122
FXUS63 KIND 261730
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
130 PM 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

&&

.FORECAST UPDATE...
Issued at 952 AM EDT Sun Jul 26 2026

Trimmed high temperatures back a couple/few degrees with low clouds
and fog impacting morning insolation. Clouds are beginning to
scatter out however, so do not expect nearly as strong an impact to
high temperatures as what occurred yesterday, with the mid to upper
80s still well in reach today, and perhaps even a 90 degree reading
sneaking into our far southwest.

Partly cloudy skies can be expected this afternoon with warm and
humid conditions driving heat index values into the 90s across
portions of the area.

&&

.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 (18Z TAF Issuance)...
Issued at 129 PM EDT Sun Jul 26 2026

Impacts:

- Lingering MVFR ceilings at HUF early

- MVFR fog possible overnight

- Chance of thunderstorms near daybreak into the morning hours Monday


Discussion:

Low clouds have gradually scattered out in many places this morning,
but MVFR ceilings linger at HUF. VFR should return there in the next
few hours.

With plentiful low level moisture and light to calm winds overnight,
expect fog development again, though not quite to the same degree as
this morning, with mid and high cloud working against radiational
cooling. Will take the outlying sites down to 3-4SM.

There is a highly conditional thunderstorm threat late tonight into
the morning hours Monday, and will carry PROB30 at all sites for a 4
hour or so period somewhere in the 09-15Z time frame depending on
the site. Confidence in this is low, but any storms that do impact
the area will have the potential to be strong, so wanted a mention
of some kind in.

Winds will be fairly light and frequently variable through the
period.

&&

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

&&

$$

UPDATE...Nield
AVIATION...Nield
DISCUSSION...Updike