756
FXUS63 KLOT 310651
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
151 AM CDT Fri Jul 31 2026

.KEY MESSAGES...

- Periods of rain this afternoon through Saturday evening with
  a chance of thunderstorms.

- The potential exists for locally heavy rainfall with areas of
  2"+ rainfall totals.

- High waves and dangerous swimming conditions at Lake Michigan
  beaches late tonight through Monday morning.

&&

.DISCUSSION...
Issued at 151 AM CDT Fri Jul 31 2026

Low pressure will move southeast across IA today then across
south/central IL tonight and across the Ohio River valley
Saturday as it slows. Showers and at least a chance for
thunderstorms will spread across the area this afternoon. As the
low approaches later today, the southern cwa may remain in the
warm sector allowing for a better chance of thunderstorms, a few
of which may be strong to locally severe. Though it appears the
best chance of any severe thunderstorms will remain southwest
of the local area.

Periods of rain will continue tonight into Saturday morning
along with a continued chance for thunderstorms, which current
timing trends would suggest the best chance in the evening into
the early overnight of Saturday morning. The rain during this
time period will likely be moderate to heavy at times with
precipitable water values in the 2 inch range. With the system
slowing as it moves southeast, at least scattered showers are
expected to continue Saturday and these may continue into
Saturday night, especially across northwest IN. Models differ
quite a bit for storm total rainfall but amounts in the 1 to 3
inch range look reasonable, highest amounts across the northern
cwa. There may be some locally higher amounts as well.

A prolonged period of northeast winds is expected, gusting to
30-35 mph across southern Lake Michigan. This will allow for
high waves and dangerous swimming conditions at Lake Michigan
beaches late tonight through early Monday morning and plan to
issue a beach hazard statement with this morning`s forecast.

High pressure will bring dry weather back to the area early next
week with precip chances possibly returning late next week. cms

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 109 AM CDT Fri Jul 31 2026

Key Messages:

- SHRA develop west-to-east this afternoon.

- Increasing threat for embedded thunderstorms with heavy rain
  and MVFR to IFR conditions mid to late this evening through
  Friday night.

- SSE winds shift easterly and increase later today into
  tonight.

A weather disturbance across portions of the Dakotas early this
morning will shift east-southeastward across the Midwest into
the lower Great Lakes regions today into tonight. As it does,
expect light rain do develop eastward across the northern IL
terminals this afternoon (potentially as early as 18Z at RFD and
~20Z at the Chicago terminals). The rain showers will become
more pronounced across the area this evening and tonight as the
center of the system begins to shift into northwestern IL.
Steepening mid-level lapse rates associated with the
approaching mid-level system will also support increasing
chances for embedded non-severe storms with heavy downpours into
the overnight hours. Accordingly, we have opted to include a
PROB30 mention for TS in the TAFs after 04Z at the Chicago
terminals and after 02Z at RFD. The threat of rain and low
flying conditions is likely to persist into Saturday (beyond the
current 24 to 30 hour forecast period).

Otherwise, expect southeasterly winds to increase from the east
later this afternoon and tonight, in association with the
approaching area of surface low pressure.


KJB

&&

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

&&

$$

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