817
FXUS63 KLOT 141159
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
659 AM CDT Fri Aug 14 2026

.KEY MESSAGES...

- Thunderstorms with torrential rainfall may continue across
  areas southwest of the Chicago metro this morning.

- A low pressure system is expected to bring showers and
  thunderstorms with locally torrential rain and potential
  flooding late tonight into Saturday morning for portions of
  northern Illinois.

- A stormy pattern is expected to remain in place through the
  weekend.

&&

.DISCUSSION...
Issued at 334 AM CDT Fri Aug 14 2026

Ongoing significant rainfall and potential flooding over far
southern portions of the CWA should subside soon. However,
continued weak low-level isentropic ascent combined with
sufficient elevated instability may foster continued development
across the southwest CWA through at least daybreak before the
existing modest LLJ veers and decays. Will need to monitor if
any MCV develops within ongoing convection over central Iowa.
This would reinvigorate scattered convection with locally heavy
rain late this morning into the afternoon across, with the most
likely MCV track favoring western portions of the CWA.

A robust convective complex currently over south-central
Nebraska is significantly enhancing a mid-level wave across the
central Great Plains. Based on latest guidance, the vast amount
of convection is expected to turn this wave into a warm core low
through this morning. This wave/low will drift along a broader
ridge through tonight, with latest trajectories favoring a track
over or slightly north of the forecast area late tonight into
Saturday morning. Given high-end PWAT values of 2.3" to possibly
upward of 2.5" and expected slow forward motion of the wave,
significant rainfall rates of over 2" per hour are possible near
and along the track of the associated surface wave.
Additionally, strong southeast winds of advisory caliber (at
least 45mph) cannot be ruled out along the southern periphery of
the track. A Flood Watch may be needed for areas roughly around
and north of I-80 for late tonight and Saturday morning. Will
also need to monitor a threat for elevated convective linear
elements capable of transporting corridors of damaging wind to
the surface ahead of the wave.

Another wave expected to become convectively enhanced in the
lee of the central Rockies tonight will track north of the area
late Saturday night, dragging a cold front with showers across
the CWA sometime during the daytime hours on Sunday.
Thunderstorm chances will be dictated by the expected timing of
the front, with a later arrival in the afternoon supporting
higher coverage of storms and a marginal damaging wind risk.

High pressure will build southward over the area early next
week, supporting seasonable temperatures and a decent chance of
a dry stretch Monday and Tuesday. Another stronger wave and cold
front will bring chances of showers and storms on Wednesday,
with the front expected to stall well south of the area late in
the week.

Kluber

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 659 AM CDT Fri Aug 14 2026

Key aviation forecast messages:

- Lingering MVFR to near IFR VSBYs and CIGs through mid morning.

- 30% chance for SHRA developing ahead of approaching system
  this evening.

- SHRA and TSRA likely sometime late tonight into Saturday AM,
  lower confidence on onset timing.

Showers from the overnight period have focused mainly south of
I-80 this morning other than some shallow showers that have
developed over the lake near UGN. Residual MVFR to near IFR CIGs
and VSBYs will very gradually improve through mid morning with
most areas returning to VFR to midday.

While a stray shower can`t be ruled out through the afternoon
the majority of the day is expected to remain dry at the
terminals. Winds will mainly be out of the east to northeast
around 5-10 kt.

A disturbance moving across Nebraska will bring our next
potential for widespread showers and thunderstorms sometime late
tonight into Saturday morning. Out ahead of this feature there
is guidance that attempts to develop showers and isolated
thunderstorms ahead of this feature which could move into the
terminals during the evening. Have introduced PROB30 groups to
account for this potential for now. Confidence in SHRA/TSRA
then increases late tonight. Have maintained PROB30 groups for
TS mainly due to lower confidence in onset timing, but
prevailing or TEMPO TS or VCTS will likely be needed with later
updates.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Flood Watch until 10 AM CDT this morning for ILZ010-ILZ019-
     ILZ021-ILZ023-ILZ032-ILZ033-ILZ039.

IN...Flood Watch until 10 AM CDT /11 AM EDT/ this morning for
     INZ010-INZ011-INZ019.

LM...None.

&&

$$

Visit us at weather.gov/chicago