Flood Potential Outlook
Issued by NWS Milwaukee/Sullivan, WI

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127-101-059-161800-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
214 PM CST THU FEB 13 2020

...Above average risk of flooding this spring...

This outlook references information from the following partners
including The United States Geological Survey (USGS), The US Army
Corps of Engineers, Regional Climate Centers, US Drought Monitor,
The Climate Prediction Center, and NOAA Office of Water Prediction.

2019 was the wettest year on record for Wisconsin. Soils are very
saturated which will cause increased runoff and flooding potential.
Stream flows are much above average and runoff into rivers that are
already high increases flood potential. Minor flooding is expected
but more impactful flooding is possible, especially with a rapid
snow melt or heavy rain. Flooding could be widespread. River
flooding in southern Wisconsin typically occurs in March and April,
with a rapid snow melt and/or heavy rain.

There is an above normal risk of flooding along the mouths of rivers
into Lake Michigan. Lake Michigan water level continues to be near
record level. This may slow down rivers as water piles up at the
mouth. Backwater and inundation flooding near river mouths is also
possible, especially when the wind blows into rivers over a period
of time.

Ice jam flooding risk is low to moderate. Mild temperatures winter
have limited the development of river ice. Some ice development is
still possible with any colder temperatures this winter. But,
without the development of thick river ice the threat for spring
break up jams is low to moderate.

...Flood Outlook Factors...
Precipitation last fall was 150 to 200 percent of normal across
southern Wisconsin, and this winter so far it is 75 to 150 percent
of normal. This past fall was much wetter than last year and winter
has been similar to last year. Soil moisture values are in the 99th
percentile and stream flow values are in the 76 to 90th percentile.
This indicates values are well above average. Streamflow values are
slightly higher than last year. Currently there is one half inch to
3 inches of water contained in the snow pack across southern
Wisconsin. This is close to average for this time of year. Snow
water equivalent values for the Upper Wisconsin River basin are 4 to
8 inches, which is in the 90th percentile. This snowpack will
eventually make its way down the Wisconsin River into southern
Wisconsin. Snow water equivalent values are slightly higher than
this time last year. These factors create an elevated flood risk for
southern Wisconsin.

Frost depth is generally 3 to 12 inches. This is below to near
normal. The mild winter combined with the recent snow pack has
limited frost depth. A shallower frost will thaw sooner which would
normally limit runoff, but due to the saturated soils it will not be
much of a benefit this year.

...Weather/Climate Outlook...
Milder temperatures are expected later in February. This may melt
some snow and cause some river rises. But, much of the snow pack will
likely remain. A drier than normal period is favored for the later
part of February. There is an increased chance for below normal
temperatures for the Feb-March-April time period with slightly
increased odds for above average precipitation. This suggests
additional snow is possible. While there is a great deal of
uncertainty in long range outlooks, it reinforces the likelihood of
a rapid snow melt scenario once the warmer temperatures arrive later
this spring.

...Probabilistic River Flood Information...

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:  02/17/2020 - 05/17/2020

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Rock River
Watertown            5.5    6.0    6.5 :  24   15   10    9   <5   <5
:Crawfish River
Milford              7.0    9.0   10.0 :  34   34   10    8   <5   <5
:Rock River
Jefferson           10.0   11.0   13.0 :  38   33   25   20   <5   <5
Fort Atkinson       16.0   17.0   18.0 :  18   14    6    6   <5   <5
Lake Koshkonong     10.0   11.0   11.5 :  55   39   30   30   23   24
Afton                9.0   11.1   12.2 :  60   37   18   12    7    8
:Turtle Creek
Clinton              8.0   10.0   12.0 :  18   14    7    6   <5   <5
Beloit               7.5   10.5   12.5 :  18   14   <5   <5   <5   <5
:Pecatonica River
Darlington          13.5   15.0   16.0 :  24   25   15   19   13   15
:East Branch Pecatonica River
Blanchardville      11.0   14.0   16.0 :  55   35    9   <5   <5   <5
:Pecatonica River
Martintown          13.5   18.0   21.0 :  79   42   10    6   <5   <5
:Sugar River
Albany              12.0   13.0   14.0 :  <5   <5   <5   <5   <5   <5
Brodhead             5.0    8.0   10.0 :  68   38   12    7   <5   <5
:Wisconsin River
Wisconsin Dells     16.0   17.6   18.9 :  77   20   59    6   43   <5
Portage             17.0   18.0   19.0 : >95   59  >95   39   76   16
:Baraboo River
Rock Springs        18.5   21.0   23.0 :  77   46   51   33   32   20
West Baraboo         9.0   10.5   12.5 :  35   21   19   12   <5   <5
Baraboo             16.0   22.0   23.1 :  78   49   13    9    8    5
:Fox River
Princeton            9.5   11.0   12.0 :  45   13    7   <5   <5   <5
Berlin              13.0   14.5   16.0 :  57   19    9   <5   <5   <5
:Sheboygan River
Sheboygan            8.0   10.0   12.0 :  23   17    6    6   <5    5
:Root River
Franklin             8.0   10.0   12.0 :  18   23   <5   <5   <5   <5
:Root River Canal
Raymond              9.0   11.0   12.0 :  19   21   <5   <5   <5   <5
:Root River
Racine               7.0    7.5    8.0 :  <5    5   <5   <5   <5   <5
:Cedar Creek
Cedarburg           10.0   11.0   12.0 :  <5    7   <5   <5   <5   <5
:Milwaukee River
Cedarburg           11.0   13.0   14.0 :  36   36   <5    8   <5   <5
:Fox River Lower
Waukesha             6.0    8.0   10.0 :  27   33   <5   <5   <5   <5
Burlington          11.0   12.0   14.0 :  25   30    6   16   <5   <5
New Munster         11.0   13.0   14.0 :  73   65   21   28    5   16

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: 02/17/2020 - 05/17/2020
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Rock River
Watertown             3.7    3.8    4.2    4.8    5.5    6.0    6.5
:Crawfish River
Milford               4.3    4.4    5.3    6.5    7.2    9.0    9.6
:Rock River
Jefferson             6.9    7.2    7.9    9.4   11.1   12.2   12.7
Fort Atkinson        13.0   13.3   13.7   14.7   15.6   16.5   17.2
Lake Koshkonong       8.1    8.5    8.9   10.2   11.4   12.3   13.2
Afton                 7.1    7.6    8.1    9.4   10.7   11.7   12.9
:Turtle Creek
Clinton               5.2    5.4    5.9    6.7    7.3    9.0   10.5
Beloit                5.1    5.2    5.6    6.3    7.0    8.4    9.8
:Pecatonica River
Darlington            8.9    9.4   10.3   11.6   13.1   17.0   17.4
:East Branch Pecatonica River
Blanchardville        9.0    9.4   10.1   11.2   12.5   13.7   14.8
:Pecatonica River
Martintown           11.9   12.8   13.9   15.1   16.2   18.0   18.7
:Sugar River
Albany                7.1    7.2    7.9    9.5   10.3   11.1   11.5
Brodhead              3.9    4.1    4.7    5.8    6.9    8.2    8.7
:Wisconsin River
Wisconsin Dells      14.9   15.2   16.3   18.3   20.3   23.2   25.7
Portage              18.3   18.4   19.0   20.8   21.8   22.4   22.7
:Baraboo River
Rock Springs         15.6   16.8   18.8   21.2   23.5   24.8   25.3
West Baraboo          5.5    5.8    6.6    7.4    9.8   11.6   12.2
Baraboo              14.2   15.1   16.6   18.0   20.5   22.6   23.4
:Fox River
Princeton             8.2    8.6    8.8    9.4   10.2   10.8   11.4
Berlin               12.1   12.5   12.7   13.2   13.9   14.5   14.8
:Sheboygan River
Sheboygan             4.9    5.1    5.7    6.9    7.8    8.8   11.5
:Root River
Franklin              5.7    5.9    6.4    7.0    7.5    8.3    8.4
:Root River Canal
Raymond               5.2    5.7    6.6    7.4    8.5    9.6   10.5
:Root River
Racine                4.2    4.3    4.6    4.9    5.5    6.2    6.3
:Cedar Creek
Cedarburg             7.1    7.3    7.7    8.4    9.0    9.6    9.9
:Milwaukee River
Cedarburg             8.7    8.9    9.5   10.3   11.6   12.7   12.9
:Fox River Lower
Waukesha              4.6    5.0    5.3    5.7    6.0    6.3    7.2
Burlington            8.5    8.8    9.3   10.3   11.0   11.7   12.1
New Munster           9.5   10.0   10.8   12.1   12.7   13.6   14.0

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: 02/17/2020 - 05/17/2020
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Rock River
Watertown             2.3    2.3    2.3    2.2    2.1    1.9    1.8
:Crawfish River
Milford               3.1    3.1    2.9    2.6    2.4    2.2    2.2
:Rock River
Jefferson             5.0    5.0    4.9    4.6    4.2    3.8    3.8
Fort Atkinson        12.0   11.9   11.9   11.7   11.3   11.1   11.1
Lake Koshkonong       6.7    6.7    6.6    6.2    5.9    5.8    5.8
Afton                 5.8    5.8    5.8    5.7    4.6    4.0    3.0
:Turtle Creek
Clinton               3.8    3.8    3.8    3.7    3.6    3.5    3.5
Beloit                3.9    3.9    3.9    3.8    3.7    3.6    3.6
:Pecatonica River
Darlington            3.2    3.2    3.2    3.2    3.2    3.1    3.0
:East Branch Pecatonica River
Blanchardville        5.2    5.2    5.2    5.2    5.1    5.0    4.9
:Pecatonica River
Martintown            6.6    6.6    6.6    6.6    6.4    6.2    6.1
:Sugar River
Albany                4.3    4.3    4.3    4.2    4.1    4.0    4.0
Brodhead              1.7    1.6    1.6    1.4    1.3    1.2    1.2
:Wisconsin River
Wisconsin Dells       3.7    3.6    3.6    3.3    2.7    2.2    1.5
Portage              10.1   10.1   10.0    9.9    9.6    9.2    8.7
:Baraboo River
Rock Springs          9.7    9.7    9.7    9.7    9.6    9.5    9.4
West Baraboo          2.8    2.8    2.8    2.8    2.8    2.8    2.8
Baraboo               8.0    8.0    8.0    7.9    7.8    7.7    7.7
:Fox River
Princeton             5.9    5.9    5.8    5.7    5.6    5.4    5.3
Berlin               10.4   10.4   10.3   10.2   10.1    9.9    9.9
:Sheboygan River
Sheboygan             2.4    2.4    2.4    2.3    2.3    2.2    2.2
:Root River
Franklin              2.3    2.3    2.2    2.1    2.0    2.0    2.0
:Root River Canal
Raymond               2.6    2.6    2.5    2.3    2.2    2.1    2.1
:Root River
Racine                2.8    2.7    2.7    2.6    2.5    2.4    2.4
:Cedar Creek
Cedarburg             5.5    5.5    5.5    5.4    5.3    5.3    5.2
:Milwaukee River
Cedarburg             6.0    6.0    5.9    5.9    5.8    5.7    5.7
:Fox River Lower
Waukesha              3.0    3.0    3.0    2.9    2.9    2.8    2.8
Burlington            7.2    7.2    7.0    6.7    6.5    6.3    6.2
New Munster           7.1    7.1    6.8    6.3    5.9    5.6    5.5

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/mkx for more weather and water
information.

The next outlook will be issued February 27, 2020.

$$

Marquardt


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