Flood Potential Outlook
Issued by NWS Chicago, IL

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FGUS73 KLOT 022115
ESFLOT
ILC007-011-031-037-063-075-089-091-093-097-099-103-105-111-
141-197-201-INC073-089-111-127-032100-

Probabilistic Hydrologic Outlook
National Weather Service Chicago/Romeoville IL
315 PM CST Thu Mar 02 2017

...2017 SPRING FLOOD AND WATER OUTLOOK NUMBER 2...

This outlook is for streams within the National Weather Service
Chicago Hydrologic Service Area, which includes Illinois River
Tributaries in northeast Illinois and northwest Indiana.  It includes
the Illinois River down to La Salle.  It also includes streams within
the Rock River basin in north central Illinois and the Rock River
from Rockton down to Dixon Illinois.  This outlook is for the time
period from early March through early June.


...OUTLOOK BRIEF SUMMARY...

Based on current conditions...The risk of flooding is Normal.  The
amount of rainfall or additional snow and subsequent snowmelt in the
coming weeks will determine the severity of any future flooding.

Ice jams and ice jam flooding remain possible and can result in
rapid rises in water levels in a very short time should there be a
rapid drop-off in temperatures to well below freezing.

This Spring Outlook is based on hydrologic conditions including the
current soil moisture, snowpack and streamflow conditions at the time
of issuance.  It should be noted that hydrologic conditions can
change rapidly during late winter and early spring.  These outlooks
are issued each late winter and early spring in addition to the 7 day
river forecasts that are issued when river forecast locations are in
flood or are forecast to rise above flood stage.


...CURRENT SNOW COVER AND WATER EQUIVALENT...

As of March 2nd, there is no snowpack.  Therefore, the the water
equivalent is zero.


...PAST TEMPERATURE AND PRECIPITATION...

Fall of 2016 concluded with above normal temperatures. Precipitation
this past fall over northern Illinois was near normal. Precipitation
was only slightly above normal over northwestern Indiana.  There
were a few heavy rainfall events over the region from September 1st
through November 30th, but none lead to significant, extended
flooding. Precipitation was below to much below normal for December,
but rebounded to 150 percent of normal in January 2017.

Snowfall so far this winter has been below to much below normal.
Locations along the Illinois, Kankakee and Iroquois Rivers and
associated tributaries received around 50 percent of normal snowfall.
Locations closer to the Wisconsin border, including the Rock and Fox
River basins received around 75 percent of normal snowfall.


...SOIL MOISTURE AND FROST DEPTH...

Soil moisture started out the fall near normal and decreased slightly
through the fall.  Soil moisture was near normal to begin the winter
season.  Soil moisture levels are currently near normal.

Soil remained unfrozen well into December.  A period of very cold
conditions in mid December lead to the first period of frozen soil,
with a frost depth to 7 inches.  A warmup in late December lead to a
complete soil thaw.  Another cold period in January lead to a frost
depth of 10 inches.  Temperatures were above normal in January and
and February.  Currently, soil is completely unfrozen across the
area.


...RIVER CONDITIONS...

Streamflow on rivers in northwestern Illinois is slightly above
normal at the current time, largely due to upstream snowmelt.
Streamflow on the Illinois, Des Plaines, Kankakee and Iroquois
Rivers, and associated tributaries, saw a rapid increase due to a
heavy rain event that occurred from the afternoon of February 28th
into early March 1st.  One to 3 inches of rain fell over these river
basins.  The heavy rainfall was due to training of strong
thunderstorms over this area.  While flood warnings were issued for
several river forecast points and an areal flood warning was issued
for portions of these watersheds, river levels decreased quickly and
there should be no lasting impact that would affect the Flood
Outlook for this spring.

Ice jam flooding was particularly active in December from freeze-up
jams due to a rapid significant cooling in mid December.
There was subsequent break-up jamming in late December and January.
Currently, there is no ice on area rivers.


...WEATHER OUTLOOKS...

The 6 to 10 day outlook valid from March 7th to March 11th indicates
above normal temperatures and above normal precipitation.  The
latest outlook for the month of March indicates above normal
temperatures and equal chances of above or below normal
precipitation.  The latest 3 Month Outlook valid March through May
indicates above normal temperatures and above normal precipitation
for far northern Illinois, with equal chances of above or below
normal precipitation for central Illinois and northwestern Indiana.


...FLOOD POTENTIAL SUMMARY...

Based on current conditions, the risk of flooding this spring is
normal.  However, given the the expected conditions for above normal
temperatures for the next few weeks, the probability for any
significant snowfall and associated snowmelt is low.  Any flooding
risk would likely be associated with locally heavy rainfall due to
thunderstorms, such as was the case with the heavy rain event of
February 28th into March 1st.

Ice jams and ice jam flooding remain possible and can result in
rapid rises in water levels in a very short time should there be a
rapid drop-off in temperatures to well below freezing.  However,
given that area rivers and streams are currently ice-free and no
significant cold conditions that could lead to freeze-up ice jamming
are likely for the next several weeks, the probability for ice jam
flooding is low.



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:  03/05/2017 - 06/03/2017

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Hart Ditch
Dyer                12.0   13.0   14.0 :  <5   <5   <5   <5   <5   <5
:Thorn Creek
Thornton            10.0   15.0   16.0 :   6    6   <5   <5   <5   <5
:Little Calumet River
Munster             12.0   14.0   17.0 :  37   41   14   19   <5   <5
South Holland       16.5   18.0   20.0 :  <5   <5   <5   <5   <5   <5
:North Branch Chicago River
Chicago Albany Av    7.0    7.5    8.0 :  <5    6   <5   <5   <5   <5
:Kankakee River
Dunns Bridge        10.0   12.0   13.0 :  27   33   <5    6   <5    5
Kouts               11.0   13.0   14.0 :  28   34   <5    6   <5    5
Shelby               9.0   11.0   12.5 :  85   80   28   39   10   17
Momence              5.0    6.5    9.0 :  27   34   12   13   <5   <5
:Iroquois River
Rensselaer          12.0   14.0   15.0 :  26   34    8   10    7    8
Foresman            18.0   22.0   24.0 :  19   22   <5   <5   <5   <5
Iroquois            18.0   24.0   25.0 :  50   52   <5    6   <5   <5
:Sugar Creek
Milford             18.0   22.0   26.0 :  48   47   11   16   <5   <5
:Iroquois River
Chebanse            16.0   18.0   20.0 :  16   14    7    9   <5    6
:Kankakee River
Wilmington           6.5    8.0   10.0 :  15   19    8    8   <5   <5
:Des Plaines River
Russell              7.0    9.0   10.0 :  78   80   <5    9   <5   <5
Gurnee               7.0    9.0   11.0 :  35   41   <5    9   <5   <5
Lincolnshire        12.5   14.0   15.5 :  18   23   <5    9   <5   <5
Des Plaines         15.0   18.0   19.0 :  20   23   <5    8   <5   <5
River Forest        16.0   17.5   18.5 :  <5   <5   <5   <5   <5   <5
Riverside            7.0    8.0    9.0 :  16   19   <5   11   <5   <5
Lemont              10.0   11.0   12.0 :  46   45   14   17   <5    6
:W Br Du Page River
Warrenville         11.5   14.5   17.5 :  14   20   <5   <5   <5   <5
:East Branch Du Page River
Bolingbrook         19.5   21.0   23.0 :  49   49   13   11   <5   <5
:Du Page River
Plainfield          12.0   14.0   15.0 :  <5   <5   <5   <5   <5   <5
Shorewood            6.5    8.0   10.0 :   6    8   <5   <5   <5   <5
:Mazon River
Coal City           12.0   14.0   17.0 :  14   16   <5   <5   <5   <5
:Fox River
Algonquin Tailwat    9.5   10.5   12.0 :  43   52   25   38   14   20
Montgomery          13.0   14.0   15.0 :  40   49    5   13   <5   <5
Dayton              12.0   14.0   24.0 :  31   43   11   14   <5   <5
:Vermilion River
Pontiac             14.0   15.0   18.0 :  12   13    9    9   <5   <5
Leonore             16.0   21.0   26.0 :  35   37    8   10   <5   <5
:Pecatonica River
Shirland            12.0   14.0   15.5 :  36   40   11   12   <5   <5
:Rock River
Rockton             10.0   11.0   14.0 :  25   27   15   14   <5   <5
Latham Park         10.0   11.0   14.0 :  25   27   15   13   <5   <5
Rockford             9.0   10.0   11.0 :  <5   <5   <5   <5   <5   <5
:Kishwaukee River
Belvidere            9.0   10.0   12.0 :   6   13   <5    6   <5   <5
:South Branch Kishwaukee River
De Kalb             10.0   11.0   12.5 :  <5   <5   <5   <5   <5   <5
:Kishwaukee River
Perryville          12.0   18.0   22.0 :  23   38   <5   <5   <5   <5
:Rock River
Byron               13.0   14.0   16.0 :  21   18   11   13   <5    7
Dixon               16.0   18.0   20.0 :  11   14   <5    6   <5   <5
:Illinois River
Morris              16.0   18.0   22.0 :  35   38   22   24    5   <5
Ottawa             463.0  466.0  469.0 :  28   33   13   16    5   <5
La Salle            20.0   27.0   31.0 :  72   70   15   17   <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: 03/05/2017 - 06/03/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Hart Ditch
Dyer                  3.5    3.7    4.6    5.7    6.5    7.5    8.2
:Thorn Creek
Thornton              4.7    5.3    6.5    7.3    8.4    9.5   10.6
:Little Calumet River
Munster               8.7    9.1   10.0   10.8   12.5   14.4   15.0
South Holland         8.7    9.5   10.8   12.0   13.6   14.5   15.0
:North Branch Chicago River
Chicago Albany Av     3.6    3.7    4.6    5.2    5.9    6.6    7.0
:Kankakee River
Dunns Bridge          7.0    7.0    8.3    9.0   10.2   10.6   10.9
Kouts                 8.1    8.2    9.5   10.2   11.3   11.8   12.1
Shelby                8.0    8.1    9.2   10.3   11.3   12.5   13.5
Momence               3.0    3.3    3.7    4.5    5.0    6.9    8.2
:Iroquois River
Rensselaer            6.6    8.2    9.7   10.8   12.1   13.2   17.6
Foresman             11.9   12.7   14.5   16.3   17.6   18.8   21.3
Iroquois             11.9   13.2   15.7   17.9   21.2   22.1   23.8
:Sugar Creek
Milford              10.4   12.5   16.2   17.9   19.9   22.1   24.2
:Iroquois River
Chebanse              7.8    9.0   10.5   12.4   15.2   16.4   19.6
:Kankakee River
Wilmington            3.0    3.2    4.3    5.1    5.9    6.8    8.9
:Des Plaines River
Russell               6.0    6.7    7.1    7.7    8.0    8.3    8.8
Gurnee                4.2    4.5    5.3    6.0    7.5    8.1    8.7
Lincolnshire          8.8    9.2   10.1   10.7   12.0   13.1   13.6
Des Plaines          10.0   10.7   11.9   13.2   14.4   16.6   17.9
River Forest          6.5    7.7    9.8   11.4   12.8   14.5   15.3
Riverside             3.5    4.0    5.2    6.2    6.8    7.6    7.9
Lemont                6.9    7.4    8.8    9.9   10.6   11.4   11.8
:W Br Du Page River
Warrenville           9.1    9.3    9.7   10.5   11.2   11.8   12.3
:East Branch Du Page River
Bolingbrook          17.5   17.8   18.8   19.4   20.5   21.0   21.3
:Du Page River
Plainfield            8.5    8.6    9.1    9.8   10.5   10.9   11.2
Shorewood             3.4    3.6    4.4    5.0    5.8    6.2    6.6
:Mazon River
Coal City             3.5    4.7    7.5    9.5   10.7   12.8   13.4
:Fox River
Algonquin Tailwat     7.6    7.6    8.2    9.4   10.5   13.1   13.9
Montgomery           12.2   12.2   12.5   12.9   13.3   13.8   14.0
Dayton                8.0    8.3    9.8   11.4   12.4   14.2   15.0
:Vermilion River
Pontiac               5.4    6.6    7.4    9.7   11.8   14.3   17.6
Leonore               7.6    9.0   10.6   13.8   17.4   20.9   22.1
:Pecatonica River
Shirland              9.7    9.7    9.9   11.4   12.8   14.1   15.0
:Rock River
Rockton               7.3    7.3    7.3    8.0    9.9   11.9   13.0
Latham Park           7.7    7.7    7.7    8.3    9.9   11.7   12.9
Rockford              3.5    3.5    3.5    3.7    4.3    5.5    6.3
:Kishwaukee River
Belvidere             2.7    3.0    4.4    5.5    7.2    8.6    9.1
:South Branch Kishwaukee River
De Kalb               4.0    4.9    5.8    6.8    7.9    8.8    9.1
:Kishwaukee River
Perryville            6.9    7.8    9.2   10.4   11.9   13.3   14.2
:Rock River
Byron                 9.4    9.4    9.6   10.7   12.2   14.2   15.1
Dixon                11.4   11.4   11.6   12.6   13.9   16.2   17.7
:Illinois River
Morris                7.5    8.4   12.3   14.3   16.7   20.5   22.3
Ottawa              459.0  459.2  460.4  461.8  463.5  467.6  469.1
La Salle             14.0   15.5   19.5   22.9   25.0   28.4   29.5

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: 03/05/2017 - 06/03/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Hart Ditch
Dyer                  2.1    2.1    2.1    2.0    2.0    1.9    1.9
:Thorn Creek
Thornton              3.0    3.0    3.0    2.9    2.8    2.8    2.8
:Little Calumet River
Munster               5.4    5.3    5.2    5.1    5.0    4.9    4.9
South Holland         5.5    5.5    5.4    5.3    5.2    5.1    5.0
:North Branch Chicago River
Chicago Albany Av     1.6    1.5    1.4    1.3    1.2    1.1    1.0
:Kankakee River
Dunns Bridge          4.7    4.5    4.3    4.0    3.7    3.4    3.2
Kouts                 5.6    5.5    5.2    4.9    4.7    4.3    4.1
Shelby                6.1    6.0    5.7    5.3    4.9    4.6    4.3
Momence               2.3    2.2    2.1    2.0    1.8    1.7    1.6
:Iroquois River
Rensselaer            4.5    4.5    4.3    4.0    3.8    3.6    3.4
Foresman              7.4    7.3    6.9    6.4    5.9    5.7    5.2
Iroquois              7.0    7.0    6.4    5.9    5.5    5.2    4.8
:Sugar Creek
Milford               4.2    4.1    3.8    3.7    3.6    3.4    3.2
:Iroquois River
Chebanse              4.5    4.3    4.0    3.7    3.4    3.2    2.9
:Kankakee River
Wilmington            1.9    1.8    1.7    1.6    1.4    1.4    1.2
:Des Plaines River
Russell               4.7    4.6    4.5    4.4    4.2    4.1    4.1
Gurnee                2.9    2.8    2.6    2.5    2.2    2.0    1.9
Lincolnshire          7.7    7.7    7.4    7.3    7.0    6.8    6.7
Des Plaines           9.1    9.0    8.8    8.6    8.3    8.1    8.0
River Forest          5.0    4.6    4.2    3.9    3.3    2.9    2.6
Riverside             2.6    2.4    2.3    2.1    1.9    1.7    1.6
Lemont                6.1    5.9    5.7    5.5    5.2    5.0    4.9
:W Br Du Page River
Warrenville           7.4    7.4    7.3    7.3    7.2    7.1    7.1
:East Branch Du Page River
Bolingbrook          14.9   14.9   14.8   14.7   14.6   14.5   14.5
:Du Page River
Plainfield            6.9    6.9    6.8    6.8    6.7    6.7    6.7
Shorewood             2.4    2.3    2.2    2.2    2.1    2.1    2.1
:Mazon River
Coal City             2.1    2.0    1.9    1.8    1.6    1.4    0.5
:Fox River
Algonquin Tailwat     6.0    5.4    5.2    4.8    4.5    4.2    4.1
Montgomery           11.6   11.5   11.3   11.2   11.1   11.0   11.0
Dayton                7.0    6.7    6.3    6.0    5.7    5.4    5.3
:Vermilion River
Pontiac               3.6    3.6    3.4    3.3    3.2    3.1    2.9
Leonore               4.7    4.5    4.4    4.2    4.0    3.8    3.5
:Pecatonica River
Shirland              7.2    6.9    6.2    5.5    5.0    4.7    4.5
:Rock River
Rockton               5.3    4.8    4.3    3.5    2.9    2.6    2.5
Latham Park           6.0    5.6    5.2    4.6    4.2    4.0    3.9
Rockford              3.2    3.1    3.0    2.8    2.6    2.5    2.5
:Kishwaukee River
Belvidere             2.4    2.2    2.0    1.9    1.6    1.4    1.2
:South Branch Kishwaukee River
De Kalb               3.3    3.2    3.2    3.1    3.1    3.0    2.9
:Kishwaukee River
Perryville            6.4    6.2    6.1    5.9    5.7    5.5    5.3
:Rock River
Byron                 8.0    7.3    6.9    6.2    5.7    5.5    5.3
Dixon                10.2    9.7    9.3    8.8    8.3    8.1    8.0
:Illinois River
Morris                5.6    5.5    5.4    5.2    5.0    4.9    4.6
Ottawa              458.7  458.7  458.6  458.6  458.5  458.5  458.5
La Salle             12.0   12.0   11.8   11.4   11.1   10.9   10.8

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/lot for more weather and water
information.

The next outlook will be issued toward the end of next month.

$$



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