NWS Chicago Decision Support Briefing - Forecast

958
FXUS63 KLOT 061852
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1252 PM CST Fri Nov 6 2026

.KEY MESSAGES...

- Lake effect rain showers may periodically affect portions of
Porter County, IN through this evening.

- Below freezing temperatures are expected across a large
portion of northern Illinois tonight. Near or below freezing
temperatures may then be observed once again Saturday night
and Sunday night in some locations.

- Dry conditions and a warming trend are expected this weekend
into early next week.

&&

.DISCUSSION...
Issued at 1252 PM CST Fri Nov 6 2026

The coldest airmass so far this season over the area has led to
temps struggling to rise out of the mid 40s early this
afternoon, with 50 degrees looking to be out of reach for a vast
majority of the area. With a surface ridge drifting toward the
area from the west, limited non-diurnal cloud cover upstream,
and cool daytime temps, we are well on our way to the coldest
night and first hard freeze for many this fall. Do have some
concern that shallow stratus attempts to expand inland off Lake
Michigan this evening, but lowering inversion heights through
the night should erode any potential lingering stratus
overnight. Overall, temps tonight are expected to fall into the
mid to upper 20s away from the core of the Chicago metro and
northwest Indiana downwind of Lake Michigan. In colder areas
tonight, shallow fog may develop in lieu of heavy frost.
Otherwise, isolated lake effect rain showers will persist into
mainly northern Porter County through early evening before
exiting to the east.

A series of weak mid-level troughs and ridges within broader
WNW flow aloft will cross the northern Great Lakes through early
next week, leading to precip-free conditions and daytime highs
gradually moderating back to the low to mid 60s Monday and
Tuesday.

Consensus ensemble guidance suggests that an increasingly
amplified mid-level pattern with hints at a developing omega
block will develop across much of North America late next
week/weekend. The eastern trough of this pattern does show signs
of settling over the Great Lakes region during this period.
With the main ridge situated in a SSW to NNE orientation into
Hudson Bay, seasonably cool temps and north to northeast low-
level flow will support periods of lake effect rain showers
aimed into both northwest Indiana and northeast Illinois. Cannot
fully rule out our first snow flakes of the season given some
ensemble members supporting a more westward presentation of the
trough and corresponding colder airmass. Will need to keep a
close eye on any trends toward colder solutions as early as
Thursday morning but especially into Friday.

Kluber

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1114 AM CST Fri Nov 6 2026

Patchy MVFR stratocumulus clouds (based between 2000 and 2500
ft) will continue through the afternoon as a low-level cold pool
tied to a strong fall vort max slides overtop the warming
boundary layer. Clouds may dissipate after sunset as the
backside of the cyclonic shear axis (inside of core of the vort
max) shifts eastward, though can also see any remaining clouds
getting trapped beneath a lowering inversion. Will maintain an
end time of MVFR 06Z at most terminals and let trends dictate
AMDs.

Winds will remain out of the west-northwest through the entire
TAF period. If clouds do clear tonight, a more westerly
component (270 to 300 deg) may be observed at MDW/ORD overnight in
response to the development of a land breeze circulation.

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 3 AM CST Saturday for the IL
nearshore waters.

Small Craft Advisory until 3 PM CST Saturday for the IN
nearshore waters.

&&

$$

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