Severe Thunderstorm Warning 258, NWS Lincoln, IL

Area Forecast Discussion
National Weather Service Lincoln IL
835 PM CDT Thu Jun 11 2026

.KEY MESSAGES...

- A line of severe thunderstorms is forecast to produce damaging
  winds and several embedded tornadoes across central Illinois
  this evening (risk level 4 of 5). The window for the most
  intense storms will be 4-10pm.

- While the risk is lower (level 2 of 4), there could be some
  localized flooding with these storms as well, especially north
  of I-72 and west of I-57 where many locations received
  several inches of rainfall yesterday.

- More showers and thunderstorms are likely (60-80% chance)
  Saturday night, with a level 1 of 5 (marginal) risk for
  severe weather and excessive rainfall.

&&

.UPDATE...
Issued at 835 PM CDT Thu Jun 11 2026

A squall line of severe storms was racing eastward around 60
mph across central IL late this afternoon and early evening.
Currently the line of storms was along and just south of I-72
and still producing severe storms with several counties having
severe thunderstorm warnings and going into west central and nw
Indiana where some tornado warnings were in effect. This squall
line had a history of widespread damaging winds, and some large
hail and tornadoes over central and northeast IL. This line of
storms is moving quicker and will likely stay severe as it moves
into southeast IL late this evening. Very unstable air mass
still ahead of these storms with MLCAPES of 2500-3500 j/kg and
increasing bulk shear values moving into southeast IL next few
hours. The convection was se of a Bloomington to Jacksonville
line and the flood watch will be allow to expire at 9 pm cdt.
The latest HRRR has line of strong to severe storms moving inot
far southeast IL between midnight and 1 am and ending in se IL
between 3-4 am. Lows overnight 55-60F from I-72 north (coolest
in Galesburg) to mid 60s in southeast IL.

&&

.DISCUSSION...
Issued at 230 PM CDT Thu Jun 11 2026

***** SEVERE WEATHER OUTBREAK THIS EVENING *****

At 230pm, temperatures and dewpoints across central and southeast
Illinois were in the mid-upper 80s and mid 70s, respectively amidst
southerly flow, evapotranspiration "ET" (mostly evaporation this
early in the growing season), and sunshine. RAP mesoanalysis
suggests this is contributing to MLCAPE values of 1000-3500 J/kg - a
sharp gradient across the area with higher values to the south.
Surface heating should continue to boost both temperatures and
instability and reduce convective inhibition (CIN) throughout the
afternoon ahead of an approaching cold front, which will sweep the
area west-east during the mid to late evening hours. RAP/HRRR/NAM
suggest MLCAPE will peak around 4000-5000 J/kg with 35-45 kt deep
layer shear ahead of that front, which should provide sufficient
forcing to maintain the ongoing storms across west-central IL and
result in development further to the south. This highly volatile
convective environment should favor organized convection capable
initially of all severe hazards (tornadoes, large hail, and damaging
winds), with an increasing wind and quasilinear convective system
(QLCS) tornado threat as storms grow quickly upscale into bowing
lines. PWATs approaching 2 inches will favor precip loading,
especially in the taller cores which will feature melting hail,
while steep mid level lapse rates and wide CAPE profiles will
enhance potential for RIJ formation in bowing segments; this will
increase the risk for high-end (75+ mph) and long-duration (20+
minutes) straight-line winds which would result in swaths of
enhanced damage (trees down, shingle damage, power outages). SPC has
issued a level 4 of 5, "moderate," risk for severe weather, driven
by wind and tornadoes, which could be strong north of a Macomb to
Bloomington line. Winds ahead of these storms may gust up to 40 mph
from the south, as descending hydrometeors from anvils aid in
momentum transport from a 40-50 kt LLJ (strongest over northern IL).

***** LOW RISK FOR FLASH FLOODING *****

With some locations north of I-72 and west of I-57 having received
over 3 inches of rainfall yesterday (and multiple rounds of heavy
rainfall in days prior), there is concern that flash flooding could
occur with storms this afternoon and evening. This is especially
true with the ongoing training storms north of a roughly Macomb to
El Paso line. 3 hour FFG in some of these areas is under a half an
inch, and with various CAMs advertising 1 hour rain rates >1 inch it
makes sense there could be some issues, especially in urban and poor
drainage areas. A Flood Watch was issued for Cass to Dewitt, and
counties further north, in effect until 9pm.

***** LESS WARM AND MUGGY STARTING TONIGHT *****

Behind the cold front, conditions will turn much less humid and,
with some clearing, temperatures are forecast to fall into the mid
to upper 50s overnight west of roughly I-57. High temperatures
tomorrow should only climb into the low 80s, making it feel much
more pleasant heading into the weekend. Warm air advection (WAA)
will bring a slightly more humid airmass into the region tomorrow
night into Saturday ahead of another shortwave trough, but
convection to our southwest should limit the northward extent of
deep layer moisture - resulting in a low (albeit nonzero) risk for
severe weather and heavy rainfall Saturday/night in our neck of the
woods. Both SPC and WPC have us in marginal risks for each hazard.

Behind that second front, much cooler conditions return, with NBM
only giving a 15-30% chance high temperatures reach 75 degrees on
Sunday. Temperatures are slated to moderate gradually towards the
middle of next week, as southwest flow returns ahead of the next
upper level low pressure system.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 640 PM CDT Thu Jun 11 2026

Strong to severe thunderstorms are currently moving through the
area. These storms are currently producing strong winds with
recorded gusts up to about 50 knots or potentially greater. A
tornado is also possible with this line of storms as it pushes
through the area. These storms are moving through quickly though
and will exit the area between 01z to 02z. Brief drops to MVFR
ceilings is expected in the storms and potentially for an hour
or so behind them as well. Visibility will drop to IFR levels
within the storm. The good news is that quiet conditions will
return in the wake of the departing thunderstorms. Winds will
remain out of the northwest before weakening this evening while
backing to out of the west. With calmer winds in place, there
could be isolated patches of fog or low stratus. However, the
probability of fog or low ceilings is low at a <=20% chance.
Have kept this potential omitted from all TAFs at this time but
trends will be monitored through the night. Otherwise, light
west/northwest winds are expected for the rest of the TAF period
as high pressure moves into the region.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 9 PM CDT this evening for ILZ031-037-038-
041>043-047-048.

&&

KEY MESSAGES...Bumgardner
UPDATE...07
DISCUSSION...Bumgardner
AVIATION...Meyers

Hazardous Weather Outlook
National Weather Service Lincoln IL
405 PM CDT Thu Jun 11 2026

ILZ027>031-036>038-040>057-061-122115-
Knox-Stark-Peoria-Marshall-Woodford-Fulton-Tazewell-McLean-Schuyler-
Mason-Logan-De Witt-Piatt-Champaign-Vermilion-Cass-Menard-Scott-
Morgan-Sangamon-Christian-Macon-Moultrie-Douglas-Coles-Edgar-Shelby-
405 PM CDT Thu Jun 11 2026

This Hazardous Weather Outlook is for central Illinois, east
central Illinois and west central Illinois.

.DAY ONE...Tonight.

Severe thunderstorms are expected through this evening. Damaging
winds over 70 mph, large hail, and tornadoes are all possible with
the strongest storms. Heavy rain may also lead to flash flooding,
especially where heavy rain fell the last several days.

River flooding is ongoing or expected to develop along the Spoon, La
Moine, Illinois and Mackinaw Rivers.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Additional thunderstorms are expected Saturday night. A few of these
will be capable of producing strong wind gusts.

River flooding is ongoing or expected to develop along the Spoon, La
Moine, Mackinaw, and Illinois Rivers.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed through late this evening.

Expected storm motion is toward east between 35-45 mph.

ILZ062-063-066>068-071>073-122115-
Cumberland-Clark-Effingham-Jasper-Crawford-Clay-Richland-Lawrence-
405 PM CDT Thu Jun 11 2026

This Hazardous Weather Outlook is for east central Illinois and
southeast Illinois.

.DAY ONE...Tonight.

A line of severe thunderstorms is expected to move across the area
this evening. These storms will be capable of damaging wind gusts
and a couple tornadoes. In addition, locally heavy rain may
aggravate any lingering flooding from recent storms.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Additional thunderstorms are expected Saturday night. A few of these
will be capable of producing strong wind gusts.

Minor flooding will continue along the Wabash River into next week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed through late this evening.

Expected storm motion is toward the east-southeast around 35-45 mph.

NMA

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