Flood Potential Outlook
Issued by NWS Grand Rapids, MI

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FGUS73 KGRR 151710
ESFGRR

ARBESFGRR
MIC005-015-025-035-037-045-057-065-067-073-075-077-081-085-
105-107-117-121-123-127-133-139-159-141600-

Probabilistic Hydrologic Outlook
National Weather Service Grand Rapids MI
1157 AM EST Thu Feb 15 2018

...2018 SPRING FLOOD AND WATER RESOURCES OUTLOOK NUMBER 1...

This Spring Flood and Water Resources Outlook is for the rivers in
Southwest Lower Michigan.

...Flood Outlook Highlights...

For much of Southwest Lower Michigan there is near normal risk for
flooding this spring.  The Muskegon basin has a less than normal
risk for flooding. Tributaries in the upper Grand River have a
greater than normal risk for minor or moderate flooding. Tributaries
in the Kalamazoo basin have a slightly greater than normal risk of
minor flooding.

Snowpack is a major factors in the forecast with much less snow than
normal across the Muskegon basin.  Further south the snowpack
contained more water than usual. These forecasts do not include the
impacts of the ice in the rivers. The Saginaw basin has a near to
below normal risk for 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 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
structures and roads.  Significant evacuations of people and/or
transfer of property to higher elevations will be needed.

...Probabilistic Outlook...

For much of Southwest Lower Michigan there is near normal risk for
flooding this spring.  The Muskegon basin has a less than normal
risk for flooding. Tributaries in the upper Grand River have a
greater than normal risk for minor or moderate flooding. Tributaries
in the Kalamazoo basin have a slightly greater than normal risk of
minor flooding. The Saginaw basin has a near to below normal risk
for minor flooding.

Snowpack is a major factors in the forecast with much less snow than
normal across the Muskegon basin.  Further south the snowpack
contained more water than usual. These forecasts do not include the
impacts of the ice in the rivers.

...Past Precipitation...

Precipitation across the area this past fall and winter has been
greater than normal.  Snowfall has been greater than normal for all
but the upper Muskegon basin where values are close to normal.

...River Conditions...

Many of the river levels were ice impacted around the region.  The
gages in the Kalamazoo basin with accurate readings indicated near
normal levels.

...Soil Moisture and Frost Depths...

Soil moisture conditions were near normal across Southwest Lower
Michigan. Frost depths varied from less than 3 inches to around a
foot.

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

Generally snow cover ranged from 4 to 6 inches around the area. The
water equivalent was 0.5 to 1.0 inch with the greatest amounts in
the Kalamazoo and Grand basins.  The least amount of water
equivalent was in the upper Muskegon basin.

...Weather Outlook...

The 90 day outlook for March through May calls for equal chances of
below, above or near normal temperatures. However, the odds favor
above normal precipitation.

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.

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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Grand River
Jackson             14.0   15.0   16.0 :  50   43   33   21   18   15
Eaton Rapids         6.0    8.0    9.0 :   8    5   <5   <5   <5   <5
Dimondale           13.0   14.0   16.0 :  <5   <5   <5   <5   <5   <5
:Red Cedar River
Williamston          9.0   10.0   10.5 :  <5   <5   <5   <5   <5   <5
East Lansing         7.0   10.0   13.0 :  42   25   <5   <5   <5   <5
:Sycamore Creek
Holt                 8.0    9.0   10.0 :  63   30   12    6   <5   <5
:Grand River
Lansing             11.0   13.0   15.0 :  25   11   <5   <5   <5   <5
Grand Ledge         11.0   13.0   15.0 :  <5   <5   <5   <5   <5   <5
Portland            12.0   14.0   16.0 :   6   <5   <5   <5   <5   <5
:Looking Glass River
Eagle                7.0    9.0   11.0 :  92   78   35   26   <5    5
:Maple River
Maple Rapids         9.0   11.0   13.0 :  74   65   <5   <5   <5   <5
:Grand River
Ionia               21.0   23.0   25.0 :  19   17   <5   <5   <5   <5
:Flat River
Smyrna               8.5    9.5   10.5 :  <5   <5   <5   <5   <5   <5
:Grand River
Lowell              15.0   18.0   20.0 :  22   21   <5   <5   <5   <5
:Thornapple River
Hastings             7.0    9.0   10.0 :  45   34   <5    7   <5   <5
Caledonia           10.0   12.0   14.0 :  18   18   <5   <5   <5   <5
:Grand River
Ada                 20.0   22.0   25.0 :  17   12   <5   <5   <5   <5
:Rogue River
Rockford             8.0   10.0   11.0 :  10   10   <5   <5   <5   <5
:Grand River
Grand Rapids        18.0   21.0   23.0 :  17   12   <5   <5   <5   <5
:Pere Marquette River
Scottville           5.5    6.5    7.0 :  <5   <5   <5   <5   <5   <5
:White River
Whitehall            6.0    7.0    8.0 :   6    5   <5   <5   <5   <5
:Muskegon River
Evart               12.0   13.0   14.0 :  10   26   <5    7   <5   <5
:Little Muskegon River
Morley               6.0    7.0    8.0 :  <5   <5   <5   <5   <5   <5
:Muskegon River
Croton               9.0   11.0   12.0 :  24   34   <5   <5   <5   <5
:Kalamazoo River
Marshall             8.0    9.0   10.0 :  10   10    5    9   <5    8
:Battle Creek
Battle Creek         4.0    5.0    6.0 :  <5   <5   <5   <5   <5   <5
:Kalamazoo River
Battle Creek         9.0   10.0   11.0 :  <5   <5   <5   <5   <5   <5
Comstock             9.0   10.0   11.0 :  13    7   <5   <5   <5   <5
New Richmond        17.0   19.0   21.0 :  12    8   <5   <5   <5   <5
:St Joseph River
Burlington           6.5    9.0   11.0 :  17   16   <5   <5   <5   <5
:Portage River
Vicksburg            5.0    7.0    8.0 :  65   44   <5   <5   <5   <5
:Chippewa River
Mt Pleasant          8.0   11.0   13.0 :  16   14   <5   <5   <5   <5
:Pine River
Alma                 8.0   10.0   12.0 :   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%
--------            ------ ------ ------ ------ ------ ------ ------
:Grand River
Jackson              12.3   12.5   13.3   14.0   15.5   16.6   18.8
Eaton Rapids          4.3    4.5    4.6    4.9    5.4    5.8    6.6
Dimondale             7.4    8.0    8.3    8.9    9.9   10.9   12.0
:Red Cedar River
Williamston           6.5    6.8    7.3    7.7    8.2    8.7    8.8
East Lansing          5.6    5.8    6.4    6.8    7.6    8.3    8.6
:Sycamore Creek
Holt                  7.1    7.2    7.7    8.2    8.6    9.1    9.4
:Grand River
Lansing               7.3    8.0    8.8    9.5   11.0   12.4   12.8
Grand Ledge           6.9    7.3    7.8    8.2    9.2    9.8   10.0
Portland              8.5    8.9    9.5   10.0   10.9   11.5   12.1
:Looking Glass River
Eagle                 6.8    7.2    7.8    8.6    9.3   10.2   10.7
:Maple River
Maple Rapids          8.5    8.7    9.0    9.2    9.6    9.9   10.0
:Grand River
Ionia                16.6   17.4   18.2   19.3   20.3   21.8   22.1
:Flat River
Smyrna                5.1    5.3    5.7    6.0    6.7    7.4    7.8
:Grand River
Lowell                9.9   10.8   11.7   12.8   14.6   16.4   16.6
:Thornapple River
Hastings              5.0    5.6    6.0    6.7    7.6    8.2    8.7
Caledonia             6.1    6.6    7.1    8.3    9.4   10.7   11.1
:Grand River
Ada                  13.7   14.7   15.8   17.1   18.9   20.6   21.0
:Rogue River
Rockford              5.5    5.9    6.2    6.7    7.5    8.1    8.6
:Grand River
Grand Rapids          9.9   11.3   13.0   14.8   16.7   18.7   19.3
:Pere Marquette River
Scottville            3.0    3.4    3.6    4.1    4.6    5.0    5.2
:White River
Whitehall             3.3    3.6    4.0    4.4    5.2    5.7    6.0
:Muskegon River
Evart                 8.7    9.1    9.7   10.2   11.4   12.0   12.5
:Little Muskegon River
Morley                3.0    3.2    3.6    4.0    4.4    5.1    5.4
:Muskegon River
Croton                6.6    7.1    7.5    8.1    9.0    9.7   10.5
:Kalamazoo River
Marshall              5.6    5.7    6.0    6.4    6.7    7.8    9.1
:Battle Creek
Battle Creek          1.8    1.9    2.1    2.4    2.7    3.1    3.4
:Kalamazoo River
Battle Creek          4.3    4.5    4.8    5.3    6.0    7.0    7.3
Comstock              5.5    6.0    6.4    7.1    7.9    9.2    9.7
New Richmond         14.1   14.5   14.8   15.4   16.1   17.2   17.3
:St Joseph River
Burlington            5.3    5.3    5.6    6.0    6.3    6.8    7.3
:Portage River
Vicksburg             4.7    4.8    4.9    5.1    5.3    5.5    5.6
:Chippewa River
Mt Pleasant           5.0    5.3    5.8    6.3    7.4    8.4    9.3
:Pine River
Alma                  4.3    4.9    5.4    5.8    6.7    7.7    8.1

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%
--------            ------ ------ ------ ------ ------ ------ ------
:Grand River
Jackson              10.3   10.2    9.9    9.8    9.6    9.5    9.3
Eaton Rapids          3.9    3.9    3.8    3.8    3.7    3.7    3.7
Dimondale             6.0    6.0    5.8    5.6    5.5    5.3    5.2
:Red Cedar River
Williamston           4.2    4.1    3.8    3.3    3.1    3.0    2.9
East Lansing          4.0    3.9    3.7    3.6    3.6    3.5    3.4
:Sycamore Creek
Holt                  3.6    3.5    3.4    3.4    3.3    3.3    3.3
:Grand River
Lansing               4.5    4.4    4.2    3.9    3.8    3.5    3.4
Grand Ledge           5.7    5.7    5.6    5.5    5.4    5.3    5.2
Portland              6.6    6.5    6.4    6.2    6.1    5.8    5.8
:Looking Glass River
Eagle                 4.6    4.5    4.3    4.1    3.8    3.7    3.5
:Maple River
Maple Rapids          6.0    5.7    5.3    4.8    4.3    4.1    3.9
:Grand River
Ionia                11.3   11.1   10.7   10.3    9.9    9.4    9.1
:Flat River
Smyrna                4.0    4.0    3.9    3.9    3.8    3.7    3.6
:Grand River
Lowell                6.9    6.8    6.7    6.5    6.2    5.9    5.6
:Thornapple River
Hastings              3.7    3.7    3.6    3.5    3.4    3.3    3.2
Caledonia             4.3    4.2    4.1    4.0    3.8    3.6    3.5
:Grand River
Ada                   9.3    9.1    8.7    8.4    8.0    7.3    6.9
:Rogue River
Rockford              4.4    4.4    4.3    4.3    4.2    4.1    4.0
:Grand River
Grand Rapids          4.8    4.7    4.3    4.0    3.8    3.6    3.5
:Pere Marquette River
Scottville            2.1    2.1    2.0    2.0    1.8    1.7    1.6
:White River
Whitehall             1.9    1.9    1.8    1.7    1.7    1.6    1.5
:Muskegon River
Evart                 7.7    7.6    7.6    7.5    7.4    7.3    7.2
:Little Muskegon River
Morley                2.4    2.4    2.3    2.3    2.3    2.3    2.3
:Muskegon River
Croton                5.5    5.5    5.4    5.3    5.2    5.0    4.9
:Kalamazoo River
Marshall              4.5    3.2    3.2    3.2    3.2    3.2    3.2
:Battle Creek
Battle Creek          1.1    1.1    1.1    1.0    1.0    1.0    0.9
:Kalamazoo River
Battle Creek          3.7    3.6    3.5    3.5    3.4    3.2    3.1
Comstock              4.8    4.7    4.6    4.5    4.4    4.3    4.2
New Richmond         12.9   12.9   12.7   12.6   12.3   12.0   11.9
:St Joseph River
Burlington            4.4    4.3    4.2    4.1    4.0    4.0    3.9
:Portage River
Vicksburg             4.1    4.1    4.0    4.0    4.0    3.9    3.8
:Chippewa River
Mt Pleasant           3.4    3.4    3.3    3.3    3.2    3.2    3.2
:Pine River
Alma                  2.0    2.0    1.9    1.8    1.6    1.5    1.4

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/grr for more weather and water
information.

This is the first Spring Flood Outlook for this year.  The next
issuance will be on March 1st.

$$

BMH



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