Flood Potential Outlook
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3
000
FGUS73 KLSX 051938
ESFLSX
ILC001-009-013-027-051-149-MOC051-053-071-073-099-111-113-127-
137-151-163-173-183-189-221-112359-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE ST. LOUIS MO
135 PM CST THU MAR 05 2015

...Spring Flood and Water Resources Outlook Number 2...
...Flooding less likely along the Mississippi and Missouri Rivers...
...Local tributaries have mixed flood chances this spring...

This updated 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 Beardstown Illinois to its confluence with the
Mississippi River, and for tributary rivers in eastern Missouri, and
west central and southwest Illinois.

There is no flooding anywhere within the St. Louis Service Area, so
the probabilities within this outlook are not skewed by any ongoing
flooding.

This outlook is based on current streamflows and soil moisture over
the area, upstream snowpack in the Mississippi, Missouri, and
Illinois river basins, and forecast rainfall over the next two weeks
to three months.  More than expected rainfall could cause additional
flooding over the area, while less than expected rainfall could
rivers from reaching expected crests.

The chances of flooding along local tributaries in the St. Louis
Service Area over the next 90 days are mixed.  Across  Central
Missouri, flood chances are between 6 and 8 percent below the
seasonal average on the Maries River, the Gasconade River, and the
Moreau River.  However, after several recent snow events, flood
chances along tributaries in northeastern Missouri and western
Illinois are mostly 4 to 8 percent above the seasonal average.
Thanks to several inches of snow water equivalent across much of
north central Illinois, flood chances along the Illinois River and
the Kaskaskia River are also above average.  Snowpack in the upper
Illinois River basin contains 1 to 3 inches of water equivalent,
leading to flood probabilities more than 10 percent above the
historical average.  Similar water equivalent in the snowpack across
the Kaskaskia River basin is generating flood chances at least 23
percent higher than the historical average.  In the Meramec River
basin, the flood chances are within 6 percent of seasonal norms.
This reflects the typical lack of significant snowpack and near
normal soil moisture.

Meanwhile, this outlook update along the Mississippi and Missouri
rivers indicates the spring flood chances are below the seasonal
average.  In fact, flooding this spring is not likely from Canton,
Missouri to Saverton, Missouri, except at Hannibal, where flood
chances sit at 52 percent.  Minor flooding appears to be a bit more
likely downstream of Louisiana, but those chances of flooding remain
well below an average spring.  In addition, moderate flood chances
are running 10 to 23 percent below historical averages.  While
snowpack in the upper Mississippi River basin is widespread, it is
also quite shallow.  Simply put, this has been a lean year for
snowfall across the upper Midwest, and most of the upper Mississippi
River basin has much less snow on the ground than we typically see.
In the Missouri River basin, snow depths are also below the seasonal
average, with many areas south of the Missouri River having lost all
snowcover.  This combined with a soil moisture conditions ranging
from near to above normal over the lower Missouri River basin leads
to slightly below normal chances of flooding along lower Missouri
River this spring.

In the near term, the Climate Prediction Center calls for a strong
likelihood of above average temperatures in the 6 to 10 day and 8 to
14 day outlooks.  Precipitation in the 6 to 10 day outlook should be
below average, and near average during the 8 to 14 day period.  For
the month of March, temperatures will most likely be below average,
and there will be equal chances of precipitation being above
average, near average, or below average.  For the period March
through May, there are equal chances that temperatures and
precipitation will be above average, near average, or below average.

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:  3/9/2015 - 6/7/2015

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Dardenne Creek
St. Peters          18.0   20.0   23.0 :  38   38   24   24   13   13
:Mississippi River
Canton LD20         14.0   20.0   25.0 :  47   64   <5   15   <5   <5
Quincy              17.0   18.0   22.5 :  47   64   33   60    7   24
Hannibal            16.0   22.0   24.0 :  52   67    6   16   <5    7
Saverton LD22       16.0   20.0   22.0 :  46   63   13   35    6   21
Louisiana           15.0   20.0   25.0 :  64   69   10   33   <5   <5
Clarksville LD24    25.0   31.0   33.0 :  64   69    7   27   <5   12
Winfield LD25       26.0   30.0   34.0 :  53   67   18   40   <5    7
:North Fabius River
Ewing               11.0   14.0   18.0 :  47   43   23   24    9   10
:Middle Fabius River
Ewing               12.0   17.0   19.5 :  52   44   13   13    9    9
:South Fabius River
Taylor               9.5   14.0   19.0 :  60   53   16   15   <5   <5
:North River
Palmyra             13.0   16.0   22.0 :  50   44   23   20   <5   <5
:Mid Fork Salt River
Holliday            17.0   22.0   26.0 :  50   49    6   <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 :  58   52   30   30    7    7
Old Monroe          24.0   27.0   30.0 :  36   58   13   24   <5   10
:Meramec River
Steelville          12.0   20.0   25.0 :  44   40   <5   <5   <5   <5
Sullivan            11.0   20.0   29.0 :  69   70   15   13   <5   <5
:Bourbeuse River
Union               15.0   22.0   26.0 :  47   46    7    7   <5   <5
:Meramec River
Pacific             15.0   23.0   27.0 :  52   53    9    9   <5   <5
:Big River
Byrnesville         16.0   20.0   28.0 :  70   64   29   26   <5   <5
:Meramec River
Eureka              18.0   25.0   30.0 :  46   47   20   16   10   10
:Kaskaskia River
Carlyle TW         423.5  431.0  435.0 :  70   47   <5   <5   <5   <5
Vandalia            18.0   24.0   26.0 : >95   72   32   23   15    9
:La Moine River
Ripley              22.0   23.0   27.0 :  47   40   43   38   10    9
:Moreau River
Jefferson City      17.0   25.0   29.0 :  68   76   25   29   11   11
:Maries River
Westphalia          10.0   15.0   20.0 :  29   35   10    9   <5   <5
:Gasconade River
Rich Fountain       20.0   25.0   30.0 :  14   21   <5    7   <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: 3/9/2015 - 6/7/2015
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Dardenne Creek
St. Peters            9.5   10.1   11.7   15.4   20.8   24.2   24.8
:Mississippi River
Canton LD20           8.9    9.6   11.6   14.0   15.9   18.6   20.2
Quincy               12.9   13.2   14.8   17.0   19.2   22.1   24.2
Hannibal             12.5   13.1   14.3   16.3   18.2   20.4   22.6
Saverton LD22         9.8   10.8   12.7   15.9   18.2   20.9   23.2
Louisiana            12.1   12.2   13.3   16.3   18.2   20.1   22.5
Clarksville LD24     20.0   20.9   23.0   26.5   28.7   30.7   33.1
Winfield LD25        20.2   21.2   23.2   26.6   28.8   30.7   33.0
:North Fabius River
Ewing                 6.9    7.3    8.8   10.9   13.9   18.3   20.7
:Middle Fabius River
Ewing                 6.2    6.9    9.3   12.3   15.3   19.1   21.4
:South Fabius River
Taylor                6.7    7.1    7.9   10.2   12.4   15.1   17.5
:North River
Palmyra               8.2    8.5   10.6   13.3   15.9   20.2   21.2
:Mid Fork Salt River
Holliday             11.7   12.1   15.5   17.2   18.5   20.8   22.3
:Salt River
New London            9.5    9.6    9.9   10.6   12.2   14.7   16.1
:Cuivre River
Troy                 13.1   14.6   18.4   23.4   25.7   28.2   30.1
Old Monroe           16.9   17.6   20.1   22.7   25.5   28.5   30.0
:Meramec River
Steelville            4.3    5.6    8.1   11.5   13.7   15.8   18.8
Sullivan              6.8    7.5   10.0   14.5   17.6   21.7   25.5
:Bourbeuse River
Union                 9.1   10.2   12.3   14.9   18.2   21.1   23.9
:Meramec River
Pacific               4.9    7.1   10.7   15.3   18.9   23.0   24.6
:Big River
Byrnesville           8.8   12.0   15.2   18.0   20.8   23.6   25.8
:Meramec River
Eureka                8.5    9.7   13.3   17.1   24.3   30.5   33.1
:Kaskaskia River
Carlyle TW          422.8  423.2  423.5  424.3  425.7  426.4  426.5
Vandalia             21.1   21.2   21.8   22.6   25.3   26.9   27.5
:La Moine River
Ripley               14.6   16.4   19.8   21.7   25.0   27.3   28.2
:Moreau River
Jefferson City        5.3    9.5   15.8   19.4   25.0   30.1   34.7
:Maries River
Westphalia            2.9    3.1    4.3    7.1   10.8   14.8   17.2
:Gasconade River
Rich Fountain         5.2    6.5    8.4   11.4   17.3   21.9   23.4

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: 3/9/2015 - 6/7/2015
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Dardenne Creek
St. Peters            3.4    3.4    3.2    3.2    3.1    3.0    3.0
:Mississippi River
Canton LD20           4.0    3.6    3.3    3.2    3.2    3.1    2.5
Quincy               11.6   11.3   11.1   11.0   10.9   10.9   10.9
Hannibal             10.4   10.1   10.0   10.0    9.9    9.8    9.6
Saverton LD22         5.6    5.3    5.1    5.0    4.9    4.6    4.1
Louisiana            11.9   11.9   11.9   11.9   11.9   11.8   11.8
Clarksville LD24     16.0   15.8   15.5   15.3   14.9   14.2   13.7
Winfield LD25        15.8   15.6   15.4   15.2   14.8   14.1   13.5
:North Fabius River
Ewing                 3.3    3.2    3.1    3.0    2.9    2.8    2.8
:Middle Fabius River
Ewing                 3.2    3.1    3.0    2.9    2.9    2.8    2.8
:South Fabius River
Taylor                2.4    2.2    2.1    2.0    1.8    1.7    1.7
:North River
Palmyra               4.4    4.4    4.3    4.2    4.1    4.1    4.0
:Mid Fork Salt River
Holliday              4.7    4.6    4.5    4.5    4.4    4.3    4.3
:Salt River
New London            6.1    5.3    5.0    3.5    2.2    2.2    2.2
:Cuivre River
Troy                  6.0    5.8    5.5    5.3    5.1    5.0    5.0
Old Monroe           12.8   12.6   12.2   11.9   10.6    9.7    9.4
:Meramec River
Steelville            2.4    2.2    2.0    1.9    1.8    1.7    1.6
Sullivan              3.3    3.1    2.8    2.6    2.4    2.2    2.1
:Bourbeuse River
Union                 2.1    1.9    1.8    1.6    1.5    1.3    1.2
:Big River
Byrnesville           3.7    3.4    3.1    2.7    2.4    2.2    2.1
:Meramec River
Eureka                3.1    2.9    2.7    2.5    2.3    2.2    2.1
:Kaskaskia River
Carlyle TW          417.5  417.4  417.3  417.3  417.2  417.1  417.0
Vandalia              9.7    9.6    9.4    9.4    9.3    6.2    4.0
:La Moine River
Ripley                6.3    6.1    5.9    5.6    5.0    4.6    4.5
:Moreau River
Jefferson City        2.1    2.0    1.9    1.8    1.7    1.6    1.6
:Maries River
Westphalia            1.8    1.8    1.5    1.4    1.3    1.2    1.1
:Gasconade River
Rich Fountain         3.4    3.3    3.3    3.1    2.9    2.7    2.5

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/lsx for more weather and water
information.

The next outlook is scheduled to be issued the last week of this
month.

Fuchs
$$










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