Flood Potential Outlook
Issued by NWS Marquette, MI

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FGUS73 KMQT 072056
ESFMQT
MIC013-053-061-071-103-131-072150-

Probabilistic Hydrologic Outlook
National Weather Service Marquette MI
253 PM EST Thu Mar 07 2019

...Spring Flood and Water Resources Outlook Number 2...

This Spring Flood and Water Resources Outlook is for the rivers of
Upper Michigan from Tahquomenon Falls westward.

...Flood Outlook Highlights...

The risk of flooding from late winter into spring remains above
normal, and the potential exists for the spring flood risk to become
well above normal. A deep, wet snowpack exists over Upper Michigan as
of March 7th, 2019. This will cause area rivers, streams, and low
lying areas to become vulnerable to flooding this spring. We will
likely be adding more water to the snowpack (see weather outlook
below) than it will lose in the foreseeable future.

Although a lot will still depend on the characteristics of the
impending spring warm up and whether or not snowmelt is exacerbated
by heavy rainfall events, chances are increasing that at least minor
flooding may occur on several area rivers. At this time, the most
likely basins to experience flooding are the Michigamme, Paint,
Sturgeon, and Escanaba river basins, though other areas like the
Black River and Chocolay River will also have an elevated risk of
minor flooding.

...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...

February 2019 was one of the wettest winter months on record in Upper
Michigan. A few locations in Iron and Dickinson Counties received
more than 4 times their average February precipitation, and virtually
all of the UP recieved at least twice the average. Even going back to
September 2018, precipitation has been well above average despite a
relatively dry December into part of January, leading to already wet
soils and above normal streamflows heading into the melt season.

...River Conditions...

Ice coverage is above normal and nearly ubiquitous across area
rivers. Additionally, river flows were generally above normal this
fall heading into winter. Evolution of ice conditions through the
spring remains uncertain, but break-up ice jam potential does appear
to be near to above normal at this time.

...Soil Conditions and Frost Depths...

Soil moisture is above normal in terms of both daily and monthly
averages, essentially at the 95th percentile or above for this time
of year. One experimental product from UCLA that combines SWE and
soil moistures indicates that total moisture storage is above the
90th percentile across the UP and above the 98th percentile over the
east.

Frost depth is generally just a few inches over the northern UP where
snow insulation started early, and between about 20 and 40 inches for
locations near the WI border, greatest far south central where snow
cover took a while to fill in in the fall. In locations where frost
depths are deeper, an early snowmelt could lead to increased runoff
into rivers, streams, and resorvoirs.

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

Per the NOHRSC analysis and North Central River Forecast Center,
higher elevation areas of western and central Upper Michigan as well
as the northeastern Upper Peninsula Snowbelts have areas of over 10
inches of water equivalent at this time, with a few locations
approaching 15 inches. Snow depths range from 20 inches to the upper
40s and lower 50s, with a few locations as high as 60 inches. A
comparison of the current snow water equivalent analysis to a study
of climatological SWE done in 1999 shows that much of the area is
likely more than one standard deviation wetter than than average.
Below are selected recent Snow Water Equivalent (SWE) observations.

Location             Snow  Snow  date
                     depth water

Bruce Crossing        31   6.5   03/01
Copper Harbor         41   11.5  03/01
Gladstone             27   5.9   03/07
Norway                27   6.9   03/04
NWS Marquette         47   11.0  03/07
Marquette City        26   4.1   02/25
Mcfarland             29   5.8   03/07
Mohawk                42   8.0   03/01
Painesdale            58   14.1  03/01
Rockland              46   11.2  03/01
Stambaugh             31   6.5   03/04
Sault Ste Marie       39   8.2   03/06

...Weather Outlook...

We are expecting a storm Saturday night into Sunday that will likely
add a widepread half inch of liquid equivalent, with isolated totals
as low as a third of an inch and as high as three quarters of an
inch.

The 6 to 10 and 8 to 14 day outlooks from the Climate Prediction
Center (CPC) call for a likelihood of a brief reprieve from below
normal temperatures March 12-15, but a 40-50 percent chance of below
normal temperatures returning after that. Normal high temperatures
have increased to near or above freezing already, and will continue
to climb to the low to mid 40s by the end of March. But given the
current outlook, it seems likely that much of the snowpack will be
sticking around into April, especially across the north.

CPC also indicates that there is a 70 percent chance of above normal
precipitation for March 13th through the 17th, adding further
unneeded water, although chances are increasing for a drier period
the 16th through the 21st.

...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:  03/11/2019 - 06/09/2019

                                       :    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 :  70   27   47   17   15    5
:Paint River
Crystal Falls        7.0    8.0    9.5 :  54   14   28   <5   <5   <5
:Black River
Bessemer            10.0   12.0   14.0 :  37   11    9   <5   <5   <5
:Ontonagon River
Rockland            25.0   26.0   28.0 :   8   <5    6   <5   <5   <5
:Sturgeon River
Sidnaw              12.0   15.0   17.0 :   6   <5   <5   <5   <5   <5
Alston               8.0   11.0   14.0 :  95   23   11   <5   <5   <5
:Chocolay River
Harvey              10.0   11.5   13.0 :  15   <5   <5   <5   <5   <5
:East Branch Escanaba River
Gwinn                7.0    9.0   12.0 :  52   <5   <5   <5   <5   <5
:Middle Branch Escanaba River
Humboldt             6.5    8.0    9.0 :  52   14   <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: 03/11/2019 - 06/09/2019
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake            7.9    8.3    8.8    9.9   11.0   12.5   14.3
:Paint River
Crystal Falls         5.8    6.1    6.5    7.1    8.1    9.1    9.4
:Black River
Bessemer              7.0    7.5    8.7    9.6   11.0   11.9   12.6
:Ontonagon River
Rockland             15.4   16.2   17.4   18.8   21.7   23.9   26.2
:Sturgeon River
Sidnaw                7.9    8.2    8.6    9.1   10.3   11.2   12.3
Alston                8.0    8.3    8.7    9.2   10.1   11.2   12.3
:Chocolay River
Harvey                7.0    7.5    8.1    8.5    9.3   10.2   10.6
:East Branch Escanaba River
Gwinn                 5.5    6.0    6.6    7.0    7.7    8.2    8.5
:Middle Branch Escanaba River
Humboldt              5.7    5.9    6.2    6.6    7.0    7.6    7.9

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: 03/11/2019 - 06/09/2019
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Michigamme River
Witch Lake            2.6    2.6    2.6    2.6    2.6    2.6    2.6
:Paint River
Crystal Falls         2.2    2.2    2.2    2.1    2.1    2.1    2.1
:Black River
Bessemer              2.1    2.1    2.1    2.1    2.1    2.1    2.1
:Ontonagon River
Rockland              5.9    5.9    5.9    5.8    5.7    5.5    5.5
:Sturgeon River
Sidnaw                4.0    4.0    4.0    4.0    4.0    4.0    3.9
Alston                3.9    3.9    3.9    3.9    3.8    3.8    3.8
:Chocolay River
Harvey                2.8    2.8    2.8    2.8    2.7    2.7    2.7
:East Branch Escanaba River
Gwinn                 0.6    0.6    0.6    0.5    0.5    0.5    0.5
:Middle Branch Escanaba River
Humboldt              1.9    1.9    1.8    1.8    1.8    1.8    1.8

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.

Visit https://water.weather.gov/ahps2/index.php?wfo=mqt (all lower
case) for more river information, including graphs of the
probablistic information above, as well as latest streamgage
observations.

Long range probablistic outlooks such as those given in the
above tables are issued during the last week of every month.
The next outlook will be issued near the end of March.

$$






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