998
FGUS73 KMQT 131252
ESFMQT
MIC013-053-061-071-103-131-DDHHMM-

Probabilistic Hydrologic Outlook
National Weather Service Marquette MI
745 AM EST Thu Feb 13 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.

...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 30% at all of the Upper
Michigan forecast locations. 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 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 slightly below-normal across most of Upper Michigan
due to persistent dry conditions away from Lake Superior since last
Fall. Frost depth in Negaunee Township was 11 inches on Feb 10th and
ranges between 20 and 30 inches across much of Upper Michigan,
especially in areas where there is little to no snowpack. 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 much below-normal across
interior west and central Upper Michigan. Below to near normal snow
water equivalent values are observed in the east and near Lake
Superior. The only area with above normal snow water equivalent
values is northeastern Upper Michigan where the northwest wind lake
effect snow is favored. Even though the U.P. winter is far from
over, snowpack is currently near or at record lows and there aren`t
any major systems in the forecast at this time.

...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, snowmelt concerns are already below the historical
normals in the region. While the snowfall season in Upper Michigan
is far from over, the current forecast out to 2 weeks favors
slightly drier than normal with no indications of significant snow
storms to impact the area. At this time, the Climate Prediction
Center`s probabilistic forecast through April is for 33-40% chance
for above normal precipitation, so there is some chances for
increased snowpack prior to spring melt. That said, the outlook also
has a 33-40% chance for below normal temperatures. With cooler
conditions favored during the Spring warm up, a slower melt would
reduce flood risks. If the dry pattern is persistent but cooler
temperatures continue, the flood risk could lower to no risk at all.
The current threat for springtime flooding is lower than normal, but
much of the Spring Flooding Outlook hinges on weather conditions
over the next 4 to 8 weeks.

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:  02/17/2025 - 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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Michigamme River
Witch Lake           9.0   10.0   12.0 :  23   30    8   17   <5   <5
:Paint River
Crystal Falls (Pa    7.0    8.0    9.5 :   7   18   <5    5   <5   <5
:Black River
Bessemer            10.0   12.0   14.0 :  11   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 :  19   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 :   7   12   <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: 02/17/2025 - 05/18/2025
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake            5.8    6.1    6.7    7.5    8.9    9.8   10.5
:Paint River
Crystal Falls (Pa     3.8    4.1    4.5    4.9    5.5    6.3    7.3
:Black River
Bessemer              4.6    4.8    5.6    6.5    7.2   10.2   10.8
:Ontonagon River
Rockland             10.5   11.1   12.3   13.5   15.1   17.3   20.0
:Sturgeon River
Sidnaw                6.1    6.3    6.6    7.0    7.4    8.4    8.9
Alston                6.2    6.4    6.8    7.3    7.8    8.7    9.6
:Chocolay River
Harvey                4.1    4.4    5.2    6.0    6.8    7.7    8.4
:East Branch Escanaba River
Gwinn                 3.1    3.3    3.9    4.5    5.1    5.7    6.5
:Middle Branch Escanaba River
Humboldt              4.5    4.6    5.0    5.5    5.8    6.3    6.8

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%
--------            ------ ------ ------ ------ ------ ------ ------
: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              0.6    0.6    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    0.2    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    0.0    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 February 27, 2025.

$$

Jablonski