Flood Potential Outlook
Issued by NWS Grand Rapids, MI

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FGUS73 KGRR 292123
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PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE Grand Rapids MI
1108 AM EST Thu Feb 29 2024

...2024 SPRING FLOOD AND WATER RESOURCES OUTLOOK NUMBER 2...

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

...Flood Outlook Highlights...

The overall flood risk this spring is below average across all of
Southwest Michigan (Grand and Kalamazoo River basins) and much below
average across West-Central Lower Michigan (Muskegon River basin).
This reduced risk is mainly the result of significantly less snowpack
than normal for this time of year as well as the fact that there is
no ice remaining on any of our rivers.

...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 inundation 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...

The flood risk this spring is below normal in all river basins in
Southwest and West-Central Lower Michigan. The chance of flooding is
less than 50% at all of the forecast locations on our rivers.

...Past Precipitation...

The fall and early winter period was much drier than normal. A few
weeks during the middle of January brought wetter than normal
conditions, but it`s been generally drier than normal since then.

...River Conditions...

Water levels on the rivers were near-normal for most of the fall and
early winter, before climbing to well above-average by late January
as heavy rain and complete snowmelt runoff found its way into the
river systems. Water levels are now back to near or even below-normal
levels for this time of year, and it`s entirely possible that we`ve
seen our spring "high water" episode already.

...Soil Moisture and Frost Depths...

Soil moisture is near-normal right now, only because of the rain and
snowmelt episode Lower Michigan experienced in late January. The
record-warm winter conditions so far also mean that there is
virtually no frozen ground to speak of - even up north near the
headwaters of the Muskegon River.

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

The snow cover - including the amount of water being held in that
snow - is near historic lows for mid February. There is essentially
zero snowpack anywhere in the Lower Peninsula, other than an inch or
two of snow in the lake-effect areas of Northern Lower Michigan.
Liquid water content is less than 0.5 inches at all locations.

...River Ice Conditions...

The rivers in the Grand and Muskegon River basins briefly formed a
stable ice cover during the cold snap in mid January, but by the end
of January all of this river ice had melted and broken up. There is
no significant river ice to speak of anywhere in the area.

...Weather Outlook.

The single biggest factor affecting flood risk is the weather
pattern during the sensitive period of melting snow. A slow snow
melt with little or no rainfall is ideal to avoid flooding. On the
other hand, a rapid warmup accompanied by heavy rain is a much worse
scenario for spring flooding - especially if the rivers are covered
with ice. At this time, the long range weather forecast calls for a
continuation of warmer-than-normal temperatures and near-normal
precipitation for the first half of March.

With no significant ice in any of the rivers, and virtually all of
the snowpack already melted, our future flood risks will be linked
entirely to heavy rain events. Currently, there are no
major indications of heavy rain storms on the horizon over the next
week or two, but as we head through March this will remain a concern.

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.

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:  03/04/2024 - 06/02/2024

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Grand River
Jackson             14.0   15.0   16.0 :  20   30   <5   12   <5    6
:Buck Creek
Grandville           9.0   10.5   12.0 :  12   12    6    5   <5   <5
:Grand River
Eaton Rapids         6.0    8.0    9.0 :  <5   <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 :  12   22   <5   <5   <5   <5
:Sycamore Creek
Holt                 8.0    9.0   10.0 :  34   32    7    7   <5   <5
:Grand River
Lansing             11.0   13.0   15.0 :   6   13   <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 :  <5   <5   <5   <5   <5   <5
:Looking Glass River
Eagle                7.0    9.0   11.0 :  33   42    6    9   <5   <5
:Maple River
Maple Rapids         9.0   11.0   13.0 :  47   73   <5   <5   <5   <5
:Grand River
Ionia               21.0   23.0   25.0 :  12   22   <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 :  11   20   <5   <5   <5   <5
:Thornapple River
Hastings             7.0    9.0   10.0 :  21   38   <5   <5   <5   <5
Caledonia           10.0   12.0   14.0 :   7   15   <5   <5   <5   <5
:Grand River
Ada                 20.0   22.0   25.0 :  <5   11   <5   <5   <5   <5
:Rogue River
Rockford             8.0   10.0   11.0 :  11   21   <5   <5   <5   <5
:Grand River
Grand Rapids        18.0   21.0   23.0 :   6   15   <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    9   <5   <5   <5   <5
:Muskegon River
Evart               12.0   13.0   14.0 :  <5   25   <5    9   <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 :  11   40   <5    5   <5   <5
Newaygo             11.0   14.0   15.0 :  20   55   <5   10   <5    6
Bridgeton           13.0   16.0   17.0 :  20   55   <5   11   <5    6
:Kalamazoo River
Marshall             8.0    9.0   10.0 :  <5   11   <5    8   <5    7
: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 :  <5   10   <5   <5   <5   <5
New Richmond        17.0   19.0   21.0 :  <5    9   <5   <5   <5   <5
:St. Joseph River
Burlington           6.5    9.0   11.0 :   6   12   <5   <5   <5   <5
:Portage River
Vicksburg            5.5    7.0    8.0 :  <5    7   <5   <5   <5   <5
:Chippewa River
Mt. Pleasant         8.0   11.0   13.0 :   6   20   <5   <5   <5   <5
:Pine River
Alma                 8.0   10.0   12.0 :   9   16   <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: 03/04/2024 - 06/02/2024
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Grand River
Jackson              11.0   11.6   12.3   13.1   13.8   14.4   14.7
:Buck Creek
Grandville            6.1    6.9    7.0    7.6    8.4    9.4   11.6
:Grand River
Eaton Rapids          4.0    4.0    4.2    4.5    4.9    5.2    5.5
Dimondale             6.3    6.5    7.1    7.8    8.8    9.8   10.1
:Red Cedar River
Williamston           4.4    5.0    5.9    6.6    7.3    8.0    8.4
East Lansing          4.2    4.6    5.2    5.7    6.5    7.4    8.1
:Sycamore Creek
Holt                  5.8    6.3    6.9    7.4    8.3    8.8    9.1
:Grand River
Lansing               4.9    5.6    6.5    7.7    8.6   10.8   11.1
Grand Ledge           5.9    6.1    6.6    7.3    7.8    9.1    9.3
Portland              7.0    7.3    7.9    8.8    9.6   10.6   10.9
:Looking Glass River
Eagle                 4.5    4.9    5.4    6.3    7.4    8.6    9.3
:Maple River
Maple Rapids          7.3    7.7    8.1    8.9    9.4   10.2   10.3
:Grand River
Ionia                13.3   14.0   15.6   17.8   19.4   21.4   21.8
:Flat River
Smyrna                4.7    4.9    5.1    5.6    6.3    7.4    7.9
:Grand River
Lowell                8.3    8.5    9.3   10.8   12.8   15.1   15.8
:Thornapple River
Hastings              4.4    4.5    5.0    5.7    6.8    7.7    8.4
Caledonia             4.8    5.0    5.8    6.5    8.4    9.6   10.2
:Grand River
Ada                  11.4   11.9   13.0   15.0   17.1   19.2   19.8
:Rogue River
Rockford              5.1    5.1    5.5    6.3    7.1    8.2    8.9
:Grand River
Grand Rapids          8.0    8.3    9.8   11.8   14.8   17.6   18.1
:Pere Marquette River
Scottville            2.0    2.5    3.0    3.5    4.2    4.6    4.9
:White River
Whitehall             2.6    3.1    3.6    4.2    5.3    5.7    6.1
:Muskegon River
Evart                 8.0    8.2    8.6    9.1    9.8   11.1   11.7
:Little Muskegon River
Morley                2.8    2.9    3.2    3.7    4.3    5.1    5.3
:Muskegon River
Croton                6.1    6.2    6.7    7.4    8.2    9.1   10.0
Newaygo               8.4    8.6    9.1    9.8   10.8   11.9   13.4
Bridgeton             9.4    9.6   10.3   11.4   12.8   14.3   15.7
:Kalamazoo River
Marshall              4.9    5.0    5.2    5.9    6.4    6.9    7.5
:Battle Creek
Battle Creek          1.3    1.4    1.6    1.9    2.2    2.6    2.8
:Kalamazoo River
Battle Creek          3.8    3.9    4.1    4.7    5.2    6.1    6.4
Comstock              4.8    5.0    5.2    6.2    6.8    8.2    8.5
New Richmond         12.9   13.0   13.8   14.4   15.2   16.2   16.6
:St. Joseph River
Burlington            4.7    4.9    5.2    5.4    5.8    6.2    6.6
:Portage River
Vicksburg             4.2    4.4    4.6    4.9    5.1    5.3    5.4
:Chippewa River
Mt. Pleasant          4.4    4.5    5.0    5.5    6.6    7.3    8.2
:Pine River
Alma                  4.1    4.5    4.9    5.4    6.6    7.9    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: 03/04/2024 - 06/02/2024
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Grand River
Jackson              10.3   10.1    9.8    9.6    9.4    9.1    9.0
:Buck Creek
Grandville            4.9    4.8    4.7    4.6    4.6    4.5    4.5
:Grand River
Eaton Rapids          3.9    3.8    3.8    3.7    3.7    3.6    3.6
Dimondale             5.9    5.8    5.6    5.3    5.0    4.8    4.6
:Red Cedar River
Williamston           2.8    2.8    2.7    2.5    2.5    2.3    2.3
East Lansing          3.7    3.6    3.5    3.4    3.4    3.2    3.2
:Sycamore Creek
Holt                  3.2    3.2    3.1    3.1    3.1    3.0    3.0
:Grand River
Lansing               4.2    4.1    3.8    3.5    3.1    2.9    2.7
Grand Ledge           5.6    5.5    5.4    5.3    5.2    5.0    4.9
Portland              6.3    6.2    6.0    5.8    5.6    5.4    5.3
:Looking Glass River
Eagle                 3.7    3.6    3.5    3.3    3.2    3.0    3.0
:Maple River
Maple Rapids          5.4    4.9    4.5    4.2    3.9    3.7    3.6
:Grand River
Ionia                11.2   11.0   10.5   10.1    9.8    9.5    9.1
:Flat River
Smyrna                4.0    4.0    3.9    3.7    3.6    3.5    3.4
:Grand River
Lowell                6.8    6.6    6.3    6.0    5.8    5.5    5.2
:Thornapple River
Hastings              3.5    3.5    3.4    3.3    3.1    3.1    3.0
Caledonia             4.0    3.9    3.8    3.6    3.4    3.3    3.2
:Grand River
Ada                   9.0    8.7    8.2    7.6    7.1    6.7    6.2
:Rogue River
Rockford              4.5    4.4    4.2    4.1    4.0    3.9    3.8
:Grand River
Grand Rapids          4.6    4.3    3.6    3.0    2.7    2.2    1.8
:Pere Marquette River
Scottville            1.7    1.6    1.4    1.2    1.1    1.0    0.9
:White River
Whitehall             2.1    1.9    1.8    1.7    1.6    1.5    1.4
:Muskegon River
Evart                 7.6    7.5    7.4    7.2    7.0    6.8    6.7
:Little Muskegon River
Morley                2.4    2.4    2.4    2.3    2.3    2.2    2.2
:Muskegon River
Croton                5.6    5.5    5.3    5.1    4.9    4.7    4.6
Newaygo               7.9    7.8    7.7    7.5    7.3    7.2    7.1
Bridgeton             8.6    8.5    8.2    7.9    7.6    7.4    7.3
:Kalamazoo River
Marshall              4.1    4.0    3.2    3.2    3.2    3.2    3.2
:Battle Creek
Battle Creek          1.1    1.1    1.0    1.0    0.9    0.9    0.8
:Kalamazoo River
Battle Creek          3.5    3.4    3.2    3.1    3.1    3.0    2.9
Comstock              4.6    4.5    4.4    4.2    4.1    4.1    3.9
New Richmond         12.2   11.9   11.7   11.4   11.3   11.0   10.8
:St. Joseph River
Burlington            4.2    4.1    4.0    3.9    3.7    3.6    3.6
:Portage River
Vicksburg             4.0    4.0    3.9    3.9    3.8    3.7    3.6
:Chippewa River
Mt. Pleasant          3.7    3.6    3.5    3.4    3.3    3.3    3.2
:Pine River
Alma                  2.4    2.3    2.0    1.8    1.6    1.4    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.

The next outlook will be issued on March 14.

$$

AMD




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