399
FXUS63 KIND 041336
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
936 AM EDT Sat Jul 4 2026

.KEY MESSAGES...

- Heat Advisory through 9PM today

- Greater thunderstorm coverage compared to Friday, storms may
  impact afternoon and evening activities

- Damaging winds and heavy downpours will be the main threats

- Trending cooler into next week with daily chances for showers and
  storms

&&

.FORECAST UPDATE...
Issued at 936 AM EDT Sat Jul 4 2026

This morning, radar was showing a boundary moving across northern
portions of the area. Satellite shows a weak upper impulse across
Illinois with stronger pieces of upper energy across Iowa and
Kansas. Earlier convection across the area has dissipated.

Forecast is in good shape given the uncertainties in convective
coverage today. With earlier convection having dissipated, and
satellite showing little in the way of convective cloud development,
removed PoPs for a couple of hours across the south this morning.
Across the north, where a boundary is located, left isolated PoPs.

With at least one boundary and a weak impulse across the area,
expect convection to be around by early this afternoon. Coverage
will increase with increasing instability, but uncertainty remains
on just how widespread it will become this afternoon. For now left
likely PoPs by mid afternoon. Will continue to adjust if needed.

Still looks like the stronger upper impulses to the west could
generate convection across Illinois that could organize and move
into the forecast area early this evening. If so, PoPs after 00Z
would have to be raised.

The severe threat still looks good with localized
downbursts/damaging winds the primary threat. If the storms become
organized in Illinois, damaging winds would still be the primary
threat. High temps look good given expected conditions.

&&

.DISCUSSION (Today through Friday)...
Issued at 104 AM EDT Sat Jul 4 2026

Overview.

Scattered thunderstorms are expected to develop across central
Indiana this afternoon and evening, with a few storms capable of
producing localized damaging winds. Warm and humid conditions will
persist through the weekend. A stronger cold front is projected to
move through the region mid-to-late next week, bringing more
widespread rain chances and a return to seasonal temperatures.

Today Through Sunday.

The convective environment across central Indiana today will feature
high thermodynamic instability paired with weak kinematic support.
Water vapor imagery and 500mb charts show the sub-tropical ridge
axis flattening and shifting slightly south of the Ohio Valley,
allowing a weak shortwave impulse and an associated surface trough
to move into northern and central Indiana.

In the near-term, we are tracking a complex of sub-severe storms
slowly sliding to the southeast across northeastern Illinois and
northwestern Indiana. Cloud tops are gradually warming, so expect
the thunderstorms to continue to gradually weaken, but at least a
few rumbles of thunder and brief heavy rain look likely for much
of north central Indiana towards the late overnight.

The next round of convective initiation is expected during peak
diurnal heating with highest confidence in storms generally between
19Z and 02Z. CAMs show a wide range of solutions which is typical in
weakly-forced environments like this. CAMs also have underdone
convective initiation, so will be bumping up POPs quite a bit and
trying to focus the highest POPs where any boundaries from the storm
complex to the north settles out.

Model soundings show a profile favorable for wet microbursts. MLCAPE
values are forecast to reach 3000 to 3500 J/kg, driven by surface
dew points in the mid-70s and ambient temperatures in the low 90s.
Soundings also exhibit a well-mixed lower troposphere with 0-3 km
lapse rates near 7.5 C/km and a layer of mid-level dry air, yielding
DCAPE values over 1200 J/kg. With PWAT values around 2.0 inches,
heavy precipitation loading is anticipated within storm cores. As
these cores descend, negative buoyancy and evaporative cooling will
enhance the potential for localized downbursts capable of producing
straight-line winds up to 60 mph. Because 0-6 km bulk shear remains
under 15 knots, storms will be slow-moving and outflow-dominant,
which introduces additional uncertainty regarding storm longevity
and the potential for localized heavy rainfall.

Convection coverage should increase towards the late evening
hours with the loss of solar heating, but there are some signs
that a more organized complex of storms may be moving east out of
Illinois which could be enhanced by cold-pooling of afternoon
storms. If this occurs, evening firework activities will likely be
impacted with highest confidence across western Indiana. Sunday
will see additional storms with similar conditions to Saturday,
although the instability looks lower which will also lower the
severe threat.

Monday Through Friday.

Central Indiana will remain positioned on the southern edge of a
progressive northwest flow regime aloft through early next week.
This pattern will keep the area susceptible to minor shortwave
ripples and the remnants of convective complexes moving out of the
Upper Midwest. Scattered, mainly diurnal showers and thunderstorms
will remain possible Monday and Tuesday within a humid and minimally
capped boundary layer.

Long-range guidance is in good agreement on a more significant
pattern change by mid-week. A robust northern stream shortwave
trough is forecast to dig into the Great Lakes region on Wednesday,
driving a cold front southward through Indiana. This front will
provide the necessary lift for more widespread showers and
thunderstorms Wednesday afternoon and evening. The severity of the
convective threat will depend on the exact timing of the frontal
passage and available instability. Behind the front, strong Canadian
high pressure will overspread the Midwest for Thursday and Friday.
This will usher in a much cooler and drier air mass, bringing
temperatures back into the upper 70s and low 80s and lowering dew
points into the comfortable 50s by the end of the week.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 606 AM EDT Sat Jul 4 2026

Impacts:

- Isolated TSRA as early as 18Z, becoming scattered towards 22Z

Discussion:

Rain is quickly coming to an end across central Indiana with a lull
expected through the morning hours. Additional thunderstorm
development is expected this afternoon with uncertainty as to the
timing and coverage. Confidence is highest in the 22Z to 03Z
timeframe with best chances at HUF. VFR conditions expected outside
of convection with winds generally southwesterly at 5-10kts.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM EDT this evening for INZ021-028>031-
035>049-051>057-060>065-067>072.

&&

$$

UPDATE...50
AVIATION...White
DISCUSSION...White