Flood Potential Outlook
Issued by NWS La Crosse, WI

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WIC001-011-019-023-043-053-057-063-081-103-119-121-123-282359-

Probabilistic Hydrologic Outlook
National Weather Service La Crosse WI
916 AM CST Thu Feb 25 2021

...Second Spring Hydrologic Outlook and Summary...

The overall risk for flooding remains near normal along the main
stem of the Mississippi River this year. Risk for flooding along the
tributaries is also near normal, except across portions of northeast
Iowa and far southwest Wisconsin, where the risk remains slightly
above normal depending on how the Spring thaw transpires.

The next Spring Flood Outlook release will be on Thursday March 11th.

This information is the second of three planned hydrologic outlooks
providing spring snow melt and flood potential information for the
coming spring. The information that goes into this outlook was
collected from a number of partners of the National Weather Service
including the United States Geological Survey, the US Army Corps of
Engineers, the Midwest Region Climate Center, the High Plains
Regional Climate Center, US Drought Monitor, the Climate Prediction
Center, and the National Operational Remote Sensing Center.

This outlook is a summary of the past and present basin conditions
for parts of southeast Minnesota, northeast Iowa, and southwest into
central Wisconsin.

...Flood Potential Highlights...

The overall flood risk for the Upper Mississippi River Basin is near
normal due to continued drier than normal conditions in many areas
and limited snowpack.  Early this winter, storm systems brought
rains to portions of Iowa and far southern Wisconsin increasing soil
moisture slightly. Also, a few winter systems brought heavier snow
to these same areas, therefore the flooding risk is near to slightly
above normal for a few locations.

Snow cover is around normal and even a little below in some areas.
However, in the band of snow over portions of northeast Iowa and
southern Wisconsin there is as much as 12 to 18 inches with a water
content of 2 to 4.5 inches.

The cold temperatures during the first half of February resulted in
more river ice and also helped drive the frost depth a little deeper
into the soil, with frost depths ranging from 5 to 16 inches. River
ice conditions could increase the potential for a couple of ice jams
depending on temperature and precipitation trends as we go into the
thaw.

...Climate Outlook Information...

From December 1 through February 24, precipitation deficits are up
to 2 inches below normal.  The largest deficits are found across
northeast Iowa, southeast Minnesota, and in west central into north
central Wisconsin.  Due to the lack of precipitation from late
summer 2020 through mid-February 2021, these aforementioned areas
are abnormally dry according to the U.S. Drought Monitor.

Looking ahead to March, the Climate Prediction Center (CPC) has
forecast enhanced chances of above normal temperatures across
northeast Iowa and southwest Wisconsin.  Elsewhere, there is no
strong climate signal, so the forecast is for equal chances of
warmer, near, and colder than normal.  The March CPC precipitation
forecast is slightly tilted toward wetter than normal across
Wisconsin, and equal chances of drier, near, and wetter than normal
for northeast Iowa and southeast Minnesota.  During March, the 1981-
2010 precipitation normals range from 1.6 to 2.2 inches.

During La Ninas, Aprils tend to see near normal temperatures in the
Upper Mississippi River Valley.  They are typically wetter than
normal across northeast Iowa, southeast Minnesota, and southwest
Wisconsin, and near normal in west central through north central
Wisconsin.  However, neither signal is statistically significant, so
confidence is not high that will occur this April. During April,
precipitation normals range from 2.50 to 3.25 inches north of
Interstate 90 and 3.25 to 4.00 inches across the remainder of the
area.

Things can change as we get into the Spring thaw, so continue to
monitor the latest information from the National Weather Service.

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 greater 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

--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Mississippi River
Lake City           16.0   18.0   20.0 :  18   26    9    9   <5    5
Wabasha             12.0   14.0   16.0 :  52   60   14   23    6    8
Alma Dam 4          16.0   17.0   18.0 :   5    7   <5    6   <5   <5
MN City Dam 5      660.0  662.0  665.0 :  18   28    9   16   <5    6
Winona Dam 5A      655.0  659.0  661.0 :  23   41    8    9   <5    6
Winona              13.0   15.0   18.0 :  31   47   17   24    7    8
Trempealeau        647.0  649.0  651.0 :  22   38   10   16   <5    6
La Crescent        641.0  643.0  645.0 :  19   31   10   14   <5    7
La Crosse           12.0   13.0   15.5 :  30   49   17   26    6    8
Genoa              631.0  634.0  636.0 :  38   51   10   14   <5    7
Lansing             17.0   19.0   20.0 :   9   12   <5    7   <5   <5
Lynxville          625.0  628.0  631.0 :  18   25    7    9   <5   <5
McGregor            16.0   19.0   22.0 :  53   55   16   32    8   10
Guttenberg          15.0   18.0   21.0 :  39   48   14   15   <5    5
:Zumbro River
Zumbro Falls        18.0   24.0   26.0 :   6   10   <5   <5   <5   <5
:South Fork Zumbro River
Rochester           14.0   18.0   20.0 :  <5   <5   <5   <5   <5   <5
:Root River
Houston             15.0   17.0   18.0 :  17   10   <5   <5   <5   <5
:South Branch Root River
Lanesboro           12.0   16.0   18.0 :  <5   <5   <5   <5   <5   <5
:Cedar River
Lansing             18.0   20.0   22.0 :  <5    6   <5   <5   <5   <5
Austin              15.0   18.0   20.0 :  <5    7   <5    5   <5   <5
Charles City        12.0   15.0   18.0 :  11   22   <5    8   <5    7
:Turtle Creek
Austin              10.5   12.0   14.0 :  22   17   12   11   <5   <5
:Turkey River
Elkader             12.0   16.0   20.0 :  67   51   32   22   11    5
Garber              17.0   20.0   23.0 :  53   40   34   23   24   17
:Upper Iowa River
Decorah             12.0   13.0   14.0 :  <5   <5   <5   <5   <5   <5
Dorchester          14.0   17.0   19.0 :  15   23    6    8   <5    5
:Trempealeau River
Arcadia              8.0    9.0   10.0 :  13   <5   <5   <5   <5   <5
Dodge               10.5   11.0   12.0 :  17   13   12    5   <5   <5
:Black River
Neillsville         18.0   20.0   22.0 :  <5   <5   <5   <5   <5   <5
Black River Falls   47.0   51.0   55.0 :  53   62   26   28   <5    8
Galesville          12.0   13.0   15.0 :  51   56   38   37   <5   <5
:Kickapoo River
La Farge            12.0   13.0   14.0 :  <5   <5   <5   <5   <5   <5
Viola               14.0   16.0   18.0 :  25   12   <5   <5   <5   <5
Readstown           11.0   14.0   16.0 :  60   39   <5   <5   <5   <5
Soldiers Grove      13.0   16.0   19.0 :  36   30   <5   <5   <5   <5
Gays Mills          13.0   15.0   17.0 :  75   50   <5   10   <5   <5
Steuben             12.0   13.0   15.0 :  38   26   13   10   <5   <5
:Wisconsin River
Muscoda              9.0   10.0   11.0 :  14   18    6    6   <5   <5
:Yellow River
Necedah             15.0   16.5   18.0 :  71   78   39   50   17   19


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%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Lake City            10.6   11.1   12.8   13.8   15.0   17.0   18.9
Wabasha               9.7   10.0   11.5   12.0   12.8   14.4   16.3
Alma Dam 4            7.7    8.1    9.6   10.6   11.9   14.0   16.0
MN City Dam 5       654.2  654.7  656.5  657.8  659.1  661.6  664.1
Winona Dam 5A       649.7  650.2  652.0  653.4  654.8  657.5  660.0
Winona                8.2    8.7   10.6   11.8   13.3   16.1   18.6
Trempealeau         642.7  643.1  644.6  645.7  646.8  649.0  650.6
La Crescent         635.8  636.7  638.3  639.4  640.5  642.9  644.5
La Crosse             7.7    8.6   10.1   11.3   12.2   14.3   15.6
Genoa               626.6  627.7  629.3  630.5  631.5  633.9  635.6
Lansing               9.2    9.7   11.0   12.3   13.6   16.5   18.5
Lynxville           618.6  619.4  620.9  622.6  623.8  626.8  629.1
McGregor             11.6   12.6   14.1   16.3   18.1   21.3   22.9
Guttenberg           10.7   11.5   13.0   14.6   16.1   18.6   19.8
:Zumbro River
Zumbro Falls          7.7    8.2    9.0   10.9   12.3   13.7   18.5
:South Fork Zumbro River
Rochester             4.3    4.5    5.3    6.2    7.0    9.2   11.9
:Root River
Houston               7.1    7.9    9.9   11.1   13.5   16.2   16.6
:South Branch Root River
Lanesboro             4.1    5.0    6.0    7.1    8.3    9.7   10.9
:Cedar River
Lansing              13.2   13.5   14.2   15.1   15.8   16.4   17.1
Austin                6.8    7.2    8.3    9.7   11.0   12.4   14.3
Charles City          4.6    5.0    6.1    7.4    9.1   12.2   14.8
:Turtle Creek
Austin                5.5    5.8    7.3    8.4    9.8   12.3   13.6
:Turkey River
Elkader               8.6    9.3   11.2   13.5   17.3   20.3   21.9
Garber               11.2   12.7   14.4   17.6   21.6   25.1   27.8
:Upper Iowa River
Decorah               3.2    3.3    4.0    4.4    5.5    7.2    8.3
Dorchester            9.0    9.2   10.1   10.8   12.2   15.6   18.2
:Trempealeau River
Arcadia               5.6    5.8    6.7    7.2    7.5    8.2    8.4
Dodge                 8.1    8.5    8.9    9.7   10.3   11.3   11.4
:Black River
Neillsville           8.0    8.6    9.2   10.7   12.8   13.9   15.4
Black River Falls    42.2   42.9   44.1   47.3   51.2   52.8   54.1
Galesville            8.8    9.4   10.6   12.1   13.2   13.7   13.9
:Kickapoo River
La Farge              5.6    5.9    6.6    7.5    9.1   10.4   10.9
Viola                10.2   10.4   11.1   12.2   14.0   15.1   15.4
Readstown             8.5    9.0   10.4   11.2   12.0   12.7   12.8
Soldiers Grove        9.9   10.5   12.0   12.7   13.7   14.2   14.3
Gays Mills           11.4   12.1   13.1   13.5   14.2   14.8   14.9
Steuben               9.8   10.3   10.9   11.7   12.4   13.0   13.2
:Wisconsin River
Muscoda               4.7    4.9    6.1    7.0    8.0    9.4   10.1
:Yellow River
Necedah              13.3   14.0   14.6   15.9   17.1   18.4   19.2

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: 03/01/2021 - 05/30/2021
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Lake City             5.9    5.9    5.9    5.9    5.9    5.9    5.8
Wabasha               6.9    6.9    6.9    6.9    6.9    6.9    6.8
Alma Dam 4            4.3    4.3    4.3    4.3    4.2    4.2    4.2
MN City Dam 5       651.1  651.1  651.1  651.1  651.0  651.0  651.0
Winona Dam 5A       645.6  645.6  645.6  645.6  645.6  645.6  645.6
Winona                5.2    5.2    5.2    5.2    5.2    5.2    5.2
Trempealeau         639.5  639.4  639.4  639.4  639.4  639.4  639.4
La Crescent         631.3  631.3  631.3  631.3  631.3  631.3  631.3
La Crosse             4.9    4.9    4.8    4.8    4.8    4.8    4.8
Genoa               620.9  620.9  620.8  620.8  620.8  620.8  620.7
Lansing               7.8    7.8    7.8    7.8    7.8    7.7    7.7
Lynxville           612.6  612.6  612.5  612.5  612.4  612.4  612.3
McGregor              7.4    7.4    7.4    7.4    7.4    7.3    7.3
Guttenberg            4.2    4.2    4.1    4.1    4.0    4.0    4.0
:Zumbro River
Zumbro Falls          5.1    5.1    5.1    5.1    5.0    5.0    5.0
:South Fork Zumbro River
Rochester             2.7    2.7    2.7    2.6    2.6    2.6    2.6
:Root River
Houston               3.0    3.0    3.0    3.0    3.0    3.0    3.0
:South Branch Root River
Lanesboro             1.5    1.5    1.5    1.5    1.5    1.5    1.5
:Cedar River
Lansing               9.1    9.1    9.1    9.1    9.1    9.1    9.1
Austin                3.1    3.0    3.0    3.0    3.0    3.0    3.0
Charles City          2.0    2.0    2.0    2.0    2.0    2.0    2.0
:Turtle Creek
Austin                1.3    1.3    1.3    1.3    1.3    1.3    1.2
:Turkey River
Elkader               5.0    5.0    5.0    5.0    5.0    5.0    5.0
Garber                6.1    6.1    6.1    6.1    6.1    6.1    6.1
:Upper Iowa River
Decorah               1.1    1.1    1.1    1.1    1.1    1.0    1.0
Dorchester            6.7    6.7    6.7    6.7    6.7    6.7    6.7
:Trempealeau River
Arcadia               3.2    3.2    3.2    3.2    3.2    3.2    3.2
Dodge                 5.1    5.0    5.0    5.0    5.0    4.9    4.9
:Black River
Neillsville           2.8    2.8    2.8    2.8    2.8    2.8    2.8
Black River Falls    35.9   35.9   35.9   35.9   35.9   35.9   35.9
Galesville            3.3    3.3    3.3    3.3    3.2    3.2    3.2
:Kickapoo River
La Farge              3.0    3.0    3.0    3.0    2.9    2.9    2.9
Viola                 7.3    7.2    7.2    7.2    7.2    7.2    7.1
Readstown             3.8    3.8    3.8    3.7    3.7    3.7    3.7
Soldiers Grove        4.2    4.1    4.1    4.0    4.0    3.9    3.9
Gays Mills            6.5    6.4    6.4    6.4    6.3    6.3    6.3
Steuben               6.0    5.9    5.9    5.9    5.8    5.8    5.7
:Wisconsin River
Muscoda               1.0    1.0    0.9    0.9    0.8    0.8    0.8
:Yellow River
Necedah               9.3    9.3    9.3    9.3    9.3    9.3    9.3


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 and 90 day long-range
outlooks of temperature and precipitation. By providing a range
of probabilities...the level of rise associated with long-range
planning decisions can be determined. These probabilistic
forecasts are part of the National Weather Service`s Advanced
Hydrologic Prediction Service.

All of this information is also available in graphical format
on the internet at:

http://www.weather.gov/lacrosse

The next outlook will be issued in late March.

$$


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