|
|
|
|
Every spring the National Weather Service (NWS) prepares a series of flood outlooks for the potential of river flooding as a result of snow pack melt.
Each outlook takes into account anticedent conditions and current snowpack levels to anticipate the overall flood risk. The rate and timing of melt, in addition to future precipitation, can alter conditions as well.
These outlooks contain information about the potential for flooding throughout the spring months. The information can help decision makers and those with river interests prepare, in order to protect life and property.
Spring Snowmelt Flood Outlook Release Dates:
...NEAR TO SLIGHTLY BELOW NORMAL RISK OF FLOODING THIS SPRING FOR
CENTRAL AND NORTHEAST WISCONSIN...
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`s Office of Water
Prediction.
This is the first of three spring flood outlooks. The next outlook
will be provided on Thursday February 27th, 2025.
Flood outlook factors...
Soil moisture values across all of northeast Wisconsin is near
normal. An area of below normal soil moisture is present 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.
Streamflows have settled to around normal across the area after
being elevated for parts of the winter thus far. This generally
will result in a decrease to the overall flood risk.
Snow water equivalent analysis indicated that much of northeast
Wisconsin remains well-below normal, due to well-below normal
snowfall. This will lead to a decreased flood risk.
Frost depth this season is considered normal to above normal. This
is due to the frequent cold snaps that have occurred through the
winter. Frost depths currently range from 15 inches to as deep as 38
inches, which 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 primary factors that results in an
increased flood risk.
Lake Michigan water levels continue to run only 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 lower this year.
The frequent cold snaps for most of January and in February thus far
have led to thicker ice on area rivers this season. This shows up as
freezing degree days are already observed over 500 days for the
entire area and are over 900 days north of a line from Wausau to
Iron Mountain. Any values over 400 signal potential for sufficiently
thick ice for break up ice jams, given there is sufficient flow on
the rivers. At this point, there is a medium risk of break up ice
jamming on area rivers this season. The potential for ice jams
generally increases with heavy rainfall events before the ice is out
of the river system.
...Weather/climate outlook...
There is an increased risk of below normal temperatures through the
end of February and into the first portion of March. After the
recent active weather, there is an enhanced risk of below normal
precipitation late February into early March. Looking further ahead,
for the March through May period, there is no clear signal for
whether above normal or below normal temperatures will occur. There
is a slight chance for above normal precipitation during this period.
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: 02/17/2025 - 05/18/2025
: 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 : 6 22 <5 <5 <5 <5
ROTHSCHILD 25.0 27.0 28.0 : 8 21 <5 8 <5 6
:YELLOW RIVER
BABCOCK 12.0 15.5 17.0 : 65 82 15 21 <5 8
: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 : 13 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 : 61 44 9 5 <5 <5
NEW LONDON 9.0 10.5 11.1 : 65 55 10 6 <5 <5
:LITTLE WOLF RIVER
ROYALTON 5.0 8.0 10.0 : 28 40 <5 <5 <5 <5
:WAUPACA RIVER
WAUPACA 6.0 7.5 9.0 : <5 8 <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 : 13 32 <5 14 <5 <5
VULCAN 15.0 17.0 19.0 : 8 25 <5 6 <5 <5
MCALLISTER 15.0 18.0 19.0 : 28 52 <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: 02/17/2025 - 05/18/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:WISCONSIN RIVER
MERRILL 6.5 6.9 7.4 8.2 9.2 10.2 11.1
ROTHSCHILD 17.8 18.5 19.5 20.9 22.6 24.4 25.8
:YELLOW RIVER
BABCOCK 7.2 8.2 11.2 13.0 14.7 16.0 16.8
:WISCONSIN RIVER
WISCONSIN RAPIDS 5.4 5.7 6.5 7.5 8.7 10.5 11.5
:OCONTO RIVER
OCONTO 6.5 6.6 7.1 7.7 8.4 9.5 10.0
:UPPER WOLF RIVER
LANGLADE 8.5 8.6 8.8 8.9 9.2 9.4 9.6
:WOLF RIVER
SHIOCTON 9.0 9.5 10.4 11.4 12.4 13.4 14.1
NEW LONDON 7.8 8.2 8.8 9.3 10.1 10.5 10.8
:LITTLE WOLF RIVER
ROYALTON 3.2 3.3 3.7 4.5 5.1 6.0 6.5
:WAUPACA RIVER
WAUPACA 2.8 2.9 3.6 4.5 5.1 5.5 5.7
:FOX RIVER
APPLETON 6.4 6.6 6.8 7.4 7.9 7.9 7.9
:MENOMINEE RIVER
FLORENCE 5.4 5.7 6.5 7.3 8.4 9.9 10.6
NIAGARA 8.0 8.5 9.3 10.3 11.6 13.3 14.2
VULCAN 8.4 9.0 10.0 11.0 12.8 14.4 15.6
MCALLISTER 11.8 12.3 12.9 13.6 15.1 16.5 17.3
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: 02/17/2025 - 05/18/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:WISCONSIN RIVER
MERRILL 1.3 1.2 1.2 1.1 1.1 1.1 1.1
ROTHSCHILD 1.4 1.4 1.3 1.3 1.2 1.2 0.9
:YELLOW RIVER
BABCOCK 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:WISCONSIN RIVER
WISCONSIN RAPIDS 0.2 0.2 0.2 0.2 0.2 0.2 0.2
:OCONTO RIVER
OCONTO 0.3 0.3 0.3 0.3 0.3 0.3 0.3
:UPPER WOLF RIVER
LANGLADE 0.2 0.2 0.2 0.2 0.2 0.2 0.2
:WOLF RIVER
SHIOCTON 0.8 0.8 0.7 0.7 0.7 0.7 0.7
NEW LONDON 1.1 1.1 1.1 1.0 1.0 1.0 1.0
:LITTLE WOLF RIVER
ROYALTON 0.2 0.2 0.2 0.2 0.2 0.2 0.2
:WAUPACA RIVER
WAUPACA 0.2 0.2 0.2 0.2 0.2 0.2 0.2
:FOX RIVER
APPLETON 3.0 3.0 2.9 2.2 0.8 0.0 0.0
:MENOMINEE RIVER
FLORENCE 0.4 0.4 0.4 0.4 0.4 0.4 0.4
NIAGARA 0.6 0.6 0.6 0.6 0.6 0.6 0.6
VULCAN 0.7 0.7 0.7 0.7 0.7 0.7 0.7
MCALLISTER 1.3 1.3 1.3 1.3 1.3 1.3 1.3
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 next outlook will be provided on Thursday February 27th, 2025.
COMING SOON!
COMING SOON!
References
River Levels
|
Safety |
Follow us on X
Follow us on Facebook
Follow us on YouTube
GRB RSS Feed