Flood Potential Outlook
Issued by NWS La Crosse, WI

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HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE LA CROSSE WI
340 PM CST Thu Mar 1 2018

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

The following information is the second of two planned hydrologic
outlooks providing spring snow melt and flood potential information.
This outlook contains information which was collected from a number
of sources, including the United States Geological Survey (USGS),
the US Army Corps of Engineers (USACE), Midwest Regional Climate
Center (MRCC), High Plains Regional Climate Center (HPRCC), US
Drought Monitor (NIDIS), and the National Operational Remote Sensing
Center (NOHRSC).

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

If required by conditions, a third outlook may be issued on
Thursday, March 15th.

*** Flood Potential Highlights ***

The updated flood potential for the spring shows a near to
slightly above normal risk for flooding as of March 1st for much
of the area. The locations most likely to experience mainly minor
flooding include those along the main stem of the Mississippi
River.

During meteorological winter of December through February,
temperatures across the region ranged from near normal to 3
degrees colder than normal. Meanwhile, precipitation anomalies
since November are running anywhere from 0 to 2 inches below
normal.

As of March 1st, snowpack generally averaged 3 to 15 inches
north of Interstate 90. The highest total was at Medford WI. This
snowpack has anywhere from 1 to 2 inches of water within it, with
isolated 3 inch amounts in the Minnesota, St Croix, Chippewa, and
upper portions of the Mississippi watersheds.

With longer stretches of cold weather this winter, frost depths
continue average 24 to 36 inches currently, and many rivers have
partial to total ice cover. Deeply frozen ground may play a role
over the next few weeks, with any heavy rain that occurs likely to
runoff quickly. In addition, rivers with ice may experience ice
jamming should heavy rains occur.

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: 03/11/2018 - 06/02/2018

                                       :    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 :  45   25   18    9    8    5
Wabasha             12.0   14.0   16.0 :  89   59   32   19   15    8
Alma Dam 4          16.0   17.0   18.0 :  14    8   10    6    6   <5
MN City Dam 5      660.0  662.0  665.0 :  50   27   22   12   11    6
Winona Dam 5A      655.0  659.0  661.0 :  69   38   17    9   10    6
Winona              13.0   15.0   18.0 :  76   44   43   22   16    9
Trempealeau        647.0  649.0  651.0 :  67   37   24   13   12    7
La Crescent        641.0  643.0  645.0 :  57   30   20   12   11    7
La Crosse           12.0   13.0   15.5 :  74   45   46   26   14    8
Genoa              631.0  634.0  636.0 :  77   48   20   11   11    7
Lansing             17.0   19.0   20.0 :  17   10   12    8    7   <5
Lynxville          625.0  628.0  631.0 :  42   23   16    9    7   <5
McGregor            16.0   19.0   22.0 :  79   52   41   27   16    9
Guttenberg          15.0   18.0   21.0 :  70   46   17   14   10   <5
:Zumbro River
Zumbro Falls        18.0   24.0   26.0 :  37    8    8   <5    5   <5
:South Fork Zumbro River
Rochester           14.0   18.0   20.0 :  34   <5    8   <5   <5   <5
:Root River
Houston             15.0   17.0   18.0 :  37   10    7   <5   <5   <5
:South Branch Root River
Lanesboro           12.0   16.0   18.0 :  25   12    6   <5   <5   <5
:Cedar River
Lansing             18.0   20.0   22.0 :   6    5   <5   <5   <5   <5
Austin              15.0   18.0   20.0 :   7    9   <5    5   <5   <5
Charles City        12.0   15.0   18.0 :  20   19    9    9    5   <5
:Turtle Creek
Austin              10.5   12.0   14.0 :  31   16   14    9   <5   <5
:Turkey River
Elkader             12.0   16.0   20.0 :  31   43   12   22   <5   <5
Garber              17.0   20.0   23.0 :  27   37   19   21   11   14
:Upper Iowa River
Decorah             12.0   13.0   14.0 :  <5   <5   <5   <5   <5   <5
Dorchester          14.0   17.0   19.0 :  10   19   <5    6   <5   <5
:Trempealeau River
Arcadia              8.0    9.0   10.0 :  15   <5   <5   <5   <5   <5
Dodge                9.0   11.0   12.0 : >95   62   28    6    6   <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 :  59   57   30   27   <5   <5
Galesville          12.0   13.0   15.0 :  56   55   42   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 :  48   32   <5   <5   <5   <5
Readstown           11.0   14.0   16.0 :  56   38   <5   <5   <5   <5
Soldiers Grove      13.0   16.0   19.0 :  37   30   <5   <5   <5   <5
Gays Mills          13.0   15.0   17.0 :  65   50    8    9   <5   <5
Steuben             12.0   13.0   15.0 :  39   23   12   10   <5   <5
:Wisconsin River
Muscoda              9.0   10.0   11.0 :  14   17    6    8   <5   <5
:Yellow River
Necedah             15.0   16.5   18.0 :  68   73   42   48   18   14


Legend
CS = Conditional Simulation (Current Outlook)
HS = Historical Simulation
FT = Feet


*** Climate Information ***

Looking ahead to March, the latest trends indicate slightly tilted
odds for above normal temperatures, while there is an increasing
signal for above normal precipitation. In fact, there are some signs
that the midweek period next week may feature significant
precipitation across much of the area.

Should significant rain or snow accumulate across the area the
next one to two months, the risk for spring snow melt flooding
will increase. As such and based on conditions, an update to this
flood risk may be issued Thursday, March 15th.


*** Flood Exceedance Information ***

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: 03/11/2018 - 06/02/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Lake City            13.0   13.6   15.0   15.9   16.9   19.8   20.9
Wabasha              11.6   11.9   12.8   13.4   14.3   17.2   18.2
Alma Dam 4            9.8   10.5   11.8   12.7   13.9   17.0   18.2
MN City Dam 5       656.6  657.4  659.0  660.0  661.5  665.1  666.3
Winona Dam 5A       652.2  653.0  654.7  655.9  657.4  661.0  662.1
Winona               10.7   11.5   13.2   14.4   16.0   19.4   20.2
Trempealeau         644.7  645.4  646.7  647.6  648.9  651.2  652.0
La Crescent         638.2  639.1  640.1  641.3  642.5  645.2  646.1
La Crosse            10.1   10.9   11.9   12.9   14.0   16.2   16.9
Genoa               629.3  630.1  631.1  632.1  633.5  636.3  637.5
Lansing              10.9   11.8   13.0   14.4   16.2   19.4   21.0
Lynxville           620.8  622.0  623.2  624.6  626.4  630.0  632.0
McGregor             13.4   14.6   16.5   18.2   20.0   24.3   26.0
Guttenberg           12.2   13.2   14.5   16.0   17.5   21.0   22.2
:Zumbro River
Zumbro Falls         12.5   13.0   14.4   16.8   19.9   23.0   27.0
:South Fork Zumbro River
Rochester             9.9   10.6   12.1   12.9   15.5   16.8   18.8
:Root River
Houston               9.6   10.9   12.4   13.7   15.9   16.7   17.1
:South Branch Root River
Lanesboro             6.5    7.0    7.9    9.5   12.0   15.2   16.1
:Cedar River
Lansing              13.6   13.8   14.7   15.5   16.2   17.2   18.2
Austin                7.7    8.0    9.5   10.7   12.3   14.5   15.8
Charles City          6.2    6.3    7.9    9.0   11.3   14.1   18.1
:Turtle Creek
Austin                6.4    6.7    7.6    9.2   11.0   12.8   13.9
:Turkey River
Elkader               7.8    8.5    9.1   10.4   12.7   17.9   18.8
Garber                9.9   10.7   11.9   14.6   17.2   24.6   29.8
:Upper Iowa River
Decorah               3.7    4.0    4.5    5.0    5.9    7.0    8.0
Dorchester            9.1    9.3   10.1   10.8   12.0   14.2   16.9
:Trempealeau River
Arcadia               6.1    6.7    7.2    7.5    7.8    8.5    8.8
Dodge                 9.2    9.7   10.1   10.6   11.1   11.7   12.0
:Black River
Neillsville           8.9    9.1   10.1   11.9   13.7   14.6   15.7
Black River Falls    42.9   43.6   44.7   49.2   52.1   53.4   53.9
Galesville            9.4    9.9   10.7   12.6   13.4   14.1   14.3
:Kickapoo River
La Farge              5.9    7.0    8.2    9.2   10.8   11.5   11.8
Viola                11.5   12.3   13.1   13.8   15.0   15.6   15.9
Readstown             7.7    8.5   10.0   11.3   12.1   13.0   13.7
Soldiers Grove        9.9   10.7   11.7   12.8   13.5   14.4   15.2
Gays Mills           10.7   11.3   12.4   13.5   14.1   14.9   15.1
Steuben               9.8   10.3   10.9   11.6   12.3   13.1   13.2
:Wisconsin River
Muscoda               4.1    4.7    5.8    7.1    8.2    9.4   10.1
:Yellow River
Necedah              13.6   13.9   14.5   16.1   17.2   18.3   18.6

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 video briefing
format on the internet at:

http://www.weather.gov/lacrosse

The next outlook will be issued March 15th if required.

$$

Lawrence/Boyne/DJT


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