5
:Bourbeuse River
Union               15.0   22.0   26.0 :  34   16   13    7   <5   <5
:Meramec River
Pacific             15.0   23.0   27.0 :  25   14    6   <5   <5   <5
:Big River
Byrnesville         16.0   20.0   28.0 :  34   14   15    8   <5   <5
:Meramec River
Eureka              19.0   26.0   31.0 :  24   15   11    6    7   <5
Valley Park         18.0   21.0   27.0 :  31   17   19   16   15   14
Fenton              23.0   29.0   32.0 :  28   17   15   15   12   10
Arnold              24.0   35.0   38.0 :  31   28   16   15    9   11
:Kaskaskia River
Vandalia            18.0   24.0   26.0 :  39   28   19    9    6   <5
Carlyle TW         423.5  431.0  435.0 :  <5   <5   <5   <5   <5   <5
:La Moine River
Ripley              22.0   23.0   27.0 :  19   19   16   16    6    8
:Moreau River
Jefferson City      17.0   25.0   29.0 :  50   41   28   23   15   12
:Maries River
Westphalia          10.0   15.0   20.0 :  36   30   15   12   <5   <5
:Gasconade River
Rich Fountain       20.0   25.0   30.0 :  21   20   12   11    5    5
:Missouri River
Jefferson City      23.0   25.0   30.0 :  30   28   28   24   15   16
:Osage River
St. Thomas          23.0   30.0   35.0 :   5    6   <5   <5   <5   <5
Mari-Osa Campgrou   19.0   22.0   25.0 :  25   26   10   13    7   11
:Missouri River
Chamois             17.0   28.0   31.0 :  39   39    6    9   <5   <5
Gasconade           22.0   34.0   37.0 :  37   38   <5   <5   <5   <5
Hermann             21.0   26.0   33.0 :  40   38   21   20    9   10
Washington          20.0   28.0   31.0 :  35   32   10   10    5    9
St. Charles         25.0   30.0   36.0 :  36   33   18   18    5    9

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: 08/31/2020 - 11/29/2020
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Canton                4.8    4.8    5.9    8.9   12.2   15.2   17.0
LaGrange              5.7    5.7    6.8    9.8   13.1   16.1   17.9
Quincy               11.9   11.9   12.2   12.9   15.3   18.2   20.2
Lock & Dam 21         5.4    5.4    6.4    9.9   13.8   17.1   18.9
Hannibal             10.4   10.5   11.0   12.7   14.9   17.3   19.2
Saverton              6.2    6.3    7.3   10.2   13.6   17.2   19.4
Louisiana            11.9   12.0   12.0   12.1   14.1   17.7   19.1
Clarksville          16.1   16.3   17.4   20.6   23.9   28.2   29.6
Winfield             15.9   16.2   17.2   20.9   24.1   28.3   29.6
Grafton              15.0   15.1   15.3   15.7   18.4   23.3   26.0
Mel Price LD          6.7    7.0    9.3   12.5   19.9   27.7   34.7
St. Louis             6.6    8.1   11.0   16.1   26.5   35.5   42.8
Chester              10.7   11.4   13.8   19.5   29.3   40.5   43.8
:North Fabius River
Ewing                 3.4    3.6    4.5    6.2   10.8   15.5   17.0
:Middle Fabius River
Ewing                 3.1    3.3    3.8    6.1   13.3   18.8   19.7
:South Fabius River
Taylor                2.7    3.1    4.5    6.5   12.0   17.6   19.9
:North River
Palmyra               4.9    5.0    5.8    6.8   12.0   17.4   19.0
:Mid Fork Salt River
Holliday              5.4    5.7    7.6   11.4   17.9   21.1   22.6
:Salt River
New London            3.2    4.2    6.6    9.2   10.3   13.1   14.4
:Cuivre River
Troy                  9.6    9.6   11.1   16.8   24.2   27.1   29.3
Old Monroe           12.3   12.6   13.6   17.6   23.0   27.3   29.4
:Dardenne Creek
St. Peters            6.9    9.6   13.1   15.6   18.2   21.2   21.8
:Meramec River
Steelville            1.9    1.9    2.8    6.8   10.4   15.6   17.5
Sullivan              3.1    3.2    5.4    8.7   12.6   20.2   22.7
:Bourbeuse River
Union                 2.6    3.5    5.4   11.4   17.2   22.8   24.0
:Big River
Byrnesville           3.9    4.6    6.9   12.7   17.1   22.1   27.0
:Meramec River
Eureka                4.2    4.8    7.7   12.8   18.2   26.7   34.7
Fenton                4.0    6.3   12.2   17.0   23.5   32.6   33.4
Arnold                8.5    9.6   12.3   17.3   26.8   37.9   40.6
:Kaskaskia River
Vandalia             10.5   10.5   12.4   16.0   22.0   25.3   26.5
Carlyle TW          415.5  415.5  416.3  418.3  419.7  421.9  422.4
:La Moine River
Ripley                4.7    5.6    8.7   11.0   18.5   26.2   27.5
:Moreau River
Jefferson City        2.0    2.0    4.3   17.1   26.2   32.5   38.0
:Maries River
Westphalia            1.0    1.1    3.0    7.3   12.7   16.1   17.4
:Gasconade River
Rich Fountain         2.9    3.2    5.2   10.4   18.0   25.3   29.6
:Missouri River
Jefferson City        7.9    9.0   12.8   16.5   26.3   32.6   35.2
:Osage River
St. Thomas            4.7    4.7    5.1   10.1   13.7   17.7   21.6
Mari-Osa Campgrou     4.7    5.8    8.7   10.9   19.0   22.1   29.1
:Missouri River
Chamois               3.5    5.2    8.0   12.5   21.9   26.1   29.4
Gasconade             6.3    6.7    9.9   15.5   26.7   30.6   32.9
Hermann               7.8    8.9   11.7   16.0   25.4   31.6   34.8
Washington            4.7    5.6    8.3   12.6   21.9   28.1   31.4
St. Charles          12.7   13.6   15.9   19.5   27.6   33.6   36.6

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--Nonexceedance Probabilities...

                            Chance of Falling Below Stages
                                 at Specific Locations
                          Valid Period: 08/31/2020 - 11/29/2020
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Canton                4.7    4.6    3.8    3.0    2.8    2.5    2.4
LaGrange              5.6    5.5    4.7    3.9    3.7    3.4    3.3
Quincy               11.8   11.8   11.5   10.9   10.9   10.9   10.9
Lock & Dam 21         5.3    5.1    4.4    3.5    3.3    3.0    2.9
Hannibal             10.4   10.3   10.0    9.8    9.7    9.6    9.6
Saverton              6.1    5.9    5.2    4.5    4.3    4.1    4.0
Louisiana            11.9   11.9   11.9   11.8   11.8   11.8   11.8
Clarksville          16.1   15.8   15.0   14.0   13.7   13.5   13.4
Winfield             15.9   15.6   14.8   13.8   13.6   13.3   13.2
Grafton              14.9   14.9   14.8   14.6   14.5   14.5   14.4
Mel Price LD          5.5    5.3    4.5    3.6    3.0    2.6    2.3
Chester               7.2    6.9    5.9    4.2    3.0    2.1    1.1
:North Fabius River
Ewing                 3.0    3.0    3.0    2.9    2.8    2.8    2.8
:Middle Fabius River
Ewing                 2.8    2.8    2.7    2.7    2.7    2.6    2.6
:South Fabius River
Taylor                1.6    1.6    1.4    1.4    1.3    1.2    1.2
:North River
Palmyra               4.3    4.2    4.1    4.1    4.1    4.0    4.0
:Mid Fork Salt River
Holliday              4.2    4.2    4.1    4.1    4.1    4.1    4.1
:Salt River
New London            5.1    4.7    4.0    3.1    2.2    2.2    2.2
:Cuivre River
Troy                  5.5    5.4    5.3    5.1    5.1    5.0    5.0
Old Monroe           11.9   11.7   10.5    9.5    9.4    9.4    9.3
:Dardenne Creek
St. Peters            1.1    1.1    1.0    1.0    0.9    0.9    0.9
:Meramec River
Steelville            1.5    1.5    1.4    1.2    1.1    1.1    1.0
Sullivan              2.7    2.6    2.4    2.3    2.2    2.0    2.0
:Bourbeuse River
Union                 2.2    2.1    2.0    1.9    1.7    1.6    1.6
:Big River
Byrnesville           2.5    2.4    2.0    1.7    1.6    1.4    1.3
:Meramec River
Eureka                3.7    3.6    3.4    3.3    3.2    3.1    3.0
Fenton                2.0    2.0    1.8    1.3    1.1    1.0    0.7
Arnold                6.9    6.9    6.7    6.5    6.3    6.3    6.1
:Kaskaskia River
Vandalia              3.0    2.8    2.4    2.3    2.2    2.2    2.2
Carlyle TW          412.7  411.2  411.2  411.2  411.2  411.2  411.2
:La Moine River
Ripley                4.5    4.5    4.5    4.4    4.3    4.3    4.2
:Moreau River
Jefferson City        1.4    1.4    1.4    1.4    1.3    1.3    1.3
:Maries River
Westphalia            0.3    0.3    0.3    0.3    0.3    0.3    0.3
:Gasconade River
Rich Fountain         2.6    2.6    2.4    2.1    2.0    2.0    2.0
:Missouri River
Jefferson City        6.0    5.8    5.5    4.5    4.2    3.9    2.8
:Osage River
St. Thomas            2.5    2.5    2.5    2.5    2.5    2.4    1.1
:Missouri River
Gasconade             6.3    6.3    6.3    6.3    6.3    6.3    6.3
Hermann               5.0    4.9    4.7    3.8    3.2    2.7    1.5
St. Charles          10.3   10.2   10.0    9.2    8.7    8.3    7.2

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.

Visit our web site weather.gov/lsx for more weather and water
information.

$$



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