Flood Potential Outlook
Issued by NWS Central Illinois

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ILC009-017-025-033-057-079-095-101-113-123-125-129-137-143-147-
155-159-167-169-179-183-203-171900-

Probabilistic Hydrologic Outlook
National Weather Service Lincoln IL
100 PM CST Thu Feb 16 2017

...2017 Spring Flood and Water Resources Outlook Number 1...

...Near normal potential for minor flooding across central and
southeast Illinois...

This flood outlook covers the Lincoln Hydrologic Service Area (HSA)
which encompasses 35 counties in central and southeast Illinois. It
includes the following rivers...

- Illinois River from Henry to Beardstown
- Spoon River from London Mills to Seville
- Mackinaw River at Congerville
- Sangamon River from Monticello to Chandlerville
- Salt Creek at Greenview
- Little Wabash River near Clay City
- Embarras River from Ste. Marie to Lawrenceville

These flood outlooks are issued in 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. They are based on current streamflows, soil conditions, snow
pack, as well as short/long range weather forecasts.


FLOOD OUTLOOK HIGHLIGHTS...

The risk of flooding from the late winter into early spring is
overall near normal across central and southeast Illinois. This means
that those locations that usually flood in the spring will have
similar likelihood this season.


WINTER WEATHER REVIEW...

--December--

Information, courtesy of the Illinois State Climatologist, shows that
December was both cooler and drier than normal. The statewide average
temperature in December was 28.6 degrees, which is 1.3 degrees below
normal. The average statewide precipitation for December was 1.41
inches, which is 1.28 inches below normal. December snowfall was
absent in far southern Illinois and increased northward. Only
northern Illinois received above normal snowfall.

Across the ILX Hydrologic Service Area (HSA), monthly temperature
averages for December were below normal as well. They generally
ranged from 0.5 to 2 degrees below normal. Daily high temperatures
were wide-ranging, from around 10 degrees to the low 60s. Normal
highs for December range from the low 30s to the mid 40s. Low
temperatures ranged from the single digits below zero to the upper
30s in December. They normally range from the teens to the upper 20s.

Across the ILX HSA, precipitation totals for December were below
normal. Monthly precipitation ranged from 0.53 inches in Mattoon to
2.14 inches in Danville. These totals ranged from 2.24 to 0.69 inches
below normal, respectively. This equates to precipitation that
roughly ranged from around 20 to 75 percent of normal. Snowfall
amounts were light overall, with many locations seeing amounts
totaling around 50% to 75% of normal.

Almost no flooding was observed in the ILX HSA in December. U.S.
Geological Survey (USGS) streamflow values for December were overall
in the normal percentile range.


--January--

The State Climatologist notes that the statewide average temperature
for Illinois was 31.4 degrees, 5.0 degrees above normal and the 14th
warmest January on record. The statewide average precipitation was
2.16 inches, 0.09 inches above normal. The statewide snowfall was
below normal across the state.

Across the ILX HSA, monthly temperature averages for January were
well above normal overall. Monthly temperatures generally ranged from
5.5 to 7.5 degrees above normal. Daily high temperatures ranged from
the single digits to the mid 60s. Normal highs for this month range
from the low to mid 30s. Low temperatures across the area ranged from
the single digits below zero to the upper 40s. They typically range
in the teens.

Precipitation totals across the ILX HSA for January were a mixed bag.
Locations in western and central Illinois saw amounts below normal,
with locations in eastern sections of the state seeing above normal
precipitation. Monthly precipitation totals ranged from 1.00 inch in
Havana to 4.17 inches in Palestine. These totals ranged from 1.08
inches below normal to 1.08 inches above normal, respectively.

Most of the heavier precipitation fell mid to late month. As such,
minor flooding occurred along portions of the Illinois, Sangamon,
Little Wabash, and Embarras Rivers from mid January into early
February. USGS monthly streamflows for January showed overall near
normal to above normal values across the ILX HSA. Many locations in
northern Illinois saw values above normal to much above normal, while
areas of southern Illinois were near normal.


--February--

The first half of February has seen temperatures across Illinois that
are much warmer than normal, averaging around 4 to 5 degrees above
normal values. Precipitation through mid-month has averaged below
normal with deficits of 0.50 to 1 inch across central and southeast
Illinois. This generally equates to 10 to 50 percent of normal for
this time of year. With the warm and relatively dry conditions there
has been no new flooding this month and no snow cover to speak of as
of this outlook.


SOIL MOISTURE AND FROST DEPTH CONDITIONS...

Soil moisture conditions across central and southeast Illinois are
overall near normal. However, some drier soil conditions are
beginning to show up in some of the analyses for Illinois.

The warm January temps continued into February, which has kept soils
thawed for some time. As mentioned earlier, there is currently no
snow cover to speak of across central and southeast Illinois.
Therefore, any near term snowfall/snow melt and/or rain is expected
to initially go toward recharging the soils versus mostly running off
due to frozen ground, which would be more common this time of year.

Drought conditions have changed somewhat over the winter season. In
early December there were large bands of D0 (Abnormally Dry)
conditions across portions of northwest, central and southern
Illinois. There was also a small area of D1 (Moderate Drought) in far
southern Illinois at that time. As of the latest Drought Monitor
issuance, there has been a reduction in area of the DO conditions.
They are now confined to small areas in west-central and southwest
Illinois. The D1 in southern Illinois is gone. However, a small band
of D1 conditions have developed in west-central Illinois.


RIVER CONDITIONS...

Currently, there is no river flooding being observed across central
and southeast Illinois. Information, courtesy of the U.S. Geological
Survey (USGS), shows that streamflow conditions across the area are
near normal for this time of year, trending toward below normal.

With the above normal temperatures forecast over the next two weeks,
any precipitation that falls will likely be in the form of rain.
Initial rains will largely go toward recharging soils. River levels
may respond slightly, but no significant flooding is expected in the
short term.


WEATHER OUTLOOKS...

The weather pattern across the Midwest will be quiet through this
weekend, turning more active beginning early next week. The forecast
for Illinois over this time period calls for temperatures well above
normal with highs ranging mainly in the 50s and 60s and lows in the
40s.

The 8 to 14 day outlook (Feb 23rd to Mar 1st) indicates a greater
than 50 percent likelihood for above normal temperatures across
Illinois. There is also a greater than 33 percent likelihood for
above normal precipitation for Illinois during this time period.

The 30 day outlook for March indicates equal chances for temperatures
above normal, near normal, or below normal across the state during
this period. The same goes for precipitation.

The 90 day outlook (March, April, and May) for Illinois indicates
that there is a greater than 40 percent likelihood for above normal
temperatures. There are no strong signals for precipitation.
Therefore, equal chances are outlined for most of Illinois over the
next 90 days.


FLOOD OUTLOOK SUMMARY...

Overall near normal probabilities for minor flooding are forecast
for central and southeast Illinois this spring. The likelihood for
minor flooding is highest along portions of the Illinois, Embarras,
and Little Wabash Rivers. However, these locations typically
experience at least minor flooding during the spring.

Overall, any significant flooding across central and southeast
Illinois will be largely driven by spring rains or additional snow
and subsequent snow melt. However, building any snow pack does not
seem likely over the next few weeks with expected above normal
temperatures.

---------------------------------------------------------------------

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:  02/19/2017 - 05/20/2017

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Illinois River
Henry               23.0   24.0   31.0 :  53   55   40   45   <5   <5
Peoria              18.0   22.0   28.0 :  65   64   25   28   <5   <5
Peoria L/D         447.0  449.0  455.0 :  51   53   31   31   <5   <5
Havana              14.0   17.0   23.0 :  72   72   36   41   <5   <5
Beardstown          14.0   18.0   28.0 :  81   82   50   56   <5    5
:Mackinaw River
Congerville         13.0   14.0   20.0 :  18   19   15   17   <5   <5
:Spoon River
London Mills        15.0   21.0   24.0 :  45   56   10   11   <5   <5
Seville             22.0   25.0   30.0 :  36   46   18   18   <5   <5
:Sangamon River
Monticello          13.0   17.0   20.0 :  63   73    5    7   <5   <5
Riverton            23.0   26.0   29.0 :  11   15   <5   <5   <5   <5
Petersburg          23.0   24.0   33.0 :  12   15    7   10   <5   <5
:Salt Creek
Greenview           16.0   17.0   20.0 :  15   23   11   14    8    8
:Sangamon River
Oakford            471.0  472.9  478.5 :  28   41   16   20   <5   <5
Chandlerville      456.6  459.0  462.0 :  39   51   16   21   <5   <5
:Embarras River
Lawrenceville       30.0   37.0   41.0 :  70   78   15   20   <5   <5
Ste. Marie          19.0   20.0   27.0 :  28   30   18   22   <5   <5
:Little Wabash River
Clay City           18.0   22.0   25.0 :  62   92   12   21   <5   <5
:Vermilion River
Danville            18.0   22.0   28.0 :  18   23    7   13   <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: 02/19/2017 - 05/20/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Illinois River
Henry                16.1   16.7   20.1   23.3   25.5   26.7   27.7
Peoria               12.9   13.2   16.0   19.7   22.1   23.1   24.5
Peoria L/D          435.8  436.5  443.8  447.1  449.5  450.4  452.1
Havana                9.6   11.2   13.6   15.6   18.6   19.8   21.7
Beardstown           10.9   11.7   16.0   18.0   23.0   25.0   26.7
:Mackinaw River
Congerville           3.9    5.1    6.5    9.6   11.9   15.2   16.4
:Spoon River
London Mills          6.0    7.4   11.5   14.6   17.8   21.1   23.1
Seville               9.7   10.7   15.4   19.1   23.7   27.0   29.6
:Sangamon River
Monticello            9.6   10.7   12.3   13.6   14.8   16.0   17.3
Riverton              8.8   10.9   15.5   17.6   20.0   23.3   25.7
Petersburg            7.2    9.2   12.5   15.5   18.9   23.6   26.7
:Salt Creek
Greenview             4.4    5.8    8.0   10.9   13.4   18.2   21.3
:Sangamon River
Oakford             458.9  461.1  464.1  467.9  471.4  474.5  476.3
Chandlerville       446.2  448.5  451.6  455.4  457.8  460.4  461.6
:Embarras River
Lawrenceville        25.6   26.5   29.5   32.0   34.8   38.1   39.9
Ste. Marie            8.2    9.0   13.4   16.1   19.5   20.6   23.0
:Little Wabash River
Clay City            10.9   12.4   16.3   19.5   20.8   22.1   23.2
:Vermilion River
Danville              8.2    8.8   10.7   14.2   16.4   19.8   23.7

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: 02/19/2017 - 05/20/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Illinois River
Henry                15.4   15.3   15.1   14.9   14.7   14.6   14.5
Peoria               12.4   12.4   12.2   12.0   11.4   10.6   10.6
Peoria L/D          434.5  434.3  433.3  432.0  431.1  430.7  430.4
Havana                7.8    7.3    6.8    5.6    5.0    4.9    4.9
Beardstown           10.6   10.5   10.2    9.8    9.6    9.3    9.1
:Mackinaw River
Congerville           2.0    1.8    1.7    1.5    1.3    1.1    1.1
:Spoon River
London Mills          3.7    3.4    3.4    3.2    2.9    2.6    2.3
Seville               6.6    6.5    6.4    6.1    5.8    5.4    5.0
:Sangamon River
Monticello            7.3    7.0    6.6    6.4    6.1    5.7    5.6
Riverton              5.8    5.5    5.2    4.8    4.5    4.3    3.7
Petersburg            6.2    5.8    5.7    5.4    5.3    5.2    4.9
:Salt Creek
Greenview             1.9    1.8    1.6    1.4    1.3    1.2    1.0
:Sangamon River
Oakford             457.7  457.4  457.2  456.9  456.7  456.5  456.2
Chandlerville       444.8  444.6  444.5  444.2  444.0  443.8  443.4
:Embarras River
Lawrenceville        19.4   19.0   18.5   18.2   18.0   17.9   17.7
Ste. Marie            3.2    3.1    2.7    2.5    2.3    2.2    2.0
:Little Wabash River
Clay City             6.1    5.4    4.8    4.5    4.2    3.9    3.7
:Vermilion River
Danville              3.9    3.8    3.6    3.5    3.2    3.1    3.1

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.

---------------------------------------------------------------------

FLOOD TERMINOLOGY...

Minor flooding is used to indicate minimal or no property damage.
However, some public inconvenience is possible.

Moderate flooding is used to indicate some inundation of structures
and roads near the river. Transfer of property to a higher elevation
or another location may be necessary. Some evacuations may also be
required.

Major flooding is used to indicate extensive inundation and property
damage, usually characterized by the evacuation of people and
livestock and closure of both primary and secondary roads.

FOR MORE INFORMATION...

Visit our web page at www.weather.gov/ilx for more official NWS river
and weather information. To view graphical AHPS information,
including forecasts, select Rivers and Lakes from along the top menu
bar. Full AHPS graphics are available for all forecast points in the
ILX HSA.

For 30 to 90 day temperature and precipitation outlooks, visit the
web page of the Climate Prediction Center at www.cpc.ncep.noaa.gov.

The next scheduled issuance of the Spring Flood and Water Resources
Outlook for central and southeast Illinois will be on Thursday, March
2nd. The NOAA National Spring Flood Outlook will be issued on
Thursday, March 16th. Flood Safety Awareness Week is March 13th to
the 17th.

$$

DRH





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