426
FXUS63 KIWX 311920
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
320 PM EDT Sun Aug 31 2025

.KEY MESSAGES...

- Seasonable and dry conditions continue through Tuesday. Highs near
  80 degrees.

- A strong cold front still looks on track to sweep across the
  area late Wednesday afternoon through early Thursday. Showers
  and a few isolated storms will likely accompany the front
  along with much cooler conditions.

- Highs only in the 60s Thursday and Friday with near record
  lows well into the 40s. The much below normal temperatures are
  expected to continue through much of next weekend.

- There is a Moderate Swim Risk for southeast Lake Michigan
  Beaches late Wednesday afternoon into Wednesday evening. There
  is a High Swim Risk for southeast Lake Michigan beaches on
  Thursday.

&&

.DISCUSSION...
Issued at 320 PM EDT Sun Aug 31 2025

An expansive low level anticyclone from the Upper Midwest to
northeast CONUS will continue to provide quiet weather through
the early parts of the week. A dry low level easterly flow will
continue to provide low humidity through the first half of the
week. Low level thermal advection has been continued weak today
and with clear skies/light winds once again today, a persistence
forecast has been utilized for below normal low temperatures
tonight (mid 40s to around 50).

A northern latitude ridge across southern Ontario will drift across
southern Quebec on Monday with rex block pattern setting up as
two negative upper height anomalies persist to the south of this
feature (broad upper low across Mid Atlantic and a negative
upper height perturbation dropping southeast across the
Plains). The local area will be positioned in broad weak
subsidence regime in this pattern which should allow for
continued moderation of a low level airmass early this week.
With another day of near full insolation expected on Monday,
will continue idea of previous several forecasts with highs in
upper 70s to around 80 for both Monday and Tuesday.

By late Monday and especially into Tuesday a zone of weak low level
moisture transport is expected to setup downstream of the southeast
digging Plains upper trough. Latest guidance is increasingly
suppressing the better moisture transport with this feature across
the Lower Ohio Valley and will continue to maintain a dry forecast
through Wednesday AM.

A more active pattern still looks to take shape late Wednesday into
next weekend. A vigorous upper level trough will drop into the
western Great Lakes late Wednesday, eventually driving a strong cold
front into the region late Wednesday afternoon into early Thursday.
Moisture return ahead of this feature is not overly impressive but
frontal convergence will allow for at least a narrow axis of
better pooled moisture in vicinity of the front. Given strong
nature to upper forcing and strong frontal response, will
maintain likely PoPs Wednesday night. No change made to just
isolated thunder PoPs for late Wednesday as strength of large
scale forcing/lift should limit mid level lapse rates and
evaporative cooling of initial dry subcloud layer will limit
low level lapse rates/instability magnitudes. Medium range
guidance is beginning to converge in a secondary strong cold
frontal reinforcement for Thursday night/early Friday with
additional showers possible. Much below normal temperatures will
characterize the Thursday through the weekend period with highs
in the 60s and lows in the 40s.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 122 PM EDT Sun Aug 31 2025

An expansive low anticyclone from western Wisconsin into PA/NY
will continue to be the dominant feature this forecast cycle.
Dry, easterly low level flow will keep clouds to a minimum with
primarily just some few-sct VFR cu. Another weak lake breeze
could favor more of north-northeast direction at KSBN late this
afternoon/early this evening, but otherwise light easterly flow
persists.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Marsili
AVIATION...Marsili