467
FXUS63 KIWX 161807
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
207 PM EDT Thu Jul 16 2026

.KEY MESSAGES...

- Air quality alerts continue today and into Friday, in part
  due to smoky conditions.

- Increasing chance (30% to 70%) for showers and thunderstorms
  by Friday afternoon. Storms may produce heavy rain.

- Thunderstorms on Saturday afternoon may produce damaging wind
  gusts.

- Not as warm starting Sunday.

&&

.DISCUSSION...
Issued at 204 PM EDT Thu Jul 16 2026

Surface high pressure beneath a subtle sag in northwesterly flow
aloft has ushered in plenty of wildfire smoke over our area. Based
on surface visibility observations, near-surface smoke has been most
prevalent north of US 30, especially along the southern Michigan
state line. There, visibility has been below 2 miles most of
today, with instances of 1 mile visibility. This has also
notably limited temperatures today. Within the heat advisory,
some upper-80s are noted with heat indicies in the mid-90s. As
we approach peak- heating, we`ll keep the (marginal) Heat
Advisory in place for now. Available forecast guidance
indicates these smoky conditions may spread further south
tonight and remain in place after sunrise Friday. However,
conditions may improve as the day progresses as surface high
pressure drifts east in response to an incoming upper Great
Lakes trough and an advancing warm front.

Look for increasing coverage of showers and thunderstorms tomorrow
afternoon as a warm front advances from the southwest. Shear will be
incredibly limited (less than 20 knots) keeping the severe
weather risk in check. In contrast, due to an overall absence
of upper-level flow, slow-moving storms may produce heavy
rainfall as PWATs push 2 inches by the afternoon.

A marginal to slight risk of severe storms is highlighted by the
Storm Prediction Center for Saturday. A well-organized upper-
level low sweeps through Wisconsin and Michigan amid an
environment with plenty of instability (>1,500 j/kg) and only
marginal shear shy of 30 knots. Guidance generally suggests
discrete storms along a cold front may mature into linear
segments, posing a risk for damaging wind gusts.

High pressure briefly settles in sunday and Monday bringing cooler
and less humid conditions. Energetic northwest flow spills over the
Great Lakes by midweek presenting renewed chances for wet weather
while keeping afternoon high temperatures near-normal (mid-80s)
or just a few degrees shy of normal.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 200 PM EDT Thu Jul 16 2026

Deteriorating conditions have been noted at terminals through
early this afternoon, particularly at KSBN which has
transitioned to IFR vsbys in smoke from Canadian wildfires.
Forecast confidence in vsby trends is on the low side, although
concern that is that at least MVFR vsbys will linger through
much of this TAF period. The possibility exists for some
improvement at KSBN late afternoon/early evening to MVFR, but
would expect some early morning Friday deterioration with
smoke/br combination. A short wave trough approaching from the
west will allow a weak boundary across north central IL/west
central IN to retreat northeast as a warm frontal feature on
Friday. This should tend to help improve sfc vsbys toward end of
this forecast valid period, but will result in increased risk
of scattered showers and thunderstorms Friday afternoon.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert until midnight EDT /11 PM CDT/ Friday night
     for INZ005>009-012>015-017-018-022>027-032>034-104-116-
     204-216.
     Heat Advisory until 8 PM EDT this evening for INZ013-015-020-
     022>027-032>034.
     Air Quality Alert from midnight tonight to midnight EDT Friday
     night for INZ020.
     Air Quality Alert until midnight CDT Friday night for INZ103-
     203.
OH...Air Quality Alert until midnight EDT tonight for OHZ001-002-
     004-005-015-016-024-025.
MI...Air Quality Alert until midnight EDT Friday night for
     MIZ078>081-177-277.
MARINE...Dense Smoke Advisory until 8 PM EDT Friday for LMZ043-046.

&&

$$

DISCUSSION...Brown
AVIATION...Marsili