Flood Potential Outlook
Issued by NWS Chicago, IL

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000
FGUS73 KLOT 151917
ESFLOT
ILC007-011-031-037-063-075-089-091-093-097-099-103-105-111-
141-197-201-INC073-089-111-127-271700-DDHHMM-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE Chicago/Romeoville IL
115 PM CST Thu Feb 15 2024

...2024 Spring Flood and Water Outlook Number 1...

...Locations Covered by this Outlook...

This outlook is for rivers and streams within the National Weather
Service Chicago Hydrologic Service Area (HSA). The Chicago HSA
covers most of northeastern Illinois and a portion of far
northwestern Indiana. This includes the Illinois River downstream to
just below La Salle, and numerous Illinois River tributaries
including the Fox, DuPage, Des Plaines, Calumet, Iroquois, Kankakee,
and Vermilion Rivers. This also includes the Rock River from near
Rockton downstream to near Dixon, and Rock River tributaries
including the Pecatonica and Kishwaukee Rivers. This outlook covers
the time period from early March through late May.

...Outlook Brief Summary...

Based on current conditions, the risk of flooding is near average
across the area. Weather patterns over the next several weeks may
change the risk of flooding in later outlooks.

...Risk Factors for Spring Flooding...

To determine the relative risk of spring flooding, numerous factors
are considered including snow cover, soil moisture, and current
river conditions. Snow cover with a high water content can increase
the chance of flooding as melting changes the snow to liquid. High
soil moisture conditions can increase the chance of flooding by
reducing the amount of water that infiltrates into the ground. Above
average river levels can increase the chance for flooding because
lower amounts of water would be required to reach flood stage.

...Snow Cover and Liquid Water Equivalent...

Current snow cover across area river basins is generally near 0
inches, which contains 0 inches of liquid water equivalent. All
river basins generally have no snow cover.

...Soil Moisture and Frost Depth...

Current soil moisture values across the area range from near average
to slightly above average. Values are the lowest in northwestern
Illinois, at the 30th to 70th percentile for this time of year.
Values are highest near Lake Michigan, exceeding the 70th percentile.
Frost depth is near 0 inches across all area river basins.

...Current River Conditions...

As of February 15, river levels across the area range from near
average to slightly above. Highest streamflow values were in
northwestern Illinois.

River ice spotters, river gauges, and satellite imagery indicate
that little-to-no river ice exists on area rivers. The risk of ice
jam related flooding is very low this spring based upon current
conditions.

...Fall 2023 Weather Summary...

Temperatures were near average to above average across northeastern
Illinois and northwestern Indiana during fall 2023. Temperatures
were 1-2F above average in far northern and northwestern Illinois,
with other areas generally within 1F of average.

Precipitation was near average in northeastern Illinois and
northwestern Indiana during fall 2023. Almost all areas were within
3 inches of average.

...Winter 2023-2024 Weather Summary...

Temperatures for winter 2023-2024 through early February have
averaged about 5F to 9F above average in northeastern Illinois and
northwestern Indiana. Most days have been near average to above
average, with one notable period of significant cold weather
observed in mid-January. Precipitation in winter 2023-2024 through
early February has ranged from 0 inches to 4 inches above average in
northeastern Illinois and northwestern Indiana.

The first measurable snowfall (>0.1 inches) across northeastern
Illinois and northwestern Indiana occurred near the average date,
within a range from late October to early November for most areas.
Season-to-date snowfall ranges were from about 6 inches to about 24
inches across northeastern Illinois and northwestern Indiana, with
the highest snow totals in southern Wisconsin and far northwestern
Illinois. Observed snowfall was generally near average in northern
Illinois and below average in northwestern Indiana and near the Lake
Michigan shore

...Spring Weather Outlook...

The long term (next couple months) outlook from the Climate
Prediction Center indicates no strong signal for above or below
average temperatures into early March. The outlook also indicates no
strong signal for above or below average precipitation into early
March.

Although snow cover, soil moisture, and recent river levels can
provide some indication of the relative risk of spring flooding, any
weather system that produces heavy rainfall could cause flooding.
Spring flood outlooks are not able to assess the risk of flooding
due to heavy rainfall more than a week or so in advance.

...Detailed Flood Outlook...

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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Pecatonica River
Shirland            12.0   14.0   15.5 :  27   37    5   17   <5   <5
:Rock River
Rockton             10.0   11.0   14.0 :  23   35   12   21   <5    8
Latham Park          9.0   11.0   13.5 :  25   36    9   13   <5    7
Rockford (Auburn     6.0    8.5   10.0 :   5   10   <5   <5   <5   <5
:Kishwaukee River
Belvidere            9.0   10.0   12.0 :   5   12   <5    7   <5   <5
:SB Kishwaukee River
DeKalb              10.0   11.0   12.5 :  <5   10   <5   <5   <5   <5
:Kishwaukee River
Perryville          12.0   18.0   22.0 :  28   40   <5   <5   <5   <5
:Rock River
Byron               13.0   14.0   16.0 :  12   15    7   13   <5    9
Dixon               16.0   18.0   20.0 :   7   16   <5    7   <5   <5
:North Branch Chicago River
Chicago (Pulaski    18.0   20.0   21.0 :  <5   <5   <5   <5   <5   <5
:Des Plaines River
Russell              7.0    9.0   10.0 :  33   41   <5    6   <5   <5
Gurnee               7.0    9.0   11.0 :  30   33   <5    8   <5   <5
Lincolnshire        12.5   14.0   15.5 :  16   17   <5    9   <5    6
Des Plaines         15.0   18.0   19.0 :  23   20    5    7   <5   <5
River Forest        16.0   17.5   18.5 :   6   <5   <5   <5   <5   <5
Riverside            7.5    8.0    9.0 :  17   22   11   13   <5   <5
Lemont              10.0   13.0   15.0 :  47   45   <5   <5   <5   <5
:WB Du Page River
Warrenville         11.5   14.5   17.5 :  12   19   <5   <5   <5   <5
:East Branch Du Page River
Bolingbrook         20.0   22.0   24.0 :  <5    7   <5   <5   <5   <5
:Du Page River
Plainfield          12.0   14.0   15.0 :  <5    5   <5   <5   <5   <5
Shorewood           15.5   17.5   19.5 :  30   33    9   12   <5   <5
:Fox River
Algonquin Lock &     9.5   10.5   12.0 :  50   43   18   24   <5   11
Montgomery          13.5   15.0   16.0 :  11   14   <5   <5   <5   <5
Dayton              12.0   14.0   24.0 :  41   46   16   18   <5   <5
:Kankakee River
Dunns Bridge        10.0   12.0   13.0 :  21   30   <5    7   <5    6
Shelby              10.5   11.5   12.5 :  42   52   20   25   11   16
Momence              5.0    6.5    9.0 :  28   31   12   12   <5   <5
:Iroquois River
Rensselaer          12.0   14.0   15.0 :  28   34    8   12    8    9
Foresman            18.0   22.0   24.0 :  34   39    5    6   <5   <5
Iroquois            18.0   24.0   25.0 :  69   73    6    7   <5    5
:Sugar Creek
Milford             18.0   22.0   26.0 :  50   51   12   16    5    5
:Iroquois River
Chebanse            16.0   18.0   20.0 :  18   16    8   11    7    9
:Kankakee River
Wilmington           6.5    8.0   10.0 :  19   19    8    9   <5   <5
:Mazon River
Coal City           12.0   16.0   19.0 :  20   23   <5   <5   <5   <5
:Vermilion River
Pontiac             14.0   15.0   18.0 :  14   14    9   10   <5   <5
Leonore             16.0   21.0   26.0 :  38   35   13   14   <5   <5
:Hart Ditch
Dyer                12.0   13.0   14.0 :  <5   <5   <5   <5   <5   <5
:Thorn Creek
Thornton             9.0   14.0   15.5 :  16   20   <5   <5   <5   <5
:Little Calumet River
Munster (Hohman A   12.0   14.0   17.0 :  48   53   15   22    7   12
South Holland       16.5   18.0   20.0 :  <5   <5   <5   <5   <5   <5
:Illinois River
Morris              16.0   18.0   22.0 :  35   38   22   26   14   13
Ottawa             463.0  467.0  471.0 :  38   39   17   18   <5    5
La Salle            20.0   27.0   31.0 :  77   73   20   22   <5    9

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%
--------            ------ ------ ------ ------ ------ ------ ------
:Pecatonica River
Shirland              7.3    7.8    9.0   10.8   12.1   13.0   14.0
:Rock River
Rockton               6.1    6.3    7.3    8.6    9.8   11.2   13.1
Latham Park           5.6    5.7    6.4    7.7    9.0   10.5   12.6
Rockford (Auburn      3.0    3.0    3.1    3.3    3.7    4.6    6.0
:Kishwaukee River
Belvidere             3.1    3.6    4.8    5.9    7.2    8.7    9.1
:SB Kishwaukee River
DeKalb                4.8    5.5    6.1    6.8    8.1    9.4    9.9
:Kishwaukee River
Perryville            8.1    8.6    9.7   10.7   12.2   13.4   14.7
:Rock River
Byron                 8.0    8.3    9.1   10.7   11.8   13.4   14.9
Dixon                10.3   10.5   11.1   12.4   13.4   14.8   16.6
:North Branch Chicago River
Chicago (Pulaski     12.5   13.1   14.0   14.8   15.5   17.0   17.7
:Des Plaines River
Russell               4.6    5.2    6.0    6.7    7.1    7.6    8.3
Gurnee                4.0    4.7    5.4    6.4    7.2    8.1    8.6
Lincolnshire          8.3    8.9    9.4   10.5   11.7   13.5   14.0
Des Plaines          10.0   11.2   12.1   13.6   14.9   16.9   18.2
River Forest          7.3    8.4    9.9   11.4   12.7   14.7   16.0
Riverside             4.0    4.5    5.3    6.3    7.0    8.1    8.8
Lemont                7.5    8.1    9.1    9.9   10.5   11.7   12.6
:WB Du Page River
Warrenville           8.9    9.1    9.6   10.4   11.2   11.6   11.9
:East Branch Du Page River
Bolingbrook          16.6   16.8   17.2   18.0   18.8   19.4   19.8
:Du Page River
Plainfield            8.2    8.2    8.9    9.9   10.5   11.3   11.8
Shorewood            11.7   12.0   12.7   13.9   15.3   16.7   17.3
:Fox River
Algonquin Lock &      7.2    7.7    8.3    9.5   10.2   11.2   11.6
Montgomery           12.1   12.3   12.6   12.9   13.2   13.5   13.6
Dayton                8.3    9.1    9.9   11.6   12.5   15.3   16.7
:Kankakee River
Dunns Bridge          6.1    7.1    7.9    8.7    9.8   10.8   11.2
Shelby                7.8    8.4    9.1   10.2   11.2   13.3   14.8
Momence               3.0    3.2    3.5    4.3    5.1    7.6    8.2
:Iroquois River
Rensselaer            7.6    8.5    9.6   11.0   12.2   13.6   18.3
Foresman             13.1   14.2   15.6   17.3   18.8   20.4   22.3
Iroquois             14.2   15.8   17.7   19.2   21.3   22.5   24.6
:Sugar Creek
Milford              12.0   13.3   16.3   18.0   19.8   22.9   26.1
:Iroquois River
Chebanse              8.3    9.4   11.0   12.6   15.2   16.9   20.2
:Kankakee River
Wilmington            3.3    3.6    4.2    5.1    6.0    7.8    8.7
:Mazon River
Coal City             4.5    5.4    7.6   10.0   11.2   13.6   13.9
:Vermilion River
Pontiac               5.2    6.2    7.7    9.8   11.7   14.6   17.5
Leonore               7.7    9.7   11.9   14.6   17.6   21.6   24.3
:Hart Ditch
Dyer                  3.7    4.1    4.9    5.7    6.7    7.8    8.3
:Thorn Creek
Thornton              4.6    5.2    6.3    7.4    8.7   10.0   11.3
:Little Calumet River
Munster (Hohman A     8.9    9.7   10.6   11.9   13.2   15.7   17.9
South Holland         9.0    9.8   11.1   12.2   13.8   14.8   15.3
:Illinois River
Morris                7.7    8.2   10.9   14.2   17.5   22.6   23.9
Ottawa              459.2  459.3  460.5  461.9  464.7  469.2  470.0
La Salle             15.5   16.0   20.2   23.4   25.8   30.1   30.9

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: 02/19/2024 - 05/19/2024
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pecatonica River
Shirland              6.8    6.4    6.0    5.5    4.9    4.6    4.5
:Rock River
Rockton               5.9    5.5    5.3    4.6    4.0    3.6    3.3
Latham Park           5.4    5.2    5.1    4.8    4.5    4.3    4.1
Rockford (Auburn      3.0    2.9    2.9    2.8    2.6    2.4    2.4
:Kishwaukee River
Belvidere             2.0    1.9    1.8    1.6    1.4    1.3    1.2
:SB Kishwaukee River
DeKalb                3.4    3.3    3.3    3.2    3.2    3.1    3.1
:Kishwaukee River
Perryville            6.5    6.4    6.3    6.0    5.8    5.7    5.6
:Rock River
Byron                 7.4    7.3    7.0    6.6    6.0    5.6    5.5
Dixon                 9.7    9.5    9.3    8.9    8.4    8.0    7.9
:North Branch Chicago River
Chicago (Pulaski     11.1   11.1   11.0   10.9   10.9   10.8   10.7
:Des Plaines River
Russell               3.3    3.2    3.1    3.0    2.9    2.7    2.6
Gurnee                2.4    2.3    2.2    1.9    1.8    1.5    1.4
Lincolnshire          7.0    6.9    6.8    6.5    6.4    6.2    6.1
Des Plaines           8.7    8.7    8.6    8.3    8.2    8.0    7.9
River Forest          4.8    4.6    4.3    3.8    3.6    3.2    2.9
Riverside             2.6    2.5    2.4    2.2    2.0    1.9    1.8
Lemont                6.0    6.0    5.8    5.6    5.3    5.2    5.0
:WB Du Page River
Warrenville           7.7    7.6    7.6    7.5    7.5    7.4    7.4
:East Branch Du Page River
Bolingbrook          14.6   14.5   14.5   14.4   14.3   14.2   14.1
:Du Page River
Plainfield            6.8    6.8    6.8    6.7    6.6    6.6    6.6
Shorewood            10.4   10.4   10.3   10.2   10.1   10.1   10.1
:Fox River
Algonquin Lock &      6.2    5.9    5.6    5.4    5.0    4.8    4.5
Montgomery           11.7   11.7   11.5   11.3   11.2   11.1   11.0
Dayton                7.3    6.9    6.5    6.1    5.8    5.5    5.4
:Kankakee River
Dunns Bridge          4.5    4.3    4.0    3.7    3.5    3.2    3.0
Shelby                6.1    5.9    5.7    5.3    5.0    4.8    4.5
Momence               2.2    2.2    2.1    1.9    1.8    1.7    1.6
:Iroquois River
Rensselaer            4.9    4.8    4.7    4.4    4.2    4.0    4.0
Foresman              7.6    7.4    7.0    6.6    6.1    5.8    5.7
Iroquois              8.8    8.6    8.0    7.4    6.7    6.2    6.1
:Sugar Creek
Milford               4.1    3.9    3.8    3.7    3.5    3.4    3.4
:Iroquois River
Chebanse              4.5    4.3    4.1    3.8    3.6    3.3    3.2
:Kankakee River
Wilmington            2.0    2.0    1.9    1.8    1.7    1.5    1.5
:Mazon River
Coal City             1.9    1.9    1.8    1.7    1.6    1.4    1.3
:Vermilion River
Pontiac               3.6    3.6    3.5    3.4    3.2    3.1    3.0
Leonore               4.7    4.5    4.4    4.2    4.1    3.9    3.7
:Hart Ditch
Dyer                  2.1    2.0    2.0    2.0    1.9    1.9    1.8
:Thorn Creek
Thornton              3.0    3.0    3.0    2.9    2.9    2.8    2.8
:Little Calumet River
Munster (Hohman A     5.8    5.7    5.6    5.5    5.4    5.3    5.3
South Holland         5.8    5.8    5.6    5.5    5.5    5.4    5.3
:Illinois River
Morris                5.3    5.3    5.1    5.0    4.9    4.9    4.8
Ottawa              458.7  458.7  458.6  458.6  458.5  458.5  458.5
La Salle             12.1   12.1   11.8   11.6   11.2   11.0   10.9

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/lot for more weather and water
information.

The next outlook Spring Flood Outlook will be issued February 29.

$$






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