510
FXUS63 KLOT 052018
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
318 PM CDT Mon Oct 5 2026

.KEY MESSAGES...

- Near to above normal temperatures with predominantly dry
  conditions are expected through much of this week.

&&

.DISCUSSION...
Issued at 318 PM CDT Mon Oct 5 2026

Dry conditions are expected to persist into tomorrow as a
sprawling ~1025 mb surface high continues to exert its influence
across the region. The surface pressure gradient will tighten
as the center of this surface high repositions itself to our
east and a ~996 mb surface low tracks from northern Manitoba
into northern Ontario with an associated cold front pressing
southeastward towards the Great Lakes. This will yield breezy
southwesterly flow here tomorrow -- primarily across the
northern half of our forecast area, where some gusts into the
25-30 mph range are likely during the afternoon. The same dry
air mass that has allowed for air temperatures to overperform
most raw model guidance today will remain in place for tomorrow,
suggesting that a similar theme of overperforming temperatures
will be followed for yet another day. Accordingly, our gridded
forecast for tomorrow contains high temperatures in the low-mid
70s that fall in the upper echelon of available forecast
guidance.

The aforementioned cold front will track across our forecast
area early Wednesday, though it won`t really seem like much of a
cold frontal passage as relatively deep post-frontal mixing
into drier air aloft should largely offset the modest post-
frontal cold air advection. When coupled with mostly clear
skies, high temperatures on Wednesday actually look like they
will be slightly warmer then Tuesday`s highs and could even
reach the low 80s across our southern CWA, in spite of the
frontal passage. Cooler high temperatures in the mid 60s to mid
70s are ultimately expected on Thursday as modest northwesterly
to northerly winds persist and the heart of the cooler air mass
settles into the region. Similar temperature readings are then
favored again on Friday before strengthening south to
southwesterly low-level flow helps facilitate another warm-up
into this weekend.

With a dearth of moisture accompanying Wednesday`s frontal
passage and surface high pressure settling back into the region
thereafter, no precipitation is expected on Wednesday or
Thursday. There remains a signal in ensemble guidance for some
combination of a low-amplitude shortwave, isentropic ascent,
weak frontogenesis, and somewhat steepened mid-level lapse rates
to come together and induce a wave of showers or sprinkles
somewhere in the region sometime in the Thursday night into
Friday time frame. However, there isn`t much spatiotemporal
consistency with this at this time, and even if things were to
come together just right to support precipitation in our
forecast area during this time frame, the persisting parched
low-mid-level air mass would likely play some role in limiting
the amount and/or the spatial footprint of any measurable
precipitation.

Ensemble guidance then supports precipitation-free conditions
across our area on Saturday and mostly favors those conditions
continuing into Sunday at this time. Will note that there is
some potential for deeper moisture associated with a tropical
disturbance currently over the Bay of Campeche to be approaching
our latitude come Sunday, though there is still a high degree
of uncertainty at this point with how that tropical disturbance
will evolve and whether its associated moisture will eventually
be advected in the general direction of the Great Lakes or be
pulled more northeastward towards the Mid-Atlantic.

Ogorek

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1223 PM CDT Mon Oct 5 2026

VFR conditions are forecast through the period. Light and
variable winds will turn NE to E up to 10 kt behind a weak lake
breeze at the Chicago terminals within the next hour or two.
Winds gradually veer SE into this evening and overnight under
10 kt then to a SSW direction after daybreak, with gusts into
the lower 20 kt range developing by mid to late morning.

Petr

&&

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

&&

$$

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