IND issues Area Forecast Discussion (AFD) at Sep 1, 2:58 PM EDT770
FXUS63 KIND 011858
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
258 PM EDT Tue Sep 1 2026
.KEY MESSAGES...
- Heat Advisory in effect for all of central Indiana from Tuesday
afternoon through Thursday evening
- Increasingly hot and humid conditions through the middle of this
week. Peak heat index values up to 105 are possible each afternoon
Tuesday through Thursday.
- Isolated to scattered thunderstorms will be possible at times
late this week through the weekend.
&&
.DISCUSSION (This evening through Tuesday)...
Issued at 257 PM EDT Tue Sep 1 2026
Deep ridging over the central CONUS will be the predominant driver
of our upcoming weather over the next several days. Warm SW flow has
pushed temperatures well above normal, with high temperatures in the
low to mid 90s through Thursday. This in combination with dew points
in the low 70s will push heat index values above 100 each afternoon,
prompting a Heat Advisories until 8PM Thursday.
The main source of uncertainty will be the amplitude of the
aforementioned ridge over the lower Great Lakes and Ohio Valley.
Diabatic processes from upstream convection and upper level water
vapor will mitigate pressure rises a bit, keeping the apex of the
ridge just north of central Indiana. Confidence in convection on the
northern periphery of the ridge is high, but how far south this area
of convection reaches is where confidence wanes. Currently the
expectation is for a majority of any precipitation tomorrow through
Thursday afternoon to remain north of the area, but the margin for
error is small. Any rainfall and associated cloud cover that does
occur will limit diurnal temperature gains, thus temperature
gradients across the state could be significant.
Within the super-geostrphic upper level flow, a short wave is
expected to develop late tomorrow through Thursday. As this
shortwave dives south into the east Great Lakes, modest lift along
the leading edge will likely lead to an area of more organized
convection late Thursday through Thursday night. Ensemble spread on
where this convection will focus is still high, but generally most
members agree on an area from northeast IN through northern OH. The
severe threat will be greatest over this area, but parameter spacing
is sufficient for damaging wind gusts over central Indiana if enough
lift is able reach this far west and initiate convection.
Depending on where diabatic pressure chances occur with the
previously mentioned MCS, a weak surface trough may develop near or
within central Indiana Thursday night. This area of troughing will
likely lead to additional rain and storm chances, but confidence on
location is low at this time. A deepening trough over the East
Coast, will push the ridge westward towards the end of the week,
leading to increased uncertainty this weekend onward as the ridge
axis falls west of the area and potential shortwaves increase
chances for rain.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 1253 PM EDT Tue Sep 1 2026
Impacts:
- Wind gusts to 15kt Wednesday afternoon
Discussion:
VFR conditions will continue through the period, with high clouds
from time to time. A few cumulus will likely develop over the next
few hours, and diminish just before sunset.
Winds will be predominately out of the SW throughout the TAF period.
This afternoon sustained winds to 8kt are expected, becoming lighter
overnight. Chances for gusts increase tomorrow, with gusts of 15kt
likely, potentially even higher at KLAF.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Thursday for INZ021-028>031-035>049-
051>057-060>065-067>072.
&&
$$
AVIATION...Updike
DISCUSSION...Updike
Source:
IND issues Area Forecast Discussion (AFD) at Sep 1, 2:58 PM EDT---------------
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