514
FXUS63 KIND 261023
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
623 AM EDT Sun Jul 26 2026

.KEY MESSAGES...

- Areas of dense fog possible this morning

- Hot and humid conditions expected Sunday into Monday

- One or more thunderstorm complexes possible Sunday night and
  Monday night, with damaging winds and heavy rainfall the
  primary threats

&&

.DISCUSSION (Today through Saturday)...
Issued at 127 AM EDT Sun Jul 26 2026

Today:

Central Indiana will be within a transition zone early this morning
into the afternoon as an upper level trough exits eastward and a
broad ridge builds in from the west. Initially, this will promote
subsidence through the mid-levels, and in combination with prior day
low level saturation will maintain a compressed saturated layer near
the surface throughout the morning hours. This saturated layer
will likely remain thin enough to avoid drizzle formation, but
there may be enough latent heat fluxes over the Wabash valley for
pockets of dense fog between 09-12Z this morning.

As stated, central Indiana will remain within this transition zone
until the ridge axis nears overnight. This transition will consist
of moderate WAA over the area throughout the day. WAA along with
weak westerly surface winds should mix out the low level saturated
layer during the morning hours, with the remainder of the day
consisting of mostly upper level clouds within the strong jet stream
and blow off from upstream convection. The resulting temperatures
are likely to push into the upper 80s this afternoon, but likely
will stay below 90 as the cloud cover dampens the typical diurnal
temperature curve.

Forecast confidence is moderately high during the daytime today
with one caveat, a current ongoing convective cluster over NW
Iowa. The aforementioned transition zone will be narrow with a
deep unstable airmass only a few hundred miles to the west of
central Indiana. Although this area of convection is expected to
pulsate throughout the night as it pushes to the E/SE, its
resulting cold pool should remain consistent and will likely
continue to initiate additional convective clusters over northern
and central IL this morning.

The CAPE gradient is expected to remain west of the Indiana border
as this cold pool nears from the west, likely shifting the overall
storm motion southward and keeping thunderstorms to the west of our
area. That said, there is a low chance that the cold pool and
resulting convection remains strong enough to push into the less
favorable atmosphere and is able to clip far western portions of
central Indiana. If this does occur, severe wind gusts cannot be
completely ruled out, and it would likely be between 14-17Z. As
stated, this is a very low threat, but one that should be mentioned
nonetheless. The other impact from this convective cold pool would
be additional cloud cover and cooler air over the Wabash Valley, of
which may lead to slightly cooler temperatures than points to the
east.

Sunday Night through Monday Night:

The aforementioned deep instability will shift eastward with time as
the ridge axis moves resulting in 3000+ MUCAPE late tonight through
Monday night. Shear will also be plentiful as the jet stream
remains aloft, with 35-50kt of effective shear. The combination of
high instability and plentiful bulk shear will lead to a potent
airmass, but we are still missing one key ingredient; a forcing
mechanism. This is where most of the uncertainty resides as the
source of initiation for these thunderstorms will be highly
volatile and difficult to forecast with certainty more than 6-12
hours in advance with CAMs continuing to struggle to converge on
a scenario. The other source of uncertainty will be storm motion.
Unlike strongly forced events, storm motion will greatly depend on
placement of any developing cold pools and its relation to the
ongoing thermodynamic parameters. This could lead to a storm
motion range from 320 degrees to potentially 20 degrees over the
course of this event. The culmination of highly variable forcing
mechanisms and a range in storm motions will lead to a wide
envelope of scenarios over central Indiana for tonight through
Monday; from little to no convection, to multiple potent
convective complexes pushing into the area with damaging wind
potential.

As far as chances for precipitation, they will initially remain below
40 percent for tonight, but will slowly increase throughout Monday
as the number of convective complexes over the region is expected to
increase and a greater source of forcing nears from the north is the
form of a cold front. Greater coverage of thunderstorm complexes on
Monday will also lead to linger outflow boundaries over the region
providing additional sources of lift and therefor higher chances for
rain. the front is expected to move through Monday night, ending
rain chances late Monday night into Tuesday morning.

Temperatures will also be variable on Monday as any areas that see
rain over expansive convection will likely remain considerable
cooler than areas that do not. The high end potential for Monday is
rather oppressive with the potential for afternoon highs to reach
the low to mid 90s with dew points in the mid to upper 70s (Heat
Indices between 103-107).

Tuesday onward...

Cold frontal passage Monday night into early Tuesday will bring
temperatures back down closer to seasonal normals from mid week
onward, with a largely dry forecast until very late in the week as
surface high pressure dominates the area. As the ridge aloft
retrogrades slightly, upper level disturbances late in the week may
promote rain chances, though significant disagreement on these
systems precludes more than a slight chance at this point.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 618 AM EDT Sun Jul 26 2026

Impacts:

- IFR VIS possible until 13Z, mainly at KLAF/KHUF
- Widespread MVFR until 15-16Z
- Low confidence thunderstorms threat overnight


Discussion:

Subsidence through the mid-levels in combination with prior day low
level saturation will maintain a compressed saturated layer near the
surface. This has led to widespread MVFR CIGs and pockets of fog
over western sites. Fog should lift shortly after issuance with MVFR
CIGs improving after 15Z. VFR conditions are then expected through
the rest of the TAF period outside of a low confidence thunderstorm
threat after 07Z tonight.

Winds to be calm or light/variable through the morning hours. After
14Z winds should become light out of the west under 7KT

&&

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

$$

AVIATION...Updike
DISCUSSION...Updike