772
FXUS63 KLOT 130457
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1157 PM CDT Thu Sep 12 2024

.KEY MESSAGES...

- Summer-like daytime warmth continues.

- Persistent dry weather will maintain a heightened threat for
  grass and brush fire starts.

- Scattered showers possible at times mainly well inland through
  the weekend, though chances of widespread beneficial rain will
  remain low.

&&

.DISCUSSION...
Issued at 204 PM CDT Thu Sep 12 2024

Through Friday Night:

High-level cloud cover will begin to increase across the area
tonight as the tropical remnants of Francine gradually pivots
north-northwestward into northeastern AR while weakening.
Continued weakening of the system is anticipated on Friday as the
center circulation becomes quasi-stationary for a period over AR
before gradually sliding back to the east into parts of
northern MS and southwestern TN into Saturday. Unfortunately,
persistent easterly low-level trajectories north of the system
across our area will not be favorable for advancing the deeper
moisture far enough northward into our area to support in any
meaningful precipitation. For this reason, no more than a few
light showers are possible (~20% chance) across my far southern
counties through Friday night, though most will remain dry.
Nevertheless, expect more high-level cloud cover overhead on
Friday. Temperatures with the increased cloud cover will likely
end up a couple of degrees cooler than today, with the coolest
readings in the upper 70s to low 80s expected near the Illinois
shore, and across the far southern CWA. East-southeasterly winds
will gust up to 20-25 mph.

KJB


Saturday through Thursday:

Forecast thinking during this period has not changed.

Guidance continues to suggest that Francine`s remnant circulation
will become cut off from the mean flow and will begin to meander
across the Tennessee Valley this weekend. While several peripheral
vorticity spokes around the northern fringes of the circulation
will translate across the region, overall large scale forcing for
ascent is expected to remain only modest on Saturday and Sunday.
The deepest tropospheric moisture is also forecast to slosh mainly
to our west and south over the weekend. As a result of all of
this, while there will be some chances for showers over the
weekend, the highest coverage is expected focus the farther south
and west across the CWA you go. Many locales across our northeast
Illinois and northwest Indiana counties will probably remain
dry this weekend and into Monday.

Through the middle of next week, global guidance shows another
very dry airmass pushing westward across the Ohio River Valley and
into the Lower Great Lakes region. Both the GFS and ECMWF
advertise near -20 to -30 C dewpoints at 700 mb with this airmass.
At this point, the combination of the parched atmospheric column
and most disturbances suppressed to our south and west suggest
mainly precipitation-free conditions will continue.

Carlaw/KJB

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 1157 PM CDT Thu Sep 12 2024

There are no aviation concerns through the TAF period. Generally
easterly winds and SCT to occasionally OVC cigs at 30kft will
prevail.

Borchardt

&&

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

&&

$$

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