819
FXUS63 KIND 201654
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1254 PM EDT Mon Jul 20 2026

.KEY MESSAGES...

- Dry through today but upper level smoke will be over the area

- Growing concern for numerous strong to severe thunderstorms with
  heavy rainfall late Monday night into Tuesday

- Noticeably cooler and less humid for the second half of the week

&&

.FORECAST UPDATE...
Issued at 900 AM EDT Mon Jul 20 2026

Surface analysis early this morning shows high pressure over NY and
PA while a frontal boundary was found over MN and SD, sagging SE.
This was resulting in SE surface flow across Indiana. A convective
cluster was found over SE MN. GOES19 shows high cloud associated
with this drifting SE into NW Indiana. Otherwise, skies were clear
across Central Indiana, although haze was present in most
observations. Aloft the upper flow continued to be dominated by high
pressure in place across the central Rockies, which was allowing a
stream of Pacific moisture to flow across the NW CONUS across the
northern plains and diving southeastward toward the Ohio Valley.

Ongoing forecast remains in good shape. The surface high will
continue to drift east this afternoon as the frontal boundary to the
northwest approaches. Forecast soundings remain dry through the day
as we remain under the influence of of the departing high pressure
systems. However, diurnal CU is expected to develop this afternoon
leading to partly cloudy skies with continued haze. Thus only minor
adjustments will be needed to the ongoing forecast.

One caveat to watch, the convective cluster over MN will drift SE
today, and could reach NW parts of Central Indiana this evening.
Will need to monitor progression through the day to determine if
pops will need to be added.

&&

.DISCUSSION (Today through Sunday)...
Issued at 307 AM EDT Mon Jul 20 2026

Hazy conditions from Canadian wildfire smoke is expected again
today, although should be at least somewhat less dense than what
central Indiana saw yesterday. High pressure across the area will
maintain dry conditions throughout the day and expecting highs in
the 80s again.

The surface high will push off to the east late in the day and into
the overnight hours, with return flow, out of the SW, developing on
the backside. This will help to push more of the smoke out of the
area.

A low developing across central Canada will track north of the Great
Lakes, with the associated cold front tracking across the the region
tonight and into tomorrow. Confidence continues to increase in an
MCS developing to our northwest and diving towards the region
tonight due to this feature.

While there remain differences with respect to the actual evolution
and track of a convective cluster, the presence of a surface wave
along the boundary will promote an enhancement of speed and
directional shear in addition to higher SRH values across the lower
Great Lakes. Timing will be a factor in whether severe convection
will make it into the forecast area and if so how far, but the
greatest risk from an MCS moving into the region will be damaging
winds especially if a mature cold pool develops. The orientation and
strength of the low level jet in tandem with a rapid influx of deep
moisture and PWATS near 2 inches supports heavy rainfall and
flooding concerns as well and this may end up being the main impact
with the potential of a late night/predawn timing early Tuesday.
Rainfall rates will be efficient with the freezing level near 15kft.
Still details to be worked out but potential for impactful
convection late tonight and early Tuesday continues to grow.

The timing and extent of the overnight/early morning convection will
have a direct impact on what takes place during the day Tuesday with
the cold front across the area. In the wake of the convective
cluster, significant uncertainty exists regarding the degree of
destabilization as there is potential for an extended period with
leftover cloud debris limiting heating. Considering the kinematic
environment, any redeveloping convection along the front would carry
an inherent severe risk. The most likely scenario however is that
the greatest potential for severe weather will be to the southeast
of the forecast area Tuesday afternoon and evening. All hazards will
be possible with this redevelopment, but damaging winds pose the
greatest threat. Any convection will depart central Indiana late
Tuesday evening as broad surface high pressure takes over with a
cooler and drier airmass.

The surface high is expected to persist through the end of the week
allowing for growing confidence in high temperatures to range from
the mid 70s to low 80s and lows down into the 50s for a couple of
nights. The cooldown won`t last long as models show the high exiting
and returning surface flow from the south to southwest with
temperatures likely returning to near to above normal.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1254 PM EDT Mon Jul 20 2026

Impacts:

- Smoke/Haze continues this afternoon.

- Showers with some thunderstorms expected overnight into Tuesday
morning. MVFR conditions possible.

Discussion:

High pressure east of Indiana continues to provide subsidence and
haze across the TAF sites. Some afternoon CU is expected to develop
given expected inverted V soundings. Overall this will result in
some MVFR visibilities this afternoon and evening.

Any CU is expected to diminish after sunset.

An upper wave and cold front is expected to arrive from the
northwest across Indiana late tonight and into Tuesday. This feature
will have sufficient moisture and instability overnight to generate
some showers and storms. HRRR projects arrival and passage during a
09Z-14Z window, thus have used VCSH/VCTS and some tempo groups
during that time. Any TSRA that strikes a TAF site may produce
MVFR/IFR conditions.

In the wake of the storms after 14Z...VFR conditions will return
along with NW surface flow.

&&

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

$$

UPDATE...Puma
AVIATION...Puma
DISCUSSION...Ryan/KF