457
FXUS63 KLOT 162325
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
525 PM CST Sun Nov 16 2025

.KEY MESSAGES...

- Periods of rain late Monday into Tuesday.

- Additional periods of rain/showers are likely Thursday-
  Thursday night, possibly lingering into the start of next
  weekend.

&&

.DISCUSSION...
Issued at 300 PM CST Sun Nov 16 2025

Through Tuesday:

Weak surface high pressure moving overhead tonight into early
Monday coming off the very low dew points this afternoon will
yield good radiational cooling conditions. Leaned towards colder
guidance in favored cool spots of northern Illinois (localized
low 20s), with mid-upper 20s elsewhere except low-mid 30s in
Chicago and near the NW Indiana shore.

Monday will start out calm and dry with clear/mostly sunny skies
giving way to increasing high clouds and then gradually lowering
bases during the afternoon. This will be in advance of a closed
mid-upper low and associated weak surface low pressure tracking
eastward across the Central Plains.

Warm advection aloft will tighten the thermal gradient draped
across the region, with f-gen processes likely resulting in the
development of banded precip into the evening, initially aloft
due to the very dry antecedent lower levels. Some sprinkles are
possible towards sunset for the northwest 2/3 to 3/4 of the CWA.

It will take some time for top-down saturation to fully fight
through the lingering dry air, so steady/measurable precip
coverage may be somewhat spotty until later in the evening. In
addition, due to the antecedent dry lower levels, there may be
enough evaporative/wet bulb cooling for wet snow to mix in
across portions of far northern Illinois, especially during the
evening (or even spotty ice pellets at onset). Well above
freezing air temps and mild ground temps will preclude any
impacts even if wet snow occurs, however.

Increasing large scale forcing will result in widespread light
to at times moderate rain overnight Monday night into early
Tuesday, albeit probably still with some banded component. Some
embedded convective elements are possible near/west of I-39,
though forecast soundings don`t look favorable for any thunder
mention. The footprint of steady rain will probably contract and
focus northeast half or so of the area during the day on Tuesday
as the closed low weakens into an open wave. Lingering light
rain will taper off and end by mid to late Tuesday afternoon as
the system finally exits east. Clouds and periodic rain will
keep temps down in the lower-mid 40s in most spots on Tuesday.

Tuesday Night through Sunday:

Stratus should linger Tuesday night through Wednesday night,
limiting the diurnal temperature ranges, amidst otherwise quiet
weather. The late in the workweek timeframe continues to be the
main period of interest for the next round(s) of rain. Ensemble
guidance has continued to exhibit considerable variability
regarding the overall synoptic evolution, owing to the
trajectory and strength of a short-wave potentially ejecting
northeast from the Southern Plains.

A warm front will lift north on Thursday, probably paired with
increasing shower coverage, particularly during the afternoon,
likely continuing into Thursday night (perhaps with isolated
embedded t-storms). This is when the guidance variability
really lowers forecast confidence, with the ECMWF/EPS suite the
most bullish in bringing the trough into our area into Friday.
Even within the EPS suite, there`s less than half member support
for the strong, slow moving synoptic system depicted on the 12z
operational run. How this all plays out will ultimately
determine if Friday ends up having inclement weather and the
unsettled conditions possibly even hanging on into early
Saturday. The weekend should then end on a dry and seasonable note.

Castro

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 525 PM CST Sun Nov 16 2025

Only real aviation forecast concern is with precipitation
development late Monday. Otherwise, light winds and VFR flight
conditions expected through Monday evening.

Surface high pressure ridge axis from the upper Midwest to the
lower Ohio Valley will drift slowly east across the forecast
area overnight into Monday. The weakening surface pressure
gradient, combined with a very dry air mass, will allow winds to
quickly diminish with sunset this evening. Winds should
generally maintain a light northwesterly direction ahead of the
surface ridge, though they may become light/variable or calm as
the ridge passes overhead early Monday morning. Winds will then
eventually turn light east-southeast later in the day
Monday/Monday evening as the ridge drifts off to the east and
an area of low pressure develops over the Central Plains in
association with an approaching mid-level disturbance.

Mainly clear skies are expected into Monday morning, before
increasing VFR mid level cloud cover spreads east ahead of the
aforementioned disturbance. Can`t rule out a few sprinkles late
in the afternoon/early evening as mid-clouds thicken, though
greater precipitation chances don`t really arrive before mid-
late Monday evening. Initially dry low-levels may support
enough evaporative cooling to allow some wet snow or a few ice
pellets to mix in before things saturate completely, though
above-freezing surface temps should prevent any impacts at the
surface. Have introduced PROB30s for the last couple hours of
the ORD/MDW 30-hour forecasts for precip onset, though a
prevailing mention will likely be needed beyond 06Z Tues.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 10 PM CST this evening for Winthrop
     Harbor IL to Gary IN.

     Small Craft Advisory until 9 AM CST Monday for Gary to Burns
     Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

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