Berwyn, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

862
FXUS63 KLOT 022341
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
641 PM CDT Wed Jul 2 2025

.KEY MESSAGES...

- Small chance (10-15%) for a gusty thunderstorm along the lake
  breeze in northeast Illinois through early evening.

- Isolated to widely scattered storms possible Thursday with a
  gusty downburst threat.

- Hot July 4th and Saturday but not as oppressively humid as the
  previous rounds of heat recently (~95-100F heat indices).

- More appreciable thunderstorm chances return Saturday night
  and Sunday with a slowly approaching cold front. There may be
  a few days of quieter weather to start next work week.

&&

.DISCUSSION...
Issued at 316 PM CDT Wed Jul 2 2025

Weak high/surface-based capping remains present across the
forecast area this afternoon as evident by scattered larger and
flatter cumulus on IL/visible satellite. A subtle mid-level
impulse across southern Wisconsin is assisting with slightly
higher coverage of the cumulus, but is not providing enough
ascent to overcome the remaining capping. With that said, as
this wave encounters the lake breeze across far northeast
Illinois and southeast Wisconsin this evening, a couple widely
isolated thunderstorms cannot be ruled out. Modest mid-level
shear and a prominent inverted-V profile in the low levels would
support gusty winds with any thunderstorm.

A pocket of slightly higher low-level moisture will pivot
northeastward around the surface ridge tonight through Thursday.
Little to no surface capping during the afternoon and evening
may allow for an axis of isolated to widely scatted showers and
some storms to develop, particularly if a passing weak upper-
level wave provides additional support concurrent with peak
diurnal heating. The favored axis where these features align is
located from southwest WI toward the Kankakee River Valley. It
is possible overall coverage could be quite low, especially with
more aggressive mixing of dew points.

Mid-level ridging will then quickly move over the western Great
Lakes Thursday night, with the ridge axis crossing the CWA
sometime later Friday afternoon into the evening. There will be
a notable absence of a subsidence inversion under this ridge,
promoting only weak surface-based inhibition Friday afternoon.
With weak flow under 20 knots throughout the column and no
appreciable forcing aloft, the potential for any very sparse
convection will be relegated to a weak lake breeze pinned along
the Illinois shore. But with only marginal surface convergence
on the boundary and the likelihood that dew points mix out more
than currently forecast, will maintain a dry forecast for
Independence Day. Temps/heat index values will top out in the
low/mid 90s amid partly cloudy skies.

Phasing troughs over the central and northern Great Plains on
Friday will become increasingly sheared while encroaching on the
departing ridge this weekend. Increasing low-level isentropic
ascent may allow for more organized thunderstorms over Iowa
Saturday afternoon to reach the far western CWA while in a
decaying phase Saturday evening. Otherwise, Saturday will
feature another hot day with temps and heat index values
reaching the mid 90s.

A cold front associated with the sheared trough will drift SSE
across the forecast area late Saturday night through Sunday
while encountering increased moisture pooling and resultant
higher surface dew points. With weak-shear and generally
unidirectional flow parallel to the front, will need to monitor
for increasing chances of localized corridors of heavy rain
Sunday afternoon and evening.

There is some question as to when the front fully clears the
CWA on Monday, with slower solutions suggesting additional
convection and heavy rain developing across the southern third
of the forecast area Monday afternoon. Behind the front on
Monday and across the entire area on Tuesday, seasonable temps
and less humid conditions are expected. Shower and thunderstorm
chances will increase again late Tuesday into Wednesday with a
larger trough axis crossing the region.

Kluber

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 641 PM CDT Wed Jul 2 2025

Generally expecting VFR conditions and winds less than 10 kt
through the upcoming TAF cycle.

Lake breeze which had been approaching MDW and ORD late this
afternoon has been retreating back toward the lake and appears
unlikely to reach either terminal this evening. Westerly winds
Thursday are expected to be a bit lighter than today and will
probably allow the lake breeze to move across both MDW and ORD
late Thursday afternoon or early Thursday evening. Winds behind
the lake breeze should shift to easterly, but probably remaining
mostly below 10 kt.

An isolated shower or two is possible this evening, particularly
at RFD, ORD, and DPA. Isolated SHRA/TSRA are possible Thursday
afternoon and evening, but at this time, chances of them impacting
the terminals appears to be just below the 30 percent threshold
for inclusion in the TAFs. So other than the very low
possibility of a shower or storm early this evening or Thursday
afternoon and evening, conditions will remain VFR.

- Izzi

&&

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

&&

$$

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