370
FXUS63 KILX 172302
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
602 PM CDT Tue Jun 17 2025

.KEY MESSAGES...

- There is a risk for severe weather across all of central
  Illinois on Wednesday...with the greatest risk (level 3 of 5)
  focused along and southeast of a Champaign to Taylorville line.

- Hot and humid weather will develop by the end of the week. High
  temperatures are progged to rise into the lower to middle 90s
  both Saturday and Sunday, resulting in peak heat index readings
  above 100 degrees.

&&

.DISCUSSION...
Issued at 236 PM CDT Tue Jun 17 2025

...Scattered Thunderstorms This Evening...

A short-wave trough currently over northwest Missouri will trigger
scattered thunderstorms across west-central Illinois this evening.
The 19z/2pm regional radar mosaic shows isolated storms forming
ahead of the wave across far northern Missouri. Most CAMs suggest
this area of convection will increase in areal coverage as it
tracks E/NE into western Illinois late this afternoon and evening.
The HRRR has consistently focused on locations along/west of I-55
between 5pm and 10pm...and this looks reasonable based on the
latest upstream satellite/radar trends. While widespread severe
weather is not likely, a few cells may tap into MLCAPEs of
1500-2000J/kg to produce gusty winds and small hail along with
locally heavy downpours.

...Severe Weather Risk on Wednesday...

As the nocturnal low-level jet strengthens across the Southern
Plains tonight, a prominent outflow boundary extending across
central Kansas will serve as the focus for a cluster of severe
convection. While these storms will follow the boundary and
gradually sink southeastward toward the greatest instability
across the Ozarks into Arkansas, an outflow boundary from the
system will sweep eastward into western Illinois toward dawn
Wednesday...then further east across much of the KILX CWA during
the morning. Scattered non-severe thunderstorms may accompany the
boundary, followed by a lull in precip chances from mid-morning
through early afternoon. After that, we will need to keep a close
eye on both the remnant outflow boundary, as well as the synoptic
cold front as it pushes eastward across the Mississippi River
later in the day. The atmosphere across the region will only be
modestly unstable...with the 12z HREF showing the highest SBCAPEs
in excess of 2500J/kg focusing well east of the I-57 corridor into
the Ohio River Valley. The NAM continues to show 0-6km bulk shear
increasing to 30-40kt...which will be enough to overcome the
limited instability and allow scattered convective development
along both the outflow and cold front. The most favorable
instability/shear/forcing will be in place along/southeast of a
Champaign to Taylorville line where SPC has upgraded the severe
risk to Enhanced (level 3 of 5). The primary storm risks will be
damaging wind gusts greater than 60mph and hail larger than
quarters: however, isolated tornadoes cannot be ruled
out...especially along/south of I-70 where an MCV may provide
enhanced low-level shear. The primary time frame for severe will
be 2pm to 10pm.

...Hot Weather by the End of the Week...

Once the Wednesday system departs, a period of slightly cooler and
drier conditions will be on tap for Thursday before upper heights
rise and temperatures increase markedly. 12z NBM shows a high
probability (70-100% chance) of exceeding 90 degrees across all
of central Illinois next Saturday and Sunday. These temperatures
combined with seasonally high dewpoints in the lower to middle
70s will produce heat index values well over 100 degrees.

Barnes

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 601 PM CDT Tue Jun 17 2025

A few waves of showers and storms are expected across central
Illinois through the period. The first wave of storms currently
over NE MO will lift across the I-55 corridor late this evening.
While earlier guidance kept this west of CMI/DEC, there has been a
trend for storms to reach further east so have introduced a prob30
at those two sites while a tempo remains for the western
terminals. The next wave of storms will develop over KS/MO late
this evening and continue east overnight. Remnants of this line of
storms will push across central Illinois Wednesday morning. Some
weak convection is possible, but confidence in details precludes
more than a prob30 mention at this time. The last wave of storms
will be with a synoptic cold front late Wednesday afternoon and
evening turning winds more SW to Wrly late in the period.
Coverage of storms appears more scattered with this last wave and
details will hinge on out the earlier line of showers and storms
pans out, so again a prob30 covers this third wave of storms.

Deubelbeiss

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$