Zionsville, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

845
FXUS63 KIND 271633
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1233 PM EDT Fri Jun 27 2025

.KEY MESSAGES...

- Heat Advisory remains in effect through 8 PM this evening

- Scattered showers and thunderstorms expected again today into
  tonight, with isolated strong storms perhaps approaching severe
  limits - damaging winds, small hail, and heavy rain/localized flooding
  are all threats

- Scattered daily afternoon showers/t-storms through at least Monday,
  isolated strong wind gusts are possible as well as localized flooding

- Drier and slightly cooler conditions expected Tuesday and Wednesday

&&

.FORECAST UPDATE...
Issued at 957 AM EDT Fri Jun 27 2025

Temperatures quickly warming again this morning with abundant
sunshine across much of the region. One difference so far versus
previous days is that winds are a bit stronger from the southwest
with a slightly tighter surface pressure gradient ahead of a weak
frontal boundary to our northwest. 1330Z temperatures were already
into the lower and mid 80s with heat indices as high as the lower
90s.

The forecast is in good shape for the rest of the day and
essentially serves as a carbon copy to the last two days as
scattered convection will develop this afternoon within an unstable
environment as convective temps near 90 are met within the next few
hours. Low level lapse rates will be steep but weaker lapse rates in
the mid levels combined with very little shear yet again supports
pulse intensity convection that should largely remain below severe
levels. That being said...the approach of the weak frontal boundary
and a subtle infusion in deeper low level moisture courtesy of an
increase in 850mb flow will present at least the potential for a few
of the stronger cells to carry a threat for localized damaging
downburst winds as cores collapse. Northern portions of the forecast
area in particular look to have the greatest potential for stronger
cells but potential will exist across most if not all of central
Indiana as the afternoon progresses with outflow boundaries serving
as additional catalysts for convective development. Locally heavy
rainfall with the potential to produce flooding from excessive rates
will again be likely with storms as well.

The heat will also remain a primary concern with the heat advisory
continuing through 00Z. Low level thermals support low to mid 90s
yet again this afternoon...marking the 7th consecutive day above 90
for most across the region. Heat indices will top out above 100
degrees for many.

Zone and grid updates out.

&&

.SHORT TERM (Today and tonight)...
Issued at 305 AM EDT Fri Jun 27 2025

Friday should be quite similar to the past several days, with the
minor exception of the approach of a weak cold front from the west,
as low pressure at the surface and aloft moves through the Great
Lakes. This will likely promote a slight uptick in coverage of
convection this afternoon and evening, and will carry some likely
PoPs northwest nearest the boundary during the peak heating hours.

Relatively weak shear and modest mid-level lapse rates will
significantly limit any severe threat, with mainly small hail and
perhaps a few near-severe downbursts associated with the strongest
cores, which may be helped along by some dry air aloft promoting
evaporative cooling and downdraft acceleration. Localized flash
flooding cannot be ruled out given relatively slow storm motions and
precipitable water values in excess of 90th percentile
climatologically as the airmass remains very humid.

Thunderstorm activity will likely continue into the evening and
perhaps overnight, though coverage and intensity will certainly wane
with nocturnal low level stabilization.

While an uptick in thunderstorm coverage may impact heat indices,
yet another day is expected with peak values around 100 degrees give
or take, and will keep the ongoing heat advisory in place for its
final day. Improvement appears likely Saturday, though in a relative
sense, as it will remain quite warm and humid nonetheless.

Lows overnight will be slightly cooler tonight, though still warm
and sticky with temperatures dropping into the upper 60s to low 70s,
near the expected dewpoints. Will have to keep an eye on fog
potential, though at this point, it appears cloud cover may keep a
lid on much of this.

&&

.LONG TERM (Saturday through Thursday)...
Issued at 305 AM EDT Fri Jun 27 2025

Saturday through Monday night..

Expect a weak boundary associated with a departing upper wave to
stall near south-central Indiana at the start of the period. North
of the boundary, increasing subsidence from weak high pressure and
drier air filtering in will likely inhibit any precipitation. South
of the boundary, diurnal heating atop a moist PBL could promote
scattered diurnal convection.

Locations near or south of I-70 are currently favored for the
potential of diurnal convection. However, there are a few models
which show the boundary pushing almost completely through central
Indiana Saturday afternoon. This would lead to lower convective
coverage across the south due to more dry air so POPs may need to be
refined in future updates. Models trends will continue to be
monitored.

Quiet weather is expected Saturday night with weak high pressure
overhead. This will be short lived though as moisture begins to
return northward on Sunday ahead of an approaching shortwave. Look
for scattered diurnal convection to develop once again due to strong
daytime heating and moisture surging back north. Increasing dynamics
from the upper wave moving in will lead to higher rain chances
Sunday night into Monday. The system should then begin to shift east
Monday night with rain chances diminishing. Expect highs to
generally be in the upper 80s to near 90F over the weekend and mid-
upper 80s on Monday.

Tuesday onward...

Mostly quiet weather conditions are expected Tuesday and Wednesday
as weak high pressure settles in. Low rain chances (20% or less) do
linger across far southeast portions of central Indiana on Tuesday
though. This is due to model discrepancies which leads to some
uncertainty, but most guidance suggest a dry forecast. Marginal low-
level moisture could promote isolated diurnal showers or storms so
will keep these low rain chances in the forecast.

In addition to a drier forecast, slightly cooler temperatures in the
mid 80s are expected Tuesday and Wednesday. Dewpoints falling into
the 60s should also feel more comfortable compared to the miserable
humidity over the past week. Ensemble guidance suggest moisture
begins to stream back into the region late week providing
opportunities for diurnal convection.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1233 PM EDT Fri Jun 27 2025

Impacts:

- Wind gusts near 20kts this afternoon

- Scattered thunderstorms this afternoon into the evening

- A few storms may linger into the early overnight

Discussion:

Convection has developed early this afternoon across eastern
Illinois into northwest Indiana in advance of a weak frontal
boundary approaching the region. With peak heating over the next
several hours...anticipate further upscale growth to scattered
storms expanding east into central Indiana. Any storm will be
capable of brief restrictions and strong winds with KLAF having the
greatest opportunity for convective impacts as the boundary moves
into the northern Wabash Valley this afternoon. Outside of
storms...expect VFR conditions and breezy southwest winds into the
evening.

Convective coverage will diminish towards sunset with the loss of
diurnal heating but the presence of the boundary in the region into
the overnight may spark additional convection. Will utilize PROB30s
with lower confidence in coverage and impacts after sunset. Winds
will veer to a more westerly direction late tonight into Saturday as
the boundary sags into southern Indiana. Additional scattered storms
may develop by midday Saturday but will be focused mainly south of I-
70.

&&

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

&&

$$

UPDATE...Ryan
SHORT TERM...Nield
LONG TERM...Melo
AVIATION...Ryan