660
FXUS63 KIND 021728
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
128 PM EDT Tue Sep 2 2025

.KEY MESSAGES...

- Seasonable and dry through Wednesday afternoon

- Rain expected Wednesday night with amounts of 0.25" to 0.75"

- Low threat for additional rain late Friday into Saturday

- Another round of cooler and drier air late week into next weekend

&&

.SHORT TERM (This evening through Wednesday night)...
Issued at 126 PM EDT Tue Sep 2 2025

Rest of Today and Tonight.

As of early this afternoon coverage of diurnal cu continues to
slowly increase with saturation at the top of the boundary layer
as surface temperatures are warming into the upper 70s to low 80s.
Winds will become increasingly variable through the evening with
little to no wind from the surface to the top of the boundary
layer. A weak surface trough and associated with a mid-level vort
max will bring some mid and high level clouds to the southern
portions of the forecast area but otherwise mostly clear skies are
expected again tonight. Surface dew points will be a bit higher
tonight which will help to moderate the overnight lows a bit with
most areas only falling into the mid to upper 50s.

Wednesday and Wednesday Night.

Another day of near normal temperatures is expected for Wednesday
ahead of a strong frontal system that is expected to bring
widespread rain and a few rumbles of thunder to central Indiana.
Models are well capturing the overall synoptic pattern and timing of
the front with a strong upper level low centered over southern
Canada and a cold front stretching southward into the southern Ohio
Valley. On the mesoscale side there are some fairly significant
differences in the individual shortwaves within the broader trough
that lead to the axis of heaviest rain being shifted north to south.

The broader synoptic models keep the heaviest rain across northern
Indiana with the main surge of synoptic forcing, but there is
increasing confidence in a secondary axis across southern Indiana
where higher resolution models are trending towards a stronger LLJ
with a better connection to Gulf moisture. Plan on trending the
forecast more towards this outcome as this lines up well with
typical conceptual models of overnight frontal passages in the
convergence zone of a strengthening LLJ.

Precipitation may begin across the far northwestern counties as
early as 5PM but is more likely to be more towards the 9-11PM time
frame with scattered to numerous showers and storms continuing
through the night with a gradual southeastern progression. Total QPF
looks to be in the 0.25" to 0.75" range with locally higher amounts
in locations that see more than one round of showers. There may be a
few lingering showers towards daybreak tomorrow, but the majority of
the rain will have exited the area by morning.

&&

.LONG TERM (Thursday through Tuesday)...
Issued at 126 PM EDT Tue Sep 2 2025

Thursday Through Sunday.

Another surge of cooler air will move in behind the exiting upper
level trough with precipitation expected to be exiting the are by
12Z. Clouds will likely linger behind into the early afternoon as
drier air slowly works in from the northwest, but by mid afternoon
skies should be partly cloudy to mostly clear. Models have backed
off on the strength of the cold air initially with a second and much
stronger cold front passing through Friday. The atmosphere will be
fairly starved of moisture ahead of the front with the previous
system pushing southward and trapping the Gulf air which should
limit the coverage and intensity of any shower that forms. That
being said, models have begun to more strongly hint that there could
be a shortwave within the broader trough that would bring another
round of rain to the Ohio Valley but there are significant model
differences as to where this axis of rain would set up along with
the amounts.

Where confidence is much higher is that temperatures will be much
below normal through the weekend with lows in the low to mid 40s
across portions of north central Indiana with highs struggling to
reach 70.

Monday and Tuesday.

Forecast confidence is low going into next week with a wide model
spread on the synoptic pattern. There are hints in a stronger upper
level low developing in the lee of the Rockies and tracking
northeast, but timing and strength remain very uncertain. If the low
develops and deepens as the GFS suggests, heavy rain will be
possible across central Indiana, but will need to see more
consistent runs before latching onto that solution. Temperatures
will begin to warm closer to normal by mid-week but much of the
details will be dependent on the broader pattern.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 126 PM EDT Tue Sep 2 2025

Impacts:

- None.

Discussion:

VFR conditions are expected through the TAF period with mostly clear
skies expected outside of afternoon diurnal cu today and some
passing cirrus tonight. Expect winds to remain light and variable
through the period with a predominately easterly to northeasterly
direction.

&&

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

$$

SHORT TERM...White
LONG TERM...White
AVIATION...White