180
FXUS63 KLOT 061126
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
626 AM CDT Sun Sep 6 2026

.KEY MESSAGES...

- Moderate Swim Risk this morning at Illinois Lake Michigan
  beaches.

- Seasonably warm conditions today and Monday, although cooler
  and more comfortable than recent days.

&&

.DISCUSSION...
Issued at 220 AM CDT Sun Sep 6 2026

Conditions are nice and quiet out there this morning as we`re
off to a mild start to our Sunday. Relatively cooler, but still
seasonably warm, weather is in store for today following a
stretch a hot, humid conditions. High temperatures are forecast
in the lower 80s today away from the lake and middle to upper
70s closer to the lakeshore. Dewpoints are still hanging out in
the upper 60s this morning, but steady dry advection from high
pressure building in from the northeast should pull dews down
into the upper 50s by late this afternoon. This means we`re not
looking at much of a heat index factor today and conditions
should feel close to what the thermometer reads.

Breezy ENE winds over the lake have gradually been subsiding
through the night and waves have responded similarly. Moderate
wave action will likely be present at Illinois beaches through
the morning which could make swimming hazardous for those who
aren`t strong swimmers. So we`re advertising a Moderate Swim
Risk to start the day at Illinois beaches, although conditions
will be easing through the day. Conditions look generally
favorable for Labor Day tomorrow, but keep in mind high
temperatures are forecast in the 70s both today and tomorrow
along the lakeshore, maybe close to 80 tomorrow at Indiana
beaches.

Similar to today, temperatures for Labor Day are forecast in
the lower 80s away from the lake. High pressure over the
northern Great Lakes will keep rain chances away and bring
mostly sunny skies.

During the middle of the week, a tighly-wound upper low will
track east across Ontario and a cold front will get dragged
across the area sometime Wednesday bringing our next opportunity
for rain and thunderstorms. Temperatures should trend up again
beginning on Tuesday in anticipation of this system with highs
forecast in the middle and upper 80s on Tuesday and Wednesday.
There remains a great deal of uncertainty regarding this system
from the timing of the frontal passage to the ambient
environment near the front. Lapse rates aloft look generally
poor as the cooler mid level air looks to stay wrapped up in the
upper low to the north, and a prominent high across the SE US
may also impinge on low level moisture feed ahead of the front
further constraining instability. There will also be a diurnal
factor to consider but is not yet clear. Considerable spread
exists even within individual ensemble system regarding the
thermodynamic environment. The Euro and GFS also have quite
different ideas on the kinematic environment around the front,
so it`s unclear what quality of shear or kinematic forcing we`ll
have to work with, but the more supportive shear should also
focus to our north near the base of the upper low. The more
bullish scenarios do support a marginal severe threat for
Wednesday, so something to keep an eye on over the next few
days.

The main upper trough axis will swing over early Thursday and
drive a secondary cold front across the area, but layer moisture
looks to get shunted to our south after Wednesday and precip
potential currently looks low during the day on Thursday. Behind
the departing trough, a series of shortwave impulses traversing
a generally zonal upper flow pattern will drive sporadic rain
chances through next weekend with a larger synoptic system
favored by medium range guidance to traverse the region in the
late Sunday-Monday window.

Doom

&&

.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 626 AM CDT Sun Sep 6 2026

Some patch low end MVFR to high end IFR CIGS will blow in off
the lake this morning, potentially leading to brief CIGS at MDW
and a slight chance into ORD. These CIGS are likely to scatter
out and dissipate by mid morning.

Elsewhere, a bank of LIFR CIGS and dense fog has developed over
northern IL to the southeast of RFD and northwest of DPA. This
bank of low clouds and fog is slowly moving westward and could
have some impacts into RFD before diminishing diurnally this
morning. Opted to maintain a TEMPO for DPA for MVFR VSBY given
the low T/Td spread, but chances for MVFR seem to be waning
quickly.

Otherwise, expecting mostly VFR conditions with east or
northeasterly winds through the TAF cycle.

- Izzi

&&

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

&&

$$

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