416
FXUS63 KIND 181853
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
253 PM EDT Fri Sep 18 2026

.KEY MESSAGES...

- Hot temperatures will continue at times into the weekend
  especially south. Heat indices around 100 again today southwest.

- Thunderstorms possible SW of the I-74 corridor this afternoon
  and evening.

- Shower and storm chances persist for much of the time into
  early next week, with temperatures turning cooler next week

&&

.DISCUSSION (This evening through Friday)...
Issued at 249 PM EDT Fri Sep 18 2026

Today through Sunday...

A synoptic boundary will continue to work its way into central
Indiana tonight into tomorrow, with a large theta-e gradient across
the state tomorrow. This gradient will generally be aligned just
north of the I-74 corridor with temperatures in the low 80s and
upper 70s to the N/E and upper 80s to the S/W.

The convection overnight created a mesoscale boundary, and has
stalled over SW portions of the state. This is being reinforced by
differential heating this afternoon, and will be the primary focus
for additional thunderstorm development over the next 6-8 hours. The
aforementioned synoptic boundary will slowly push to the SW with
time, of which will eventually will impede and push convection to
the SW as well. Until then, a broad 20-30% PoPs will be in the
forecast for areas SW of the I-74 corridor.

This all said, there is a more organized area of convection over
eastern Illinois as of 1830Z. This convection has been able to for a
cold pool, and should be able to sustain itself as it enters central
Indiana between 3-4PM. For this reason 40-60% PoPs have been added
for western central Indiana. A fairly deep stable layer in the low
levels will likely try and push this cold pool southward with time.
There still some uncertainty if this convective system will be able
to stay in balance as it continue to push through central Indiana as
the effective shear is rather limited with eastern extent. The lack
of shear and strong surface lapse rates should keep the severe wind
gust threat small, but given the strong cold pool, isolated gusts to
45MPH will be possible for a brief period this afternoon.

The remainder of the weekend will be a constant push/pull of this
lingering stationary boundary over the region creating both a minor
swing in temperatures and persistent rain chances. The best
chances for rain will be Saturday afternoon as a weak shortwave
moves SE over the stationary boundary. This wave will increase
overall shear across the area enough to support a few organized
thunderstorm clusters and a marginal risk for damaging wind gusts.

Temperatures are expected to remain warm, with some uncertainty
depending on boundary placement and cloud cover extent; general
expectations are for highs in the upper 80s each afternoon for
Indianapolis.

Tuesday and Beyond...

Surface high pressure will nudge into the area mid to late week next
week with mostly dry weather likely Wednesday onward. Temperature
are also expected to drop much closer to seasonal for the middle of
next week with highs in the mid 70s and lows in the 50s. Will have
to watch for an inverted trough just to the east, which could bring
a few showers if it ends up being farther west than expected.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 141 PM EDT Fri Sep 18 2026

Impacts:

- IFR at KLAF, MVFR at KIND until 20Z
- Showers and storms return for KLAF and KIND tomorrow

Discussion:

An area of MVFR/IFR ceilings will continue at the northern sites
over the next few horus until mixing allows for higher and scattered
decks to occur. KLAF will be the last one to enter VFR around 21-
22Z.

Winds will be fairly consistent out of the east throughout the day,
then veer to the SE and eventually S tonight into tomorrow. Winds
should stay below 10kt outside of thunderstorms throughout the TAF
period.

A more organized are of showers and thunderstorms is expected to be
within central Indiana between 15-21Z tomorrow afternoon. Greatest
confidence in rainfall is at KLAF, but KIND may also be impacted as
well.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

AVIATION...Updike
DISCUSSION...Updike