Flood Potential Outlook
Issued by NWS Central Illinois
Issued by NWS Central Illinois
508
FGUS73 KILX 132118
ESFILX
ILC009-017-025-033-057-079-095-101-113-123-125-129-137-143-147-
155-159-167-169-179-183-203-142200-
PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE Lincoln IL
318 PM CST Thu Feb 13 2025
...2025 Spring Flood and Water Resources Outlook Number 1...
...Overall near normal likelihood for springtime flooding across
central Illinois with above normal likelihood in the southeast...
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 multi-season scenarios from more than 30
years of climatological data, current streamflows, soil conditions,
snow pack, as well as short/long range weather forecasts.
FLOOD OUTLOOK HIGHLIGHTS...
- Risk of flooding this spring is overall near normal across central
Illinois with above normal likelihood across the southeast.
- Some factors limiting flood potential this spring include: near
normal to below normal streamflows, limited snowpack, shallow frost
depth, deep layer soil moisture deficits.
- Springtime rains expected to be the primary driver for flooding.
WINTER WEATHER REVIEW...
--December--
Statewide Temperatures/Precipitation:
Information, courtesy of the Illinois State Climatologist, shows that
the preliminary statewide average temperature in December was 33.4
degrees. This was 1.8 degrees below normal and tied for 36th warmest
on record going back to 1895.
Day to day temperature variability in Illinois is highest in
climatological winter, and December followed suit with regular dips
and jumps in daily temperature. Daily average temperatures were 10 to
20 degrees below normal in the first week of the month, were 15 to 25
degrees above normal in the final week of the month, and jumped
around in between.
When taken altogether, December average temperatures ranged from high
20s in northern Illinois to the low 40s in southern Illinois, between
1 and 5 degrees above normal. The warmest place in the state was
Olmstead in Pulaski County with an average December temperature of
41.4 degrees. The coolest place in the state was Stockton in Jo
Daviess County with an average December temperature of 26.6 degrees.
The milder days in December broke 3 daily high maximum temperature
records and 54 daily high minimum temperature records. Meanwhile the
cooler days broke 23 daily low maximum temperature records and 6
daily low minimum temperature records in Illinois.
The preliminary statewide average total December precipitation was
2.90 inches, 0.47 inches above normal and tied for 31st wettest on
record statewide.
December wasnt a washout anywhere but brought enough precipitation
to continue improving water conditions from peak fall drought.
December total precipitation ranged from over 6 inches in far
southern Illinois to around 1.5 inches in northern Illinois. Most
areas of the state south of Interstate 64 were 1 to 3 inches wetter
than normal last month, while parts of northern Illinois were around
1 inch drier than normal.
The wettest part of the state was, again, Olmstead in Pulaski County,
which picked up just over 10 inches in the final month of the year.
The driest place in the state in December was Freeport, with only
0.89 inches for the month.
As is often the case in milder Decembers, snowfall was a little
harder to come by across Illinois. December total snowfall ranged
from around 5 inches in far northern Illinois to less than a tenth of
an inch in far southern Illinois, between 1 and 6 inches below
normal. Snowfall so far this season has also been below normal across
Illinois, to the tune of 1 to 10 inches.
Local Temperatures/Precipitation/River Conditions:
Temperature averages for December were well above normal across the
ILX Hydrologic Service Area (HSA). Temperatures generally ranged from
2 to 4 degrees above normal. Daily high temperatures ranged from the
teens to the low 60s. Normal highs for December typically range from
the low 30s to the mid 40s. Low temperatures across the area ranged
from the single digits to the upper 40s. They typically range from
the teens to the upper 20s.
Rainfall totals across the ILX HSA were a mixed bag in December.
Southern sections of our HSA were well above normal for the month,
while other areas were below normal. Monthly precipitation generally
ranged from 1.53 inches in Lacon to 4.82 inches in Lawrenceville.
These totals ranged from 0.64 inches below normal to 2.16 inches
above normal, respectively. This equates to roughly 70 to 180 percent
of normal precipitation for the month. Although drought conditions
saw slight improvement across the state, nearly 60 percent of
Illinois remained in some form of drought. Nearly 40 percent were in
D0 conditions (Abnormally Dry), while 30 percent were in D1 (Moderate
Drought).
Flooding was observed, albeit brief, along the Little Wabash River
below Clay City in our southeast HSA. This was in conjunction with
the heaviest rains in our area. However, the flooding was minor and
only lasted a couple of days into the new year.
U.S. Geological Survey (USGS) monthly average streamflow values for
December show that most of the state was in the normal range. There
were outliers, however. The most notable was the Illinois River
basin, with streamflows that were well below normal for the month.
--January--
Statewide Temperatures/Precipitation:
The Illinois State Climatologist notes that the preliminary statewide
average temperature in January was 22.3 degrees. This was 4.4 degrees
below normal and tied for the 34th coldest on record going back to
1895.
All four of Illinois distinct seasons are getting warmer. However,
winter is warming far faster than the other seasons. As a result, we
have experienced many more mild winters in recent decades. This trend
made Januarys persistently cold weather seem particularly extreme.
Daily temperatures and departures from normal show much of the first
and third weeks of the month had temperatures that were consistently
5 to 30 degrees below normal.
January average temperatures ranged from the high teens in northwest
Illinois to the low 30s in southern Illinois, between 2 and 8 degrees
below normal. Persistent snowpack in southern Illinois helped depress
temperatures farther below normal than in relatively snowless
northern Illinois. The warmest point in the state last month was Du
Quoin at 31.7 degrees, and the coldest point in the state was
Stockton at 16.9 degrees. The few warm spells in January broke 10
daily high maximum temperature records. The extreme cold in the
middle of the month broke 23 daily low maximum temperature records
and 15 daily low minimum temperature records, including -20 degrees
in Springfield.
The preliminary statewide average total January precipitation was
1.25 inches, 1.06 inches below normal and tied for the 32nd driest on
record statewide.
Depending on who you talk to, January was either a very active winter
weather month or quite a boring one. An active storm track setup
across the southern half of the state in the first week of January,
pushing multiple winter storms through the state, which produced
multiple rounds of heavy snow mostly along and south of Interstate
70. The result was a strong gradient of snowfall opposite of what is
typical for this time of the year, with more in southern Illinois
than northern Illinois.
January total snowfall ranged from over 12 inches in south-central
Illinois to less than 1 inch in northwest Illinois. Much of the
southern half of the state had 1 to 8 inches more snowfall than
normal in January, while northern Illinois racked up snowfall
deficits of 1 to 8 inches. This was the fifth snowiest January on
record in Fairfield with 15.6 inches and the snowiest since 1996.
Meanwhile, Moline had only 2.3 inches of snow in January, the lowest
amount since 2018 and fourth lowest there since 1989.
Other than a couple of noteworthy snow and ice events, January was
otherwise mostly dry across Illinois. Total January precipitation
ranged from just over 5 inches in far southern Illinois to less than
a quarter of an inch in far northwest Illinois. Most of northern and
central parts of the state were around 1 to 2 inches drier than
normal last month and only the southern seven counties were wetter
than normal.
Local Temperatures/Precipitation/River Conditions:
Temperature averages for January were well below normal across the
ILX HSA. Temperatures generally ranged from 3 to 7 degrees below
normal. Daily high temperatures ranged from the single digits to the
low 50s. Normal highs for January typically range into the low to mid
30s. Low temperatures across the area ranged from the single digits
below zero to the upper 30s. They typically range into the teens.
Liquid precipitation totals across the ILX HSA were overall below
normal for January, with a few exceptions. Monthly precipitation
generally ranged from 0.44 inches in Hoopeston to 2.59 inches in
Mackinaw. These totals ranged from 1.68 inches below normal to 0.42
inches above normal, respectively. This equates to roughly 20 to 120
percent of normal precipitation for the month. Drought conditions
continued to improve, mainly across portions of central Illinois.
D0-D1 conditions went from 60 percent coverage, down to 35% in
January. By the of the month, drought conditions were largely
confined to the northern third of Illinois.
The only river flooding in the HSA was a carryover from December.
Minor flooding was briefly seen along the Little Wabash River below
Clay City. However, it quickly came to an end in early January.
The persistently cold temperatures in January caused appreciable ice
development on area rivers. Thankfully, temperatures in the last week
of January and into February allowed for considerable melting. There
were many instances of the ice melting in place along the smaller
creeks and streams. However, we did observe ice flowing down many of
the larger rivers in our HSA. Thankfully, there was not much in the
way ice jam development.
USGS monthly streamflow for January shows that most of the state was
in the normal range. Outside of that, there were a couple of basins
in the below normal range across portions of central and northern
Illinois.
--February--
Local Temperatures/Precipitation/River Conditions:
The month of February, to this point, has seen daily average
temperatures that are well above normal. They ranged from around 4 to
6 degrees above normal across the ILX Hydrologic Service Area(HSA).
In contrast, precipitation has averaged below normal. It has
ranged from around 0.40 to 0.60 inches below normal.
Thanks to a recent winter storm, we have a snowpack across the area
as of this issuance. Snow depth amounts range from 2 to 4 inches
across our northern counties, decreasing to zero or trace amounts as
you move toward our southeastern areas.
SOIL MOISTURE AND FROST DEPTH CONDITIONS...
Deep layer soil moisture conditions (down to 39 inches) across
central Illinois are well below normal for this time of year. As you
move toward our southeastern areas, soils are trending closer to
normal...but are still showing a deficit.
Drought conditions in Illinois have seen modest changes through the
winter season. At the end of November, 45 percent of the state was
experiencing D0 (Abnormally Dry) conditions with about 20 percent in
the D1 (Moderate Drought) category. Drought conditions were largely
confined to the northern two-thirds of Illinois. By early February,
conditions had retreated to the northern half of the state. However,
the latest Drought Monitor has again shown an expansion of D0
conditions further south. Abnormally dry conditions cover nearly 60
percent of Illinois with moderate drought impacting around 15
percent.
Frost had not been much of a concern for the first half of winter. It
was only with the very cold temperatures in later January that we
started seeing frost depths down to around a foot across portions of
central Illinois. A significant erosion of the frost occurred with
the warmer temperatures heading into February. Most indications are
that we only have shallow frost, down to around the inch, in central
Illinois with no frost in our southeast. This may change in the near-
term as we are expecting another blast of arctic air across the
region as we push into the second half of the month. It remains to be
seen if the recent snowpack is insulative enough to stifle additional
frost penetration. With that said, there is some near-term potential
for enhanced runoff with any rapid warmup/snowmelt/rainfall event
that may occur.
RIVER CONDITIONS...
River flooding through the winter season thus far has been minimal.
Only a few of the basins have pushed into minor flood. Those have
largely been short-lived and minimally impactful. As of this
issuance, there is no flooding occurring or currently forecast for
central and southeast Illinois.
Information, courtesy of the U.S. Geological Survey (USGS), shows
that streamflow conditions across the ILX Hydrologic Service Area are
overall near normal to below normal for this time of year.
Thanks to the warmer temperatures the past few weeks, river ice is
not currently a problem for our area. However, the below normal
temperatures forecast for the remainder of February may allow for
increased ice development. This will need to be watched as late
season river ice could have greater potential for mechanical breakup
and ice jam formation. This can pose a flash flood risk for areas
near and upstream of any jam that forms.
WEATHER OUTLOOKS...
The weather pattern over the next week looks to be somewhat active.
There will be a couple opportunities for a mix of winter
precipitation and rainfall over that time period. From there, the
remainder of February looks like it will end on an overall drier
note. After a couple days in the 30s, temperatures will drop
considerably across central and southeast Illinois. As we head into
next week, highs are largely expected to be in the teens and 20s.
The 8 to 14 day outlook (Feb 21 to Feb 27) favors below normal
temperatures across Illinois. Below normal precipitation is also
favored across the state during the period.
The most recent outlook for this spring (March / April / May) does
not favor any dominant trends for temperature across Illinois. In
contrast, most of Illinois is favored for above normal precipitation.
The highest likelihood is projected for the southeastern half of the
state.
FLOOD OUTLOOK SUMMARY...
The risk of flooding this spring is overall near normal across
central Illinois with above normal likelihood in the southeast. With
that said, those locations that typically experience flooding in the
spring can expect similar likelihood this year. Minor flooding
would be most common with possibly isolated moderate flooding,
especially in southeast Illinois.
Currently, there is no river flooding across our HSA. Streamflows are
in the normal to below normal range for this time of year. Deep layer
soil moisture is largely in deficit across the area with little in
the way of frost. In addition, water content of our snowpack is not
of great concern at the moment. Taken altogether, these hydrologic
conditions do not currently contribute toward enhanced flood
potential for this spring.
We are expecting an active weather pattern over the next week which
will bring a mix of precipitation types. This may lead to some near-
term enhanced runoff and flood potential. The expected artic airmass
may also spur river ice development. With that, comes the potential
for ice jams and associated flooding. This is of greater concern as
we head later into the season since there is increased potential for
rapid warmups, and rainfall on top of snowpack.
Keeping all of these things in mind, the primary driver of flooding
will be the springtime rains. Current hydrologic conditions are not
expected to be significant contributing factors for longer term flood
potential.
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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: 02/17/2025 - 05/18/2025
: 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 : 46 56 39 50 <5 <5
Peoria 18.0 22.0 28.0 : 64 66 27 34 <5 <5
Peoria L/D 447.0 449.0 455.0 : 45 56 31 36 <5 <5
Havana 14.0 17.0 23.0 : 83 84 61 65 12 19
Beardstown 14.0 18.0 28.0 : 81 79 56 60 <5 6
:Mackinaw River
Congerville 13.0 14.0 20.0 : 22 21 15 16 <5 <5
:Spoon River
London Mills 15.0 21.0 24.0 : 54 53 9 5 <5 <5
Seville 22.0 25.0 30.0 : 45 44 23 18 5 <5
:Sangamon River
Monticello 13.0 17.0 20.0 : 71 73 7 7 <5 <5
Riverton 23.0 26.0 29.0 : 11 11 <5 <5 <5 <5
Petersburg 23.0 24.0 33.0 : 23 22 19 18 <5 <5
:Salt Creek
Greenview 16.0 17.0 20.0 : 17 19 11 11 5 <5
:Sangamon River
Oakford 471.0 472.9 478.5 : 40 40 17 20 <5 <5
Chandlerville 456.6 459.0 462.0 : 56 55 23 23 <5 <5
:Embarras River
Lawrenceville 30.0 37.0 41.0 : 83 79 28 19 7 <5
Ste. Marie 19.0 20.0 27.0 : 51 36 37 23 <5 <5
:Little Wabash River
Clay City 18.0 22.0 25.0 : >95 94 34 22 6 <5
:Vermilion River
Danville 18.0 22.0 28.0 : 27 25 14 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: 02/17/2025 - 05/18/2025
Location 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Illinois River
Henry 16.4 16.6 19.7 22.6 25.6 27.0 28.7
Peoria 13.0 13.1 15.1 19.0 22.1 23.5 25.1
Peoria L/D 436.0 436.4 443.0 446.5 449.6 450.8 452.4
Havana 10.7 12.2 14.9 18.0 21.1 24.6 26.0
Beardstown 11.5 12.0 15.9 19.0 23.3 27.1 28.0
:Mackinaw River
Congerville 3.9 4.8 6.2 9.4 11.9 15.7 16.3
:Spoon River
London Mills 7.0 8.9 11.4 16.3 18.9 20.8 23.5
Seville 11.0 13.9 16.0 20.5 24.5 27.2 30.2
:Sangamon River
Monticello 10.6 11.2 12.8 13.7 15.1 16.3 17.7
Riverton 13.0 15.5 17.1 19.1 21.4 23.3 25.7
Petersburg 11.2 12.7 14.8 18.8 22.1 25.6 27.3
:Salt Creek
Greenview 5.7 6.9 8.2 11.1 14.6 17.3 20.1
:Sangamon River
Oakford 462.8 464.3 466.4 470.5 472.1 473.9 475.7
Chandlerville 450.3 451.9 454.1 457.5 458.9 460.5 461.9
:Embarras River
Lawrenceville 28.0 28.4 31.9 34.1 37.4 40.4 41.4
Ste. Marie 10.3 11.9 16.2 19.1 20.8 22.5 23.4
:Little Wabash River
Clay City 18.6 19.8 20.7 21.6 22.2 23.5 25.2
:Vermilion River
Danville 9.1 10.8 12.3 15.0 18.2 23.2 28.5
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: 02/17/2025 - 05/18/2025
Location 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Illinois River
Henry 3.7 3.4 3.3 3.3 3.2 3.0 2.7
Peoria 3.7 3.4 3.4 3.3 3.2 3.1 2.8
Peoria L/D 3.8 3.5 3.4 3.4 3.3 3.2 2.9
Havana 4.3 4.1 4.0 3.9 3.9 3.8 3.7
Beardstown 7.9 7.2 6.8 6.4 6.0 5.5 4.9
:Mackinaw River
Congerville 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:Spoon River
London Mills 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Seville 0.2 0.2 0.2 0.2 0.2 0.1 0.1
:Sangamon River
Monticello 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Riverton 1.5 1.4 1.1 0.9 0.6 0.5 0.5
Petersburg 1.9 1.8 1.4 1.1 0.8 0.6 0.6
:Salt Creek
Greenview 0.5 0.4 0.4 0.4 0.3 0.3 0.3
:Sangamon River
Oakford 2.7 2.4 2.1 1.7 1.4 1.0 0.9
Chandlerville 2.8 2.5 2.2 1.8 1.4 1.1 0.9
:Embarras River
Lawrenceville 19.1 18.6 17.8 17.0 16.7 16.5 16.5
Ste. Marie 3.0 2.5 2.0 1.3 0.9 0.8 0.8
:Little Wabash River
Clay City 8.5 6.9 6.6 5.9 5.3 5.0 4.9
:Vermilion River
Danville 3.6 3.4 3.1 3.0 2.9 2.9 2.9
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 NWS-National Water Prediction Service (NWPS).
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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 NWPS information,
including forecasts, select Rivers and Lakes from along the top menu
bar. Full NWPS graphics are available for all forecast points in the
ILX Hydrologic Service Area.
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 second issuance of the Spring Flood Outlook for central and
southeast Illinois will be on Thursday, February 27th. The NOAA
National Spring Flood Outlook will be issued on Thursday, March 20th.
$$
DRH