Chicago, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

612
FXUS63 KLOT 120826
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
326 AM CDT Tue May 12 2026

.KEY MESSAGES...

- Turning warmer and windy this afternoon. Scattered showers
  this afternoon, with an isolated strong storm possible early
  this evening.

- Cooler and breezy conditions are expected on Wednesday before
  a longer-lasting warm up arrives to close the week.

- The May 16 through 19 timeframe may feature several rounds of
  showers and storms in the general region.

&&

.DISCUSSION...
Issued at 326 AM CDT Tue May 12 2026

A short wave trough shifting over ND early this morning will
amplify through the day as it digs southeastward across the
Upper Midwest and into the western Great Lakes region by early
evening. As it does, the low-level flow in advance of it will
quickly turn south-southwesterly this morning. Thereafter, a
rather windy and warm afternoon is expected for the area as wind
gusts quickly ramp up in response to deep boundary layer mixing
(in excess of 6,000 ft AGL) into 45+ kt of flow aloft.
Accordingly, frequent gusts up to 40 mph are expected this
afternoon, particularly across my IL counties. There is also the
possibility that a few stronger gusts in excess of 45 mph could
materialize for an hour or two mid to late this afternoon, but
confidence on this is low. We have thus opted to hold forecast
wind gusts generally below Wind Advisory criteria (45 mph). The
advection of a much warmer airmass on these strong southwest
winds will also push high temperatures well into the 70s to
around 80 this afternoon.

In addition to the warm and windy weather this afternoon, we
have opted to add in some patchy blowing dust in the forecast
this afternoon, primarily across the rule areas of IL south of
I-80. We do not have a good feel for how extensive the blowing
dust will become. However, with seasonal farming activity in the
upswing and continued dry weather in recent days, along with
recent occurrences in the past week, we cannot ignore the
potential. We have, however, held short of issuing a blowing
dust advisory. Instead, the plain is to handle the need for this
tactically today.

This afternoon, increasing mid-level moisture advection will
foster a corridor of scattered high based showers in advance of
the main approaching impulse and surface front. This activity is
expected to gradually sag south-southeastward across the area
through the afternoon. Fortunately, the presence of poor mid-
level lapse rates and poor low-level moisture should largely
curtail the threat of frequent lightning with this initial area
of showers. Therefore, there should not be a threat of severe
weather with this activity.

Our potential period of interest for any strong storms will be
during a short window early this evening (~6-9 pm) in the wake
of the afternoons corridor of shower activity. Renewed isolated
to widely scattered shower and thunderstorm development may
occur along the cold front early this evening (~6 pm) as it
begins to shift into northern IL in tandem with the main mid-
level vort. Confidence continues to be low regarding any
potential redevelopment along the front. Nevertheless, the
presence of slightly better low-level moisture (surface dew
points ~50F) and steepening lapse rates within the frontal
boundary supports at least a low (~20%) chance for some
additional storm development. If any storms are able to develop
with the front early this evening, they will be doing so in a
favorable kinematic environment for organized storms.
Accordingly, a low (~5 %) threat exists for an isolated instance
or two of locally strong winds and marginally severe hail. This
threat will quickly wane after about 9 pm this evening as the
front shifts through the area.

Temperatures briefly cool down again following this evenings
cold frontal passage. Breezy northerly winds developing in its
wake persist on Wednesday and the influx of a colder airmass
will result in a return to temperatures in the low to mid 60s
for Wednesday.

KJB

Thursday onward...

Toward the end of the week, the upper-level pattern will
undergo a transition from predominant toughing to quasi- zonal
flow along the US-Canadian border. As a result, the much-
anticipated transition toward warmer weather remains on track to
arrive by this weekend. Will also note an ensemble signal for
rounds of showers and storms in the general region in the May
16-19 timeframe.

Borchardt

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 1238 AM CDT Tue May 12 2026

E/ESE winds under 10 knots at TAF issuance will steadily
increase and veer this morning. While there may be a period of
SSE gusts to 20 knots around and after sunrise, winds are
expected to shift just W of S by 14-15Z at ORD/MDW. Gusts will
continue to increase through the afternoon as deep diurnal
mixing develops. SW winds will frequently gust over 30 knots
through the afternoon, including a period of the highest gusts
around 40 knots mid afternoon. Winds will slightly diminish
early this evening before shifting NW with gusts around 25 knots
behind a cold front late evening and overnight.

While conditions will remain VFR through the period, there
could be a few exceptions. Substantial virga from high-based
SHRA this afternoon may become heavy enough to reach the ground
and produce brief bouts of MVFR visibility and additional strong
gusts. There is also a 10 to 20 percent chance of TSRA with the
cold front mid- evening. Maintained a dry forecast as moisture
availability appears too low for coverage to warrant a mention
in the TAF at this time. Finally, patches of high-end MVFR
ceilings may brush the area to the northeast overnight.

Kluber

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 9 AM this morning to 7 PM CDT
     Wednesday for the IL nearshore waters.

     Small Craft Advisory from 9 AM this morning to 1 AM CDT
     Thursday for the IN nearshore waters.

&&

$$

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