018
FXUS63 KIND 220239
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1039 PM EDT Mon Jul 21 2025

.KEY MESSAGES...

- Low chances for lingering showers or storms south today, otherwise
  dry through at least early Thursday

- Hot and very humid next Wednesday-Friday, yielding widespread
  afternoon heat indices in the 100s, and multiple nights remaining
  in the low to mid 70s

- Showers and thunderstorms return this weekend.

&&

.FORECAST UPDATE...
Issued at 1039 PM EDT Mon Jul 21 2025

Main focus for tonight is the potential for fog in the Wabash River
valley and in areas which received rainfall earlier today.

Satellite imagery shows clearing skies across Indiana at this hour
as showers from earlier quickly dissipate and move south. High
pressure centered over Southern Ontario briefly nudges southwestward
over the next 24 hours, keeping conditions relatively clear and dry
over Indiana. Light winds and clearing skies tonight will result in
good radiational cooling, which may lead to fog development along
and west of the I-65 corridor and within the Wabash River Valley.
Highest confidence in fog tonight is in those areas due to
widespread recent rainfall and keeping the boundary layer near
saturation tonight. Expect fog and low clouds to quickly dissipate
after sunrise tomorrow morning. Stronger dry air advection and
lesser rainfall for the Indy Metro area and areas northeast of I-65
should inhibit widespread fog development there.

&&

.MESOSCALE UPDATE...
Issued at 644 PM EDT Mon Jul 21 2025

Satellite and radar imagery depict a line of convective showers with
isolated lightning strikes along a weak boundary stretching from
Terre Haute to Bloomington. Weak low level convergence within a
moist, and marginally unstable environment have allowed for
convective showers and a few non-severe storms to develop along this
boundary. These cells are struggling with upward growth as shear and
helicity values are too weak to support sustained updrafts...while
weak mid level lapse rates, as seen on ACARs soundings, further
inhibit upward growth and organization of these storms. Despite
being relatively weak and disorganized, the majority of the
saturated layer in the lower levels is above freezing, resulting in
efficient low level warm rain processes and very heavy rainfall
rates ranging from 1 to 2 inches per hour at times. While severe
weather is not expected, localized flooding will be possible for
areas that get repeated rounds of convective activity this evening.
Many of these same areas received heavy rain last, further
saturating the ground and making it easier for flooding to occur.

These storms are slowly pushing southeastward along the boundary.
While not perfectly parallel to the shear vector, enough of the SE
movement is parallel to the effective shear to support training
showers and storms over the same area... as seem over portions of
Clay, Owen, Greene, and Monroe Counties where MRMS radar indicates 1-
2 inches of rain has fallen in some spots. These storms are expected
to diminish after sunset.

&&

.SHORT TERM (This evening through Tuesday)...
Issued at 301 PM EDT Mon Jul 21 2025

Easterly flow has taken hold across the north and eastern parts of
our CWA as high pressure passes over the Great Lakes. A remnant
surface boundary from Terre Haute to Martinsville remains, with
winds turning more southerly across our southwestern counties.

Some showers have been noted over this boundary which have been
capped around 20k ft due to dry mid-level air. Nevertheless, heavy
rainfall rates have occurred due to the deep warm cloud layer which
extends to almost 15k ft. Despite not being tall enough to produce
lightning, amounts of 1-2 inches have fallen near Martinsville
earlier this morning.

Some additional shower development is possible this afternoon as
the boundary slowly drifts southwestward. Any activity this
afternoon should be shallow but still capable of heavy downpours.
Not expecting anything widespread as large-scale forcing is weak and
increasingly stable air arrives from the east.

TONIGHT

Quiet weather is expected as high pressure builds to our northeast.
Light winds are anticipated as the boundary layer stabilizes. A few
instances of patchy fog are possible but it should not be widespread
as dry air filters in from the northeast. Best chance of fog is
along the Wabash River and across our southwestern counties.

TUESDAY

Quiet weather continues into Tuesday with high pressure to our
northeast. Temperatures will be near normal (mid to upper 80s) with
dew points in the 60s.

&&

.LONG TERM (Tuesday night through Monday)...
Issued at 301 PM EDT Mon Jul 21 2025

A transition to hot and humid weather is expected this week as
ridging builds overhead. Ensemble guidance shows 500mb heights
roughly 1-2 sigma above the mean which isn`t extremely anomalous,
but anomalous nonetheless. Above-normal temperatures are favored but
only a few degrees above average. That still puts us into the low
90s. Combined with increasing dew points into the 70s, we`ll see
heat indices between 100-105 degrees which is approaching heat
advisory criteria (Wednesday through Friday).

Guidance shows the ridge flattening or shifting westward by late
week. Northwesterly flow aloft returns with southwesterly flow
remaining at the surface. Such a pattern is favorable for convection
as increased jet dynamics aloft overlap with instability from the
south. Convection will be hard to pin point as forcing should be
relatively weak outside of embedded shortwaves / remnant MCVs from
previous days. We`ll keep PoPs broad and moderate at this time given
the inherent uncertainty associated with such a pattern.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 747 PM EDT Mon Jul 21 2025

Impacts:

- Showers diminishing through 02z at KHUF and KBMG

- MVFR Fog possible overnight at BMG, LAF and HUF.

- MVFR Cigs for a few hours during the morning, before 15z.

Discussion:

Satellite and radar imagery this evening show showers and a few non-
severe storms along and south of a line from KHUF to KBMG. Brief
periods of erratic winds, and sub MVFR cigs and vis have been
reported within this convective activity over the past several
hours. Expect these showers to continue over the next few hours
before diminishing after sunset.

Light winds overnight within such a moist airmass may result in fog
development once again across the Wabash River valley and for any
location that received rainfall today. Added fog after 06z to KLAF,
KHUF, and KBMG, with above average confidence that fog will occur
later tonight. Brief periods of sub MVFR cigs and vis possible with
fog. Outside of fog, pockets of MVFR stratus may also develop
overnight, depicted in the KIND TAF. Any fog or stratus should lift
within the 14-15z timeframe, leading to mainly VFR conditions the
rest of the day.

Winds should remain under 10 kts and out of the ESE through the
period.


&&

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

$$

UPDATE...CM
SHORT TERM...Eckhoff
LONG TERM...Eckhoff
AVIATION...CM