336
FXUS63 KIND 161324
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
924 AM EDT Sun Aug 16 2026

.KEY MESSAGES...

- Isolated showers and thunderstorms will be possible this
  afternoon with light rain amounts possible.

- Heat index values in excess of 100 possible today in southern
  portions of central Indiana

- Dry and milder weather early in the work week

- Additional storms possible Wednesday

&&

.FORECAST UPDATE...
Issued at 922 AM EDT Sun Aug 16 2026

Surface analysis this morning low pressure in place over eastern LK
Superior, with a weak trough of low pressure stretching south to
Indiana and western KY this morning. Aloft, water vapor imagery
shows a plume of tropical moistures stretching from the American
southwest across the central Plains to the Great Lakes and Indiana.
A convective cluster was found over NE MO, moving east within the
flow and appeared to be diurnally weakening with warming cloud
tops. Radar shows an area of scattered light showers associated
with the trough, generally producing light precipitation.
Additional light showers extended west toward HUF and Central IL
and eastern MO. Given the upper flow, these appear poised to pass
across Central Indiana through the afternoon. Dew points across
Central Indiana remained quite miserable, in the middle 70s.

Forecast Soundings through the afternoon show a moist and nearly
saturated column from time to time. The surface trough is expected
to slowly push east as surface flow remains westerly. This should
allow eastern propagation of the scattered showers and isolated
thunderstorms to push across central Indiana through the afternoon.
HRRR shows the showers weakening through the next several hours, but
does re-establish isolated convective development this afternoon as
daytime heating allows high to reach the upper 80s. Thus we will
keep some chc pops in the forecast for showers that are capable of
producing low rain fall amounts. Any additional rainfall amounts
today will have little to no impact on ongoing flooding as heavy
rain is not expected.

&&

.DISCUSSION (Today through Saturday)...
Issued at 303 AM EDT Sun Aug 16 2026

THROUGH TONIGHT...

One or more upper level waves, at least partially convectively-
enhanced, will traverse the area this morning into tonight, with
attendant threats for additional showers and thunderstorms. Modest
but sufficient deep layer shear will remain in place, along with
ample instability in the continued warm and very moist environment.
Areas of low level convergence associated both with surface
boundaries and remnant convective outflows will serve as foci for
development, but given the complex situation and CAM struggles with
placement and consistency run-to-run, confidence is lowered.
Localized damaging wind gusts will remain the primary severe threat.

Needless to say, flash flood concerns will remain the most pressing
worry, however. HREF local probability matched means suggest a
threat for up to a 1-2+ inches of rain with the most intense storms,
which will continue to pose a extremely rapid onset flash flood
threat, though there is some guidance suggestion that the heavier
rainfall threat may be more central and south, which, while still
quite wet, is not quite in as rough a shape as areas from Indy metro
north and northeast.

MONDAY AND TUESDAY...

An area of surface high pressure will mercifully bring at least a
temporary end to the repeated rounds of thunderstorms early in the
week, with dry weather and near normal temperatures likely early
Monday into Tuesday.

TUESDAY NIGHT INTO WEDNESDAY NIGHT...

Unfortunately, an additional round of thunderstorms appears likely
late Tuesday night into Wednesday night as another cold front and
upper level wave accompanying a strong jet streak aloft passes
through the region. Plentiful moisture will be available, though
precipitable water values may be slightly more modest (70-80th
percentile climatologically). However, somewhat stronger deep layer
shear may be available. Another round of severe storms will
certainly be possible, though predictability is greatly limited
given the sensitivity to prior rounds of storms and model
inconsistencies 4 days out.

That said, even with a couple of days to dry out, flash flood
vulnerability will remain quite high in the face of any additional
convective rainfall given the extreme antecedent conditions, and we
will need to remain vigilant through at least mid week for these
concerns.

THURSDAY ONWARD...

Amplification of the upper ridge over the western CONUS and
southward displacement of both the frontal zone and deeper moisture
by surface high pressure and upper level troughing suggest milder
temperatures and mostly dry conditions late week and into the
weekend, though some slight chances for showers or storms may linger
across the southern portions of central Indiana. It will take quite
some time for antecedent conditions to significantly improve,
unfortunately, and any additional convective rainfall with periodic
frontal passages or upper level waves in the broader cyclonic flow
next weekend and into the following week will pose at least modest
flash flood threats.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 727 AM EDT Sun Aug 16 2026

Scattered light showers and a few storms are expected in the region
this morning through midday. The most likely locations for brief -
TSRA would be HUF/BMG, and will carry some Prob30 -TSRA. At IND/LAF,
looking more at just -SHRA. Ceilings should mostly stay VFR with
variable mid and upper sky cover. There is a brief window for some
MVFR ceilings up at LAF later this afternoon, but overall VFR should
mostly prevail. Surface winds today should be steady out of the SW,
however may go more W-E later this afternoon. Another thunderstorm
complex could arrive later tonight, and have hinted at this with
another Prob30 mention at HUF/BMG/IND. Overall confidence is low in
the timing/placement of that cluster, so will adjust as necessary
with later issuances.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch until noon EDT today for INZ021-028>031-035>049-
051>057-065.

Heat Advisory until 8 PM EDT this evening for INZ060>063-067>071.

&&

$$

UPDATE...Puma
AVIATION...BJS (WFO LMK)
DISCUSSION...Nield