820
FXUS63 KIND 280528
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
128 AM EDT Sat Jun 28 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms expected tonight

- 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 for the middle of next week

&&

.FORECAST UPDATE...
Issued at 1001 PM EDT Fri Jun 27 2025

Scattered thunderstorms continue across the far southern and
southeastern portions of central Indiana this evening. These storms
were along and ahead of the old outflow boundary from this
afternoon`s convection.

These will continue to slowly drift east and south with the
boundary. Will have chance PoPs there this evening. Meanwhile,
scattered storms are along a surface boundary across northwestern
Indiana. The remainder of the area in between is quiet.

Instability remains across central Indiana, but it will take some
weak forcing to get convection from this instability. As the surface
boundary slowly sinks into central Indiana tonight, scattered
convection should continue along it.

Adjusted PoPs to reflect the above thinking, keeping them no higher
than the chance category. Given the instability and little or no
shear, severe storms are not expected.

Adjusted temperatures as well based on latest trends in
observations, but forecast temperatures look reasonable.

&&

.SHORT TERM (This Evening through Saturday)...
Issued at 304 PM EDT Fri Jun 27 2025

A broken line of convection continues to get better organized from
western lower Michigan south into northern Indiana then across the
northern Wabash Valley southwest into eastern Illinois ahead of a
front. Ahead of the line...hot and humid conditions persisted with
18Z temperatures in the upper 80s and lower 90s with breezy
southwest winds.

The primary focus for the rest of the day will be on evolution of
the ongoing storms into the region and the potential for additional
periodic convection tonight and Saturday as a weak frontal boundary
drifts south through the area.

To this point the bulk of the storms over eastern Illinois and the
northwest forecast area have been subsevere but have seen a few
cells produce 40-50mph winds as cores aloft collapse. The
environment remains more favorable for severe convection north of
the forecast area focused more across lower Michigan and northern
Indiana where bulk shear and 850mb flow are greater in advance of a
wave aloft. Further south across central Indiana and eastern
Illinois...convection is again largely feeding off of the strong
instability and steep low level lapse rates present as shear is
largely non existent. This is promoting a messy multicellular mode
pulsing in intensity but largely remaining below severe levels. That
being said...the boundary layer flow is a bit stronger this
afternoon than the last two days with 850mb flow expected to
gradually strengthen into the evening further south across the
forecast area.

Anticipate a broken line of scattered convection to continue to
progress east into the forecast area through early evening with a
particular focus across the northwest half of the forecast area. As
has been the case the last few days...these storms will carry a
localized downburst threat and DCAPE values already this afternoon
are over 1000 j/kg across the area. Convective wind gusts will
largely cap in the 50-55mph range but cannot rule out gusts briefly
approaching severe levels from any stronger cell...something that
has already occurred this afternoon with a storm near KMTO in
Illinois. PWATS near 2 inches will support a torrential rain threat
as well with the potential for localized flash flooding...although
convection has been moving at a faster speed this afternoon than the
last few days. And not to be forgotten but considering it is a
summer Friday afternoon...cloud to ground lightning will be a
primary threat to any outdoor activities into this evening.

As diurnal heating is lost this evening...expect a downturn in
convective coverage as has occurred the last couple nights. There
are two main differences however that will likely lead to additional
isolated to scattered convection later this evening and into the
overnight...1) the presence of the aforementioned frontal boundary
as it drifts into the forecast area and 2) the development of a
subtle increase in westerly low level flow through the early portion
of the overnight. The focus with overnight storms will be more on
locally heavy rainfall but the parameters remain in place that any
stronger storm could produce gusty winds as the core aloft
collapses.

The decrease in 850mb flow during the predawn hours should lead to a
further decrease in convection that will last through much of
Saturday morning. The front will push south and be located across
southern Indiana Saturday...with the focus for scattered convective
development largely aligning south of I-70 by the afternoon before
shifting south and diminishing entirely Saturday evening.

Finally...the Heat Advisory continues through 00Z this evening. This
already has been the 7th day with temps above 90 for much of the
forecast area with heat indices in the 100-105 range over the last
several days. The passage of the aforementioned front will nudge
temps down and lower dewpoints from the north through the day on
Saturday. With max heat indices in the mid 90s expected...there are
no plans to extend the Heat Advisory further beyond today.

Temps...expect another night with lows above 70 degrees. Much of the
area is likely to remain below 90 degrees on Saturday making the air
feel a bit more bearable. Low level thermals support upper 80s for
much of central Indiana.

&&

.LONG TERM (Saturday Night through Friday)...
Issued at 304 PM EDT Fri Jun 27 2025

Broad ridging responsible for the recent stretch of hot and humid
weather looks to break down this weekend, with more pronounced
troughing taking hold over the northeastern US. A gradual return to
more seasonable temperatures is therefore expected as we head into
next week.

The best chance of rain in the long term looks to be early in the
week. As the eastern trough develops, a shortwave and attendant cold
front are modeled to pass through the area on Monday. Guidance is in
good agreement regarding this feature, with the blend coming in at
near 100 percent PoPs which is impressive for the long term. This
may be a bit high, despite better forcing than what we`re currently
seeing it still looks rather weak. Precipitation coverage is
therefore in question thus necessitating lower PoPs for now. We will
still go likely PoPs (around 80 percent) given the strong model
agreement.

After that, a stretch of dry weather is possible Tuesday through
Friday before another shortwave/cold front approches from the
northwest. Model agreement is far less in line with this feature and
so uncertainty increases towards the end of the week. We`ll leave
what blended guidance shows, which is around 20 percent PoPs.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 127 AM EDT Sat Jun 28 2025

Impacts:

- Spotty MVFR conditions possible just before daybreak

- Isolated to scattered thunderstorms again Saturday, primarily south

Discussion:

Ample low level moisture in the presence of a weak boundary may
promote development of MVFR conditions, either ceilings or
visibilities, just before to near daybreak this morning. This is
fairly uncertain, and will carry SCT020 decks all but LAF, where
skies are a bit clearer, and fog may develop. Will carry a TEMPO fog
group there.

Once these conditions, if any, dissipate, expect scattered to broken
VFR cumulus, with convection potentially developing over the
southern third to half of the area. Will carry a PROB30 thunder
group at BMG, but IND/HUF may not be entirely out of the woods.

Light winds and eventually clearing skies overnight tomorrow night
may promote fog development, but this is far too uncertain for a
mention at this time.

&&

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

&&

$$

UPDATE...50
SHORT TERM...Ryan
LONG TERM...Eckhoff
AVIATION...Nield