Weavers Weather

960
FXUS63 KLOT 011923
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
223 PM CDT Sat Nov 1 2025

.KEY MESSAGES...

- A few showers will dot the landscape through this evening,
  especially in the Chicago metro area.

- After tonight, mostly dry conditions are expected through
  middle of next week with fairly seasonable temperatures.

&&

.DISCUSSION...
Issued at 223 PM CDT Sat Nov 1 2025

Looking at water vapor imagery this afternoon, attention is
immediately drawn to the large mid- upper level low over the
mid-Mississippi Valley. While the center of the upper low is
just west of our area, the pocket of cold air aloft has allow
for spotty diurnal showers to flare up this afternoon with even
a report of some graupel. This activity is expected to fade with
sunset, however a shear axis extending east-northeast from the
center of the upper low is draped across southern WI and across
central/southern Lake Michigan. There is a slightly greater
concentration of isolated-scattered showers associated with this
feature, which is progged to move south across our area tonight.

Guidance generally depicts a weakening of this shear axis, which
combined with loss of diurnal heating, should lead to a decrease
in the coverage of shower activity through the evening hours as
it shifts slowly south into into northern IL. One possible
wrench in this trend is the presence of a weak mesolow over
southern Lake Michigan which is embedded within a broader weak
sfc trough stretching west from the mesolow across IL-WI border.
The mesolow could lead to some enhanced convergence near this
trough this evening, which could allow for a slightly greater
coverage of showers lingering past sunset across the Chicago
metro area closer to the influence of the mesolow.

The entire mid-upper level low and trough will move well
southeast of the area Sunday and be replaced by a zonal flow
across the Lower 48 through much of the upcoming work week.
While there will be some northern stream troughs rippling
quickly eastward through the fast zonal flow this week, the
brunt of the forcing with these waves are progged to remain
north of our CWA. This should result in occasional, likely
moisture starved cold fronts moving across our area with rather
mild Pacific air in the wake of these fronts. There will likely
be some slight fluctuations in temps during the upcoming week
associated with these fronts, but in general look for near to
probably trending slightly above average temps during the
upcoming work week.

There are indications that a more amplified trough could
approach late in the week into next weekend potentially bringing
with it some better rain chances, but that is still a long way
off, so the modest chance (20-40%) pops from the NBM look plenty
reasonable at this distance.

- Izzi

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1226 PM CDT Sat Nov 1 2025

Key messages for the 18Z TAF period:

* Occasional MVFR cigs possible at DPA and RFD this afternoon

* A southward push of lake-induced showers in the vicinity of
  the Chicagoland terminals this evening and tonight with
  associated MVFR and squirrelly winds possible

A plume of lake-induced showers is very gradually inching
southward from the MKE area down the western lakeshore. Showers
are expected in the vicinity of ORD by this evening and are
likely to remain nearby through most of the night. Coverage may
extend as far west as RFD before being mostly confined to
lakeside counties later this evening. The signal for precip is
strongest at ORD while model guidance favors most rain coverage
holding just east of MDW. Nonetheless, intermittent showers will
be possible at MDW as well. Cigs and vis may get dragged down
to MVFR with these showers. Rain should come to a close prior to
daybreak.

W winds this afternoon will veer to NNW this evening and should
gradually fall back to W overnight and then onto SW for Sunday.
It`s possible though that, with the showers and associated
convergent axis nearby, wind direction could get pretty erratic
for a few hours while remaining largely below 10 kt.

Doom

&&

.MARINE...
Issued at 223 PM CDT Sat Nov 1 2025

Mesolow, located about 30 NM southwest of Grand Haven, MI, over
southern Lake Michigan this afternoon will push gradually south
through tonight. Scattered-numerous lake effect showers continue
across central and southern Lake Michigan due to the strongly
unstable marine boundary layer and enhanced convergence with
this mesolow. Recent radar trends would suggest a perhaps
somewhat more outflow dominant east-west oriented convergence
axis pushing south and about to enter into our waters.
Certainly couldn`t rule out waterspouts associated with that
activity, but suspect the better waterspout potential over
our waters will be this evening as convergence increases in
response to nocturnal strengthening of land breeze circulation.

Some lake effect showers could continue after midnight,
particularly if the mesolow gets left behind over southern
portions of the lake as some high-res guidance suggest. While
the shower threat may continue after midnight, the waterspout
potential should decrease quickly after midnight as inversion
heights/lake induced equilibrium levels begin to crash in
response to the departure of the upper low/trough.

Have issued a MWS (marine weather statement) to highlight the
waterspout potential this evening. Special marine warnings may
be needed if radar trends and/or spotter reports suggest an
increased likelihood of waterspout activity.

- Izzi

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 3 PM Sunday to 10 AM CDT Monday for
     the IL nearshore waters.

     Small Craft Advisory from 6 PM Sunday to 10 AM CDT Monday for
     the IN nearshore waters.

&&

$$

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