Flood Potential Outlook
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
990
FGUS73 KMQT 271819
ESFMQT
MIC013-053-061-071-103-131-272300-
Probabilistic Hydrologic Outlook
National Weather Service Marquette MI
219 PM EST Thu Feb 27 2025
...2025 SPRING FLOOD AND WATER RESOURCES OUTLOOK...
This Spring Flood and Water Resources Outlook is for the rivers in
western and east-central Upper Michigan.
...Flood Outlook Highlights...
The overall flood risk this Spring is below-normal across all of
Upper Michigan. The primary factor contributing to a below-normal
flood risk is below normal water content in the snowpack over much of
the UP.
...Flood Terminology...
The term minor flooding is used to indicate minimal or no property
damage. However, some public inconvenience is possible.
The term moderate flooding is used to indicate some inundations of
structures and roads near streams. Some evacuations of people and/or
transfer of property to higher elevations may be needed.
The term major flooding is used to indicate extensive inundation of
structure and roads. Significant evacuations of people and/or
transfer of property to higher elevations will be needed.
...Probabilistic Outlook...
The chance of minor flooding is less than or equal to 25% at all of
the Upper Michigan forecast locations, except the Sturgeon River at
Alston where it is 32%. The chance of moderate flooding is less
than 10% at all of the Upper Michigan forecast locations.
...Past Precipitation...
Precipitation last Fall until November was below normal for most of
Upper Michigan. So far this Winter, the below normal precipitation
pattern has continued due to the lack of system snow passing over
the region. However, the persistent lake effect patterns dominating
this Winter has lead to above normal snow over northeast Upper
Michigan and the Keweenaw Peninsula where northwest wind lake effect
snow is favored.
...River Conditions...
Streamflow has broadly remained near normal across Upper Michigan
this winter. Periods of colder than normal temperatures have lead to
some river ice development.
...Soil Moisture and Frost Depths...
Soil moisture is above normal in the lake effect snow belts of the
western and eastern UP and near normal elsewhere. Frost depth in
Negaunee Township was 11 inches on Feb 27th and ranges between 20 and
40 inches across much of interior Upper Michigan. These conditions
have not changed much since mid-January when the first significant
cold airmass moved over the region.
..Snow Cover and Liquid Water Content...
Current snow water equivalent values are variable across the UP. Well
below-normal values exist over the south-central UP, near to below-
normal values exist over the north-central and southwestern UP, and
above normal values exist in the lake effect snow belts of the
northwestern and northeastern UP. There is potential for accumulating
snow in the early part of March to add to SWE values and snow depths.
...River Ice Conditions...
Initially, above normal temperatures in December limited ice
formation on rivers across Upper Michigan. Near to slightly below
than normal temperatures in January and February have allowed modest
ice growth. The potential for ice jams and associated minor flooding
cannot be ruled out, but is not likely (<20% chance).
...Weather Outlook...
The biggest factor affecting Spring flood risks are the weather
conditions during the period of snow melt. With the current snowpack
below normal outside of the lake effect belts, snowmelt concerns are
already below the historical normals over most of the region.
However, there is potential for accumulating snow during the first
week of March, and the Climate Prediction Center`s probabilistic
forecast March 4-8 is for a 33-50% chance of above normal
precipitation. The forecast for March as a whole is for a 40-60%
chance of above normal precipitation. If snow water equivalent values
increase during this period, the potential for flooding could rise;
however, the current threat for springtime flooding across the UP is
lower than normal at this time.
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: 03/03/2025 - 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
-------- ----- ----- ----- : --- --- --- --- --- ---
:Michigamme River
Witch Lake 9.0 10.0 12.0 : 25 30 9 17 <5 6
:Paint River
Crystal Falls (Pa 7.0 8.0 9.5 : 8 18 <5 5 <5 <5
:Black River
Bessemer 10.0 12.0 14.0 : 9 11 <5 <5 <5 <5
:Ontonagon River
Rockland 25.0 26.0 28.0 : <5 <5 <5 <5 <5 <5
:Sturgeon River
Sidnaw 12.0 15.0 17.0 : <5 <5 <5 <5 <5 <5
Alston 8.0 11.0 14.0 : 32 33 <5 <5 <5 <5
:Chocolay River
Harvey 10.0 11.5 13.0 : <5 <5 <5 <5 <5 <5
:East Branch Escanaba River
Gwinn 7.0 9.0 12.0 : <5 6 <5 <5 <5 <5
:Middle Branch Escanaba River
Humboldt 6.5 8.0 9.0 : 8 13 <5 <5 <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%
-------- ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake 6.4 6.6 7.1 7.6 9.0 9.7 11.2
:Paint River
Crystal Falls (Pa 3.9 4.2 4.7 5.1 5.6 6.5 7.3
:Black River
Bessemer 4.9 5.3 5.9 6.5 7.3 9.6 10.7
:Ontonagon River
Rockland 11.8 12.3 13.0 14.9 16.6 18.8 21.0
:Sturgeon River
Sidnaw 6.5 6.6 6.9 7.4 8.0 8.7 9.2
Alston 6.6 6.8 7.1 7.7 8.4 9.1 9.8
:Chocolay River
Harvey 4.3 4.5 5.2 6.1 7.1 7.6 8.4
:East Branch Escanaba River
Gwinn 3.2 3.4 4.0 4.7 5.1 5.8 6.4
:Middle Branch Escanaba River
Humboldt 4.8 4.9 5.1 5.5 5.9 6.4 6.9
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%
-------- ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake 0.1 0.1 0.1 0.1 0.1 0.1 0.1
:Paint River
Crystal Falls (Pa 0.2 0.2 0.2 0.2 0.2 0.2 0.2
:Black River
Bessemer 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:Ontonagon River
Rockland 0.5 0.5 0.5 0.5 0.5 0.4 0.4
:Sturgeon River
Sidnaw 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Alston 0.2 0.2 0.2 0.2 0.1 0.1 0.1
:Chocolay River
Harvey 0.1 0.1 0.1 0.1 0.1 0.1 0.1
:East Branch Escanaba River
Gwinn 0.1 0.1 0.1 0.1 0.0 0.0 0.0
:Middle Branch Escanaba River
Humboldt 0.0 0.0 0.0 0.0 0.0 0.0 0.0
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/mqt for more weather and water
information.
The next outlook will be issued March 13, 2025.
$$
Thompson