NWS Chicago Decision Support Briefing - Forecast

577
FXUS63 KLOT 191757
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1157 AM CST Thu Feb 19 2026

.KEY MESSAGES...

- Another period of showers and thunderstorms expected later
today into this evening. A low (5-15%) chance for severe
thunderstorms continues this afternoon/early evening,
primarily across central IL and IN.

- Temperatures will tumble tonight into Friday. A rain/snow mix
may graze the Illinois and Wisconsin state line.

- Another period of strong winds is expected Friday, with
westerly wind gusts in excess of 40 mph.

&&

.DISCUSSION...
Issued at 330 AM CST Thu Feb 19 2026

A lead mid-level impulse tracking overhead has fired off a
cluster of elevated storms in the vicinity of a lower-level
frontal boundary across east central IL into IN early this
morning. The strongest storm in this cluster recently moved
across southern Benton County and parts of Warren county IN and
was reported by a storm chaser to have produced hail to the size
of quarters on State Rd 41 just west of Pine Village. These
showers and storms are likely to fester for a couple more hours
in the vicinity of this boundary in my far southern counties
early this morning before waning. Otherwise, the main forecast
focus quickly shifts to the storm system continuing to take
shape across the central Plains early this morning.

A stout 995 mb surface low taking shape over KS, early this
morning will track eastward across the Kansas City area around
midday today, then lift northeastward into northern IL, while
deepening to around 990 mb late this evening and overnight. A
region of showers and thunderstorms is expected to develop in
association with this system across eastern MO later this
morning. This activity is then expected to spread east-
northeastward through the day, impacting central and southern
portions of IL this afternoon. A strongly sheared environment
will support some severe storm potential, including supercells,
with this activity today. However, our area is expected to
largely remain north of these severe storms through the day.

As the main storm system begins to lift northward into our area
this evening, additional elevated showers and storms are
expected to develop and track north-northeastward across the
area through the evening. The severe threat with these storms
will be low, and primarily limited to some possibility of
marginally severe hail. The systems mid-level dry slot is
expected to punch northward across the area late this evening
and overnight, which should result in a quick south to north
transition over to low clouds and possibly some lingering
drizzle and fog. This will particularly be the case across
northern IL in the vicinity of the surface low track.

Finally, as the deepening surface low tracks northeastward
towards western lower MI late tonight into early Friday morning,
a strong cold front will surge eastward across the area. In its
wake, strong pressure rises along the southwestern periphery of
the surface low will drive a quick onset of strong and gusty
(40+ mph) westerly winds around, or even a couple hours prior
to, daybreak Friday morning. Expect these gusty winds to persist
on Friday, though speeds should be on a downward trend through
the afternoon. A Wind Advisory may be needed for this period.

In addition to the wind, a band of snow is expected within the
systems mid-level deformation zone along the west-northwestern
periphery of the low. Currently, it appears the main
accumulating snow axis will remain west-northwest of our area.
However, guidance continues to depict some of this activity
trying to work eastward with the colder airmass into parts of
northern IL before ending on Friday morning. Accordingly, some
minor accumulation of an inch or less of wet snow cannot be
ruled out Friday morning, mainly northwest of I-55 and north of
I-80. Dry weather is slated for the afternoon hours of Friday,
but temperatures will remain in the 30s with blustery
conditions.

KJB

Friday night Onward:

Forecast thinking in the extended period has not changed from
the previous discussion below.

This weekend, somewhat disorganized upper-level cyclonic flow
(with an embedded orphaned ridge "bubble") will be in place
across the Great Lakes region. With all embedded shortwaves more
or less far from our area on Saturday, relatively benign
weather is in store locally with seasonable highs in the mid to
upper 30s, northwesterly winds of 10 to 15 mph, and partly
cloudy skies.

On Sunday, several upper-level shortwaves will merge and dive
southeastward across the Great Lakes. Tumbling 850mb
temperatures toward the minus 10 to minus 12 range will lead to
a corresponding drop in temperatures, with highs only expected
to top off near the freezing mark. Increasing over-water
instability will support lake effect snow showers as well, with
predominantly northwesterly flow favoring northwestern Indiana.
Sunday night looks like it`ll be relatively chilly with a
continuation of breezy northwesterly winds and overnight lows in
the teens contributing to wind chills falling toward the single
digits.

Lake effect snow may continue into early Monday morning before
the cyclonic shear axis of the upper-level cyclonic flow slides
overhead. Ensemble guidance continues to exhibit a signal for
broad quasi- zonal flow to become reestablished next week
allowing for a steady feed of relatively mild Pacific flow to
return to the area. Accordingly, the expectation is for
temperatures to warm into next week (back into the 40s).
Ensemble 24-hour meteograms from the EPS and GEFS favor the next
opportunity for widespread precipitation materializing sometime
toward the end of next week.

Borchardt

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1158 AM CST Thu Feb 19 2026

Main Concerns:

- Potential for TSRA at times late today through this evening.

- Reduced flight categories in DZ and BR possible early Friday.

- Strong west winds and snow showers/flurries at Chicago area
sites on Friday, with a period of accumulating wet snow
possible at RFD.

Initial relatively quiet conditions featuring east winds around
10 kt with occasional gusts and 2-4kft AGL CIGs will turn more
active later today through the rest of the period. Showers with
embedded TS should develop/lift into the area late this
afternoon, possibly followed by a break, and then another round
later in the evening. Opted to lengthen the PROB30 TSRA for now
to encompass both plausible windows. After this activity lifts
north, east-northeast winds will shift to southeast and then
gusty southwest overnight with gusts pushing 30 kt as low
pressure tracks over the area. Earlier rain and moist low
levels may be supportive of BR and a period of lower CIGs.

From the predawn hours until about mid-morning Friday, if
precip occurs at the Chicago metro sites, forecast soundings
suggest it will be in the form of drizzle (with temps solidly
above freezing). Later in the morning into the afternoon, much
colder air and additional upper level disturbances will support
flurries and the potential for more robust snow showers at times
(PROB30 mention). At RFD, a period of heavier snow Friday
morning may bring a slushy accumulation up to 1".

Aside from the snow potential on Friday, expect strong westerly
winds gusting up to 35-45 kt and MVFR CIGs which may scatter late.

Castro

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Gale Watch from Friday morning through Friday afternoon for
the IL and IN nearshore waters.

&&

$$

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