Flood Potential Outlook
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
Versions:
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FGUS73 KGRB 271939
ESFGRB
WIC125-085-041-037-075-069-067-083-073-115-125-078-029-141-097-
135-087-061-009-137-139-015-071-042100-
PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE GREEN BAY WI
138 PM CST THU FEB 27 2025
...Spring Flood Outlook for Central and Northeast Wisconsin...
The overall flood risk this spring is NEAR TO SLIGHTLY BELOW
AVERAGE.
This outlook references information from the following partners
including: the United States Geological Survey (USGS), the U.S.
Army Corps of Engineers, Regional Climate Centers, U.S. Drought
Monitor, the Climate Prediction Center and NOAA Office of Water
Prediction.
This is the second of three spring flood outlooks. The third and
final outlook will be provided on Thursday March 13th, 2025.
Flood outlook factors...
...Snow Depth and Snow Water Equivalent...
Even with the snow that has occurred since the last outlook, snow
depths are normal to below normal while snow water equivalent is
well below normal. Much of the recent snow has melted over much of
central and northeast Wisconsin. Both of these factors related to
snow on the ground continue to decrease the overall flood risk.
...Soil moisture and Frost Depths...
Soil moisture values across the area remain around normal. There is
also an area of below normal soil moisture in northern Wisconsin,
where moderate drought (D1) persists. Overall, the lack of snowfall
this winter will allow for more moisture to be absorbed into the
soils and will generally decrease the flood risk.
Frost depths at current is normal to above normal for this time of
year. This is due to the frequent cold snaps that have occurred
through the winter. Frost depths range from 15 inches to as deep as
39 inches, which is similar to the last outlook issued. The frost
depth is much deeper than was observed at this time last year. The
deeper frost depth may result in increased runoff as the more frozen
ground will not allow water to readily pass through the surface.
This is one of the main factors that increases the flood risk.
...River Ice and Streamflow Conditions...
The frequent cold snaps this winter up to this point have led to
thicker ice on area rivers. This shows up as freezing degree days
that are already observed over 900 days for the entire area and are
over 1300 days north of a line from Wausau to Iron Mountain. Values
over 400 signal potential for sufficiently thick ice for break up
ice jams. At current, there is an increased risk of ice jams on some
of the rivers and some minor ice jams have been observed. The
potential for ice jams will remain elevated with heavy rainfall
events before the ice is completely flushed out of the rivers.
Streamflows vary from normal to above normal, which is an increase
compared to the last outlook. Areas of above normal are located
across portions of the Wolf River and Upper Fox River basins.
Otherwise, streamflows are near normal over the rest of northern and
northeast WI. Where streamflows are elevated, there will be a slight
increase to the overall flood risk.
...Lake Michigan Water Levels...
Lake Michigan water levels continue to run slightly above normal
which has been the case the past three years. This level will allow
for decreased flooding impacts this season. For a comparison of
impacts, there were very few impacts in 2022 through 2024, and Lake
Michigan levels are slightly lower this year.
...Weather Outlook...
After a dip in temperatures this weekend, plan on another period of
above normal temperatures for the first week of March. There is also
an opportunity for widespread rain and even some snow in the Tuesday
and Wednesday time frame. Beyond next week, temperatures are
expected to lean above average while precipitation will be above to
possibly above average for the middle of March. Looking farther
ahead, precipitation is still expected to lean above average for the
rest of spring, for April through June. There still is no clear
signal for above normal or below normal temperatures during this
time.
In Table 1 below, the current (CS) and historical (HS) or normal
probabilities of exceeding Minor...Moderate...And Major flood stage
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: 03/03/2025 - 06/01/2025
: 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 : 5 24 <5 <5 <5 <5
ROTHSCHILD 25.0 27.0 28.0 : 6 21 <5 8 <5 6
:YELLOW RIVER
BABCOCK 12.0 15.5 17.0 : 52 82 11 22 <5 7
:WISCONSIN RIVER
WISCONSIN RAPIDS 12.0 13.5 14.5 : <5 11 <5 <5 <5 <5
:OCONTO RIVER
OCONTO 9.0 12.0 14.0 : 8 24 <5 <5 <5 <5
:UPPER WOLF RIVER
LANGLADE 11.5 12.5 14.0 : <5 <5 <5 <5 <5 <5
:WOLF RIVER
SHIOCTON 11.0 13.5 15.0 : 38 44 <5 5 <5 <5
NEW LONDON 9.0 10.5 11.1 : 50 55 <5 6 <5 <5
:LITTLE WOLF RIVER
ROYALTON 5.0 8.0 10.0 : 20 28 <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 : 18 37 <5 14 <5 <5
NIAGARA 13.0 15.0 16.0 : 12 32 <5 14 <5 5
VULCAN 15.0 17.0 19.0 : 10 25 <5 6 <5 <5
MCALLISTER 15.0 18.0 19.0 : 24 53 <5 14 <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: 03/03/2025 - 06/01/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:WISCONSIN RIVER
MERRILL 6.6 7.0 7.4 8.0 9.0 9.6 11.0
ROTHSCHILD 17.8 18.4 19.2 20.7 21.9 23.4 25.3
:YELLOW RIVER
BABCOCK 6.1 7.1 9.1 12.2 13.6 15.6 16.3
:WISCONSIN RIVER
WISCONSIN RAPIDS 5.2 5.5 6.0 7.3 8.2 9.7 10.9
:OCONTO RIVER
OCONTO 6.3 6.4 6.7 7.2 8.0 8.9 10.0
:UPPER WOLF RIVER
LANGLADE 8.5 8.6 8.8 8.9 9.1 9.3 9.6
:WOLF RIVER
SHIOCTON 8.6 9.1 9.8 10.6 11.7 12.8 13.1
NEW LONDON 7.3 8.0 8.5 9.0 9.5 10.0 10.2
:LITTLE WOLF RIVER
ROYALTON 2.9 3.0 3.6 4.0 4.7 5.6 5.8
:WAUPACA RIVER
WAUPACA 2.6 2.8 3.3 4.2 5.0 5.3 5.8
:FOX RIVER
APPLETON 6.2 6.4 6.6 7.0 7.6 7.9 7.9
:MENOMINEE RIVER
FLORENCE 5.5 6.1 6.8 7.5 8.5 10.2 10.6
NIAGARA 8.1 8.7 9.5 10.3 11.7 13.8 14.2
VULCAN 8.5 9.2 10.1 11.2 12.6 14.9 15.6
MCALLISTER 11.8 12.3 13.1 13.8 14.9 16.5 17.6
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: 03/03/2025 - 06/01/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:WISCONSIN RIVER
MERRILL 1.3 1.3 1.2 1.2 1.1 1.1 1.1
ROTHSCHILD 1.7 1.6 1.5 1.4 1.2 1.2 1.0
:YELLOW RIVER
BABCOCK 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:WISCONSIN RIVER
WISCONSIN RAPIDS 0.5 0.4 0.4 0.3 0.3 0.3 0.3
:OCONTO RIVER
OCONTO 0.7 0.6 0.5 0.5 0.4 0.4 0.4
:UPPER WOLF RIVER
LANGLADE 0.3 0.3 0.3 0.3 0.2 0.2 0.2
:WOLF RIVER
SHIOCTON 1.2 1.2 1.2 1.0 0.9 0.8 0.8
NEW LONDON 1.9 1.8 1.7 1.5 1.3 1.2 1.1
:LITTLE WOLF RIVER
ROYALTON 0.3 0.3 0.3 0.3 0.2 0.2 0.2
:WAUPACA RIVER
WAUPACA 0.3 0.3 0.3 0.2 0.2 0.2 0.2
:FOX RIVER
APPLETON 3.9 3.2 2.4 1.1 0.0 0.0 0.0
:MENOMINEE RIVER
FLORENCE 0.6 0.6 0.5 0.4 0.4 0.4 0.4
NIAGARA 0.8 0.8 0.8 0.6 0.6 0.6 0.5
VULCAN 0.9 0.9 0.9 0.8 0.7 0.7 0.7
MCALLISTER 1.5 1.5 1.4 1.4 1.2 1.2 1.1
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 National Water Prediction
Service.
Visit our web site at weather.gov/grb for more weather and water
information.
The third and final outlook will be provided on Thursday March 13th,
2025.
$$