725
FXUS63 KIND 162315
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
715 PM EDT Wed Jul 16 2025

.KEY MESSAGES...

- Isolated strong to severe storms are possible through the early
  overnight

- Daily storm chances continue through at least Sunday with slightly
  cooler temperatures through Friday

- Potential for hazardous heat conditions towards next Tuesday and
  beyond with heat indices in the 100s.

&&

.MESOSCALE UPDATE...
Issued at 521 PM EDT Wed Jul 16 2025

A line of broken thunderstorms associated with a weak surface
boundary is quickly approaching western portions of central Indiana.
Deep-layer wind shear is relatively weak, but has been sufficient
enough to support a well established cold pool with the approaching
storms. Moderate instability ahead of the cold pool should continue
to promote a loosely organized line of storms in the near term
before weaker deep-layer shear over Indiana leads to weakening. Some
gradual weakening has already been noted over the past hour or two
though additional storms continue to fire along the persistent
outflow boundary.

The primary threat with this line of storms will be strong wind
gusts. Look for wind gusts to mostly remain sub-severe, but isolated
damaging wind gusts cannot be ruled out. Steep low-level lapse rates
and mid-level dry air are supporting DCAPE values around 800-
1100J/KG. The greatest threat will be near far west or northwest
portions of central IN before storms begin to weaken. The well
established cold pool should limit the threat for flooding as storms
continue to move eastward relatively quickly.

&&

.SHORT TERM (This evening through Thursday)...
Issued at 212 PM EDT Wed Jul 16 2025

Rest of Today and Tonight.

As of early this afternoon, shower coverage is minimal with a few
residual showers across the far eastern counties. A frontal boundary
is currently slowly moving southeastward from Wisconsin and Northern
Illinois a bit faster than models had forecast. This may bring in
thunderstorms slightly earlier than was previously forecast.
Initiation that is ongoing is matching the NAM much better than the
HRRR or other Hi-Res models, so will be trending the forecast more
towards the NAM through 00Z, but don`t believe that a line holds
together too far into Indiana with the much more marginal
environment across central Indiana. Lapse rates are less than moist
adiabatic which is keeping instability to near 0 towards
Indianapolis with slightly better lapse rates closer to the surface
towards Lafayette.

A lack of shear should prevent any significant organization with
these storms with the most likely outcome being scattered showers
with a few storms forming during the evening in Illinois before
moving into northwestern Indiana closer to sunset. Storm motion
should be fast enough to limit the flooding threat, especially with
much of the rain expected to fall across an area that has been quite
dry over the last couple of months. The front is likely going to
then stall somewhere across central Indiana with additional showers
and storms possible through the night along where the front will
stall with a greater threat for flooding towards the I-70 corridor
which has been more wet lately.

Thursday.

Convective potential for Thursday will be greatest along the stalled
frontal boundary which remains uncertain but likely to be somewhere
between the I-70 corridor and the Ohio River. There won`t be much
moisture flux into the frontal region which will limit the coverage
of showers and storms, but with this area having seen multiple
rounds of rain in recent days, isolated flooding will be a concern
especially as these showers and storms will have minimal steering
flow.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 212 PM EDT Wed Jul 16 2025

Thursday Night Through Sunday.

By Thursday night the frontal boundary should be south of the
forecast area with only minimal chances for precipitation across the
southern counties to account for the uncertainty with the frontal
location. What remains of the front will fully dissipate towards
Friday morning but a series of weak waves will impact an area of
northern moisture advection to keep precipitation around through
early Saturday but again this should mainly impact the Ohio River
region with decreasing chances further north. Partly to mostly
cloudy skies will persist through at least early Saturday with
temperatures running slightly below normal.

A stronger system will move in from the northwest Saturday night
into Sunday with the potential for more widespread heavy rain and/or
a complex of strong to severe storms. Confidence on details is low
with a wide range in model solutions on how the system evolves.
Either way, this looks to be the greatest threat for both severe
weather and flooding over the next 7 days.

Monday Through Wednesday.

The pattern then begins to shift Monday as the ridge begins to
return but there may be some lingering potential for convection
through early Monday with ridge-riding convection across Iowa into
Illinois, but with the uncertainty as to the strength and location
of the ridge, POPs will remain broadbrushed for now. Convective
temperatures by Tuesday should be high enough to prevent anything
more than an isolated thunderstorm with the core of the ridge more
directly overhead towards Wednesday/Thursday.

With a combination of highs in the low to mid 90s and dew points in
the upper 70s to near 80, heat indices will climb well into the low
to mid 100s with a lower end potential for values towards 110. Heat
headlines will likely be needed with Heat Risk maps now showing at
least Major levels by Tuesday.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 715 PM EDT Wed Jul 16 2025

Impacts:

- Line of thunderstorms will move across the TAF sites through 04Z
  with a wind shift to W-NW and gusts from 25-40 kts.

- Areas of MVFR vis reduction late tonight.

- Additional chances of showers and thunderstorms tomorrow
ahead of a weak cold front.

Discussion:

Line of strong to isolated severe thunderstorms recently moved
through KLAF with a gust to 42 kts. The line is moving through a
very unstable airmass and is expected to move through the remainder
of the TAF sites through 03Z. As this activity continues to move SE
it will weaken between 03-05Z to isolated to widely scattered. Areas
of MVFR visibility are possible after some clearing of high
anvil clouds occurs after 06Z. Winds will remain sufficiently strong
/3-5 kts/ that no areas of ifr vis/fog are expected late tonight.

As a weak cold front moves south into Central Indiana on Thursday,
sufficient lift and instability should support another round of
showers and thunderstorms. Coverage of thunderstorms is uncertain
and therefore am only going with prob30 for this forecast cycle but
VCSH will be prevailing during the 14-00Z period.

&&

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

$$

MESOSCALE...Melo
SHORT TERM...White
LONG TERM...White
AVIATION...Crosbie