Flood Potential Outlook
Issued by NWS Marquette, MI

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Probabilistic Hydrologic Outlook
National Weather Service Marquette MI
1214 PM EST Thu Feb 15 2018

...Spring Flood and Water Resources Outlook Number 1...

This Spring Flood and Water Resources Outlook is for the rivers of
central and western Upper Michigan.

...Flood Outlook Highlights...

The risk of flooding from late winter into spring is near to below
normal.

...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 extensive inundation
of structures and roads. Significant evacuations of people and/or
transfer of property to higher elevations.

...Past Precipitation...

Snowfall so far this winter has generally been above normal in west
to northwest wind snowbelts and below normal elsewhere.

...River Conditions...

Ice coverage is generally above normal due to cold conditions so far
this winter. Evolution of ice conditions through the spring is
uncertain, but ice jam potential does appear to be above normal at
this time.

...Soil Conditions and Frost Depths...

Soil moisture is near to above normal. Frost depth is generally
between 13 and 44 inches under snow cover, greatest in the interior
portions of central Upper Michigan where snow cover is lowest.

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

Location    Snow  Snow  Date
            depth water

            Data in inches
Ironwood    19    4.7   2/12
Bessemer    17    4.0   2/12
Stambaugh   11    2.9   2/12
Negaunee    19    3.5   2/13
Marquette    9    1.2   2/13
Sault Ste M 18    3.6   2/14

...Weather Outlook...

The 6 to 10 day outlook calls for a 33 to 40 percent chance of colder
than normal conditions in the western half of the Upper Peninsula,
with equal chances of above normal, normal, or below normal
temperatures east. It also calls for a 33-40 percent chance of above
normal precipitation. The 8 to 14 day outlook indicates a 40 to 50
percent chance of above normal temperatures, with equal chances of
below normal, normal, and above normal precipitation. The 30 day
outlook indicates equal chances of below normal, normal, or above
normal for both temperature and precipitation, while the three month
outlook does indicate a 33 to 40 percent chance of above normal
precipitation.

...Flood Outlook Summary...

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:  02/18/2018 - 05/19/2018

                                       :    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 :   6   27   <5   17   <5   <5
:Paint River
Crystal Falls        7.0    8.0    9.5 :   7   14   <5   <5   <5   <5
:Black River
Bessemer            10.0   12.0   14.0 :  10    8   <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   19   <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   <5   <5   <5   <5   <5
:Middle Branch Escanaba River
Humboldt             6.5    8.0    9.0 :   6   11   <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: 02/18/2018 - 05/19/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake            4.8    5.2    5.8    6.5    7.9    8.4    9.8
:Paint River
Crystal Falls         4.2    4.3    4.8    5.2    5.8    6.4    7.7
:Black River
Bessemer              5.0    5.1    5.8    6.7    7.3    9.9   11.1
:Ontonagon River
Rockland             10.8   11.4   13.0   14.3   16.0   17.9   20.8
:Sturgeon River
Sidnaw                6.3    6.5    6.7    7.3    7.8    8.4    8.9
Alston                6.1    6.4    6.7    7.3    7.9    8.5    9.2
:Chocolay River
Harvey                4.6    4.7    5.8    6.7    7.4    8.4    9.0
:East Branch Escanaba River
Gwinn                 3.2    3.6    4.2    4.6    5.3    5.9    6.6
:Middle Branch Escanaba River
Humboldt              4.1    4.3    4.8    5.2    5.6    6.0    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: 02/18/2018 - 05/19/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake            2.7    2.7    2.7    2.7    2.7    2.6    2.6
:Paint River
Crystal Falls         2.3    2.3    2.2    2.2    2.2    2.2    2.1
:Black River
Bessemer              2.3    2.3    2.3    2.3    2.3    2.3    2.3
:Ontonagon River
Rockland              6.0    6.0    6.0    5.9    5.9    5.8    5.7
:Sturgeon River
Sidnaw                4.2    4.2    4.2    4.2    4.1    4.1    4.1
Alston                4.0    4.0    4.0    4.0    4.0    3.9    3.9
:Chocolay River
Harvey                2.8    2.8    2.8    2.7    2.7    2.7    2.7
:East Branch Escanaba River
Gwinn                 0.8    0.8    0.7    0.7    0.7    0.7    0.6
:Middle Branch Escanaba River
Humboldt              2.0    1.9    1.9    1.9    1.9    1.9    1.9

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 1st

$$







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