125
FXUS63 KIND 121315
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
915 AM EDT Wed Aug 12 2026

.KEY MESSAGES...

- Marginally severe storms through daybreak along with potential
  additional flooding

- Flood Watch continues through today with additional strong to
  severe storms through the day, mainly during the afternoon

- Damaging winds will be the main threat today outside of flooding

- Storm chances continue through the rest of the week, severe
  weather threat looks lower

&&

.FORECAST UPDATE...
Issued at 914 AM EDT Wed Aug 12 2026

Surface Analysis this morning shows a broad surface trough
stretching from IA, across northern IL to northern IN, quite similar
to yesterday. Water vapor this morning shows a steady NW flow aloft
in place, with an wave over IA, generating convection upstream.
Radar shows storms continuing over eastern Central Indiana due to
lower level jet forcing. Cloudy skies were found across the eastern
parts of the state, where the convection was, while only a few
clouds were found over western Central Indiana. Dewpoints remained
high, in the 60s as much of the area was under the influence of rain
cooled air, however along the Wabash, dew points were around 70.

Another day of active weather is ahead for Central Indiana. The NW
flow aloft is expected to continue to push the forcing over IA
toward Indiana by mid to late afternoon. Meanwhile the precipitation
across eastern Central Indiana should begin to wane and drift east
by late morning. However, more storms will be expected this afternoon
as the forcing dynamics arrive from IA. Forecast soundings,
especially along and south of I-74 will have plenty of CAPE
available, with values over 4000 J/KG and high pwats again over 2
inches. This will result in more rounds of showers and storms
through the afternoon, with heavy rain and damaging winds possible.
Will focus best pops this afternoon, particularly across along and
SW of I-74 where best instability should be located.

&&

.MESOSCALE UPDATE...
Issued at 319 AM EDT Wed Aug 12 2026

An area of slow moving elevated convection continues across the
eastern counties associated with residual outflow boundaries from
earlier today. Hourly rain rates have been as high as 2 inches per
hour at times. Precipitable water values of ~1.8" lie west of the
complex feeding additional backbuilding development. MU CAPE is 3000-
4000 J/kg across central IN with effective bulk shear around 30 kt
which further is helping to enhance renewed development.

Models have broadly captured the evolution even if it formed a bit
earlier and a bit less robust than what is currently depicted. The
complex is expected to move south-southeast through the remainder of
the overnight.  Rain amounts within the Flash Flood Warnings may
exceed 4 inches in spots.

&&

.DISCUSSION (Today through Tuesday)...
Issued at 133 AM EDT Wed Aug 12 2026

Overview.

Active weather continues into today with additional rounds of showers
and thunderstorms. A few storms could produce localized heavy rain
and strong gusty winds this afternoon and evening with best chances
across southwest Indiana. A front associated with the system will
gradually move south into early Thursday with additional marginally
severe storms through Friday. Rain chances generally look lower for
the weekend with the jet stream further north into the Great Lakes.

Rest of Tonight.

The main focus through the remainder of the overnight hours will
be additional thunderstorm development across eastern Indiana with
the LLJ ramping up. Storm coverage has been gradually increasing
over the last 2 hours with heavy rain being the main threat along
with occasional pulses leading to small hail. General expectations
are for these storms to grow upscale and move to the southeast
with additional flooding from Madison County south to Decatur
county. With the storms not backbuilding as much as they were
initially, flash flooding should remain isolated with broader
areal flooding being the main threat.

Wednesday Through Thursday.

Indiana remains locked into northwesterly flow with broad ridging
across the Central Plains and broad troughing across the Great
Lakes. Shortwaves within the upper level flow will continue to bring
periods of showers and storms  with upper-level forcing along the
exit region of a 50-60 kt mid-level jet streak aloft. A weak surface
front currently across northern Indiana is expected to slowly move
south through the day but generally will only have minimal impacts
on storm coverage timing as much of the forcing is being driven by
the jet level forcing aloft.

WAA and boundary layer heating will yield MLCAPE values ranging
between 2500-3500 J/kg again today, supported by steep lapse rates
exceeding 7.5 C/km above the boundary layer. While 0-6 km bulk shear
vector magnitudes are modest at 25-35 kt, orientation roughly 45
degrees to the initiating boundary favors mixed mode convective
structures, including multicellular clusters and bowing segments.
HREF 2-5 km UH probability sweeps show maximum signal concentrated
across central and southern Indiana between 21Z and 03Z with storms
moving in from the west. Elevated DCAPE values above 1000 J/kg
suggest damaging wind gusts will be the primary severe hazard, with
steep mid-level lapse rates occasionally supporting isolated severe
hail. PWATs nearing 1.8 to 2.0 inches, well above the 90th
percentile, will support efficient warm-rain processes and localized
torrential rainfall. Ahead of the stronger storms, initiation is
likely across northern Indiana during the early morning hours today,
but CAMs continue to struggle with properly diagnosing the current
boundaries and impacts from the front, so confidence is lower on any
impacts through the morning hours.

Additional flooding looks likely, especially in areas that saw
heavy rain during the overnight hours. LPMMs show pockets of 2-3
inches beyond what already fell, but confidence is very low in
where this may occur with broader model spread on the location of
the axis of heaviest rain. Thus, will keep the Flood Watch through
04Z and reevaluate later today.

Convection will clear the southern CWA border late tonight as the
surface cold front gradually drifts into closer to the Ohio River.
Forecast confidence is fairly low into Thursday with more
significant model divergence on the broader synoptic pattern and how
the residual front may impact conditions. North of the front,
temperatures will be much cooler with highs in the upper 70s to near
80 with minimal instability, while areas to the south of the front
are likely to end up near 90. The severe threat generally should be
on the warmer side with any convection to the north remaining
elevated.

Friday Through Tuesday.

The broad synoptic regime during the extended period will feature a
transition from post-frontal surface high pressure to mid-level
ridge amplification across the Central Mississippi and Ohio Valleys.
The 00Z GEFS and EPS are in have decent agreement through 00Z
Monday, with the ridge over the Plains strengthening and pushing the
jet stream further north into the Great Lakes. Daytime highs will
climb from the lower 80s on Friday to the upper 80s and low 90s by
Sunday as return southerly flow returns. Rain chances generally
should remain limited to just the northern counties, but even that
looks low.

By Monday into Tuesday, ensemble guidance indicates a northern
stream trough traversing the Canadian Prairies into the Great Lakes
region, acting to flatten the mid-level ridge and push a surface
cold front toward the lower Great Lakes. Guidance exhibits typical
timing disparities regarding frontal passage dynamics, with the
ECMWF and EPS ensemble mean slightly slower than the GFS and GEFS
composite. Low-level moisture return along a re-establishing 30 kt
LLJ will bring PWATs back toward 1.5-1.7 inches. Chance POPs have
been maintained for Monday afternoon through Tuesday to account for
scattered frontal convection driven by weak height falls and low-
level convergence.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 706 AM EDT Wed Aug 12 2026

Impacts:

- Isolated showers or a stray storm cannot be ruled out near IND
  this morning along with MVFR ceilings

- Additional convection later today, confidence highest towards mid
  afternoon

- Fog development expected tonight, especially near LAF/HUF

Discussion:

Brief fog development will be possible through 13Z near LAF/HUF.
Isolated showers or a stray storm cannot be ruled out near IND
this morning along with MVFR ceilings. Additional storms are
likely later today followed up by more widespread strong to severe
storms in the afternoon and evening, mainly towards BMG/IND/HUF.
Brief MVFR or worse conditions are possible with any
thunderstorms. Outside of convection, winds will generally be
south or southwesterly at 5-10kts through the TAF period.

Fog development is expected by late tonight, especially near HUF/LAF.

The LAF ASOS is currently out of service, so no AMDs are scheduled
beyond typical TAF issuances due to low confidence on present
weather.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch through this evening for INZ021-028>031-035>049-
054>057-063>065-072.

&&

$$

UPDATE...Puma
AVIATION...Melo
DISCUSSION...White