701
FXUS63 KLOT 120517
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1217 AM CDT Sat Jul 12 2025

.KEY MESSAGES...

- Level 2 to 3 of 5 severe thunderstorm threat late this
  afternoon and evening.

- Heavy rainfall will accompany the storms and could result in
  flash flooding, particularly in the areas in and around
  Rockford that were hit with very heavy rainfall last night.

- Showers and thunderstorms are possible again Saturday
  afternoon and evening, though the severe threat and coverage
  of storms should be lower than those expected this evening.

&&

.DISCUSSION...
Issued at 301 PM CDT Fri Jul 11 2025

Through next Friday:

The thinking for the severe thunderstorm threat into this evening
has not changed. Please reference the earlier issued discussion
above for more info.

Following the severe weather threat into this evening, some
widely scattered showers and storms may persist across the area
overnight into early Saturday morning just in advance of the
approaching mid-level trough moving into northern IL. The only
lingering threat with any of this overnight activity would be
some locally heavy downpours.

The threat of scattered showers and thunderstorms will continue
on Saturday as the area remains in a very warm and moist low-level
airmass in advance of an approaching cold front and a second
northern stream impulse. Accordingly, we anticipate widely
scattered showers and storms to once again develop in the
afternoon with the front as the low-level airmass destabilizes.
This will particularly be the case across roughly the
southeastern half of the area. Fortunately, the coverage of
storms looks to remain lower than that expected this evening, so
Saturday is not expected to be a washout. The severe threat
Saturday also looks to be lower than this evenings, owing to the
presence of weaker deep layer shear. Nevertheless, some
potential for locally strong wind gusts will be possible with
the strongest storms Saturday afternoon, these are just expected
to be few and far between at this point.

Following the passage of the cold front Saturday evening, surface
high pressure is slatted to shift into the region for Sunday and
Monday. This will promote a drier period of weather with lower
humidity both days. Seasonable temperatures in the mid to upper
80s are anticipated both days, but with lower humidity heat
indices will not deviate much from the actual temperature.

Unfortunately, humidity levels will begin to increase again into
the midweek period following the eastward departure of the
surface high. Also, as is typical this time of year, with the
return of low-level moisture also comes the return of shower and
thunderstorm chances. This looks to be especially the case around
midweek as the upper level weather pattern turns a bit more
unsettled across the central CONUS.

KJB

&&

.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 1217 AM CDT Sat Jul 12 2025

Cluster of showers with a few isolated thunderstorms will
continue to decay as it attempt to move eastward. Could see a
couple showers and some squirrelly winds with outflow in the
first hour of the TAFs at the Chicago terminals. Otherwise, look
for light winds, probably favoring southeast, much of the rest
of the night with VFR conditions.

Guidance continues to suggest MVFR CIGS with even a chance for
some IFR CIGS toward sunrise and lingering into the morning
hours. By late morning, conditions should trend VFR with CIGS
scattering out. Better chance of SHRA/TSRA look to remain east
of the terminals this afternoon.

- Izzi

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago