467
FXUS63 KIND 021008
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
608 AM EDT Thu Jul 2 2026

.KEY MESSAGES...

- Heat index values between 105 to 110 daily through Friday

- Extreme Heat Warning in effect through Friday evening

- Thunderstorm chances will increase Friday through the holiday
  weekend

&&

.DISCUSSION (Today through Wednesday)...
Issued at 138 AM EDT Thu Jul 2 2026

Overview.

An intense heat wave will peak across central Indiana through
Friday, maintaining dangerously hot and humid conditions with
afternoon heat index values pushing up to 110 degrees. The upper-
level ridge will begin to suppress southward this weekend, allowing
a transition to a more active, convective pattern with daily chances
for scattered showers and thunderstorms alongside a gradual cooling
trend into next week.

Today through Friday night.

The synoptic pattern through the end of the work week will be
characterized by the persistence of a robust, highly anomalous 594
dm sub-tropical ridge centered over the Ohio Valley. Intense large-
scale subsidence and strong mid-level thermal capping manifested by
700 mb temperatures remaining between +12C and +14C will continue to
inhibit deep vertical moist convection through Thursday and much of
Friday. A persistent low-level southwesterly wind component will
maintain a steady tap into rich Gulf moisture, anchoring surface dew
points in the mid to upper 70s across the forecast area. When
combined with strong diabatic solar heating, maximum afternoon
ambient temperatures in the low to mid 90s will yield dangerous peak
heat index values ranging from 105 to 110 degrees.

Consequently, Excessive Heat Warnings remain in effect through
Friday evening. By late Friday afternoon, subtle height falls on the
northern periphery of the retreating ridge axis, combined with
intense boundary layer destabilization, may support isolated
convective initiation along localized mesoscale boundaries, though
widespread storm development will remain heavily suppressed by the
lingering cap. Coverage will be greatest north of the forecast
area, but after 00Z, there may be some thunderstorms moving south
towards central Indiana.

Saturday through Wednesday.

Medium-range and ensemble guidance show a transition in the upper-
level pattern beginning Saturday as the sub-tropical ridge
deamplifies and suppresses further into the Deep South. In its wake,
a progressive northwest flow regime will establish itself across the
Great Lakes and Ohio Valley. This transition will open the door for
a series of migratory mid-level shortwave troughs and embedded
convective impulses to traverse central Indiana, interacting with an
unseasonably moist and unstable airmass. Precipitable water values
hovering near or above 2.0 inches will fuel high afternoon CAPE
values each day from Saturday through Monday. While details remain
uncertain for storm coverage and timing on Saturday, confidence is
highest from mid afternoon through sunset with coverage
decreasing after 9PM.

Given the lack of robust deep-layer vertical wind shear, the primary
convective mode through the weekend will favor pulse-type storms or
loosely organized multicell clusters capable of producing localized
downbursts and torrential rainfall rates. By Tuesday into Wednesday,
long-range guidance depicts a more potent northern stream shortwave
digging out of south-central Canada into the Great Lakes region,
propelling a surface cold front across the state. This boundary will
provide a focus for more organized convective development before
introducing a much cooler, drier Canadian airmass. Significant cold
air advection in the wake of the front will finally suppress
temperatures back to near or slightly below seasonal levels by the
conclusion of the forecast period.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 607 AM EDT Thu Jul 2 2026

Impacts:

- None.

Discussion:

VFR conditions expected through the TAF period outside of a low
chance for patchy ground fog ahead of 12Z. Mostly clear skies
expected through the TAF period with diurnally driven cu looking a
bit more widespread this afternoon compared to yesterday. Winds will
generally be southerly at 7-12kts through tonight outside of the
near calm winds this morning.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning until 8 PM EDT Friday for INZ021-028>031-
035>049-051>057-060>065-067>072.

&&

$$

AVIATION...White
DISCUSSION...White