046
FXUS63 KIND 270631
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
231 AM EDT Mon Jul 27 2026

.KEY MESSAGES...

- Hot and humid conditions through Monday

- One or more thunderstorm complexes possible tonight into Monday
  night, with damaging winds and heavy rainfall the primary
  threats, though uncertainty on exact details remains high

- Rain free Tuesday-Thursday amid near to slightly below normal
  temperatures/humidity...with northerly breezes Tuesday, Wednesday

&&

.DISCUSSION (Today through Sunday)...
Issued at 225 AM EDT Mon Jul 27 2026

Today through Tonight

An upper level ridge will continue to build eastward within modest
westerly WAA. This WAA within the lower levels will continue to push
temperatures and dew points well above normal building deep
instability across the region. MUCAPE values will exceed 3000 J/kg
by noon, with values likely pushing above 4000 J/KG towards the
middle of the afternoon through the evening. 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 the source of upward motion to
initiate these thunderstorms is still a bit of an enigma. There is
building confidence on a convective complex initiating along a weak
shortwave early this morning over the upper Great Lakes region, with
a majority of the CAMs pushing this complex southward into the Ohio
Valley this afternoon. The primary threat with this thunderstorm
complex will be wind gusts of 60-80MPH, but small hail and an
isolated tornado cannot be completely ruled out.

Even with this additional confidence in general timing, specifics on
timing and location remain fairly uncertain within the previously
mentioned window due to somewhat ambiguous storm motions. Unlike
strongly forced events, storm motion will greatly depend on the
placement of any developing cold pools and its relation to the
ongoing thermodynamic parameters. This could lead to a storm motion
range from 340 degrees to potentially 20 degrees over the course of
this event. Also, CAMs notoriously struggle with translation speed
and longevity of these thermodynamically induced convective
complexes due to underestimating cold pool density and interaction
within the ongoing environment. This is a lot of information to say,
be very hesitant on taking any CAM reflectivity output verbatim this
afternoon, and thus confidence in thunderstorm passage for any
specific location will likely have to wait until 3-6 hours ahead of
arrival.

After this first convective threat this afternoon, additional
thunderstorms are expected to develop along and ahead of a diffuse
frontal boundary between 01-08Z. As with the first round, confidence
is fairly low on any specifics, but the overall atmospheric
parameters will remain potent enough for an additional severe threat
with wind once again being the primary threat. This time, greatest
confidence will shift towards NE portions of the area, as this
portion looks to have slightly greater surface confluence and
therefor a greater confidence in convective forcing.

The temperature forecast today will also be fickle and will greatly
depend on thunderstorm timing and location. The WAA previously
mentioned will push a very humid airmass into the region with dew
points likely nearing 80 and temperatures pushing into the low 90s.
This combination will likely lead to a prolonged period of heat
index values above 100 and a few hours between 105-110. For this
reason, a Heat Advisory has been issued. The current ending time for
the advisory will be 01Z, but this could be canceled early depending
on cooling impacts from afternoon convection. As stated, a frontal
passage is expected overnight into tuesday morning. The front is not
strong, but will still push temperatures back towards seasonal for
the coming week.

Tuesday through Sunday...

Strengthening hot and humid upper subtropical ridge over western
North America...will be offset partially by progression of smaller
weaknesses plunging from north-central CONUS to Ohio Valley...which
will likely result in slightly below-normal warmth and humidity
across central Indiana through at least Thursday morning.  First
cool front progged to push south across the region around dawn
Tuesday, with northerly gusts actually up to 20-25 mph for many
locations...only allowing low to mid-80s for central/northern
counties, and noticeably lower humidity for all by late evening.

Tuesday night to Wednesday night to host most pleasant conditions,
as weak but amplified surface high pressure builds south from James
Bay into much of the Midwest...and ridge axis` alignment near the
Wabash Valley maintaining lower dewpoints and readings for most of
the region into early Thursday...with highs Wednesday around 80-85F
amid more September-like breezes...flanked by consecutive overnights
with lows around 60F.

Late work week to transition warmer and touch more humid as upper
ridge tries to build east across central US...which will at least
push the surface high out of the region, returning light southerly
breezes and perhaps a few afternoon showers/t-storms for Friday-
Saturday. Low confidence in any 90s returning late in the period as
next northern mini-wave plunges/slows down across the Midwest during
the weekend, with accompanying clouds...and what should eventually
be a flip back to northerly winds and only low-chances of convective
showers by the very end of the long term, with near normal ranges in
the 60s/80s.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 125 AM EDT Mon Jul 27 2026

Impacts:

- Fog possible tonight into the morning. Prevailing MVFR with tempo
IFR to LIFR

- Storm complexes may impact the area late morning through late
afternoon and again late this evening into the overnight

- Non-thunderstorm wind gusts out of the south this afternoon up to
18kt

Discussion:

Low lying fog is expected throughout the morning over the western 3
sites, this should clear quickly after 12Z. A BKN cloud deck at
4000ft should become scattered by 15Z, with occasional wind gusts
to 15-18kt. Highly uncertain thunderstorm forecast ahead with
primarily time line of 15-20Z and 02-08Z for central Indiana. A
frontal passage overnight will shift winds from the SW to NW with
winds remaining below 10kt.

&&

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

&&

$$

AVIATION...Updike
DISCUSSION...Updike/AGM