786
FXUS63 KIND 142256
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
Issued by National Weather Service Louisville KY
656 PM EDT Mon Sep 14 2026

.KEY MESSAGES...

- Hot and humid conditions return Tuesday and Wednesday with highs
  reaching the 90s

- Thunderstorm chances increase late Tuesday through Wednesday night
  with localized heavy rainfall

- Shower and storm risks persist through late week along a slow-
  moving frontal boundary

&&

.DISCUSSION (This evening through Monday)...
Issued at 1253 PM EDT Mon Sep 14 2026

Overview.

Hot and humid conditions return on Tuesday as high pressure slides
off to the east and warm air streams back into Central Indiana. A
stalled weather front over the region will bring periodic chances
for showers and thunderstorms from Tuesday afternoon through mid to
late week. High temperatures will top out in the lower to mid 90s
through Wednesday before a stronger cold front clears the area over
the weekend, bringing cooler and drier weather by next Monday.

Tonight Through Wednesday.

Surface high pressure drifting eastward into New England will allow
low-level return flow to intensify overnight, initiating theta-e
advection across the Mississippi and Ohio Valleys. Guidance from the
HRRR and HREF indicates an overnight 850mb LLJ of 35-40 kt
supporting upstream convection over the Upper Midwest. Remnant
convective debris and weakening showers may reach northern portions
of the forecast area Tuesday morning before the LLJ decays. Diurnal
heating within strong return flow will drive Tuesday afternoon
maximum temperatures into the lower 90s, with surface dewpoints
rising into the upper 60s and lower 70s. Model soundings display
steep low-level lapse rates below 700mb, yielding SBCAPE values
exceeding 2000 J/kg and DCAPE above 1000 J/kg. Weak tropospheric
shear will constrain storm organization, but pulse convection will
carry a localized threat for damaging microburst winds into Tuesday
evening. Outside of thunderstorms, gradient wind gusts up to 20 mph
are expected during the afternoon hours with the mixing down of
boundary layer winds.

The baroclinic zone sags southward into Central Indiana Tuesday
night into Wednesday as a series of shortwave impulses ripple
through mid-level westerly flow aloft. Substantial moisture
transport will push PWAT values to 1.75-2.00 inches across the warm
sector. Strong PVA combined with low-level convergence along the
boundary will trigger periodic convective clusters overnight Tuesday
and through Wednesday. Given deep warm-cloud depths and mean flow
oriented parallel to the surface boundary, efficient warm-rain
processes will present a risk for localized training and heavy
rainfall. High temperatures on Wednesday will exhibit a sharp
gradient, ranging from the upper 80s north of the boundary to the
mid 90s south.

Thursday Through Monday.

The synoptic pattern through late week features strong sub-tropical
ridging anchored over the southeastern states with active zonal flow
across the northern tier of the CONUS. Central Indiana remains
positioned along the northern periphery of the thermal ridge,
keeping the quasi-stationary surface front positioned over the
region. Both GFS and ECMWF deterministic solutions, along with their
respective GEFS and EPS ensemble means, project elevated mid-level
moisture and weak convective shortwaves continuing to generate
diurnally enhanced showers and thunderstorms Thursday and Friday.
High temperatures will remain elevated in the upper 80s to lower 90s
with high ambient humidity.

A pattern shift occurs over the weekend as a deeper upper-level
trough traverses the Upper Midwest and Great Lakes basin. The
associated surface cyclone will push the cold front southward
through the Ohio Valley by Saturday night. Upper-level dynamics and
strengthening PVA along the trough axis will support widespread
precipitation along the frontal zone. Strong post-frontal CAA will
establish northwest flow in the 925-850mb layer by Sunday morning,
driving a slightly cooler airmass into the region. Radiational
cooling beneath building surface high pressure will lower high
temperatures into the lower 80s by next Monday.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 653 PM EDT Mon Sep 14 2026

Impacts:

- VFR expected this TAF period

Discussion:

VFR Conditions will be expected this TAF period. High pressure centered east of
our area will continue to slowly exit east overnight. A strengthing surface pressure
gradient will allow winds to remain around 5-10 knts overnight. This with low dew points
across the area will prevent fog formation. Thus only a few passing high clouds
as seen on GOES19 will be expected. Cigs should remain unlimited.

On Tuesday, the surface high will continue to drift east as a cold front approaches from
the northwest. Forecast soundings through the day continue to
show a very dry layer within the lower levels and this should
prevent CU for much of the day, leading to VFR conditions. Some
chances for rain will be possible at IND after 00Z Wed as the cold
front arrives and saturation is noted within the mid levels.

&&

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

$$

AVIATION...JP
DISCUSSION...White