Oswego, Illinois Weather Forecast Discussion

024
FXUS63 KLOT 091926
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
226 PM CDT Tue Sep 9 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 226 PM CDT Tue Sep 9 2025
A broad trough is evident on water vapor imagery early this
afternoon digging southeastward into the Midwest. Several,
smaller vorts are embedded within this broader trough with the
most prominent one over southwest MN/northwest IA. The larger,
parent trough, with embedded vorts, will move across our area
later tonight and Wednesday.
Air mass over our area is quite dry with precipitable water of
only 0.44" on the KILX 12z sounding, which is right around the
daily record min. There is an axis with higher moisture from the
western Corn Belt northeast into the upper Great Lakes, but with
low level flow largely remaining south or even southeasterly,
this axis of greater moisture will struggle to move eastward. As
the upper trough progresses eastward, it will encounter and
increasingly parched air mass. An increase/thickening of mid-
high level cloudiness is expected tonight with cloudiness
lingering into Wednesday. Stronger ascent, likely focused near
the stronger smaller embedded vorts, will likely be enough for
plenty of virga and perhaps some sprinkles reaching the surface
late tonight and possibly into Wednesday. For now confined the
sprinkle chances in the grids to our northwestern CWA later
tonight, but certainly wouldn`t be hard to envision those
sprinkle chances needing to be extended farther east and into
the daytime hours Wednesday.
Temp forecast is a bit tricky with low level thermal fields
favoring temps warming toward if not into the lower 80s, though
extent and thickness of cloudiness could result in temps being
held a few degrees cooler, especially northern/northwestern CWA.
Sunshine returns Thursday and Friday which should allow temps to
climb into the 80s both days, though weak lakes breezes will
keep temps a bit cooler (70s) near the lake both afternoons.
A highly amplified, blocky, and fairly wonky pattern is expected
to develop over North American this weekend with highly
amplified upper ridging over the central part of the U.S. Medium
range guidance has the upper ridge center very near our area,
which favor dry, warm conditions, however, shortwave trough
digging south into the eastern Great Lakes could allow a weak
cold front to move across our area later in the weekend. Can`t
rule out a shower or storm at some point this weekend, but the
vast majority (all?) of the upcoming weekend looks dry and very
warm.
- Izzi
&&
.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1233 PM CDT Tue Sep 9 2025
No significant forecast concerns this period. South/southwest
winds around 10kt will slowly turn more south/southeast late
this afternoon into this evening, with speeds diminishing some
after sunset. Winds will turn back to south/southwest by
daybreak Wednesday morning for most of the area, including the
Chicago terminals, but may remain southeast across northwest IL
and at RFD through midday Wednesday. A lake breeze is expected
to develop Wednesday afternoon and move inland, reaching ORD and
MDW mid/late afternoon. Included this easterly wind shift with
this forecast, but timing will likely need refinement with later
forecasts.
A weak upper level wave will slowly move across the region
overnight into Wednesday bringing a chance of sprinkles and
possibly a few showers. The low levels appear to remain fairly
dry through late Wednesday afternoon. Most areas may just see
some virga. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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NWS LOT Office Area Forecast Discussion