Berwyn, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

698
FXUS63 KLOT 100721
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
221 AM CDT Fri Jul 10 2026

.KEY MESSAGES...

- Chances for showers and storms this afternoon around and south
  of I-80.

- Drier and warmer conditions are expected into early next with
  cooler conditions near Lake Michigan.

&&

.DISCUSSION...
Issued at 221 AM CDT Fri Jul 10 2026

A cold front analyzed on mesoanalysis from northeastern Iowa to
south-central Wisconsin is slowly sinking southward toward
Illinois. However, remnants of a lake breeze has kept most of
the surface winds in northern Illinois out of the northeast.
There is a weak axis of moisture convergence from Monticello,
IA to Michigan City, IN where spotty showers may continue to
fester through daybreak. Lightning has only been intermittent,
and forcing and instability is weak, suggesting that activity
will continue to weaken through sunrise. The cold front will
continue to slink southward through the morning helping to limit
max temperatures today in the low to mid 80s, with mid to upper
70s closer to the lake.

Broadening the scale of current conditions, a look at national
mosaic radar shows a large complex of showers and thunderstorms
spanning from central Nebraska to central Kansas presently.
Models are keying in on the chances that a mesoscale convective
vortex (MCV) from this complex will transit eastward ahead of a
700 mb wave into central Illinois today. While coverage of
showers and storms may wane in the morning, its arrival in
central Illinois is expected to correspond to a diurnally
favorable time of day with a largely uncapped environment and
plenty of instability and decent low level lapse rates to
redevelop showers and thunderstorms. Shear looks fairly meager,
and models are trending the track of the MCV more to the
southern part of the state. Better shower/storm coverage is
expected farther south of the forecast area, but scattered
activity could develop near US-24. Farther to the north, cannot
completely rule out a slight chance (less than 25 percent) this
afternoon of a few storms along a lake breeze and lingering
moisture gradient in the vicinity of I-80.

An upper level ridge is expected to grow tomorrow over the
central Plains and develop a southwest to northeast oriented
axis from central Colorado to the Twin Cities on Sunday. That
ridge is expected to continue to increase high pressure over the
area and spread across much of the central CONUS. This should
develop drier conditions, and as 850 mb temperatures increase
to around 20C next week, there is a chance that temperatures in
the low to mid 90s may return to the area. However, there is a
little uncertainty with models not just in the strength of the
high pressure/ridge, but also how a deep upper level low is
expected to traverse across Canada next week. While warm and
above normal temperatures are expected next week, it does not
appear (at least at this distance) to compare to the previous
heat wave that occurred at the start of the month. Not only is
the temperature signature currently notably more muted, but with
the high pressure projected to be situated over northern
Illinois, there is a chance for daily lake breezes to set up
and provide a little more relief, assuming the synoptic winds
themselves are already out of the northeast. The warmest
temperatures are currently projected around Tuesday or
Wednesday, but that may change with updated guidance.
Nevertheless, sunny and dry summer conditions are shaping up for
next week.

DK

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 1212 AM CDT Fri Jul 10 2026

The main aviation weather concerns are:

- Lingering showers and a few embedded thunderstorms in the
  central and southern parts of c90 tonight

- Developing IFR cigs and possible BR/FG overnight

An axis of showers, occasionally with a few embedded
thunderstorms, continues to shift slowly southeastward. The
general expectation is for storm coverage to diminish
overnight, but at least isolated/spotty activity will probably
fester through much of the overnight in the vicinity of an ARR-
GYY line. Coverage and confidence remains too low for any TSRA
mentions.

An area of IFR cigs continues to work its way slowly
southwestward off the lake. Currently, this area of low stratus
appears to be somewhat localized, but guidance suggests this
will expand with time overnight. Continue with various TEMPO
mentions for IFR overnight and into early Friday, with some
potential future updates may need to prevail these conditions.
In addition, some MVFR BR will be possible given the generally
light low-level flow and moist airmass. Cigs should then
gradually lift/scatter towards midday with VFR conditions
expected through the rest of the TAF period.

Light/variable to northeasterly winds tonight will get a bit of
a northeasterly boost with a lake breeze Friday afternoon.

Carlaw

&&

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

&&

$$

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