Forrest, Illinois Weather Forecast Discussion

164
FXUS63 KLOT 101908
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
208 PM CDT Wed Sep 10 2025
.KEY MESSAGES...
- Mostly dry weather expected the remainder of the work week
  with a continued gradual warming trend.
- Unseasonably warm with a (less than 30 percent) chance of
  scattered showers and some thunderstorms this weekend.
&&
.DISCUSSION...
Issued at 208 PM CDT Wed Sep 10 2025
An upper level short wave as seen on GOES 19 water vapor
imagery is slowly moving east over northern Illinois. The weak
showers associated with this wave remain over southern
Wisconsin. While these showers are decaying, there remains a
"non-zero" chance for a sprinkle for locations just south of the
state line. But confidence is low given that cloud bases remain
above 10000 feet with drier air underneath which leads more to
virga than anything.
Partly cloudy skies will linger over the area as the wave moves
gradually to the east overnight. Temperatures are expected to
dip down into the upper 50s with areas near the lake and in the
City remaining in the low 60s. As an upper level ridge builds to
the west, dry conditions are expected tomorrow. The warming
trend for temperatures will continue tomorrow as many interior
locations climb into the low 80s in the afternoon. However, with
more persistent, yet light, northeasterly winds, areas along
the lakeshore should remain in the 70s.
The upper level ridge will continue to grow through the weekend
as a pair of upper level lows flank it in southern Canada.
Steering flow aloft will turn back to southwest late in the week
as the ridge grows, allowing 850 mb temperatures to climb
toward 20C by Saturday. There has been a known warm bias in the
GEFS temperatures, but now even recent runs of the Euro ensemble
are suggesting that mean afternoon temperatures southwest of
the city could reach at or just over 90F Saturday, and
potentially Sunday. However, there is still some uncertainty on
how strong the ridge will grow, but also if there are any rain
chances. Models are still suggesting a weak wave will phase
around the upper level low to the east of the ridge that could
provide some rain chances on Saturday. But there is still some
uncertainty as many of the members of the Euro ensemble are
drier. For now, felt no reason to remove the slight to chance
PoPs the NBM provided for the weekend until there is better
agreement in models.
Models are suggesting that on Sunday another upper level trough
will move toward the Pacific Northwest from the ocean and kick
the upper level trough over the Rockies northeastward. There
remains some uncertainty with how these upper troughs may
potentially phase with each other. And while there are some
ensemble members that are suggesting some decaying showers may
pass over/near the area, the amount may not be very impactful as
the period of unseasonable temperatures and drier conditions
prevails into the middle of next
DK
&&
.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1218 PM CDT Wed Sep 10 2025
The main aviation weather concerns for the 18Z TAF period
include:
*Uncertainty in wind trends this afternoon
Light winds have been varying between ESE and SW through the
morning. A lake breeze will move across the Chicago sites and
turn winds E later this afternoon. However, there is uncertainty
in how winds will behave ahead of this front. Best guess is
that we`ll see a gradual backing to SE then to E during the
afternoon. However, there is support for winds to veer closer to
WSW for a period before a more sudden flip to E. Regardless,
magnitude should remain below 10 kt all the while. Then expect E
winds below 10 kt tonight and into Thursday. VFR is anticipated
throughout the period.
Doom
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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NWS LOT Office Area Forecast Discussion