724
FXUS63 KILX 102254
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
554 PM CDT Mon Aug 10 2026

.KEY MESSAGES...

- There is an Enhanced Risk (level 3 of 5) for severe weather
  northeast of I-74 on Tuesday. The primary hazard will be
  damaging wind gusts in excess of 70mph: however, isolated
  tornadoes cannot be ruled out.

- Typical summertime heat and humidity will persist into
  Tuesday. Locations not impacted by convective outflow will see
  afternoon heat index readings reach 100-105 degrees. As a
  result, a Heat Advisory will be issued along/southwest of a
  Macomb...to Lincoln...to Casey line.

- Several storm clusters will track through the region Tuesday
  night through Friday night...posing additional risks for
  severe weather and heavy rainfall.

&&

.DISCUSSION...
Issued at 232 PM CDT Mon Aug 10 2026

Quiet weather will continue across central Illinois this
afternoon and evening as convection develops near a lingering
outflow boundary along/north of the I-80 corridor where 19z/2pm
MLCAPEs have exceeded 4000J/kg. Given the lack of a clear
forcing mechanism and an overall more stable environment due to
the presence of a mid-level cloud deck, think CAMs such as the
HRRR and RRFS are correct in keeping central Illinois dry and
developing storms across northern Illinois, then tracking them
generally eastward into the Chicago metro and eventually into
southern Michigan/northern Indiana this evening. Additional
storm clusters may form overnight as the low-level jet
strengthens, but these will largely stay north of the KILX CWA
as well.

Confidence is growing that a more significant cluster of
thunderstorms will form over northern Iowa late tonight, then
race E/SE across northern Illinois/Indiana on Tuesday. The 12z
HRRR/RRFS are in relatively good agreement concerning the
track/timing of the storms...taking the most significant wind
risk along/just north of the northern KILX CWA boundary during
the morning into the early afternoon. The latest Day 2 Convective
Outlook highlights locations north of I-74 with an Enhanced
Risk (level 3 of 5) for severe weather. Wind gusts in excess of
70mph will be the primary hazard: however, a few tornadoes may
be embedded within the leading edge of the squall line as well.
Model consensus generally focuses the strongest wind gusts along
I-80 into north-central Indiana: however, it appears likely that
the trailing end of the line will graze the I-74 corridor. Aside
from the convection, Tuesday is also shaping up to be a very
warm and humid day. The big question will be how far south the
storms and/or the resulting outflow boundary will settle...as
this will significantly impact the temp/heat index forecast.
Based on the 12z HRRR/RRFS, have opted to issue a Heat Advisory
along/south of a Macomb...to Lincoln...to Casey line where
afternoon heat index values will peak at 100-105. Further N/NE,
outflow from the early days storms will keep temps a bit cooler.

Once the initial severe storm cluster exits into Indiana, will
need to keep an eye on possible convective development along the
trailing outflow during the afternoon/evening. Many CAMs are
initially fairly sparse with convective coverage, but then
develop activity after dark as the nocturnal jet cranks up. As
such, have kept afternoon PoPs confined to 20-30% mostly east
of I-55. Areal coverage will increase into the 30-50% range
after dark as the outflow boundary serves as the primary
focusing mechanism.

W/NW upper flow will keep central Illinois in an active
convective pattern through the remainder of the week. As the
primary baroclinic zone wavers across the area, several rounds
of showers and thunderstorms will occur Wednesday through
Saturday. While it will not be a complete wash-out on any of
those days, the risk for occasional severe weather/heavy
rainfall will be persistent. Given the favorable synoptic
pattern, the latest WPC 7-day QPF shows widespread amounts of
1.50 to 2.50 along/north of a Quincy to Lawrenceville line.
There will likely be swaths of even heavier rainfall depending
on exactly where each convective complex ultimately tracks.
Stay tuned to later forecasts for additional details.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 554 PM CDT Mon Aug 10 2026

A thunderstorm complex is expected to track east through
northern IL late Tuesday morning, likely staying north of the
central IL terminal. Included a PROB30 TSRA mention at KPIA-
KBMI-KCMI where the ouflow boundary associated with this complex
is forecast to produce scattered TSRA during the midday to
afternoon hours. Otherwise, terminals should see VFR conditions
through Tuesday afternoon. Winds will generally be S-SW at 7-12
kt.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon to 8 PM CDT Tuesday for ILZ036-040>042-
047>054-056-061>063-066>068-071>073.
Heat Advisory until 7 PM CDT this evening for ILZ040-047>052-
061>063-066>068-071>073.

&&

$$

KEY MESSAGES...Barnes
DISCUSSION...Barnes
AVIATION...25