711
FXUS63 KLOT 061959
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
259 PM CDT Tue Oct 6 2026

.KEY MESSAGES...

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

&&

.DISCUSSION...
Issued at 259 PM CDT Tue Oct 6 2026

A cold front will drop through the area from northwest to
southeast early tomorrow. The 12Z runs of the moist-biased NAM,
NAM Nest, and NSSL-WRF all try to spit out some rain in our area
as the front and an associated shortwave roll through tomorrow
morning. However, the lack of more appreciable mid-upper-level
cloud cover or any real signs of virga over North Dakota at this
hour suggest that these models are overestimating the strength
of this shortwave and the amount of moisture associated with it.
The model guidance that has a better handle of what`s currently
going on over North Dakota maintains precipitation-free
conditions along the front as it tracks through our forecast
area, so a dry frontal passage is still expected tomorrow. While
modest cold air advection will occur off of northwesterly winds
behind the front, relatively deep post-frontal mixing and
mostly sunny skies should nevertheless support high temperatures
tomorrow that will be near or slightly higher than today`s
highs in the mid 70s to low 80s (warmest in our southern
counties).

Cooler high temperatures in the mid 60s to mid 70s are
ultimately expected on Thursday amidst dry conditions as modest
northwesterly to northerly winds persist and the heart of the
cooler air mass and an attendant surface high settle into the
region. Similar to slightly warmer temperature readings are then
favored again during the daytime on Friday as southerly return
flow becomes established over the region. There remains a signal
in ensemble guidance for warm air advection/isentropic ascent
to induce some showers or sprinkles in the region on Friday as
mid-level lapse rates steepen modestly. However, there is still
not much consistency with where this precipitation may occur,
and dry low-mid air is also a factor that precludes higher
confidence in the occurrence of measurable rainfall here on
Friday. The latest NBM`s mentionable PoPs remain displaced just
to our north and northwest, and this still looks reasonable for
now.

Persisting warm air advection off of southerly winds will lead
to warmer temperatures on Saturday, with low-mid 80s high
temperatures looking likely across a good chunk of our forecast
area amidst sunny or mostly sunny skies. The forecast for Sunday
remains more up in the air, in large part due to considerable
uncertainties over how a tropical disturbance (invest 92L) in
the Gulf will evolve in the coming days. Broadly speaking, this
disturbance is expected to become an organized tropical system
before making landfall along the Gulf Coast and encountering a
broad upper-level trough. Its remnants and the associated
tropical moisture will initially surge northward before turning
northeastward towards the Mid-Atlantic/New England. How quickly
this northeastward turn occurs will dictate whether any
associated rain gets into our forecast area, which, in turn,
will also have an influence on temperatures for Sunday. While
most Grand Ensemble members still favor this activity remaining
to our southeast, ensemble support for a solution where rain
gets into at least our southeastern counties has steadily
increased over the past few model cycles. The latest NBM came in
with chance PoPs across our southeastern CWA as a result, but
if this northwestward trend continues to garner more support,
then these PoPs may need to be increased and/or expanded
further.

Ogorek

&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1229 PM CDT Tue Oct 6 2026

The only minor aviation forecast concerns are with breezy
southwest winds this afternoon, and a marginal LLWS setup
overnight.

Surface high pressure continues to drift off to the east of the
region at midday, while a cold front approaches slowly from the
northwest across MN. In between these features, a tightening
surface pressure gradient will result in southwest winds
becoming increasingly breezy, gusting near 25 kts during the
mid-late afternoon hours. Surface winds will decrease with the
approach of sunset early this evening, while a 35-40 kt low-
level jet develops aloft. With surface winds likely remaining in
the 6-10 kt range overnight, this will set up only marginal
LLWS conditions and have not included in the TAFs. The peak
low-level jet speeds (near 40 kts) would be in the 02-08Z time
frame. Surface winds will eventually shift northwest near 10 kt
Wednesday morning, as the surface cold front moves through the
area.

Otherwise, the air mass remains quite dry across the region and
only some patchy VFR cloud cover is expected through the period.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 7 PM CDT this evening for the IL
     nearshore waters.

&&

$$

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