723
FXUS63 KLOT 251129
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
529 AM CST Sat Jan 25 2025

.KEY MESSAGES...

- A chance for flurries this morning south of I-80.

- Gusty winds to 25 to 30+ mph this afternoon and evening near
  and north of I-80.

- Strong winds are expected Monday with gusts of at least 30 to
  40 mph.

&&

.DISCUSSION...
Issued at 239 AM CST Sat Jan 25 2025

Through Sunday:

Conditions are quiet out there early this morning aside from
some breezy winds as we continue to occasionally mix down some
stronger flow just off the surface. Gusts are beginning to give
out from west to east as the LLJ drifts east and winds should
be rather light by daybreak. Temperatures have been steady
through the night so far in the lower and middle 20s thanks to
some efficient warm advection following the passage of a warm
front last evening. These stagnant temperatures will allow highs
today to reach the middle 30s.

A few flurries managed to form in the warm advection last night,
but we haven`t seen anything in our area for more than a few
hours now. We do have a subtle cold front moving across the area
at the moment which is pushing the WAA off to the east.
Moisture near the front is so scarce that nothing has been able
to materialize along it. This may change as the front works into
our south and southeast later this morning and becomes
juxtaposed beneath some stronger zonal aloft offering some
baroclinic enhancement. However, where some guidance was
previously resolving just enough moisture to perhaps support
some light snow showers, model soundings now appear too dry to
support anything more than additional flurries. In the forecast,
maintained a chance for flurries through the morning mainly for
areas near and south of the Kankakee River.

Aside from this flurry potential in the morning, we`re not
expecting any precip during the day today. A second cold front
will move across the area this afternoon with much colder air
behind it than this current front. Along and behind the front,
models resolve a thin layer of saturated air roughly near 850 mb
across our northern CWA. Some previous model runs showed
saturation deep enough to maybe stir up some CAA-driven flurries
this evening, with the help of some low level vorticity on the
southern periphery of the upper trough. However, this signal has
grown even weaker over recent runs. For that reason, left a
mention of flurries out of the forecast for this evening,
however its possible to see a few flurries floating around north
of I-80 this evening.

Winds should be getting breezy again this afternoon and evening
behind the front, especially north of I-80. The cold advection
should allow for efficient mixing into some stronger low level
flow, however uncertainties remain owing to discrepancies in
both mixing heights as well as the magnitude of the flow aloft.
High res camps are far more aggressive than regional and global
guidance. The HREF paints high probabilities for a period of 30+
mph gusts across our northern half; Probabilities drop
significantly at 35 mph. The forecast calls for gusts in the 25
to 30 mph range this afternoon and evening near and north of
I-80, but could get occasionally higher.

Not much to speak on for Sunday. The cold advection will keep
highs from warming past the middle 20s and expect marginally
breezy winds out of the west. Drier air working in should keep
precip away and offer up a mix of clouds and sunshine to wrap up
the weekend.

Doom


Sunday Night through Friday:

Monday will be windy and much warmer. As alluded to in previous
AFD, it is likely that guidance is too cool with temps Monday
and later forecasts will likely need to bump temps up into the
40s. Very tight pressure gradient between deep low near Hudson
Bay and high pressure over the southern Plains should allow for
winds of 20-30 mph Monday. The unseasonably mild temps and some
sunshine should also promote enough mixing to transport some of
the higher momentum air to the surface. Bufkit soundings
strongly support frequent gusts of 30-40 mph and not hard to
envision a scenario with temps overperforming allowing boundary
layer to tap into even stronger gusts (over 40 mph) Monday
afternoon.

Cold front trailing from the Hudson Bay low will approach from
the north Monday night, but latest guidance suggests that it
will stall before making it into the CWA. This front is then
expected to lift north as a warm front as a clipper moves
quickly eastward into the upper Great Lakes by Tuesday
afternoon. The result will likely be continued mild temps
Monday night and Tuesday. NBM came in with lows in the mid to
upper 20s and highs in the lower 40s Tuesday; both of these are
probably too cool and may need to be adjusted upward in coming
days. Tuesday will be breezy, but not nearly as windy as Monday.

Cold trailing west from the clipper will move south across our
CWA Wednesday, likely result in highs early in the day, followed
by steady or even slowly falling temps during the day. Could be
a brief window where there`s some lake effect snow into
northeast Porter County late Wednesday, but winds should back
and push lake effect threat to the east of our CWA.

The ECMWF with support from its ensemble suite has been
trending farther west with the cold push behind the Wednesday
clipper. If this trend continues, wouldn`t be surprising to see
temps late Wed through Thursday trending a bit colder in time.
That colder air mass should get shunted off to the east late in
the week with milder Pacific air flooding east across the
northern half of the country. There will be a southern stream
cut off low lurking over the southwestern U.S. during the early
to mid part of the week that could eventually lift out and
affect our weather. Timing of these type of systems tends to be
not handled well in medium range guidance with systems often
moving slower than progged. Eventually, that system could move
into the region, which when it does, will result in cooler temps
and precip (mainly rain) chances. Didn`t stray from NBM low
chance pops Friday night into next weekend, but confidence is
low, a slower or more southerly ejection would result in dry
and much milder conditions heading into next weekend.

- Izzi

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 529 AM CST Sat Jan 25 2025

- Gusty southwest winds will develop late this morning and
  continue trough the afternoon.

VFR conditions are expected through the TAF cycle. Light
southwest winds early this morning will steadily ramp up and
become increasingly strong and gusty by later this morning.
Prevailing gusts of 25-30kt are expected late morning until
sunset, but given expected sunshine, it is possible there could
be some occasional gusts a bit over 30kt this afternoon. Winds
will veer westerly and gradually diminish and become less gusty
this evening.

- Izzi

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from noon today to 3 AM CST Sunday for
     the IL nearshore waters.

     Small Craft Advisory from 3 PM this afternoon to midnight CST
     tonight for the IN nearshore waters.

&&

$$

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