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The Weather Hazard Threefold

A large dome of high pressure will continue the sweltering heat in parts of the West and the central Plains. Meanwhile, a cold front will produce severe thunderstorms, capable of all hazards, the next few days from the Mid-Upper Mississippi Valley into the Ohio Valley and Great Lakes. Finally, Potential Tropical Cyclone Three will bring heavy rain and flooding to the northern Gulf Coast. Read More >

 

Figure 1: Snow Water Equivalent Image. (Courtesy of NOHRSC)
Figure 2: USGS Current Streamflow Analysis
Figure 3: 180 Day Percentage of Mean Precipitation Analysis (Courtesy of Midwest Climate Center)
Figure 4: Palmer Drought Severity Index
Figure 5: Soil Moisture (mm)
Figure 6: Three Month Temperature Outlook
Figure 7: Three Month Precipitation Outlook

NWS
St. Louis, Missouri

Spring Flood Outlook
Issued: March 11, 2021

Snow Water EquivalentCurrent Snow Water Equivalent

Streamflow AnalysisUSGS Stream Analysis

  30 Day Rainfall DeparturePrecipitation 30 Day Percentage of Mean

Soil Moisture PercentileCurrent Soil Moisture

1-Month Precip Outlook3 Month Precipitation Outlook

1-Month Temp Outlook3 Month Temperature Outlook

3-Month Precip Outlook3 Month Precipitation Outlook

3-Month Temp Outlook3 Month Temperature Outlook

Probabilistic Hydrologic Outlook
National Weather Service ST. LOUIS MO
1215 PM CST THU MAR 11 2021

...Spring Flood and Water Resources Outlook Number 3...
...Minor flooding likely along the Mississippi, Missouri, and
Illinois Rivers...
...Most local streams have a near normal flood risk this spring...

This outlook uses the term St. Louis Service Area to refer to the
Mississippi River from above Canton Missouri to above Cape Girardeau
Missouri, the Missouri River above Jefferson City Missouri to its
confluence with the Mississippi River, the Illinois River downstream
from its confluence with the LaMoine River to its confluence with
the Mississippi River, and for tributary rivers in eastern Missouri,
and west central and southwest Illinois.

While there is no ongoing flooding anywhere within the St. Louis
Service Area, minor flooding is currently forecast over portions of
central Missouri.  This near-term flooding influences the 90-day
statistics for a few of the smaller tributaries in this outlook.

This outlook is based on current streamflows and soil moisture over
the area, and upstream snowpack, particularly in the Mississippi,
Missouri, and Illinois river basins. The statistics are based on
about 30 to 60+ years of historical rainfall and stream crests. More
than normal rainfall could cause higher-than-expected crests at
individual forecast locations, while less than normal rainfall could
keep streams from reaching "likely" crests.

The Mississippi and Illinois rivers are experiencing near normal
streamflow for this time of year, while flows along the Missouri
River are now below normal streamflow through most of the past
winter.  This is providing a low to average starting point for these
rivers to accept future runoff.  Soils have dried out considerably
across the upper Midwest since last summer, while local areas have
near to below normal soil moisture.  Drier soils are the rule from
Minnesota and the Dakotas through northern Kansas. This will provide
the upper Mississippi River and middle Missouri River basins with
additional storage, which acts as a deterrent to flooding.  Finally,
snowpack across the upper Midwest and northern Plains states have
mostly melted into runoff the past two weeks. The Plains states
north through the Dakotas are essentially snow-free, except for a
band of new snowcover extending from western South Dakota and
western Nebraska into central Minnesota.  The snow water equivalent
in this area is estimated to exceed two inches over west central
Minnesota.  However, south of this snowcover the ground is bare
across Missouri, Illinois, Iowa, Wisconsin, southeast Nebraska, and
southeast Minnesota.  For locations where minor flooding is not
already imminent, this translates into mostly below normal flood
probabilities along the Missouri and Mississippi rivers.  However,
this still means minor flooding remains likely this spring along
both rivers.

For local basins, the chances for flooding at most locations
throughout the St. Louis service area are near average.  Minor
flooding remains likely along the North Fabius River, the Middle
Fork Salt River, the Cuivre River, the Meramec River, the Bourbeuse
River, the Big River, the Moreau River, the Maries River, and the
upper Kaskaskia River. For parts of the Meramec, Bourbeuse, Moreau,
and Maries rivers, this likelihood is tied to near-term forecast
rainfall.

In the near term, the Climate Prediction Center calls for below
normal temperatures throughout the bi-state region and near to below
normal precipitation chances in the 6 to 10 day outlook. By days 8
through 14, temperatures should warm to near or above normal, while
precipitation totals should mostly likely be below normal. Looking
ahead to the next 3 months of April through June, temperatures are
expected to be above normal throughout the St. Louis service area,
while precipitation chances will be above normal for all but
southwestern Illinois and equal chances of being above, below, or
near normal for southwestern Illinois and all of Missouri.

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:  03/15/2021 - 06/13/2021

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Mississippi River
Canton              15.0   20.0   25.0 :  55   63   10   16   <5   <5
LaGrange            17.0   23.0   25.0 :  30   53   <5   10   <5   <5
Quincy              19.0   22.0   26.0 :  38   56   14   28   <5   10
Lock & Dam 21       18.0   21.0   25.0 :  33   54   13   26   <5   10
Hannibal            17.0   22.0   24.0 :  56   61   10   15   <5   10
Saverton            16.0   20.0   24.0 :  66   65   21   39    7   11
Louisiana           15.0   20.0   25.0 : >95   73   18   34   <5    8
Clarksville         25.0   31.0   33.0 : >95   73   16   28    8   14
Winfield            26.0   30.0   34.0 : >95   67   22   41   <5   10
Grafton             20.0   24.0   29.0 : >95   75   21   35   <5    6
Mel Price LD        21.0   29.0   34.0 : >95   74   19   38   <5    6
St. Louis           30.0   35.0   40.0 :  56   66   28   45    6   11
Chester             27.0   35.0   40.0 : >95   79   42   57   19   24
:North Fabius River
Ewing               11.0   17.0   20.0 :  60   52   15   15   10   10
:Middle Fabius River
Ewing               12.0   17.0   20.0 :  47   47   17   14   11   10
:South Fabius River
Taylor              10.0   14.0   19.0 :  49   49   16   16   <5   <5
:North River
Palmyra             13.0   16.0   22.0 :  27   26   11   11   <5   <5
:Mid Fork Salt River
Holliday            17.0   22.0   26.0 :  69   55    7    5   <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 :  55   54   28   27    9    9
Old Monroe          24.0   27.0   30.0 :  55   61   24   26    6   14
:Dardenne Creek
St. Peters          18.0   20.0   23.0 :  30   30   19   18   <5   <5
:Meramec River
Steelville          12.0   20.0   25.0 :  53   41    6   <5   <5   <5
Sullivan            11.0   20.0   29.0 : >95   66   18   12   <5   <5
:Bourbeuse River
Union               15.0   22.0   26.0 : >95   50   11   11   <5   <5
:Meramec River
Pacific             15.0   23.0   27.0 : >95   40    8    7   <5   <5
:Big River
Byrnesville         16.0   20.0   28.0 :  67   49   26   20   <5   <5
:Meramec River
Eureka              19.0   26.0   31.0 : >95   42   21   17    7    7
Valley Park         18.0   21.0   27.0 :  63   47   38   39   17   19
Fenton              23.0   29.0   32.0 :  53   54   14   20   10   12
Arnold              24.0   35.0   38.0 : >95   76   24   27   11   21
:Kaskaskia River
Vandalia            18.0   24.0   26.0 : >95   83   39   36   19   19
Carlyle TW         423.5  431.0  435.0 :  40   41   <5   <5   <5   <5
:La Moine River
Ripley              22.0   23.0   27.0 :  45   45   34   35   12   10
:Moreau River
Jefferson City      17.0   25.0   29.0 : >98   86  >98   44   22   19
:Maries River
Westphalia          10.0   15.0   20.0 : >98   52   21   19   <5   <5
:Gasconade River
Rich Fountain       20.0   25.0   30.0 :  35   37   26   26    5    6
:Missouri River
Jefferson City      23.0   25.0   30.0 :  52   62   41   56   14   20
:Osage River
St. Thomas          23.0   30.0   35.0 :  15   16   <5   <5   <5   <5
Mari-Osa Campgrou   19.0   22.0   25.0 :  46   61   20   25   11   13
:Missouri River
Chamois             17.0   28.0   31.0 :  69   73   11   11    6    6
Hermann             21.0   26.0   33.0 :  77   78   38   51   12   13
Washington          20.0   28.0   31.0 :  56   69   13   14   10   10
St. Charles         25.0   30.0   36.0 :  66   72   26   33   10    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: 03/15/2021 - 06/13/2021
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Canton               13.5   13.5   13.8   15.2   16.8   19.9   21.2
LaGrange             14.4   14.4   14.7   16.1   17.7   20.8   22.1
Quincy               16.4   16.4   16.7   18.5   20.0   23.7   25.3
Lock & Dam 21        15.3   15.3   15.6   17.4   18.8   22.5   24.2
Hannibal             16.0   16.0   16.1   17.5   18.9   21.9   23.9
Saverton             15.4   15.4   15.7   17.4   19.1   22.5   24.4
Louisiana            15.9   16.0   16.4   17.6   18.9   21.7   23.6
Clarksville          26.1   26.2   26.6   27.9   29.4   32.3   34.1
Winfield             26.3   26.4   26.7   28.1   29.8   32.2   34.0
Grafton              20.1   20.1   20.5   22.1   23.8   25.6   26.6
Mel Price LD         21.2   21.3   22.7   24.3   28.3   31.2   32.9
St. Louis            26.7   26.8   28.6   30.8   35.7   38.8   41.2
Chester              31.4   31.4   31.8   33.7   37.5   42.2   44.5
:North Fabius River
Ewing                10.2   10.3   10.4   11.5   15.1   19.9   22.6
:Middle Fabius River
Ewing                10.6   10.6   10.7   11.6   15.4   20.2   22.4
:South Fabius River
Taylor                8.3    8.3    8.8   10.0   12.7   16.5   18.4
:North River
Palmyra               9.8    9.9    9.9   10.7   13.3   16.1   18.2
:Mid Fork Salt River
Holliday             16.9   16.9   17.0   17.5   19.3   21.1   22.2
:Salt River
New London            9.1    9.1    9.6   10.6   12.1   13.2   14.8
:Cuivre River
Troy                 18.9   18.9   19.0   22.6   25.4   27.8   29.7
Old Monroe           23.2   23.2   23.3   24.6   26.8   29.2   30.7
:Dardenne Creek
St. Peters           11.8   11.8   12.0   15.1   19.4   20.7   22.0
:Meramec River
Steelville            9.0    9.0    9.5   12.3   14.9   16.8   20.3
Sullivan             12.7   12.7   12.9   15.1   18.8   21.7   27.1
:Bourbeuse River
Union                16.0   16.0   16.1   16.4   19.8   22.9   25.9
:Meramec River
Pacific              15.5   15.5   15.7   16.1   19.5   22.4   26.7
:Big River
Byrnesville          14.9   15.0   15.3   17.0   20.3   23.2   25.9
:Meramec River
Eureka               19.2   19.4   19.5   20.0   24.4   30.3   36.2
Valley Park          17.7   17.8   17.9   18.7   26.2   31.7   38.7
Fenton               22.1   22.2   22.4   23.3   28.0   32.0   38.1
Arnold               27.9   28.0   28.3   30.0   34.0   39.7   42.3
:Kaskaskia River
Vandalia             23.4   23.4   23.5   23.6   25.7   27.3   28.9
Carlyle TW          421.9  421.9  422.5  423.2  424.0  425.5  425.9
:La Moine River
Ripley               18.4   18.4   18.7   21.2   25.2   27.4   28.6
:Moreau River
Jefferson City       26.2   26.2   26.2   26.2   28.5   33.6   40.1
:Maries River
Westphalia           10.2   10.2   10.2   11.1   14.3   17.6   18.9
:Gasconade River
Rich Fountain        12.9   12.9   12.9   17.2   25.5   29.1   30.9
:Missouri River
Jefferson City       14.0   15.7   19.2   24.0   28.1   33.9   36.1
:Osage River
St. Thomas           12.2   12.2   12.2   13.8   17.3   25.7   27.0
Mari-Osa Campgrou    12.9   13.0   14.9   18.1   20.4   25.6   29.2
:Missouri River
Chamois              13.7   13.7   16.2   20.6   23.4   28.7   31.1
Hermann              18.3   19.2   21.1   24.4   28.5   34.5   35.8
Washington           14.8   15.5   17.4   20.8   24.8   31.4   34.2
St. Charles          21.4   22.0   23.7   26.7   30.3   35.8   37.2

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: 03/15/2021 - 06/13/2021
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Canton                9.4    8.8    7.0    5.5    4.0    3.2    2.7
LaGrange             10.3    9.7    7.9    6.4    4.9    4.1    3.6
Quincy               13.0   12.8   12.4   12.1   11.6   10.9   10.9
Lock & Dam 21        10.5    9.5    7.5    6.0    4.5    3.8    3.2
Hannibal             13.0   12.3   11.4   10.7   10.0    9.8    9.7
Saverton             10.8    9.5    8.0    6.8    5.4    4.7    4.3
Louisiana            12.3   12.1   12.0   12.0   11.9   11.9   11.8
Clarksville          21.5   19.8   18.4   16.9   15.1   14.3   13.7
Winfield             21.6   19.8   18.2   16.7   14.9   14.2   13.6
Grafton              15.8   15.7   15.4   15.2   14.9   14.6   14.5
Mel Price LD         14.6   12.5   10.0    8.0    5.8    4.1    3.3
St. Louis            17.0   16.2   11.6    8.8    5.9    2.0    0.5
Chester              19.3   18.7   15.0   12.2    9.3    5.5    4.0
:North Fabius River
Ewing                 3.6    3.6    3.5    3.3    3.2    3.1    3.1
:Middle Fabius River
Ewing                 3.2    3.2    3.1    3.0    3.0    2.9    2.9
:South Fabius River
Taylor                2.6    2.5    2.4    2.2    2.1    2.0    1.9
:North River
Palmyra               4.7    4.7    4.6    4.5    4.4    4.4    4.4
:Mid Fork Salt River
Holliday              4.1    4.1    4.0    4.0    4.0    4.0    4.0
:Salt River
New London            5.0    5.0    5.0    4.9    3.1    2.1    2.1
:Cuivre River
Troy                  6.5    6.3    6.0    5.6    5.5    5.4    5.3
Old Monroe           16.6   15.2   14.3   12.7   10.7    9.7    9.4
:Dardenne Creek
St. Peters            1.6    1.6    1.4    1.3    1.2    1.2    1.2
:Meramec River
Steelville            2.4    2.1    1.9    1.7    1.6    1.4    1.4
Sullivan              3.6    3.3    3.1    2.8    2.6    2.5    2.5
:Bourbeuse River
Union                 2.7    2.7    2.5    2.3    2.2    2.1    2.1
:Big River
Byrnesville           3.7    3.3    2.8    2.5    2.2    2.0    1.9
:Meramec River
Eureka                4.7    4.3    4.1    3.7    3.5    3.4    3.3
Fenton                5.4    4.7    3.8    2.7    2.1    1.7    1.6
Arnold               14.0   13.1   10.4    8.0    7.1    6.8    6.6
:Kaskaskia River
Vandalia              9.3    7.9    4.1    3.2    3.0    2.8    2.7
Carlyle TW          419.1  419.0  419.0  411.5  411.2  411.2  411.2
:La Moine River
Ripley                7.0    6.5    5.9    5.5    5.2    4.9    4.8
:Moreau River
Jefferson City        2.1    2.1    1.9    1.8    1.7    1.6    1.6
:Maries River
Westphalia            2.0    1.8    1.6    1.4    1.2    1.2    1.1
:Gasconade River
Rich Fountain         4.3    4.3    4.2    3.6    3.2    3.2    3.1
:Missouri River
Jefferson City        7.3    7.1    5.6    4.7    3.7    3.5    3.5
:Osage River
St. Thomas            4.4    3.8    2.9    2.5    2.5    1.9    1.4
:Missouri River
Hermann               8.7    8.5    7.5    6.6    6.0    5.6    5.4
Washington            6.6    6.0    4.9    4.1    3.5    3.1    2.9
St. Charles          11.7   11.7   11.7   11.0   10.2    9.6    9.4

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.

The next outlook will be issued on the 25th of March.

$$
Fuchs