318
FXUS63 KIND 120436
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1236 AM EDT Sat Sep 12 2026

.KEY MESSAGES...

- Scattered to numerous showers along with a few storms return
  tonight and continue into Saturday

- Generally above normal temperatures through the period, with the
  exception of Monday.

- Rain chances return Sunday and again Tuesday through next Friday

&&

.FORECAST UPDATE...
Issued at 957 PM EDT Fri Sep 11 2026

Higher dewpoints returned across central Indiana late today ahead of
increasing chances of showers later tonight.  Midwest now
transitioning from brief period of seasonably milder conditions to
more of the same August-like warmth/humidity with zonal subtropical
ridge on tap to arrive from southern Plains.  For the near term,
weak mid-level wave between exiting surface high and approaching
warm ridge will twist from Middle MS Valley and up OH Valley...
bringing enough lift to push a cluster of scattered/numerous RWs
from far southern zones around 06Z to eastern counties by daybreak.
Embedded thunder is on the table, with no severe cells expected.  At
least patchy fog is favored over mainly southern central Indiana
where low 70s-dewpoints will continue to expand.  Minimum
temperatures by early Saturday are expected to range from 65F in
Carroll County to 68F inside I-465 and across most southern zones.

&&

.DISCUSSION (This evening through Friday)...
Issued at 211 PM EDT Fri Sep 11 2026

Rest of This Afternoon through Saturday...

This afternoon, an upper trough was across Missouri into Arkansas.
Most rain to the south of the area had dissipated. Thicker clouds
continued across the far southern forecast area.

The upper trough will gradually move northeast through the forecast
area through Saturday. An isolated shower or thunderstorm is
possible late this afternoon into this evening across the southern
forecast area, but better chances for rain will arrive overnight as
the upper trough gets closer.

Increasing mid level winds will lead to increasing isentropic lift
overnight, and this flow will also bring in better moisture. These
should be enough for scattered to numerous showers to develop
overnight and continue into Saturday morning. The highest coverage
will be across the eastern forecast area where forcing will be
highest.

Some thunder is possible, but severe weather is not expected.

Some patchy fog may also form overnight as the atmosphere moistens
up.

Rain chances will diminish from west to east on Saturday afternoon
as forcing from the upper trough exits.

Lows tonight will be in the 60s, with highs on Saturday in the 80s.

Sunday and Monday...

Guidance has trended stronger with an upper trough on Sunday, which
will send more cooler air into the area behind a front, which should
now move south of the area Sunday night. The front will bring
scattered convection with it, so will have some chance PoPs Sunday
into Sunday night.

Some guidance is quite aggressive with the cooler air moving in
Sunday afternoon, with falling temperatures in the late afternoon.
Am not confident of this occurring though. At any rate, temperatures
will peak in the 80s on Sunday.

High pressure should keep Monday quiet and cooler. Uncertainties
remain on just how cool it will be now. NBM 25th and 75th Max T
percentiles for Indy are 76 and 84 respectively. Will stick close to
the mean for now given the uncertainty.

Tuesday onward...

The upper ridge should quickly return north into the area on
Tuesday. This and southwest winds on the west side of exiting high
pressure will allow temperatures to quickly rebound into the upper
80s to lower 90s for highs Tuesday.

For Wednesday into Friday, an upper trough well to the north of the
area will try and push the ridge south and west again. As it does, a
surface front will attempt to move south into the area.

Guidance continues to vary in how fast this occurs, and this
increases the uncertainty in high temperatures and when the best
chances for rain will be during this period. Given this uncertainty,
see no reason to deviate from blended guidance.

This results in PoPs Wednesday through Friday, with gradually
cooling temperatures from the upper 80s/lower 90s Wednesday to upper
70s/lower 80s by Friday. However, the details will likely change.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1235 AM EDT Sat Sep 12 2026

Impacts:

- Scattered to numerous showers with embedded thunder predawn hours
  to near daybreak, especially at KBMG and KIND
- Patchy fog possible predawn hours
- MVFR ceilings developing through midday
- A few thunderstorms will develop mid to late afternoon

Discussion:

A convective cluster over the lower Ohio Valley will lift northeast
into the region over the next several hours. Should see lightning
strikes diminish from current levels as it lifts into southern
Indiana but still feel short TSRA tempo groups are warranted at KBMG
and KIND between 08Z and 11Z. MVFR ceilings will accompany the
showers and settle over all but KLAF around or shortly after
daybreak as the area of rain shifts away to the northeast. Patchy
fog may develop at KLAF in the predawn as well.

Lower clouds will linger into the early afternoon before lifting
into a broken VFR cu field. Enough instability will remain for
isolated convective development this afternoon on the back side of
the departing upper level wave...focused primarily over the eastern
half of central Indiana. Any rain threat will end by early evening
with skies clearing as weak high pressure builds in tonight.

&&

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

&&

$$

UPDATE...AGM
AVIATION...Ryan
DISCUSSION...50