920
FXUS63 KLOT 072338
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
638 PM CDT Thu May 7 2026

.KEY MESSAGES...

- Occasional chances for scattered rain showers will continue
  into next week.

- Temperatures will gradually warm through Saturday before
  trending cooler early next week.

&&

.DISCUSSION...
Issued at 111 PM CDT Thu May 7 2026

Expansive upper-level cyclonic flow remains entrenched across
the Upper Mississippi River Valley, which is leading to a
continuation of the generally cool and, at times, showery
pattern. An upper-level shortwave propagating around the outer
periphery of the cyclonic flow continues to pivot southeastward
across the area this afternoon, which with steep lapse rates
(500mb temperatures sampled near -28C on the 18Z DVN RAOB), is
supporting widely scattered showers at press time. The highest
coverage of showers through the afternoon and evening should
generally favored near and south of I-80 (near a remnant
boundary) and near the Wisconsin state line (near the core of
the coldest mid-level temperatures). Southwest winds will
remain gusty (30 to locally 40 mph) this afternoon, especially
near showers where the deep layer of dry sub-cloud air will lead
to efficient downward momentum transfer.

Tonight, coverage of showers should tend to favor areas south
of Interstate 80 as additional subtle DCVA rides atop the
aforementioned frontal boundary. A gradient in cloud cover will
set the stage for a gradient in overnight lows, with values
expected to fall toward the mid to upper 30s near the Wisconsin
state line to the upper 40s near US-24. Patchy frost formation
will be favored north of Interstate 88 and especially near the
Wisconsin state line, though will withhold a Frost Advisory
given the expectation for upper-level clouds to thicken toward
daybreak (which may stall the downward dive in temperatures).

Tomorrow, another upper-level shortwave will pinwheel through
the upper-level cyclonic flow and support the development of
showers and perhaps a thunderstorm along the stalled frontal
boundary. Forecast guidance continues to exhibit spread in the
location of the boundary by tomorrow afternoon, though have
noted a slight southward trend in the latest guidance. As a
result, will paint low-end chance (20-40%) PoPs south of I-80
tomorrow, with the highest values near US-24. Elsewhere, partly
cloudy skies and a modest push of low-level warm-air advection
will help boost highs into the mid to upper 60s. Yet another
upper-level shortwave will move across the region on Saturday,
presenting another opportunity for a few showers. Temperatures
on Saturday look to be the warmest of the past few days with
highs in the upper 60s (north) to mid 70s (south).

Another reinforcing shot of seasonably cool air will follow the
front Saturday night and result in a swift return to somewhat
below average temperatures Sunday into the beginning of next
week. With that said, ensemble guidance continues to advertise a
strong signal for a notable warming trend by the May 16 to 17
timeframe, which is in line with climatology.

Borchardt / Izzi

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 638 PM CDT Thu May 7 2026

Aviation forecast concerns for the 00Z TAFs:

- Scattered SHRA dissipating early this evening, mainly
  impacting GYY prior to about 01Z.

- Somewhat low confidence in near-term wind directions early
  this evening, due to prior convective outflow/old lake breeze
  boundary. Should see winds trend light westerly or just
  variable later this evening.

- Light south winds expected Friday. Can`t rule out a lake
  breeze affecting ORD/MDW late in the afternoon, though not
  much guidance support for reaching these airports at this
  time.

Outflow from convective showers/isolated thunderstorms and
interaction with the old lake breeze boundary has made for a
messy wind field across the terminals as of early this evening.
While synoptic flow should support generally west winds, areas
north of ORD still maintaining light east-southeast winds as of
23Z. TORD TDWR depicts a west-east boundary along the Lake/Cook
county line which could sag south into ORD, though confidence is
somewhat low in this with the loss of most of the convection
over the past 1-2 hours. Will keep an eye on this, with the
expectation that if winds do briefly shift E/NE it would be
temporary with a shift back to light west later this evening.
Light west or just light/variable winds are then expected
overnight into early Friday. By mid-late Friday morning, modest
south winds (potentially varying from 160-200 degrees) are
expected. Some high-res guidance (mainly the 18Z HRRR) indicates
a late afternoon lake breeze may affect ORD/MDW, though there is
little support for an easterly wind shift in remaining guidance
and thus low confidence that lake breeze will affect these
terminals at this time.

Otherwise, any lingering showers early this evening (primarily
affecting GYY) should continue to decay/move east of the area
by around 01Z. Showers on Friday are expected to remain south of
the terminals.

Ratzer

&&

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

&&

$$

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