549
FXUS63 KIND 251845
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
245 PM EDT Wed Jun 25 2025

.KEY MESSAGES...

- *HEAT ADVISORY* continues through late day Friday

- Heat indices up to 100-107 degrees and low temperatures near or
  above 75 degrees through Friday

- Scattered daily afternoon showers/t-storms, isolated strong to
  severe wind gusts are possible as well as localized flooding

&&

.SHORT TERM (This evening through Thursday)...
Issued at 245 PM EDT Wed Jun 25 2025

TODAY AND TONIGHT

Another hot and humid day is expected as the overall large-
scale pattern remains unchanged. Our Heat Advisory remains in effect
as the combination of temps in the low 90s and dew points in the 70s
will lead to apparent temps in the 100-107 degree range. Overnight
lows are not expected to drop below 75 for much of the area,
exacerbating the prolonged effects of the heat.

Satellite shows cumulus fields rapidly developing now that
convective temps are being reached. Isolated to scattered convection
are forming despite weak synoptic forcing. Forcing for convection
will arise from subtle boundary-layer convergence and buoyant
forces, so convection will be almost randomly scattered throughout
the area. Some areas of more enhanced surface convergence are noted
on radar, however, which has allowed for more concentrated areas of
storm activity east of Indy.

ACARS soundings out of IND show ample low-level moisture but
relatively dry air above 700mb. Additionally, these soundings show a
warm nose with associated weak lapse rates from 600 mph to almost
400mb. Lapse rates are steeper in the sub-850mb layer, however. Flow
through the column appears weak, with 20kt at 250mb being the
fastest winds found aloft at the moment.

Given the primarily buoyant nature of the atmosphere and weak flow,
single cell storms should be the primary storm type today. Dry air
and weak mid/upper lapse rates may limit storm intensity somewhat as
updrafts struggle with dry air entrainment and poor lift above
600mb. Nevertheless, low-level lapse rates are steep enough to allow
for a few stronger updrafts. Though dry air is a detriment for these
storms it may also lead to enough DCAPE for some isolated downbursts
containing strong to marginally severe wind gusts. This threat seems
low, especially with poor storm top ventilation and potential
updraft intensity...but radar will still need to be watched closely
this afternoon. Additionally, some localized flooding is possible
due to the slow-moving nature of today`s storm activity.

Storms may also try to organize into multi-cell clusters as cold
pools develop from previous convection, but lack of flow aloft
should prevent cold pool shear balance and any cluster will likely
become outflow dominant. Storm activity should rapidly decrease
after sunset as instability is lost.

THURSDAY

Essentially the same weather is anticipated for Thursday with hot
and humid conditions along with afternoon scattered showers and
storms. Even the model soundings are essentially the same, with one
minor difference. Guidance is hinting at better upper-level flow
(still low, but 30kt instead of 20kt) which may allow for increased
storm ventilation and slightly stronger updrafts. This in turn would
lead to slightly greater downburst potential compared to today.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 245 PM EDT Wed Jun 25 2025

...Heat Advisory Continues through Friday...

A Rex Block over the SE CONUS has kept a strong ridge over the Ohio
Valley, resulting in an extended heat wave for central Indiana. This
Rex Block will begin to break down by the end of the week, mostly
related to the entrance of a weak and slow moving shortwave over the
Great Lakes region. Initially, this will still lead to hot and humid
weather on Friday with highs once again near 90 and heat indices
near 100. As the shortwave nears late Friday into Saturday an
increase in lift may allow for greater coverage of showers and
thunderstorms Friday night through Saturday. There is still a lot of
uncertainty on timing of rainfall on Friday and Saturday, but
generally the expectation is for a diurnal curve with greater
convection in the afternoon.

Given the presence of the shortwave, there is likely to be some near
surface high pressure building in from the NW on Saturday, of which
will slowly alter/wane precipitation chances throughout the day from
NW to SE. This will continue to move slowly SE Saturday night
through Sunday. With greater cloud coverage on Saturday, it is
likely that temperatures will be more limited, with highs slightly
lower; in the upper 80s. Even with the shortwave present, upper
level forcing will be very weak, with marginal shear through the
lowest 6km. This should limit storm organization, with any severe
weather expected to be very isolated.

The ridge will continue to break down early next weak, with more
seasonal temperatures expected Monday through Wednesday (mid 80s).
Low to mid level moisture is expected to stick around for early next
week as well, leading to daily thunderstorm chances once convective
temperatures are reached. Generally, synoptic dynamics are expected
to remain weak, leading to the continued expectation of unorganized
thunderstorms, but model uncertainty is high on any low level
features for a more mesoscale specific threat.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 138 PM EDT Wed Jun 25 2025

Impacts:

- Scattered showers and storms after 19Z today and tomorrow

Discussion:

Generally VFR conditions expected except during showers/storms.

Cumulus has developed this afternoon and scattered storms are
ongoing across central Indiana. Scattered showers and storms are
possible at any point during the afternoon, with activity ending
near sunset around 01z.

Activity resumes during the afternoon hours on Thursday around the
same time, with activity likewise diminishing around sunset.

MVFR or lower conditions are possible during heavier showers and
storms.

Winds will generally retain a southwesterly component around 5-10
knots, with some stronger gusts possible during showers or storms.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Friday for INZ021-028>031-035>049-
051>057-060>065-067>072.

&&

$$

SHORT TERM...Eckhoff
LONG TERM...Updike
AVIATION...Eckhoff