Severe Thunderstorm Warning 268, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
320 AM 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

&&

.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 (06Z TAF Issuance)...
Issued at 155 AM EDT Mon Aug 10 2026

Impacts:

- Convection possible 08Z-14Z at KLAF/KIND...and after 00Z Tuesday,
  especially near KLAF/KIND MVFR conditions possible at times within
  storms

- Near LLWS conditions at KLAF through pre-dawn hours

- South-southwest winds gusting up to 15-20KT within 12Z-22Z

Discussion:

VFR to prevail near central Indiana terminals outside of convection
through Monday evening.  Current upstream convection most likely to
impact KLAF around 08Z-11Z with lower chances of MVFR from -TSRA at
KIND around 10Z-14Z...VFR expected to continue at KHUF/KBMG through
Monday morning. A second convective cluster is possible, most likely
after 02Z Tuesday.

Otherwise expect near-LLWS conditions over KLAF around the 10Z-12Z
timeframe.  Generally south-southwest surface winds will remain near
or just below 7KT/10KT thresholds through 11Z outside of any cells.
Flow to increase to 8-13KT by 16Z, with gusts up to 15-18KT by 15Z,
peaking 15-20KT around 16Z-20Z.

A few gusts near 20kt are possible later this afternoon. Increasing
winds aloft will bring near LLWS conditions tonight but have not
included a mention in TAFs at this time.

&&

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

&&

MESOSCALE...Nield/AGM
AVIATION...AGM
DISCUSSION...AGM

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