Flood Potential Outlook
Issued by NWS Green Bay, WI

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Probabilistic Hydrologic Outlook
National Weather Service Green Bay WI
1205 PM CST Thu Feb 15 2018

...Spring Flood and Water Resource Outlook 1...

This flood outlook is for the NWS Green Bay service area. It covers
the time period from the rest of February to May 19th.  This includes
the Yellow, Wisconsin, Wolf, Little Wolf, Waupaca, Fox, Oconto and
Menominee Rivers.

...Forecast...
For the rest of February, temperatures will fluctuate but average
near normal and possibly slightly above normal the last week of
February.  There are several chances of precipitation next week
with the potential of additional snowpack across northern Wisconsin.
A snow mix is expected over parts of central and east central
WIsconsin at this time.

The outlook for March indicates slightly below normal temperatures
and normal precipitation.  For the period of March to May, near
normal temperatures and slightly above normal precipitation are
anticipated at this time.

...Surface Conditions as of February 15th...

Due to the lack of snowfall from January and early February, frost
depths have penetrated to 2 to 4 feet across northcentral and
central wisconsin to 1 to 2 feet across east central Wisconsin.

Snow depth ranged from 2 to 6 inches across central and east
central Wisconsin, 6 to 12 across northern Wisconsin with
locally higher 12 to 18 inches across Vilas County.

Snow water content was less than an inch over locations south of
highway 29, 1 to 2 inches north of highway 29 and 2 to 4 inches
over far northern Wisconsin.

...Current Streamflows Conditions...

Going into the winter, streamflows were above normal which led to
minor ice jams on the Menominee River.  River levels have declined
to near normal across the north to slightly below normal over
central Wisconsin.

...Flood Summary and Potential Threats...

Latest conditions indicate near to slightly below normal minor
flooding potential on area rivers.  Forecast conditions through
next week indicate a potential of adding to the snowpack, especially
across northern Wisconsin.

In the coming weeks and toward March, a trend to warmer
temperatures may allow ice breakup to start which may lead to
ice jams.  This is a good time to check sump pumps before any
shift to warmer temperatures that produce a robust snowmelt.
The snowmelt combined with any rainfall may produce above normal
runoff due to deep frost.

----------------------------------------------

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:  02/18/2018 - 05/19/2018

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Wisconsin River
Merrill             11.0   13.5   15.0 :  10   18   <5    5   <5   <5
Rothschild          25.0   27.0   28.0 :   8   17   <5    7   <5    5
Wisconsin Rapids    12.0   13.5   14.5 :   6   12   <5   <5   <5   <5
:Yellow River
Babcock             12.0   15.9   16.6 :  59   73   14   12    6    9
:Oconto River
Oconto               9.0   12.0   14.0 :  24   17   <5   <5   <5   <5
:Upper Wolf River
Langlade            11.5   12.5   14.0 :  <5    5   <5   <5   <5   <5
:Wolf River
Shiocton            12.0   13.5   15.0 :  37   40    7   11   <5   <5
New London           9.0   10.5   11.1 :  45   51   <5   11   <5   <5
:Little Wolf River
Royalton             5.0    8.0   10.0 :  21   34   <5   <5   <5   <5
:Waupaca River
Waupaca              6.0    7.5    9.0 :  <5   <5   <5   <5   <5   <5
:Fox River
Appleton             8.4    9.0   10.5 :  <5   <5   <5   <5   <5   <5
:Menominee River
Florence             9.0   11.0   13.0 :  19   36   <5   11   <5   <5
Niagara             13.0   15.0   16.0 :  18   30    6    8   <5   <5
Vulcan              15.0   17.0   19.0 :  11   27   <5    6   <5   <5
McAllister          15.0   18.0   19.0 :  40   53    6    8   <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: 02/18/2018 - 05/19/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Wisconsin River
Merrill               7.2    7.5    8.2    8.8    9.7   10.9   11.8
Rothschild           18.1   18.4   20.0   21.3   22.6   24.5   26.5
Wisconsin Rapids      5.4    5.8    6.7    8.0    9.0   10.6   12.5
:Yellow River
Babcock               7.1    7.9   10.3   13.0   14.7   16.2   16.8
:Oconto River
Oconto                7.0    7.1    7.7    8.2    8.9    9.7   10.3
:Upper Wolf River
Langlade              9.4    9.5    9.8   10.1   10.5   11.0   11.2
:Wolf River
Shiocton              9.6   10.2   11.1   11.6   12.4   13.3   13.6
New London            7.7    8.0    8.5    8.8    9.4   10.0   10.4
:Little Wolf River
Royalton              2.9    3.0    3.4    4.3    4.7    5.9    6.7
:Waupaca River
Waupaca               2.2    2.4    2.7    3.1    3.7    3.9    5.6
:Fox River
Appleton              6.2    6.3    6.6    7.0    7.3    7.9    7.9
:Menominee River
Florence              5.5    6.0    6.7    7.7    8.7    9.9   10.9
Niagara               9.0    9.4   10.3   11.1   12.6   14.1   15.2
Vulcan                9.2    9.9   11.0   12.0   13.8   15.1   16.7
McAllister           12.5   13.0   13.8   14.5   16.0   17.4   18.6

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: 02/18/2018 - 05/19/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Wisconsin River
Merrill               4.8    4.7    4.6    4.5    4.5    4.3    4.3
Rothschild           13.5   13.5   13.2   13.2   13.1   12.9   12.7
Wisconsin Rapids      3.0    2.8    2.4    2.4    2.4    2.4    2.4
:Yellow River
Babcock               1.9    1.9    1.9    1.9    1.9    1.9    1.9
:Oconto River
Oconto                4.7    4.7    4.7    4.6    4.6    4.6    4.5
:Upper Wolf River
Langlade              7.7    7.7    7.7    7.7    7.7    7.7    7.7
:Wolf River
Shiocton              3.2    3.1    3.1    2.8    2.6    2.5    2.5
New London            2.2    2.2    2.1    2.0    1.9    1.8    1.7
:Little Wolf River
Royalton              1.3    1.2    1.2    1.2    1.2    1.1    1.1
:Waupaca River
Waupaca               1.3    1.3    1.3    1.3    1.3    1.3    1.3
:Fox River
Appleton              5.5    5.4    5.4    5.1    4.9    4.9    4.9
:Menominee River
Florence              3.0    3.0    2.9    2.9    2.9    2.9    2.9
Niagara               5.5    5.4    5.3    5.3    5.3    5.2    5.2
Vulcan                5.5    5.5    5.3    5.3    5.3    5.2    5.2
McAllister            9.4    9.3    9.1    9.0    9.0    9.0    9.0

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/grb for more weather and water
information.

Additional Web sites and information

Latest Snowpack from NOHRCS   www.nohrsc.noaa.gov/nsa

Current streamflows from USGS  waterdata.usgs.gov/wi/nwis/rt

Long term forecast information  www.cpc.noaa.gov

The next spring flood outlook will be issued March 1st 2018.

$$



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