695
FXUS63 KIND 181907
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
307 PM EDT Mon Aug 18 2025

.KEY MESSAGES...

- Isolated to scattered showers and storms this afternoon with
  potential for greater coverage over northern counties late this
  evening into the overnight

- Scattered strong storms Tuesday producing heavy rainfall

- Very warm to hot and humid conditions expected through Tuesday

- Dry and cooler late this week through early next week; Highs
  falling into the upper 70s and low 80s by Sunday

&&

.MESOSCALE UPDATE...
Issued at 306 PM EDT Mon Aug 18 2025

Long-lived strong thunderstorm that has steadily crossed the region
from the Upper Wabash Valley earlier this morning...is currently
impacting westernmost portions of the Indianapolis Metro. Gusts at
both KIND and KEYE have been nearing 30 mph...with possibly slightly
higher winds in eastern Hendricks County, on a trajectory towards
northeastern Morgan County.  Scattered areas of lighter rain
surround patches of moderate rainfall rates along the I-70 corridor
from near Cloverdale to the KIND airport, as well as eastern
Hendricks County.  Rain will continue tracking to the south-
southeast while continuing to slowly weaken amid an overall capped
thermal profile.

Temperatures will likely fail to reach 90F for many points from
Indianapolis and to the north/west...courtesy of remnant clouds
and some lingering -RA towards the Lafayette area.

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 223 PM EDT Mon Aug 18 2025

Mainly isolated convection continues across the northern Wabash
Valley in the vicinity of a boundary separating the oppressive and
more unstable airmass to the west.

The upper level ridge will expand into the region through the rest
of the day and into early Tuesday but will be shortlived as it
quickly retrogrades and reestablishes over the southern Rockies.
This will lead to a buckling of the mid level heights and enable a
frontal boundary currently over the northern Plains and upper
Midwest to shift south into the region on Tuesday. Model guidance in
general has sped up the southward progression of the boundary with a
growing confidence that it will be located across southern portions
of the forecast area by Tuesday evening.

The rest of the afternoon remains in a bit of flux with the presence
of the aforementioned boundary across the northwest portions of the
forecast area. Increasing instability will gradually shift east
across the forecast area this afternoo. Despite a strengthening of
the capping inversion...convection may persist from the Indy metro
west and northwest for the next few hours.

The remnants of a convective cluster over Iowa and Minnesota earlier
this morning continues in a weakened state over southwest Wisconsin.
Renewed development is likely along the remnant outflow across
northern Illinois by late day and this should progress downwind into
northern portions of Indiana this evening. Establishment of a more
mature cold pool will determine if the convection can make it as far
south as the northern Wabash Valley by late evening as wind fields
are much weaker with diminishing instability further south. At this
point...will carry precip chances into northern counties late
evening into the overnight but keep them confined primarily to the
northwest half of the forecast area. Convection should be below
severe levels by the time it arrives late this evening but a few
cells will likely produce gusty winds.

The remnants of the evening convection is likely to produce an
outflow boundary that will set up somewhere further south across the
forecast area and serve as a focal point for renewed development
Tuesday afternoon in addition to the frontal boundary. This is
likely to align more across the southeast half of the forecast area
by the afternoon. Modest instability with MLCAPE values near 3000
j/kg will combine with precip water values between 1.75 to 2 inches
to produce torrential rainfall as a primary impact. There is
potential for localized downbursts with stronger cells with DCAPEs
above 1000 j/kg and the strong heating expected ahead of the front.
Primary timing for storms will occur during the afternoon into the
evening.

Temps...A sticky afternoon ongoing with temperatures likely to top
out in the upper 80s and lower 90s in most locations with heat
indices up to 100 degrees in the Wabash Valley. After a night with
lows ranging from the mid 60s to lower 70s from east to west...
highs will rise into the upper 80s and lower 90s again for Tuesday
with an uptick in overall dewpoints into the mid 70s by afternoon.
This will create plenty of fuel for convection to fire off of later
in the day while also enabling heat indices to peak in the lower
100s over most of the forecast area. Have no plans at this time for
a Heat Advisory with much of the forecast area remaining below
criteria.

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 223 PM EDT Mon Aug 18 2025

Wednesday through Sunday...

Dry and seasonable weather is expected on Wednesday through Sunday.

A few showers may be possible on Wednesday morning as Tuesday`s cold
front may still be lingering across the far southern and eastern
parts of Central Indiana. After this departs, strong high pressure
aloft over the American southwest is expected to extend a ridge axis
to the Great Lakes. This ridge axis will progress across Indiana
through Friday and into Saturday as it reaches the Tennessee River
Valley. Surface high pressure is expected to accompany this feature.
Forecast soundings on Wednesday through Saturday show subsidence and
dry air within the mid and upper levels. These ingredients will not
be favorable for convective development. Thus a period of mostly
sunny days and mostly clear nights will be expected. The expected
dominate surface high pressure system through this time will be
found north of Central Indiana. This will result in surface flow
having a more easterly or northeasterly component, allowing for
seasonal highs in the middle to upper 80s and lows in the lower to
middle 60s.

Sunday and Monday...

Northwest flow aloft is shown to develop by Sunday and Monday,
allowing an upper level trough to push into Indiana. This system
appears to be accompanied with a surface cool front, which will
allow even cooler temperatures to arrive for next week. Given the
upper forcing and surface front expected to pass, this will be our
next best chance for rain in our forecast. Confidence is low for
rain as southerly gulf flow never really materializes. Moisture
availability remains a concern.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1227 PM EDT Mon Aug 18 2025

Impacts:

- Isolated convection possible near KLAF this afternoon then again
  mid evening into the overnight
- Scattered storms developing again by midday Tuesday
- Patchy fog possible primarily at KLAF predawn Tuesday

Discussion:

A persistent area of convection near KLAF may linger past 18Z but
the overall trend through the latter part of the afternoon will be
for limited to no impacts from storms as the ridge aloft builds in
from the west. By this evening however...a more robust convective
cluster will approach the region from the northwest and may again
impact KLAF into the overnight with restrictions and perhaps brief
gusty winds from storms as well. Any rain would contribute to an
increase risk for visibility restrictions in the predawn hours
Tuesday.

A frontal boundary will slide south into the region by early Tuesday
and will serve as a focal point for renewed convective development
by late morning Tuesday into the afternoon...especially for areas
near and south of I-70. Will carry PROB30s at KIND and KHUF after
14Z and may need to introduce one at KBMG with later TAF
issuances.

&&

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

$$

MESOSCALE...AGM
SHORT TERM...Ryan
LONG TERM...Puma
AVIATION...Ryan