Glenview, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

148
FXUS63 KLOT 191952
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
Issued by National Weather Service Lincoln IL
252 PM CDT Sat Jul 19 2025

.KEY MESSAGES...

- Next wave of thunderstorms is timed for after 2 am. Overall
  severe threat appears low. However, localized flash flooding
  could develop (10-15% chance)

- Several rounds of thunderstorms may occur early next week,
  with strong/severe thunderstorms possible along with
  torrential rain and localized flash flooding, particularly
  south of I-80.

- Dangerous heat and humidity becoming increasingly likely next
  Wednesday and Thursday.

&&

.DISCUSSION...
Issued at 251 PM CDT Sat Jul 19 2025

Through Sunday Night:

The afternoon complex of storms has primarily shifted east of
the forecast area as of 2 pm, with just a few storms churning on
the south end of Lake Michigan and surrounding land areas. In
the wake of those storms, satellite imagery is depicting some
clearing and sunshine developing from west to east. Nearly all
CAMs are remaining relatively quiet on any redevelopment through
sunset. However, satellite images show some agitated CU in NW
IL, so as sunshine increases SBCAPE values back toward 2,000
J/kg later this afternoon, we can not completely rule out
isolated storms redeveloping on outflow boundaries (10-15%).

Beyond that, the consensus of short-range ensembles are
indicating the next complex of storms will develop in an and
area of low-level isentropic ascent near a stalled frontal
boundary. That wave is already triggering showers and storms in
northeast Nebraska and SE South Dakota. The storms will likely
be elevated when they reach northern Illinois, as low level
stability returns after sunset. The primary focus area for those
storms looks to be the southern half of the CWA, where mid-level
steering flow will guide that activity around the ring of fire.
The airmass will remain primed for heavy rainfall, as PWATs
continue to linger in the 1.8 to 2.0" range through the night
into Sunday. Any slower moving storm could produce localized
flash flooding.

Sunday`s scenario appears to be tied to the lingering frontal
boundary as is shifts southward through the area. The late night
storms will linger into Sunday morning as they progress into the
eastern half of our counties. A couple of latest CAMs indicate
some northward expansion of the showers, north of I-88 in the
late morning to early afternoon time frame, but the better axis
of instability and moisture content will be south of I-80. SPC
continues to paint a Marginal Risk of severe storms in that
area, where damaging winds could develop from any updrafts that
are able to tap into the 3500 J/kg MUCAPE that will develop
along our southern CWA border. WPC has a corridor of Slight Risk
of Excessive Rainfall across the southern half of our CWA, with
ample PWATs for flash flooding still present. After the
morning-early afternoon complex, storm chances will shift
southward into early evening. Yet another complex of storms is
progged for later Sunday night into early Monday, once again
ridge riding on the NW flow into mainly the southern half of the
CWA. Wind damage threat and heavy rainfall will be the
continued hazards.

Shimon

Monday through Saturday:

After that early threat of storms Monday morning, the remainder
of Monday looks to see a break in the rain chances and the front
shifts farther south into central IL.

Then attention turns to the building heat wave as dewpoints make
a slow but steady climb through the 70s by mid to late week.
The highest heat and humidity are continuing to target Wednesday
and Thursday. The forecast guidance may not even be able to
capture the impacts of `corn sweat` from evapotranspiration -
where 3,000-4,000 gallons of water per acre can be released per
acre of corn.

That influx of moisture can cause localized areas of dewpoints
to reach the lower 80s, and nudging heat indices into the heat
advisory (105F) to near extreme heat warning levels (110F+).
The extended guidance is continuing to show a heat dome
developing under an upper level ridge, which will shift east
into Illinois Wed-Thur. High temps will likely reach the 90s
both Wed and Thursday, with heat index readings over 100F in
most areas. A heat headline will need to be considered in future
updates if these forecasts hold. The Chicago urban heat island
effect will likely come into play for that heat wave. Southerly
offshore wind patterns will be unfavorable for some cooler near
the lake conditions.

The upper ridge looks to break down and flatten enough for some
relief from the heat, or at least below heat headline levels.
The extended ensembles are indicating a storm complex will
impact our cwa at some point later Thursday night through Friday
night. We will need to keep an eye out for severe potential as
that heat wave breaks, but with temperature outlooks remaining
above normal into the last week of July, there doesn`t appear to
be a significant cool down in the offing.

Shimon

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1246 PM CDT Sat Jul 19 2025

Forecast concerns include...

Chance of thunderstorms early this afternoon.
Ifr cigs overnight/Sunday morning.
Chance of fog early Sunday morning.

A line of showers and embedded thunderstorms will be shifting
east of the terminals over the next hour or two. Once this
activity ends, dry weather is expected through at least mid
evening. There is some potential for additional showers and
thunderstorms late this evening through mid morning Sunday. If
this activity develops, current trends would support it
remaining mainly south of the terminals and have maintained a
dry forecast for now.

Low mvfr and ifr cigs have developed with this current rain and
are expected to scattered from west to east through mid
afternoon. Possible a cu field could develop, which could have
mvfr level clouds and will need to monitor trends.

A cold front will move south across the area overnight which is
expected to allow a period of ifr cigs for most of the area,
which will then lift to low mvfr Sunday morning and its possible
these mvfr cigs may persist through much of Sunday afternoon,
possibly lifting/scattering in the mid/late afternoon. Fog will
also be possible tonight and appears most favored south and west
of the Chicago terminals and added mention at RFD/DPA. The
expected widespread lower cigs may prevent fog from becoming
dense.

Wind directions may be a bit challenging for the next hour or
two but should favor south/southwest and then winds are expected
to turn more southwest this afternoon, northwest this evening
and then shift northeast with the cold front overnight with
northeast winds continuing for the rest of the period. cms

&&

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

&&

$$

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