Flood Potential Outlook
Issued by NWS Marquette, MI

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FGUS73 KMQT 221426
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MIC013-053-061-071-103-131-221500-

Probabilistic Hydrologic Outlook
National Weather Service Marquette MI
821 AM EST Thu Feb 22 2024

...2024 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 much below-normal across all of
Upper Michigan. The primary factors contributing to a below-normal
flood risk is significantly below normal snowpack and the lack of
river ice.

...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 40% at all of the Upper
Michigan forecast locations. The chance of moderate flooding is less
than 20% at all of the Upper Michigan forecast locations.

...Past Precipitation...

Precipitation last Fall was below normal across the area and this dry
pattern has continued through the winter season.

...River Conditions...

Streamflow across Upper Michigan was near to below-normal and
persistently warm temperatures combined with episodes of snowmelt has
removed most of the river ice.

...Soil Moisture and Frost Depths...

Soil moisture is below-normal across Upper Michigan due to
persistently warm and dry conditions since last fall. Frost depth in
Negaunee Township was 3 inches on Feb 20th and hasn`t changed much
since mid-January when the seasonal snowpack was established.

...Snow Cover and Liquid Water Content...

Current snow water equivalent values are much below-normal
across all of Upper Michigan. Even though the UP 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...

Well above normal temperatures this winter limited ice formation
on rivers across Upper Michigan. Continued warm temperatures suggest
reduced potential for ice jams and associated flooding.

...Weather Outlook...

The single biggest factor affecting spring flood risks are the
weather conditions during the period of snow melt. A slow snow melt
with little or no rainfall would elinimate this years flood risks. On
the other hand, a rapid warmup accompanied by heavy rain
substantially increases flood risks for portions of Upper Michigan
with several inches of snow water equivalent. At this time, the
Climate Prediction Center`s probabilistic forecast is for 30-50%
chance of below normal precipitation and above-normal temperatures
continuing through March. 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.

...Definitions...

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:  02/19/2024 - 05/19/2024

                                       :    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 :  <5   30   <5   17   <5    6
:Paint River
Crystal Falls (Pa    7.0    8.0    9.5 :  <5   18   <5    5   <5   <5
:Black River
Bessemer            10.0   12.0   14.0 :  <5   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 :   7   34   <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 :  <5   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: 02/19/2024 - 05/19/2024
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake            4.2    4.5    5.1    5.8    6.9    7.9    8.4
:Paint River
Crystal Falls (Pa     3.3    3.5    3.9    4.3    4.8    5.4    6.1
:Black River
Bessemer              3.7    3.8    4.5    5.3    6.3    8.5    9.0
:Ontonagon River
Rockland              8.9    9.2   10.3   11.7   14.2   16.2   18.0
:Sturgeon River
Sidnaw                5.5    5.6    5.9    6.3    6.7    7.4    8.0
Alston                5.3    5.5    5.8    6.4    6.9    7.8    8.3
:Chocolay River
Harvey                3.7    3.9    4.3    4.8    5.7    7.0    7.6
:East Branch Escanaba River
Gwinn                 2.5    2.8    3.3    3.8    4.4    5.2    5.5
:Middle Branch Escanaba River
Humboldt              3.4    3.6    4.2    4.7    5.2    5.7    6.2

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: 02/19/2024 - 05/19/2024
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake            2.8    2.8    2.7    2.7    2.7    2.6    2.6
:Paint River
Crystal Falls (Pa     2.2    2.2    2.1    2.1    2.1    2.1    2.0
:Black River
Bessemer              2.3    2.3    2.3    2.3    2.3    2.2    2.2
:Ontonagon River
Rockland              5.8    5.8    5.7    5.7    5.7    5.5    5.4
:Sturgeon River
Sidnaw                4.1    4.1    4.1    4.1    4.1    4.0    4.0
Alston                4.1    4.1    4.0    4.0    4.0    4.0    3.9
:Chocolay River
Harvey                2.8    2.8    2.8    2.8    2.8    2.7    2.7
:East Branch Escanaba River
Gwinn                 0.7    0.6    0.6    0.6    0.6    0.5    0.5
:Middle Branch Escanaba River
Humboldt              1.8    1.8    1.8    1.8    1.7    1.7    1.7

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

$$






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