837
FXUS63 KIND 300204
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1004 PM EDT Tue Sep 29 2026

.KEY MESSAGES...

- Warm and mostly dry through Thursday with temperatures well above
  normal.

- Moderate to heavy rain expected Thursday night into Friday.

- Chance of additional showers for southern areas Friday night into
  early Sunday.

- Dry and cooler weather expected next week with lows mainly in the
  40s with upper 30s possibly in outlying areas Tuesday morning.

&&

.FORECAST UPDATE...
Issued at 1003 PM EDT Tue Sep 29 2026

Fair weather to continue for central Indiana overnight under
increasing clouds.  Early September pattern will hold across the
Midwest with Indiana positioned between broad surface high pressure
over eastern North America...and outer periphery of next slowly
organizing weather system (thickening high clouds) that will
cross Illinois and into at least western/northern portions of
Indiana by pre-dawn. Lack of gradient between the synoptic
features will maintain light/variable flow through at least 500 AM
EDT, while increasing clouds coverage should generally deter fog
formation. Temperatures around 60F as of 945 PM EDT will fall a
few more degrees, with morning minimums ranging from 55 east/south
of Muncie to 61 in Lafayette.

&&

.DISCUSSION (This evening through Tuesday)...
Issued at 312 PM EDT Tue Sep 29 2026

Warm fall weather will be the rule through Thursday as upper ridging
builds back over the SE CONUS and 850 mb temps rise to around 17 C.
High temps will be in the 80s most areas Wednesday and areawide
Thursday. A weak upper level disturbance located over OK/KS will
rotate around the upper ridge and graze central Indiana during
Wednesday. As a result sky cover has been increased to mostly cloudy
for areas north of I-70. Steep mid level lapse rates will support
elevated showers, but low levels will remain very dry, so only
scattered sprinkles are expected from a mid level cloud ceiling.
Winds will gradually increase on Wednesday as the pressure gradient
steadily increases between surface high pressure over the srn Apps
and low pressure over the central Plains. By Thursday, this gradient
will increase sufficiently to support breezy conditions with south
gusts near 20 mph during the afternoon.

Attention turns to the main forecast challenge/event during the
period which is timing of arrival, duration and amounts of rainfall
late Thursday into the weekend. Most model guidance suggests a
fairly short period of strongest forcing/heaviest rainfall during
the 06Z-18Z period Friday as a frontal boundary shifts southward
through central Indiana. This shorter temporal rain threat than
earlier forecasts advertised is due to several factors. The primary
factors are the faster weakening of the mass fields with the remnant
shortwave over the plains and a resultant increasing tendency for a
stronger area of high pressure over the upper MS valley. The net
result is stronger pressure rises supporting a greater southward
displacement of the main baroclinic zone. As far as rainfall
amounts, PWATs are still expected to be very high for early October,
around 1.5 inches. Therefore, even with the shorter duration of
rainfall, most areas will see between 0.75 to 1.25 inch QPF during
this period. Even with a shorter duration of rainfall, these amounts
are low enough that no hydro concerns are expected.

In the wake of this rainfall, there is still a few outlier models
(AI based) showing a weak tropical surge attempting to make it up to
Indiana Friday night into early Sunday. Low pops were kept for the
outside chance of showers during this period across southern
portions of central Indiana in closer proximity to the
forcing/frontal boundary. The aforementioned reinforcing area of
high pressure combined with stronger CAA (850 temps fall around 8 C
from 18Z Sunday to 06Z Monday) should shift any threat for
additional precip well south of the area.

The coldest night of the fall is expected Monday night as a 1030mb
high pressure builds southward through the Great Lakes. Lows in the
low-mid 40s are expected areawide with a few outlying locations
possibly falling into upper 30s Tuesday morning. There will also
likely be some areas of fog during this period with light winds and
recent rainfall.

Looking further into the extended, expecting broad NW flow to
maintain a fairly typical dry and benign fall pattern through much
of next week into the following weekend with temps expected to be
near or slightly below normal with highs in the mid 60s-mid 70s and
lows in the 40s to lower 50s.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 738 PM EDT Tue Sep 29 2026

Impacts:  None

Discussion:

VFR conditions will continue to prevail over central Indiana through
Wednesday evening...as the region basks in modest southerly flow
between broad yet weaker surface high pressure over eastern North
America...and the next weather system slowly ejecting from the Four
Corners region to the central Plains.  Column to dampen, mainly
after 12Z...but with main fetch of western Gulf moisture staying to
northwest of any terminals...will translate to only high/mid
decks falling slightly through the TAF period, with mainly BKN
coverage after 06Z Wednesday. Expect clouds to thwart any fog
potential overnight, with any non-zero chances of MVFR at KBMG too
low to include in TAF.

Mainly light/variable flow tonight to yield light south-
southeasterly winds at most terminals by 10Z Wednesday...with winds
veering slightly to SSW while increasing to 6-9KT by 18Z, with a
couple gusts nearing 15KT during the afternoon.

&&

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

&&

$$

UPDATE...AGM
AVIATION...AGM
DISCUSSION...Crosbie