Greenwood Cemetery Illinois Weather Forecast Discussion

413
FXUS63 KLOT 080759
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
259 AM CDT Wed Oct 8 2025
.KEY MESSAGES...
- Patchy frost expected tonight in typically colder, rural
  locations, especially across northwest Indiana
- Generally dry with seasonable temps through the upcoming
  weekend.
&&
.DISCUSSION...
Issued at 259 AM CDT Wed Oct 8 2025
Weak secondary cold front is moving across the area early this
morning. Lake effect stratocumulus has developed over the lake
in the wake of this boundary and is heading for the NE IL
shoreline. Water vapor imagery shows the upper trough axis
moving east of Lake Michigan now, with forecast soundings
showing crashing inversion heights this morning over the lake.
Given the lack of any showers now and conditions progged to grow
less favorable with time, no plans to introduce any lake effect
showers and sprinkles. Still expect lake effect stratocumulus
to stream in off the lake into NE IL this morning, possible
going mostly cloudy at times near the lake. Should see lake
cloudiness decrease this afternoon as land-lake stability flips
diurnally.
Clear skies (except perhaps some lake effect cloudiness
developing near the NE IL shore) and light winds tonight should
set the stage for strong radiational cooling. The typically
colder outlying, wind protected areas should see lows dip into
the mid 30s, which should set the stage for some frost tonight.
Northwest Indiana, away from the lake, will probably see some
of the coldest temps and best chance of frost given their
proximity to the sfc ridge. Have expanded the mention of frost
in the grids and suspect that the day shift may need to consider
a frost advisory for portions of our area tonight, particularly
our NW IN counties.
Attention then turns to the northwest flow clipper-like system
progged to dive southeastward into the western Great Lakes late
Friday into Friday night. The run-to-run swings in the
operational GFS and ECMWF in their handling of this system have
been quite dramatic over the past few days. Possibly due to the
system being onshore and better sampled by the upper air network
over Alaska and northwest Canada, the past few runs of the GFS
and ECMWF have been more locked into a much more vigorous,
compact closed mid-upper level low diving into the Great Lakes.
There`s still variability in the track and to a lesser extent
the intensity of this system, which plays a role into whether it
will bring any shower threat to our CWA or whether showers
remain to our north. In addition, this more vigorous closed low
is more likely to result in another re-enforcing shot of cooler
air this weekend. The time-lagged nature of the NBM still has
temps pretty warm this weekend, particularly Sunday, but if
latest model trends persist, then forecast temps for Sunday will
need to be lowered, possibly by 10F+.
Pretty fascinating and complicated evolution to the pattern over
the central and eastern U.S. over the weekend into next week.
Our vigorous clipper is one of the key players, the other being
the progged development of an extratropical coastal cyclone off
the East Coast. Medium range models, with pretty good support
from their respect ensembles, show the vigorous Great Lakes
clipper phasing with the coastal cyclone and becoming a massive
cut-off cyclone with the development of a blocking pattern
across North America. Medium range guidance tends to struggle
mightily with blocking patterns and with phasing cyclones, so
forecast confidence heading into next week is lower than
average, particularly with the placement of the key features.
Current ensemble means suggests we could be under an
unseasonably warm upper ridge much of next week, but any
westward shift in these features could lessen our chances of
another big warm spell.
- Izzi
&&
.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1225 AM CDT Wed Oct 8 2025
Main Items of Note:
- Timing of wind shifts to north and then northeast at ORD and
  MDW this morning.
- Low chance for a period of MVFR CIGs this morning.
Another overall quiet 24-30 hours is in store. A secondary cold
front passage will shift winds to northerly prior to sunrise,
with some uncertainty on timing. Lake influence will cause winds
to go over to northeast sometime in the mid to late morning,
persisting into or through the evening. Lake effect clouds,
primarily VFR, should develop as well, though can`t completely
rule out a short window of 2000-2500 ft MVFR CIGs near the lake.
Castro
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 3 PM CDT this afternoon for the IL
     and IN nearshore waters.
&&
$$
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NWS LOT Office Area Forecast Discussion