301
FXUS63 KIND 181745
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
145 PM EDT Tue Aug 18 2026

.KEY MESSAGES...

- Areas of fog possible this morning, locally dense fog cannot be
  ruled out near valleys or rivers

- Low rain chances return tonight, scattered to numerous showers and
  storms are expected on Wednesday

- Localized flash flooding is possible on Wednesday

- Turning generally milder and drier late week into the weekend,
  chance for showers and storms on Saturday

&&

.DISCUSSION (Today through Monday)...
Issued at 301 AM EDT Tue Aug 18 2026

Today...

Surface high pressure across the region will provide quiet weather
conditions. Light winds combined with damp soils from recent
rainfall has led to fog development in some areas this morning.
Locally dense fog cannot be completely ruled out near valleys or
rivers through daybreak. Look for fog to quickly mix out in typical
diurnal fashion after daybreak. Partly cloudy skies are then
expected during the day under large scale subsidence. Weak cold air
advection behind a cold front which moved through on Monday supports
slightly cooler than normal highs in the upper 70s to low 80s today.

Tonight through Wednesday night...

Embedded shortwaves within longwave troughing aloft will provide
opportunities for convection towards the middle of this week. Low
rain chances return as early as tonight with an approaching
disturbance. Most guidance generally suggest lingering subsidence
induced dry air from the departing surface high late today greatly
limits the potential for precipitation. This along with marginal
forcing in place keeps POPs around 20 percent or lower through the
overnight. Expect greater rain chances during the day Wednesday once
stronger forcing and deeper moisture returns. Model variability
leads to some uncertainty regarding convective coverage. However,
daytime heating and an embedded shortwave moving across an
abundantly moist environment favors at least scattered convection by
the afternoon.

Severe weather is not expected due to limited instability. Steep low-
level lapse rates and DCAPE values approaching 600 to 700 J/KG could
still result in a few strong sub-severe wind gusts. An isolated
damaging wind gust cannot be entirely ruled out if sufficient
destabilization occurs. The greater concern appears to be localized
flash flooding given soils remain saturated from recent rainfall.
Model guidance also suggest the potential for training storms as a
weak west to east oriented cold front slowly pushes south late in
the day. The weak surface boundary meandering and another embedded
shortwave moving through keeps precipitation chances in the forecast
overnight. Loss of daytime heating should result in less convective
coverage though.

Thursday through early next week...

A weak frontal boundary meandering near south-central Indiana on
Thursday will keep low precipitation chances in the forecast. Further
north, surface high pressure begins to build in providing mostly
quiet weather conditions. Look for the surface high to build further
south Thursday night into Friday resulting in quiet weather
conditions. Another embedded disturbance moves in on Saturday
supporting at least low rain chances with sufficient moisture
advecting into central Indiana. Long range guidance generally
depicts surface high pressure building in once again late weekend
into early next week. Large scale subsidence supports mundane
weather conditions.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 145 PM EDT Tue Aug 18 2026

Impacts:

- Patchy fog possible overnight at LAF, HUF, BMG.

- Scattered showers and thunderstorms possible after 15z Wednesday.

Discussion:

Diurnal cumulus has developed this afternoon oscillating between SCT
and BKN. Generally VFR ceilings have been observed, around 4000-5000
ft agl. Cirrus likewise continues to increase overhead.

Cumulus diminishes tonight, leaving just the cirrus which will
continue to increase. The cirrus may be thin enough to allow for
another night of patchy fog, mainly in the outlying TAF sites.

A shortwave trough approaching from the northwest is expected to
bring showers and thunderstorms to central Indiana on Wednesday.
These are expected to be scattered in nature, and thus a Prob30
group was included to cover this potential.

Winds remain light and variable this afternoon and may go calm
overnight. Winds should increase from the WSW as the shortwave
approaches on Wednesday with speeds remaining under 10kt.

&&

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

$$

AVIATION...Eckhoff
DISCUSSION...Melo