Lake Station, Indiana Weather Forecast Discussion

936
FXUS63 KLOT 192334
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
634 PM CDT Fri Sep 19 2025
.KEY MESSAGES...
- Clusters of scattered showers and some thunderstorms are
  expected through Saturday morning, initially around and west
  of the Fox River Valley late this afternoon and evening, and
  generally east of I-55 overnight into Saturday morning. Any
  shower or storm through this evening will be capable of
  producing gusty winds.
- Periodic chances for showers and some thunderstorms through
  early next week, though there will continue to be plenty of
  dry hours too.
- Afternoon temperatures will remain above normal through the
  Autumn Equinox (Monday at 1:19 PM CDT), though not quite as
  warm as they`ve been the past few to several days.
&&
.DISCUSSION...
Issued at 241 PM CDT Fri Sep 19 2025
Through Saturday Night:
A messy forecast is in store through Saturday as a series of
weak perturbations rotating around an upper-level low to the
west interact with ribbons of mid-level moisture marginally
favorable for precipitation. Mid-afternoon regional analysis and
radar/satellite data indicate a trough axis arcing from far
eastern Missouri north and westward to the parent low over
eastern Nebraska. Plenty of mid and upper-level cloud cover has
steadily expanded eastward across Illinois through early
afternoon, but not before abundant morning sunshine and modest
low-level mixing allowed temps to rise into the mid to upper 80s
(locally 90) for much of the area.
Have seen several attempts and stronger showers and some
thunderstorms across central Illinois early this afternoon, but
a rather dry airmass on either side of a narrow corridor of mid-
level moisture has limited coverage and growth so far this
afternoon. This axis is east of the main trough and well east of
higher low-level moisture west of the Mississippi River.
However, veering low-level winds have become more favorable for
gradual moisture advection toward western portions of the CWA
this afternoon.
Broader expectations are for the current axis of struggling
showers over central Illinois (as far north as Bloomington as of
2pm) to continue to drift northward ahead of the main trough
over the next couple hours before increasing in coverage and
intensity as they interact with the trough and increasing low-
level moisture. This should result in an area of scattered
showers and some embedded thunderstorms to affect areas around
and west of the Fox River Valley through mid-evening. A decent
DCAPE reservoir and high cloud bases mean any shower or storm
will be capable of producing gusty winds, with outflow
boundaries possibly extending well away from mature or decaying
cells.
A trailing wave over Missouri will then shift northeastward
toward the area while overtaking the then highly-sheared and
stalled remnant trough over the southeast half of the CWA
overnight through mid-morning Saturday. Another area of
scattered showers and some storms is expected during this
period, with overall coverage less clear given marginal forcing
and the continued limited spatial extent of favorable moisture
profiles. However, mostly unidirectional and seasonably weak
deep-layer flow nearly parallel to the slowing trough will
support slower/training showers and storms in narrow SSW to NNE
corridors.
After a lull in overall activity late morning through mid-
afternoon, the combination of another wave clipping the
northwest CWA and higher low-level moisture over the area will
support an increase in potential for surface-based convection
across northern Illinois mid afternoon into the evening.
Kluber
Sunday through Friday:
Any scattered showers leftover from late Saturday night may
linger past sunrise on Sunday. There could also be an isolated
storm until mid morning mainly near/east of I-65 in Indiana.
During Sunday afternoon, forcing mechanisms continue to look
nebulous, with the main large scale height falls and DCVA
(differential cyclonic vorticity advection) focusing north of
the Wisconsin state line. The potential remains for
convectively augmented MCV(s)/flow-enhancement to serve as a
trigger for additional showers and isolated thunderstorms, as
shown on some of the recent cycles of the NAM. However, this
element has little/no predictability at this range.
The deepest boundary layer moisture may tend to be shunted off
to the east a bit as well, and as such the highest blended PoPs
(~50%) are focused into portions of northwest Indiana, with
generally 20-40% chances elsewhere. Given the modest forcing,
marginal lapse rates, and potential for extensive cloud cover,
there is a realistic scenario for little/no convective re-
development in the afternoon. Finally, if any thunderstorms are
able to develop there`s a low chance threat, albeit one worth
monitoring, for a few stronger storms, mainly into parts of
northwest Indiana. This would also be conditional upon
sufficient destabilization paired with sufficiently strong
shear.
Intermittent shower and thunderstorm chances will persist Sunday
night through Tuesday as additional disturbances ripple through
the west to northwesterly flow aloft. A chaotic upper pattern
into the middle and end of next week will likely continue to
result in lower-than-typical forecast confidence. There`s some
modest signal in the extended guidance for at least a brief
return to drier conditions (especially near/north of I-80) in
the wake of a cold front towards midweek, but depending on the
influence of another upper low towards the end of the week, this
could end up being short-lived.
Temperatures this upcoming week will start out solidly above
normal (along with fairly humid conditions as well), with highs
well into the 70s to near 80F through Tuesday, then trending
closer to normal and a bit less humid in the mid to late week.
Castro/Carlaw
&&
.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 634 PM CDT Fri Sep 19 2025
The main aviation weather concerns for the 00Z TAF period
include:
* Scattered showers and storms possible this evening and
  tonight, and again Saturday afternoon.
A train of scattered showers and storms moving through N IL
this evening will struggle to maintain themselves as they near
the terminals within the first few hours of the period. At least
isolated coverage is anticipated around the airfields late this
evening and through much of the night, although the trend in
expected coverage is on the decline. A thunderstorm or two will
also be possible toward the end of the evening and into the
overnight and may come with localized vsby reductions. The
prevailing -SHRA in the TAFs for tonight may need to be
consolidated to a VCSH as confidence in precip trends grows.
Additional storms will be possible Saturday afternoon with
lingering showers perhaps lasting into the night. Confidence in
timing and coverage is rather low at this time. Conditions
through the period will be largely VFR aside from localized
impacts due to rain and storms.
Doom
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Air Quality Alert until midnight CDT tonight for INZ001-INZ002-
     INZ010-INZ011.
LM...None.
&&
$$
Visit us at weather.gov/chicago

NWS LOT Office Area Forecast Discussion