Weavers Weather

000
FXUS63 KLOT 291105
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
505 AM CST Mon Dec 29 2025

.KEY MESSAGES...

- Strong winds will gradually ease today.

- Wind driven light snow will end this morning, though flurries
  may linger into the afternoon.

- Some light snow or flurries are possible Tuesday, with a
  slightly better chance of light snow Wed afternoon and
  evening.

&&

.DISCUSSION...
Issued at 333 AM CST Mon Dec 29 2025

Powerful cyclone responsible for the active weather over the
last 24 hours has moved to Lake Huron and deepened to around 980
mb as of 09z. Water vapor imagery early this morning shows a
well defined vort max over Wisconsin, embedded within the
broader large mid-upper level cyclone. Ascent associated with
this WI vort has been resulting in fairly widespread light snow
across WI into northern IL early this morning. Light snow of
varying intensity is likely to continue early this morning,
ending from the northwest after sunrise. Guidance has this light
snow ending between 12-15z this morning as the shortwave over
WI shifts southeastward, with the associated synoptic ascent
moving east of the area. Rough extrapolation of the back edge
of the snow matches the timing in guidance pretty closely,
adding some confidence to the snow ending this morning. Earlier
QPF guidance appears to have been running a bit high, it appears
as though accumulations should generally end up in the inch or
less range, highest north of I-88/I-290. Despite the expected
meager snowfall amounts, road impacts are likely this morning,
so plan to continue the advisory through early this morning.

Surface low is progged to continue deepening to below 980mb this
morning, but as it moves farther northeast into Quebec, the
pressure gradient is expected to ease today. The frequency of
45+ mph gusts is likely to begin waning by mid morning with
gusts expected to be generally below advisory criteria by 18z,
if not earlier, so will be pushing the ending time of the
wind advisory up to 18z.

Expansive stratus deck blankets the upper Mississippi Valley and
Midwest and should stick around today and likely into much of
tonight as well. Temperatures within the stratus deck should
generally be at or below -12C, so ice nuclei will be present and
could allow for a few flurries at times today and perhaps into
tonight. Have maintained the chance of flurries in the wake of
the light snow today. Day shift to reassess and determine if
flurries chances are needed for tonight as well.

Winds are progged to veer more northwesterly this morning in the
wake of the aforementioned shortwave trough, which could allow
for lake effect snow showers to back into northeast Porter
County. At this point, it looks like 1-3" of snow would be the
most likely worst case scenario for far northeast Porter
County.

Guidance does bring a quick moving northwest flow shortwave
zipping through the region Tuesday afternoon. It does look like
this could result in some light snow or flurries. Didn`t adjust
NBM pops at this time, but plausible that snow chances may need
to be increased for a potential coating of snow Tuesday for
mainly northeast portions of our CWA.

A somewhat more formidable shortwave will move across the
region Wednesday afternoon and evening. ECMWF has been the most
consistent in bringing some light snow to the region in
association with this disturbance, but the GEFS guidance has
been trending higher in measurable precip chances. A thermally
indirect circulation in the left region of a 140 kt jet diving
into the Midwest could lead to some enhanced low-mid level
frontogenesis helping support some slightly better snow chances.
NBM PoPs seemed too low given the increasing model agreement
and EPS and GEFS measurable precip chances, so did adjust NBM
PoPs up 10-15%. If models remain consistent, then additional
increases in PoPs can be expected in the coming days. It
generally isn`t looking like a big snow event, but it doesn`t
take a lot of snow to cause travel issues and these f-gen
enhanced snow bands can be sneaky and overproduce at times, so
something to keep an eye on for New Year`s Eve day and evening.
Brief shot of cold air is expected in the wake of that system,
followed by a bit of moderating trend for temperatures over the
weekend and into next week.

- Izzi

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 505 AM CST Mon Dec 29 2025

Key Aviation Messages for the current TAF period:

- Snow and blowing snow creating IFR/LIFR vis (with MVFR cigs)
  through mid morning. Flurries may continue through the rest of
  the day.

- Strong west-northwest wind gusts over 30 knots will continue
  this morning, gradually diminishing in the afternoon. Wind
  gusts are expected to end this evening.

- MVFR cigs are expected through tonight before VFR conditions
  tomorrow morning.

Snow showers are passing over the air space creating IFR vis
and MVFR cigs, with localized LIFR vis during the heavier
intensity snow showers. Winds remain out of the west with gusts
over 35 knots creating blowing snow at the surface. These
conditions are expected to continue for the next couple of
hours. The heavier snow showers should move off to the east, but
with cloud temps as cold as they are, it would not be
surprising for flurries to linger around through much of the day
but without any visibility restrictions.

The westerly wind gusts will slowly become more northwesterly
later this morning. Gusts over 30 knots are expected into the
afternoon, but the magnitude will gradually diminish through the
day. Gusts over 20 knots should continue through this evening
before eventually cutting off.

MVFR cigs are expected to linger through the day. Guidance is
trending more skeptical on clearing, so kept MVFR cigs through
the overnight period with a return to VFR delayed until Tuesday
morning.

DK

&&

.MARINE...
Issued at 505 AM CST Mon Dec 29 2025

No changes made to marine headlines this morning. Michgian City
is getting sustained winds near storm force with peak measured
gusts so far to 57kt the Harrison-Dever Crib has storm force gusts
to to 51kt. Storm force winds/gusts will likely continue for
early this morning, especially over the open lake and Indiana
nearshore waters. Winds should begin to gradually ease later this
morning and this afternoon.

- Izzi

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory until noon CST today for ILZ003-ILZ004-ILZ005-
     ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-
     ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-
     ILZ106-ILZ107-ILZ108.

     Winter Weather Advisory until 10 AM CST this morning for
     ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ011-ILZ012-ILZ103.

IN...Wind Advisory until noon CST /1 PM EST/ today for INZ001-
     INZ010-INZ011-INZ019.

     Wind Advisory until 3 PM CST this afternoon for INZ002.

LM...Gale Warning until 6 PM CST this evening for the IL nearshore
     waters.

     Storm Warning until 3 PM CST this afternoon for the IN
     nearshore waters.

&&

$$

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