328
FXUS63 KIND 101650
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1250 PM EDT Mon Aug 10 2026

.KEY MESSAGES...

- Hot and humid through at least mid week, with daily chances for
  showers and storms...especially through Friday morning

- Multiple rounds of severe storms will be possible from early
  today through at least Wed night...w/damaging winds, heavy
  rainfall/flash flooding the primary threats

&&

.FORECAST UPDATE...
Issued at 916 AM EDT Mon Aug 10 2026

Surface analysis late this morning shows southwest flow in place
across Indiana. This was due to a weak trough of low pressure
stretched from northern Michigan to IA and NRN KS and strong high
pressure in place across the southeastern states. GOES19 shows a
thunderstorm cluster over NRN Ohio, while a wave of clouds and light
rain were found over MI, pushing into IL. Scattered clouds were still
found across central Indiana. Dew points were quite high, in the
lower 70s. Aloft, water vapor shows mainly a NW flow in place.
streaming from MT and WY, across the upper midwest, before slipping
slightly south to the southern Great Lakes and northeastern states.

Models through the day show the NW flow to remain in place aloft.
Weak embedded short waves within this flow will continue to be
possible triggers for TSRA development, particularly across northern
parts of the forecast area, closest to the ongoing flow aloft.
Models continue to show uncertainty with positioning and timing of
these waves, but for the moment, best timing looks to be this
evening and late tonight. Latest ACARS soundings show a weak CAP in
place at the moment, but plenty of CAPE aloft, over 2000 J/KG.
Forecast soundings show even more, and very deep CAPE over 4000 J/KG
available  this afternoon, but still, a CAPE remains at that time
near 800mb. HRRR fails to show much development through the
afternoon and peak heating hours. Thus there appears to be many dry
hours ahead through the late morning and afternoon hours, but an
isolated TSRA late this afternoon cannot be ruled out due to the
strong potential instability aloft. Thus will focus some minimal
pops through the mid to late afternoon. Given our very warm
air mass in  place highs in the lower 90s appear on target.

&&

.MESOSCALE UPDATE...
Issued at 306 AM EDT Mon Aug 10 2026

Smaller yet severe mesoscale convective complex currently crossing
into northwest Indiana will enter northern portions of the IND CWA
through pre-dawn hours.  While overall slow weakening is expected,
damaging winds are possible for the Lafayette area and east...with
non-zero chances of isolated large hail or a brief, weak tornado.
This convection is expected to cross northern counties through 13Z.

Previous mesoscale discussion follows...

Fairly robust convective development has occurred in the past 90
minutes over northwest Illinois along and south of a quasi-
stationary front and at the nose of a WSW 25-35KT low level jet
associated with a weak shortwave disturbance aloft. Sufficient
effective deep layer shear exists in and upstream of central Indiana
to support storm organization, with the most likely scenario being
initial supercells growing upscale into one or more line segments
that push eastward, then gradually more east/southeastward with time
through the night. Significant uncertainty exists with how far
southward the influence of the complex will extend, but roughly the
northeastern third to half of the area, along and NE of the I-74
corridor, appear to have the greatest threat for strong to severe
storms during the overnight hours.

Modest effective SRH values suggest a non-zero tornado threat, but
upscale growth will likely support primarily an isolated damaging
wind threat, and strongly supportive environmental factors (PWAT
values around climatological 90th percentile, high freezing
levels/deep warm rain processes, and possibly training convection
along the upshear flank of the system) will support a threat for
heavy rainfall and localized flooding as well. HREF local
probability matched means show potential for isolated 1-3 inch
amounts, with higher amounts possible in the strongest cores or
if/where training occurs.

&&

.DISCUSSION (Today through Sunday)...
Issued at 316 AM EDT Mon Aug 10 2026

Early today through Wednesday...

Central Indiana will continue to rest amid the northeastern edge of
a predominant subtropical ridge occupying most of southern North
America...with seasonably modest northwest flow aloft and associated
small/weak forcings...maintaining chances of occasional convective
clusters.  Additionally, a weaker yet broad trough of surface low
pressure aligned from the central Plains across the northern
Midwest, will promote moderate southwesterly breezes...bringing very
warm to hot conditions and increasingly oppressive humidity into the
mid-week.

The resultant higher theta-E will contribute to instability
gradient, although this will likely be strongest along the local
region`s far northern/NE zones...if not even closer to the southern
Great Lakes.
Therefore convective chances within the CWA will be greatest
following upstream development (northern IL) that then trends/curls
SE-ward.
Best chances for organized/severe storms will most likely be Tuesday
PM-overnight hours, and again late Wednesday...with general focus I-
74 corridor and northeast, with lowest confidence on severe
potential over southwest counties.

That said, cannot rule out isolated RW-s at overall less favorable
times given the warm/humid boundary layer...including isolated
thunder later today north of a Lafayette to New Castle line, and
across much of the CWA tonight.  Expect temperatures through
Wednesday to range from 68-75F to 85-93F, with a distinct NNE-SSW
gradient, which may be increased by greater cloud cover over NE
counties Tue-Wed.

Thursday through Monday...

Remainder of the period to most likely feature see-saw of conditions
as quasi-stationary surface cool front along the northern side of
very broad and very humid subtropical ridge...probably slides south
by late Thursday, placing the region in milder easterly flow...with
the boundary expected to then push north, returning humid southerly
flow for the weekend.  Most periods to yield at least low POPs per
the corresponding frontal zone never really pushing south of the
CWA, although overall convective chances after Thursday night should
be much lower than the early/mid-week.  Readings to range from
mainly 60s to 80s.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1250 PM EDT Mon Aug 10 2026

Impacts:

- Convection possible around and after 00z this evening, best
  chances from LAF to IND northward.

- South-southwest winds gusting to near 20KT this afternoon.

Discussion:

Mainly VFR conditions this TAF period. High uncertainty regarding
precipitation chances due to warm and humid air in place with ACARS
soundings showing minor capping in place near 875mb. As peak heating
is reached this afternoon, Isolated convection cannot be ruled out
through the later afternoon and evening, although any coverage
should be quite limited.

Better forcing may arrive overnight, mainly impacting LAF and IND as
best dynamics should be found across northern Indiana. HRRR suggests
best chances for development will remain north of of TAF site and be
limited to the overnight hours. Thus have included a VCSH mention for
the evening and overnight hours just due the very low confidence for
possible storm development.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for INZ051>053-060>062-
067>070.

&&

$$

UPDATE...Puma
AVIATION...Puma
DISCUSSION...AGM