Flood Potential Outlook
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
632
FGUS73 KGRB 131543
ESFGRB
WIC125-085-041-037-075-069-067-083-073-115-125-078-029-141-097-
135-087-061-009-137-139-015-071-190500-
PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE GREEN BAY WI
1040 AM CDT THU MAR 13 2025
...THE 3RD 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.
Flood outlook factors...
...Snow Depth and Snow Water Equivalent...
Overall, snowfall for the season (October-March 13) is running well
below normal across much of the region. For most locations, it was
one of the driest and one of the least snowiest January`s on record.
At Green Bay, there were only 2 days during the month where the snow
depth was recorded at an inch or greater.
The snow drought came to an end in February as colder than normal
temperatures prevailed on most days between the 4th and 21st before
well above normal temperatures quickly melted much of the snow
during the last week of the month. Overall, snowfall for the month
was at or above normal, with the greatest departures from normal
across central into east-central Wisconsin. Due to the colder than
normal temperatures, many of the snowfall events resulted in lower
than normal water content.
Due to the recent mild temperatures, as of March 13 the snow has
melted across central, much of north-central and northeast Wisconsin.
The only snow pack remaining was over far north-central Wisconsin,
mainly across Vilas County where the snow depth remained from 2 to
8 inches. The remaining snow pack should melt fairly quickly this
week due to the expected unseasonably mild temperatures.
...Soil moisture and Frost Depths...
Entering the winter, soil moisture was below normal across northern
Wisconsin due to ongoing drought conditions. The rest of the area
saw near normal moisture.
Top soil moisture returned closer to normal across the north due to
the recent rain and snow over the past month. However, long
term precipitation deficits continue to show Moderate Drought (D1)
over northern Wisconsin. Soil moisture over the remainder of the area
remained near normal as of mid March.
Although snowfall was at or above normal in February, the snow was
a fluffy type snow, resulting in low water content compared to normal.
Despite the heavy rainfall and snowfall on March 4-5, much of the
heavier rainfall ran off as the subsurface ground was still frozen
during the event.
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
35 inches, which is similar to the last outlook issued. The frost
depth is much deeper than was observed at this time last year due to
the record warm winter. 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 compared to the last few winters. 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 higher
compared to the last outlook. Areas of above normal are located
across portions of the Wolf River and Upper Fox River basins. Stream
flows are above normal along the Wisconsin River in central
Wisconsin. 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...
Due to several dry periods over the last six months, Lake Michigan
water levels are running slightly below the long term average, and
over three and a half feet lower than at the record levels set in
2020.
...Weather Outlook...
Temperatures and precipitation (rain/snow) are more likely to
average above normal into early April. For the April-June period,
there is no clear signal for above, below or near normal
temperatures. There is a greater chance that precipitation will run
above normal during this period.
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.
...Lake Michigan Water Levels...
Due to several dry periods over the last six months, Lake Michigan
water levels are running slightly below the long term average, and
over three and a half feet lower than at the record levels set in
2020.
...Weather Outlook...
Temperatures and precipitation (rain/snow) are more likely to
average above normal into early April. For the April-June period,
there is no clear signal for above, below or near normal
temperatures. There is a greater chance that precipitation will run
above normal during this period.
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 at weather.gov/grb for more weather and water
information.
This is the last spring flood outlook for 2025.
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: 03/17/2025 - 06/15/2025
: 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 : <5 21 <5 8 <5 6
:YELLOW RIVER
BABCOCK 12.0 15.5 17.0 : 38 74 8 20 <5 6
: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 : 9 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 : 27 46 <5 5 <5 <5
NEW LONDON 9.0 10.5 11.1 : 39 56 <5 6 <5 <5
:LITTLE WOLF RIVER
ROYALTON 5.0 8.0 10.0 : 18 30 <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 : 23 37 <5 14 <5 <5
NIAGARA 13.0 15.0 16.0 : 8 32 <5 14 <5 5
VULCAN 15.0 17.0 19.0 : <5 25 <5 6 <5 <5
MCALLISTER 15.0 18.0 19.0 : 22 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: 03/17/2025 - 06/15/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:WISCONSIN RIVER
MERRILL 7.0 7.0 7.0 7.4 8.3 9.3 10.3
ROTHSCHILD 18.1 18.1 18.1 19.3 20.6 22.9 24.4
:YELLOW RIVER
BABCOCK 6.5 6.7 8.1 10.7 12.9 15.2 15.8
:WISCONSIN RIVER
WISCONSIN RAPIDS 5.1 5.1 5.4 6.4 7.4 8.8 9.8
:OCONTO RIVER
OCONTO 6.2 6.3 6.5 7.1 7.8 8.8 9.3
:UPPER WOLF RIVER
LANGLADE 8.6 8.6 8.7 8.8 9.1 9.3 9.5
:WOLF RIVER
SHIOCTON 9.6 9.6 9.7 10.4 11.1 11.9 12.2
NEW LONDON 8.2 8.2 8.2 8.8 9.3 9.8 9.8
:LITTLE WOLF RIVER
ROYALTON 2.8 3.1 3.5 4.0 4.8 5.4 6.0
:WAUPACA RIVER
WAUPACA 2.6 2.7 3.4 4.3 4.9 5.5 5.6
:FOX RIVER
APPLETON 6.7 6.7 6.8 7.1 7.5 7.9 7.9
:MENOMINEE RIVER
FLORENCE 6.2 6.4 6.7 7.5 8.6 9.5 10.2
NIAGARA 9.0 9.1 9.4 10.3 12.1 12.8 13.6
VULCAN 9.7 9.8 10.0 10.9 12.6 13.9 14.6
MCALLISTER 12.7 12.8 12.9 13.6 14.8 15.9 16.4
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: 03/17/2025 - 06/15/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:WISCONSIN RIVER
MERRILL 1.9 1.8 1.7 1.4 1.2 1.2 1.0
ROTHSCHILD 2.9 2.4 2.1 1.6 1.2 1.1 0.7
:YELLOW RIVER
BABCOCK 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:WISCONSIN RIVER
WISCONSIN RAPIDS 3.6 3.3 0.4 0.3 0.2 0.2 0.2
:OCONTO RIVER
OCONTO 0.7 0.6 0.5 0.4 0.4 0.4 0.3
:UPPER WOLF RIVER
LANGLADE 0.4 0.4 0.3 0.3 0.3 0.2 0.2
:WOLF RIVER
SHIOCTON 1.4 1.3 1.1 0.9 0.9 0.8 0.8
NEW LONDON 2.0 1.8 1.6 1.3 1.2 1.1 1.1
:LITTLE WOLF RIVER
ROYALTON 0.3 0.3 0.3 0.2 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 4.1 3.3 2.2 0.9 0.0 0.0 0.0
:MENOMINEE RIVER
FLORENCE 1.2 1.2 1.1 1.0 1.0 1.0 0.9
NIAGARA 1.8 1.7 1.7 1.6 1.5 1.3 1.3
VULCAN 2.3 2.2 2.1 1.9 1.7 1.6 1.5
MCALLISTER 3.5 3.3 3.0 2.7 2.4 2.2 2.2
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.
$$