932
FXUS63 KIND 190135
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
935 PM EDT Sat Oct 18 2025

.KEY MESSAGES...

- Showers and thunderstorms becoming widespread this evening and
  tonight with locally heavy rainfall possible

- A few strong to severe storms possible into tonight with damaging
  winds as the primary threat

- Cooler with rain and wind gusts peaking at 35 to 40 mph Sunday

- Seasonably cool temperatures next week

&&

.MESOSCALE UPDATE...
Issued at 935 PM EDT Sat Oct 18 2025

The second round of thunderstorms will likely reach central Indiana
in within the next few hours and continue through 07Z tonight. This
will be associated with a convergent boundary out ahead of an
occluding surface low. The main concern with this setup will be a
robust LLJ between 55-65MPH, of which could lead to 35-45MPH non-
thunderstorm wind gusts along with creating a highly sheared
environment within any convection.

Severe Threat: As stated, shear will be abundant tonight along the
convergent convective line. The main limiting factor will be the
lack of low level instability, and what is likely going to be a
relatively weak cold pool. This will lead to a wide variety of
potential outcomes. Currently, this looks most likely to be a
volatile convective line with minimal lightning, of which would
produce isolated 50mph wind gusts along and south of I-70. However,
there is still a chance for a stronger QLCS to form if this
convective line is able to tap into some limited instability within
some weak moisture return. If this does occur, severe wind gusts and
embedded weak tornadoes cannot be ruled out.

There will also be some convective showers ahead of the line, of
which could tap into the aforementioned LLJ and produce isolated
strong wind gusts.

Flood Threat: Luckily, this round of thunderstorms should not have
as deep of a convective core, resulting in less efficient rainfall.
Also, training is unlikely given shear vectors and the robust
dynamics of this low. That said, consistent stratiform rain across
NW portions of Central Indiana could lead to a fairly wide corridor
of 2+ inches of rain overnight, of which could create minor street
flooding.

&&

.SHORT TERM (This evening through Sunday)...
Issued at 210 PM EDT Sat Oct 18 2025

Rest of This Afternoon...

The initial round of forcing and area of showers and thunderstorms
will push east into central Indiana soon and then it will continue
to move east and northeast. Greatest coverage is expected to be
along and west of I-69. Given the instability that has been able to
build ahead of it along with some shear, a strong wind gust is
possible with these. Locally heavy rain will be a threat as well.

Tonight...

A strengthening upper trough will approach the area while a quickly
deepening surface low moves into lower Michigan. The low level jet
will increase to over 50kt. This will aid in transporting moisture
into the area. The strong forcing and plentiful moisture will bring
widespread rain to central Indiana, so will go high PoPs all areas.
(The initial area of rain looks to move north early tonight as the
surface low deepens, leaving only scattered convection southeast.)

A couple of embedded lines of convection will move through as higher
resolution guidance shows a prefrontal line and another with the
cold front itself. Instability will be weak, but what`s there with
some shear could cause isolated damaging wind gusts or a brief
tornado from mesovorticies along the line. Still think 04-08Z
timeframe looks best for this threat.

Another item to consider is some strong wind gusts (40 mph) ahead of
the line across the eastern half of the area. The low level jet will
strengthen, and stronger winds will get closer to the surface. Some
scattered showers ahead of the main area of convection could bring
down some of the stronger winds as they fall through an initially
dry near surface layer. Will have to keep an eye on this.

The plentiful moisture will lead to the threat of locally heavy
rain, especially closer to the path of the surface low across the
northwest forecast area. This area needs rain, so this will mitigate
flooding concerns some.

Lows will be in the 50s.

Sunday...

There may be a brief period of lower coverage of rain behind the
cold front, but forcing from the upper trough will bring more
widespread rain Sunday. Timing is a little slower than previously
thought, so rain looks to continue into the afternoon before ending
across much of the area from west to east. Will have high PoPs all
areas to start the day, with PoPs gradually diminishing from west to
east.

Relatively strong winds will continue not too far aloft on Sunday,
and some of these will mix down to produce wind gusts in the 30 to
40 mph range at times.

Temperatures will be a far cry from Saturday`s, with readings in the
50s. The wind and rain will help give a chill to the air.

&&

.LONG TERM (Sunday night through Saturday)...
Issued at 210 PM EDT Sat Oct 18 2025

Sunday night through Monday...

Some rain may linger in the far east early Sunday. Otherwise, high
pressure will keep the weather dry during this period. As the high
builds in Sunday night, winds will diminish. However, as a cold
front approaches by Monday afternoon, the tightening pressure
gradient will bring winds up with some gusts around 25mph possible.

Temperatures will be seasonable with lows in the upper 30s and highs
in the 60s.

Monday night into Wednesday...

An upper low will develop and move into the lower Great Lakes area.
At the surface, a cold front will move through Monday night. There
isn`t a lot of moisture to work with, so will go no higher than
chance category PoPs, with highest PoPs north closer to better
forcing.

The upper low may have some spokes of energy with it on Tuesday and
Wednesday, and these may be enough for an isolated shower, mainly
north. At the moment confidence is not high enough to include any
PoPs, but they may have to be added later.

Cooler air will move in, with highs in the 50s to lower 60s. Lows
will be in the 30s and 40s.

Thursday and beyond...

Uncertainty rises in this part of the long term as questions remain
on the timing and path of a southern stream upper low. It could
bring chances for rain around Friday.

Temperatures will be seasonable, and some frost is possible in parts
of the area Thursday and Friday mornings.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 752 PM EDT Sat Oct 18 2025

Impacts:

- Wind gusts up to 25kt this afternoon
- Widespread rain this evening into Sunday
- Outside of convection, worsening conditions this evening
- Winds gusting up to 30kts predawn Sunday into the day

Discussion: Rain will be widespread overnight and flying conditions
will worsen to low MVFR. A brief break in the rain may occur near 10-
12Z then scattered to numerous rain showers will return through
Sunday afternoon. Improvement to VFR will likely occur after 18Z
Sunday.

Gusty winds expected at times tonight and then continuously
tomorrow. A wind shift will occur overnight with a cold front.
Strong winds aloft will create near non-convective LLWS conditions
tomorrow night.


&&

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

$$

MESOSCALE...Updike
SHORT TERM...50
LONG TERM...50
AVIATION...Updike