501
FXUS63 KLOT 150819
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
219 AM CST Sat Nov 15 2025

.KEY MESSAGES...

- Unseasonably warm weather again today.

- Gusty today and tonight, then dry and much colder for Sunday.

- Precipitation chances return Monday night into Tuesday.

&&

.DISCUSSION...
Issued at 219 AM CST Sat Nov 15 2025

It`s a mild start to the day with temperatures sitting in the
upper 50s early this morning. Similar to yesterday, warm
advection out ahead of a northern Great Lakes low will bring
another mild day to the area with highs forecast in the middle
60s to 70 in some outlying spots. The storm`s cold front will
move across between late morning and early afternoon today. The
cold advection won`t be all that aggressive immediately in its
wake and we should continue to see temperatures climb behind the
front into the afternoon. A much cooler airmass will then
advect into the area from the northern Plains tonight dragging
low temperatures into the lower and middle 30s.

A few sprinkles or light showers will be possible offshore and
toward western lower Michigan with the frontal passage. The NAM
suite has been a bit aggressive in wanting to track light precip
across our CWA, but a large wedge of low level dry air and
general lack of support otherwise should keep the local area dry
today. Additionally, a strong low level jet is currently moving
overhead. As the boundary layer deepens after sunrise, it`s
likely that we`ll mix some of those stronger winds down to the
surface and see gusts to 25 to 30 mph through the morning,
occasionally higher, then subsiding a tad but remaining gusty
for the afternoon. The gustiness will continue through tonight
thanks to the post-frontal cold advection keeping the boundary
layer well-mixed.

High pressure will settle into the region behind the cold front
bringing sunny but cooler and very dry conditions to tomorrow.
Highs tomorrow are forecast in the upper 40s to lower 50s while
afternoon dewpoints are progged in the teens to around 20
degrees. This will yield afternoon RHs between 25 and 30%. With
marginally gusty NW winds expected and given recent dry
conditions, Sunday may see a marginally elevated fire weather
risk.

Attention then turns to an early week Rocky Mountain low that
will track across central Illinois bringing us our next chances
for rain. The system will develop out in the Plains early Monday
before the upper wave loses amplitude into the Midwest and the
surface low tracks immediately south of our CWA on Tuesday.
There`s a chance that we could see some snow mix in with the
rain, especially early in the event Monday evening and night
when drier low level air will promote some wet bulb cooling. But
it`s a very touchy setup with soundings exhibiting a nearly-
isothermal layer through the lowest couple of hundred millibars
straddling the freezing line. The Euro is notably warmer through
the low levels than the GFS and offers little in the way of
mixed or frozen precip. The Euro has been far more consistent
run by run with the storm`s track than the GFS which has been on
a steady northward trend. The latest iterations of the two show
very similar storm tracks now, but the big question is how far
north the low level warm sector/baroclinic zone will extend east
of the low. Looking at ensemble soundings, there is strong
support in the ENS suite for the low levels to be above freezing
while there is more spread among GEFS members. This adds
further confidence to the Euro`s warmer solution. A number of
other medium-range camps such as the RDPS, ICON, and UKMET also
favor a warmer solution similar to that of the Euro. The NBM
populated the forecast with all liquid precip, which was
maintained as that appears to be the favored outcome. Instances
of a wintry mix will still be possible though, particularly
Monday night, but would not contribute to any impacts aside from
perhaps some added visibility reductions.

A pool of rich Gulf moisture will track ahead of the low. The
1"+ PWATs look to stay just out of reach to our south, but as
many as 0.7-0.8" of PWAT will work into our CWA. A widespread
couple to few tenths of an inch of precip is on the table Monday
night through Tuesday. The NE quadrant of the storm will also
provide the opportunity for low level deformation and localized
swaths of heavier rainfall up to around a half inch in total.
This potential for banded precip is portrayed in some model QPF
output as well.

Another low will spin up off the lee of the New Mexico Rockies
late Wednesday and track across the region Thursday into Friday.
The warm sector looks to be laden with Gulf moisture with PWATs
progged at over 1", maybe even near 1.5". This sort of moisture
in conjunction with likely strong dynamic forcing ahead of the
high-amplitude trough will present an opportunity for widespread
soaking rain. There`s plenty of uncertainty still in where the
storm and heaviest precip will track, but medium range guidance
is pretty excited about a sizable swath of 1-2" precip totals
somewhere around the region. Given the rich moisture and fairly
steep mid level lapse rates, some elevated thunderstorms may
even be in the cards Thursday into Friday.

Doom

&&

.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1125 PM CST Fri Nov 14 2025

Aviation concerns for the 06Z TAFs:

- Low probability for brief MVFR ceilings at Chicago terminals
  Saturday morning.

- Southwest winds become breezy after sunrise, then turn west-
  northwest by late morning behind a cold front. Gusts 25+ kts
  likely, even Saturday night after perhaps a brief lull after
  sunset.

Surface pressure gradient will gradually strengthen overnight
in response to surface low pressure tracking across the northern
Great Lakes region. South winds will turn southwest and slowly
increase through sunrise with a period of gusts 25-30 kt likely
after sunrise as we briefly mix into a departing low-level jet.

A cold front will push across the area late morning, shifting
winds west-northwest and remaining gusty. There may be a bit of
a lull in gusts after sunset, though a renewed push of colder
air is expected to result in gusty conditions developing again
by late evening. Have held gusts around 25 kts, though there
could be some occasional gusts around 30 kts at times.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from noon today to 4 PM CST Sunday for
     Winthrop Harbor IL to Gary IN.

     Small Craft Advisory from 6 PM this evening to 9 AM CST Monday
     for Gary to Burns Harbor IN-Burns Harbor to Michigan City
     IN.

&&

$$

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