Des Plaines, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

179
FXUS63 KLOT 011756
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1156 AM CST Sun Nov 1 2026

.KEY MESSAGES...

- Periods of showers or sprinkles today.

- Additional periods of wet weather are likely especially mid-
  week.

- Warmer than average temperatures early in the week are
  expected to eventually trend slightly below average by next
  weekend.

&&

.DISCUSSION...
Issued at 213 AM CST Sun Nov 1 2026

Scattered small clusters of convective showers and isolated
thunderstorms were lifting across eastern portions of the
forecast area early this morning. This weak convection was
occurring in association with a sheared northwest-southeast area
of mid-level vorticity, coincident with a layer of steep lapse
rates roughly in the 800-500 mb layer, as noted in current RAP
soundings. Though model sounding ELs are just shy of -20C, MRMS
isothermal reflectivity does indicate the tallest updrafts
reaching the -20C level with some 40-45 dBZ cores. The
expectation is that these scattered showers and isolated
thunderstorms will continue to lift across far northeast IL and
northwest IN (mainly east of the I-55 and I-355 corridors) prior
to sunrise before the sheared vort lobe moves northeast of the
forecast area.

Another weak mid-level short wave was noted across the mid-
Missouri Valley early this morning, and is progged to track east
across the area later this morning and afternoon. The strongest
forcing and juxtaposition of the low-level baroclinic zone to
our south suggests greater potential for measurable rain remains
largely south of our forecast area across central IL/IN, the
presence of the mid-level trough, weak warm advection and
reasonably moist profiles should support occasional spotty light
showers or sprinkles across the CWA during the day. Have
maintained a 15-20% chance mention, highest generally
along/south of I-80. Short-wave mid-level ridging is then
indicated across the area tonight, in the wake of today`s short
wave passage.

Attention then turns to our west, focused on the evolution and
eastward progression of a complex long-wave upper trough and
it`s associated deep surface low. Guidance has come into better
agreement with the upper trough axis (and embedded closed upper
low) propagating east of the Rockies and onto the Plains late
Monday, with a deepening sub-995 mb surface low developing into
eastern South Dakota by early evening. This is forecast to
induce strong southerly return flow into the Midwest within a
tightening surface pressure gradient. For northern IL/IN, the
main impacts Monday look to be the development of somewhat
breezy southerly winds (though forecast soundings depict fairly
shallow mixing, supporting gusts around 20 mph during the
afternoon), the potential for low stratus to advect in from the
southwest, and perhaps some scattered showers as isentropic
ascent increases with an elevated warm frontal zone lifting
across the area. While warmer temperatures are expected, the
shallow mixing may limit this somewhat with forecast highs
Monday are in the mid-upper 60s.

A strong mid-level short wave (currently off the northern Baja
coast) is progged to wrap around the south/southeastern
periphery of the larger scale upper trough late Monday/Monday
night, further deepening the closed upper low over the Central
Plains. This results in new surface low development (or
redevelopment) southeastward across IA, eventually slowing as
the system begins to become more vertically stacked on Tuesday.
Forecast sounding and time/height sections indicate development
of a ~45 kt low-level jet into the forecast area Monday night
into Tuesday/Tuesday night ahead of the deepening system.
Strengthening south winds will likely keep Monday night temps
very mild with lows in the 55-60 degree range. Winds may gust in
excess of 30 mph during the day Tuesday, with temperatures
potentially topping out in the low-mid 70s.

Deeper moisture feed during this process is initially focused
west of the Mississippi River, due to the southwestern periphery
of high pressure ridging from the Gulf Coast to the mid-
Atlantic region. This moisture eventually looks to reach our
area late Tuesday/Tuesday night however, with the greatest
potential for showers and perhaps a few thunderstorms in this
moisture axis ahead of the system`s occluding cold front. The
extent of thunderstorm coverage is a little uncertain, with
models indicating a pinching off of the MUCAPE axis to the north
of the surface frontal occlusion Tuesday night.

Confidence in forecast details then decreases mid-week, due to
model differences in the further evolution of the slow-moving
upper low across the region - complicated somewhat by the degree
of phasing with a northern stream short wave across the upper
Midwest/northern Lakes. Overall, the Wednesday-Friday period
continues to look unsettled as the closed upper low and occluded
surface system track slowly east across the region, though some
timing differences linger in the guidance at this distance.
While no strong intrusion of colder air is evident at this time,
temperatures do look to eventually cool to/slightly below
average on the back side of this departing system.

Ratzer

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1156 AM CST Sun Nov 1 2026

Spotty light SHRA from a mid-level cloud layer will continue
into early afternoon, followed by perhaps a couple instances of
sprinkles into mid-evening. Otherwise, VFR conditions will
persist through at least the early morning hours as winds under
10 knots favor directions in the SE quadrant. Winds will then
settle SSW/S while increasing to over 10 knots for much of the
day Monday.

As mid-level moisture exits the area to the northeast
overnight, low-level moisture will gradually advect northward
across Illinois. Low-level MVFR ceilings are expected to shift
over the Chicago terminals within an hour or two on either side
of sunrise Monday. Ceilings may lower into IFR levels during the
morning and early afternoon, with cloud depths also becoming
sufficiently deep for DZ. Confidence was low enough to limit the
mention of lower conditions to a PROB30 at the Chicago
terminals. IFR ceiling and DZ potential will increase with
westward extent, so have prevailed lower conditions at RFD
during most of the morning.

Kluber

&&

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

&&

$$

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