538
FXUS63 KLOT 061944
AFDLOT

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

.KEY MESSAGES...

- Periods of showers and thunderstorms through Saturday morning.
  Some thunderstorms may be strong to severe, especially this
  afternoon and early Saturday morning.

- Areas of dense fog improving from south to north today, ending
  last along the IL Lake Michigan shore.

- Chance for thunderstorms next Tuesday night.

&&

.MESOSCALE...
Issued at 143 PM CST Fri Mar 6 2026

A deep cold pool from this morning`s convection across northern
Illinois has become a focus for an effective warm front early
this afternoon. Latest analysis as of 1pm shows the front
situated from extreme southern La Salle County, to just north of
Kankakee to Valparaiso. While the northward progression of the
front has been quite slow over the past couple hours, clearing
skies should allow the front to gradually mix northward through
the remainder of the afternoon. South of the front, a shallow
cumulus field has developed, with some pockets of locally deeper
growth. A recent strong storm residing on the warm front near
Valparaiso combined with forecast guidance indicates that
surface based inhibition will remain weak through the remainder
of the day. So the main question revolves around when/if any
appreciable forcing will interact with the warm sector to
generate strong/severe convection over the next several hours.

Per satellite/radar trends since last evening, an elongated
ribbon of developing convection over west-central Illinois
appears to have emanated from a small convectively-induced wave
over western Oklahoma early this morning. Over the next few
hours, this cluster of convection should track ENE/NE over
northern Illinois, with the associated forcing possibly
overlapping the warm sector in/around the Illinois River Valley.
In this area, modest MLCAPE and increasing effective deep-layer
shear poses a decent risk for a cluster of organized severe
convection. Storm mode favors bowing segments with damaging wind
and perhaps some discrete and/or embedded supercells with
damaging wind and large hail. While veered surface flow will
limit the tornado risk, any discrete cell that crosses the front
will be capable of producing brief spin-ups.

North of the warm front, including into the Chicago metro, a
higher coverage of convection should remain mostly elevated.
This suggests the primary threat being large hail with discrete
cells and sub- severe gusty winds with any storm.

Kluber

&&

.DISCUSSION...
Issued at 206 AM CST Fri Mar 6 2026

Dense fog continues across much of the area south of I-80 and
then over Lake Michigan and the lakeshore areas. Expecting
gradual improvement from south to north this morning as the warm
from lifts north but this may also allow dense fog to develop
across areas north of I-80 for a few hours before precipitation
arrives later this morning. Overall confidence is low and trends
will need to be monitored. Dense fog will likely persist along
the IL lakeshore for much of the day, finally dissipating later
this afternoon or early this evening near the IL/WI state line.

A large area of thunderstorms extending from southern MN into
far northern MO is expected to continue lifting northeast,
reaching the western cwa around daybreak and then continuing
across the northern two thirds of the area through the morning
hours. Most recent guidance suggests there may be a sharp cutoff
on the southern edge of this precipitation with the southern
third or so of the area possibly remaining mainly dry for today
and if that trend were to pan out, pops would need to be lowered
for this area with later forecasts. As this precipitation
spreads across the area, any remaining dense fog would begin to
lift/dissipate, at least slowly.

The severe threat with this morning`s activity looks to be
fairly low with possibly some isolated large hail being the main
threat during this time period. Locally heavy rain would also be
possible.

There remains quite a bit of uncertainty for additional
thunderstorms as well as coverage this afternoon into early this
evening. The warm front will be lifting north across the area
with favorable conditions for at least isolated severe storms.
It appears the best chances for additional thunderstorms would
be along and north of I-80 but given the uncertainty for how
much will develop have maintained only chance pops during this
time. If thunderstorms do develop, all modes would be possible,
large hail, damaging winds and possibly a tornado. But at this
time, low coverage is expected. This activity would end during
the early evening as the warm front is expected to be north of
the area with a lull in the precipitation expected during the
mid evening.

Additional thunderstorms are expected late this evening into
early Saturday morning ahead of a strong cold that will be
moving across the region and passing across the local area mid/
late Saturday morning. Coverage during this time looks to be a
bit better, perhaps precipitation across most of the area, but
this activity would likely be in the form of a line and moving
fairly quickly. Strong to isolated severe thunderstorms would
also be possible during this time. This activity would be
exiting the local area by mid morning Saturday.

Temps are currently holding steady in the mid 40s for much of
the area, 50 south and then upper 30s near the lake. Temps will
be steadily rising this morning with highs well into the 70s
south of I-80 later today. Temps will likely slow their rise
across northern IL with the expected precipitation through
midday. High temps could be in the late afternoon or even the
early evening in these areas. Temps by Saturday morning may
still be in the upper 50s/lower 60s for most areas and then as
the cold front moves east across the area Saturday, temps will
begin to fall and its possible that temps will be in the
lower/mid 40s by early Saturday evening.

West/northwest winds may gust into the 35-40 mph range with and
just behind the cold front Saturday and the pattern looks to
remain breezy/windy Sunday into Monday with above normal temps
in the 60s Sunday and lower 70s Monday.

Models show another potential storm system for the Tuesday/
Wednesday time period next week with a frontal boundary possibly
across the local area with a large temperature gradient. Showers
along with thunderstorms for at least part of the area would be
possible during this time period. cms

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1203 PM CST Fri Mar 6 2026

- Patchy MVFR/IFR in lingering SHRA early this afternoon,
  otherwise improvement to VFR.

- SSE winds turn S/SSW with some gusts 20-25 kts this afternoon.

- Spotty SHRA/isolated TS possible mid-afternoon into this
  evening, though coverage expected to be low w/o TAF mention
  for TS.

- Period of LLWS expected this evening/overnight.

- Additional waves of SHRA/TSRA late tonight into Saturday
  morning.

- Gusty SW winds 35-30 kt Saturday morning turn WNW in the
  afternoon.

A slow-moving surface low pressure system will lift northeast
from the central Plains across the northern/western Great Lakes
through Saturday. A warm front extending east from the low will
lift north across the terminals late today/this evening. Waves
of showers and thunderstorms (primarily this morning into early
this afternoon, and again late tonight into early Saturday) will
spread northeast across the terminals through early Saturday,
before a cold front pushes east across the area early Saturday
afternoon.

At midday, an area of SHRA/isolated TS continues to lift
northeast across the terminals, in association with a mid-level
disturbance (MCV) lifting into southern WI. Coverage of TS
coverage has already decreased markedly since this morning, and
SHRA are also expected to decrease in coverage by mid-afternoon.
Spotty SHRA/Isolated TS will remain possible from mid-afternoon
into early this evening, though coverage is anticipated to
remain low-enough to support mainly a VCSH mention in the TAFs.
Can`t rule out isolated TSRA at any particular terminal, but
will handle tactically heading into the afternoon/early evening.
TSRA and rain potential then is expected to increase across
MO/IA late this evening, and into northern IL after midnight.
Have maintained prevailing SHRA and prob30 TSRA mentions after
06/07Z as stronger large-scale forcing and a southwesterly 50 kt
low level jet develop. This period of higher precip coverage
looks to persist through/just beyond daybreak Saturday before
tapering off to drizzle/spotty light SHRA.

South-southeast winds across the terminals currently, will shift
southerly early this afternoon as the warm front south of the
I-80 corridor shifts northward. Winds may become a bit breezy
with gusts in the 20-25 kt range mid-late afternoon. South winds
should ease a bit with sunset, though the developing 50 kt SW
low level jet will support LLWS conditions from mid-evening into
the overnight hours. Surface gustiness returns late tonight and
persists into Saturday, with a peak in the 25-30 kt range
Saturday morning/early afternoon. Winds will shift WNW behind a
cold front early in the afternoon.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Dense Fog Advisory until 3 PM CST this afternoon for the IL
     nearshore waters.

&&

$$

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