169
FXUS63 KIND 091352
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
952 AM EDT Wed Sep 9 2026

.KEY MESSAGES...

- A few stronger storms this afternoon and evening with damaging
  winds as the primary threat

- More widespread showers and storms Thursday

- Warm and humid today, then cooler Thursday and Friday

&&

.FORECAST UPDATE...
Issued at 952 AM EDT Wed Sep 9 2026

Multiple waves and outflow boundaries can be seen on radar this
morning across the region. One has initiated showers across the far
northern forecast area, while another has fired convection in
central Illinois.

For now have sped up introduction of low PoPs to account for these.
Unfortunately, these waves and boundaries complicate the overall
forecast for convection today, as the initial convection from these
may interfere with the expected development this afternoon. Will
have to monitor to see which becomes the dominant feature for
convection.

Have thus continued mention of scattered convection today with the
aforementioned adjustments to PoPs this morning.

Have left high temperature forecast alone at the moment as how
convective develops will impact temperatures. Expected instability
still holds the threat for an isolated severe storm with damaging
winds.

&&

.DISCUSSION (Today through Tuesday)...
Issued at 249 AM EDT Wed Sep 9 2026

Upper level ridging will flatten throughout the day today in
response to a sharp upper trough traversing through southern Canada.
This will enable a frontal boundary to drift into the area late
today and move slowly south through Thursday producing chances for
showers and storms. The frontal boundary will wash out to the south
of the area late week as the ridge aloft flexes back into the Ohio
Valley. This will maintain warm temperatures through the weekend and
into early next week along with daily chances for scattered storms.
A more organized threat for rain and storms will accompany a cold
front on Tuesday.

Today through Thursday

The cirrus shield associated with weakening convection over Iowa and
western Illinois was expanding across the forecast area early this
morning. With light southerly flow and an overall muggy
airmass...06Z temperatures remained in the 70s.

Despite the overall downtrend in convective intensity to our
northwest early this morning...it is becoming apparent that mid and
high level clouds will be more prevalent right out of the gate this
morning focused especially across the northern half of the forecast
area. What is less clear is whether any of the ongoing activity even
as it weakens can make it into the northern Wabash Valley by late
morning. With CAMs picking up on the remnant outflow boundary
tracking into the area after 15Z...have nudged up precip chances a
bit faster than previously thought expanding that through the area
into the afternoon and early evening as the outflow progresses to
the southeast.

Thermodynamic profiles do support steepening lapse rates up through
about 700mb this afternoon but much weaker mid level lapse rates.
With deeper shear remaining bottled up to the north...convection
will be heavily dependent on available instability and be in a
scattered pulse intensity mode as the afternoon progresses. DCAPE
values peaking near 1000 j/kg suggest that the strongest elevated
cores will be capable of damaging winds via localized downbursts
with the greatest potential likely across the southern half of the
forecast area where heating through the day will be greatest
subsequently leading to better instability. Still though with the
lack of shear and deep moisture through the column...expect only an
isolated risk for severe storms this afternoon into the early
evening before deeper instability is lost. Have pulled highs down a
bit from the model blend as the increased cloud cover should keep
most areas north of I-70 in the 80s. Where clouds will be less
prevalent across southern counties highs should still make it into
the 90 to 95 degree range.

There now appears to be a lull in overall convective coverage from
mid evening into the overnight as convection diminishes along the
remnant outflow. The frontal boundary will slip south into the area
tonight but more widespread rain will likely wait to impact the
forecast area until closer to daybreak Thursday as 850mb winds
increase across the Ohio Valley and a stronger upper level wave
approaches from the west. This will set the stage for a mainly
cloudy day for much of Thursday with periodic showers and a few
storms. Could see up to an inch in some locations across the
southern half of the forecast area by Thursday evening. Temperatures
will be kept down in the upper 70s and lower 80s.

Thursday Night through Tuesday

Lingering showers will end Thursday night as the cold front shifts
south of the area before gradually washing out on Friday as the
boundary runs into the ridge over the southeast US. The nearby
presence of the remnant moisture plume with the front will
contribute to at least a risk for a few showers in the southeast
Friday with high pressure over the Great Lakes keeping dry
conditions over most of the forecast area. Highs on Friday will be
in the lower to mid 80s.

Return flow developing on the back side of the departing high
pressure will enable low level moisture to advect further north into
the region. An approaching frontal boundary will interact with the
moist and unstable airmass and likely generate better diurnal
convective coverage again focused especially across the southeast
half of the forecast area for both Saturday and Sunday. Highs will
recover as well into the mid and upper 80s.

Developing low pressure over the High Plains early next week will
shift the boundary north as a warm front by Monday enabling a brief
return of a hotter and more humid airmass prior to a cold front
sweeping through the region on Tuesday with a better chance at
showers and storms. Temperatures will remain warm through much of
next week but extended guidance continues to advertise a stronger
cold frontal passage for late next week with the first taste of
early Fall air to follow about 10 days from now.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 649 AM EDT Wed Sep 9 2026

Impacts:

- Peak wind gusts around 20kts this afternoon
- Scattered convection possible by early afternoon at KLAF and later
  in the afternoon into the early evening at the other terminals
- Additional showers late tonight

Discussion:

Mid and high level clouds will continue to overspread the region
through the morning. There remains low confidence with regards to
whether the ongoing convection can make it into central Indiana late
into the afternoon but model soundings show enough instability
present to maintain PROB30s at all of the terminals for expected
scattered convection...likely developing in the vicinity of a
remnant outflow boundary. Coverage will diminish with the loss of
heating through the evening and into the early overnight before more
widespread showers expand into the region during the predawn hours.
MVFR stratus will accompany the arrival of these showers.

Southwest winds will become gusty through the afternoon as the cold
front to the north approaches the region. The front will slide into
the area this evening with winds becoming light and variable.


&&

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

$$

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