040
FXUS63 KIND 082308
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
708 PM EDT Tue Sep 8 2026

.KEY MESSAGES...

- Heat returns today and Wednesday with peak heat indices in the
  upper 90s and low 100s Wednesday afternoon

- Strong thunderstorms possible late Wednesday; rain and storms
  continue Wednesday night into Thursday with heavy rain and localized
  flooding as the primary concern

- Cooler weather returns late week, warming up during the weekend.

&&

.DISCUSSION (This evening through Tuesday)...
Issued at 303 PM EDT Tue Sep 8 2026

Upper-level ridging over the Plains is flattening and moving
eastward as a potent shortwave digs southward into the Dakotas. This
has pushed the ridge axis over Indiana allowing temperatures to once
again warm up. Readings in the upper 80s to low 90s are expected
today and Wednesday. The shortwave`s attendant cold front arrives
late Wednesday, slowing in its forward speed and likely stalling
over southern Indiana. Upper-level flow becomes parallel to the
boundary allowing for repeated rounds of precipitation Wednesday
evening into Thursday. The vort max departs later on Thursday with
broad ridging taking hold again over the Plains as we head into the
weekend.

WEDNESDAY

Southwesterly flow increases ahead of the approaching front late
Wednesday morning into the afternoon. This will promote strong low-
level moisture advection with dew points rising into the 70s.
Combined modest cold air advection aloft / height falls, strong
instability is expected by late Wednesday afternoon. Guidance shows
between 2000-3000 J/Kg MLCAPE across southern Indiana decreasing
with northward extent. Shear increases as well due to the
approaching shortwave, easterly at around 30kt. The front itself
will provide the forcing necessary for convection.

Given a shear vector largely parallel to the front, a linear
convective mode appears likely. Marginal to poor lapse rates should
limit severe potential. Mid-level dryness could lead to a downburst
or two, given about 1000 J/Kg DCAPE. Our primary hazard appears to
be flash flooding, with storms potentially training due to the slow-
moving front and boundary-parellel flow. Convection may continue
into the night as additional rounds develop due to embedded
disturbances aloft. The best chance for both severe and hydro
threats is over our southern CWA where the front is most likely to
stall.

A potential failure mode for convection on Wednesday is related to
convection upstream tonight. Should an outflow boundary surge
southward out of Illinois tomorrow morning, a low-level stable layer
and cap may remain in place most of the day. This, as shown by the
12Z HRRR may substantially limit convective development.

THURSDAY

Guidance is in good agreement showing showers and thunderstorms
persisting into the day Thursday, with a few differences. These
differences are mainly regarding the northern extent of
precipitation chances. Global models such as the ECMWF and GFS tend
to bring a slug of heavier precip right through central Indiana,
where finer-scale models like the RAP and NAM are further south. For
now, we will nudge the forecast towards the southern side of
guidance as there has been an overall trend in that direction today.
This all depends on where the front ends up stalling, however, which
may be influenced by Wednesday`s convective evolution. Needless to
say, there is a bit of uncertainty in terms of precipitation
placement on Thursday.

FRIDAY ONWARD

Cooler weather arrives Thursday and continues into Friday before
ridging returns on Saturday. Highs near 80 are expected to end the
week with temperatures rising back towards 90 over the weekend.
Temps in the mid 80s to near 90 then persist into early next week. A
weak front may arrive from the north on Sunday but model consensus
is poor. PoPs will be limited to chance (40 percent) Sunday and
Monday. Most locations should remain dry through the weekend.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 708 PM EDT Tue Sep 8 2026

Impacts:

- Gusty SW winds around 20kt Wednesday afternoon
- Showers with scattered TS possible by 16Z north terminals,
closer to 20Z at KIND.

Discussion:

Quiet aviation weather is expected through 15Z tomorrow as S-SW low
level winds remain generally under 10 kts under SCT-BKN cirrus
clouds. A cold front will push in during the day with SW winds
increasing by Wednesday afternoon. Sustained winds are expected to
be between 8-11kt with gusts around 20kt.

Thunderstorms are expected to develop in the afternoon, but there
still remain uncertainty on the coverage and timing. Generally
speaking, ans showers/storms should move in from the NW, arriving at
KLAF and KHUF prior to KIND and KBMG. Brief IFR VIS and MVFR ceilings
are possible within these showers and storms.

&&

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

$$

AVIATION...Updike
DISCUSSION...Eckhoff