423
FXUS63 KIND 180509
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
109 AM EDT Tue Aug 18 2026

.KEY MESSAGES...

- Clearing skies are expected tonight; Areas of fog, possibly dense,
will be possible.

- Mostly Sunny and less humid on Tuesday.

- Additional thunderstorms likely mid week.

- Turning milder and drier late week into next weekend

&&

.FORECAST UPDATE...
Issued at 945 PM EDT Mon Aug 17 2026

A weak frontal boundary has passed to the SE, with dew points
starting to drop in the mid 60s across NW central Indiana. With this
winds are remaining a little elevated into the evening with
sustained winds at 8-10kt out of the NW. Winds should start to calm
by early morning as high pressure builds over the region.

The main forecast problem for tonight will be the potential for fog
formation. With dropping dew points and delayed onset of calm winds,
fog should be confined to low lying areas and river valleys.
However, given very saturated soils, elevated latent heat fluxes may
lead to some pockets of dense fog. Will continue to monitor
throughout the night if these pockets become more numerous.

&&

.DISCUSSION (This evening through Monday)...
Issued at 206 PM EDT Mon Aug 17 2026

The persistent upper level ridge to the south that has kept central
Indiana squarely in the bullseye of ring-of-fire convection for the
last week plus will finally begin to retrograde to the west and
amplify this week.

A cold front to the northwest will push through the area today, with
scattered pre-frontal showers and storms early in the day, primarily
across the southern portions of the area. Rain chances will finally
come to an end late today as the tail end of the boundary exits the
area, with dry weather expected tonight into Tuesday as surface high
pressure pushes into the region.

Light to calm winds, clearing skies, and very moist ground will
likely produce areas of fog tonight despite the decreasing
dewpoints. Dense fog will definitely be on the table given how
incredibly waterlogged most of the area is.

The next chance for thunderstorms will come late Tuesday night into
Wednesday night as one or more shortwave disturbances pivoting
around a large upper low over the eastern Canadian provinces drives
another frontal boundary through the area. Heavy rain and strong to
severe storms will again be a threat, as though instability is a bit
more modest owing to more limited moisture (though still 70th-80th
percentile climatologically), deep layer shear should be fairly
robust. Damaging winds would be the primary threat with this
activity, with at least a modest flash flood threat given the
extreme antecedent conditions.

The more amplified pattern looks to persist late week into early
next, with below normal temperatures and mostly quiet weather
appearing likely, though an occasional upper level disturbance in
the cyclonic flow aloft may necessitate a slight chance of a shower.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 108 AM EDT Tue Aug 18 2026

Impacts:

- Patchy fog this morning

Discussion:

Light northwesterly winds this morning along with damp soils from
prior rainfall will promote patchy fog development at the outlying
TAF sites between 07-13Z. Look for winds to remain light through the
period. NW winds will become westerly later today and eventually
S/SW this evening into tonight.

&&

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

$$

UPDATE...AGM
AVIATION...Melo
DISCUSSION...Puma