-- Discussion containing changed information from previous version are highlighted. --
424
FXUS63 KIND 221707
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
107 PM EDT Sat Jun 22 2024

.KEY MESSAGES...

- Hot weather persists today
- Some showers and storms overnight into Sunday. Isolated strong to
  severe storms possible.
- Potentially very hot on Tuesday
- More thunderstorms possible Tuesday into Wednesday
- A brief respite from heat and humidity late next week

&&

.FORECAST UPDATE...
Issued at 1002 AM EDT Sat Jun 22 2024

Moisture is shallow enough relative to mixing height that some
decrease in dew point is expected this afternoon. This, combined
with increasing MSLP gradient from an upstream midlevel shortwave
trough and resultant wind should keep wet bulb globe temperature
categories mostly in the moderate level. Surface-based cumulus, and
some increase in mid-high cloudiness are expected later today.
Previous forecast is in good shape and only minimal adjustments are
needed.

&&

.SHORT TERM (Today and tonight)...
Issued at 300 AM EDT Sat Jun 22 2024

Early This Morning...

Some lift in the mid and upper levels will bring some mid and high
clouds moving through. Warm and humid conditions will persist with
light winds.

Today...

Upper heights will gradually fall today as an upper wave moves
toward the Great Lakes. However, the upper high to the south will
still have influence across central Indiana. This will keep the area
dry and hot.

Some high clouds will still be moving through, and cumulus will pop
up by this afternoon. Thus, partly cloudy skies are expected. With
no significant change in airmass, still expect highs in the lower to
middle 90s across central Indiana.

Winds will increase aloft ahead of the approaching system, and
mixing will tap into these winds, bringing gusts to around 20 mph.
The mixing will also bring down dewpoints during peak heating,
keeping heat indices in the middle and upper 90s.

Tonight...

The evening will be quiet and warm across central Indiana. To the
northwest, thunderstorms will develop ahead of the upper wave and
associated cold front. These will move southeast but will not arrive
into the local area until after midnight.

The storms will be moving in during the unfavorable portion of the
diurnal cycle, with loss of heating allowing instability to weaken
as the night progresses. Shear isn`t great for severe convection.
However, if the storms can tap into some stronger winds aloft,
strong to marginally severe winds may occur.

This threat will be confined to the northwest forecast area, where
odds favor higher instability earlier in the overnight. The storms
will weaken as they move southeast into less favorable conditions.
Cold pool organization will have an impact on how fast this occurs
though.

Given the above, will go with likely PoPs across the northwest
forecast area during the overnight, with lower PoPs southeast.

Low temperatures will be in the lower to middle 70s.

&&

.LONG TERM (Sunday through Friday)...
Issued at 300 AM EDT Sat Jun 22 2024

The long term forecast features a couple of opportunities for
relative heat relief, at least one or two additional stiflingly hot
days, and a couple of opportunities for potential convection, some
of which may be organized and present at least a low potential for
strong to severe storms.

The large scale upper ridge currently over the region will steadily
retrograde into the southern Plains and Desert Southwest over the
next few days into next week, providing some heat relief but also
placing us in a potential zone for one or more rounds of convection.

Conditions will remain quite warm and humid, but slightly less so as
the ridge moves. Highs most days will be upper 80s but Tuesday is
expected to be hot with highs returning to the 90s and potentially
in the upper 90s across the southern portion of the forecast area.

The first potential for convection comes at the end of the short
term and continuing into Sunday as a system traversing the ridge
moves into the region. The storms from Saturday night may promote
redevelopment/reintensification during the day on Sunday, again with
a localized damaging wind threat but uncertainties are plentiful.

The next opportunity looks to come primarily Tuesday evening into
Wednesday. While there will also be synoptic scale support for this
round, this looks to be a bit more analogous to the traditional
"ridge rider" scenario, with very strong instability/modest shear
contributing to the development of one or more QLCSs, which then
drive south/southeastward into the instability axis Tuesday evening
into Wednesday. Uncertainties increase with time, particularly given
that prior days` convection will significantly influence subsequent
days, along with typical guidance spread, but experimental CSU
machine learning guidance is highlighting late Tuesday into Tuesday
night as a time frame to watch for an organized severe threat.

Sunday night into early Tuesday and late Wednesday and beyond appear
to have good chances of remaining dry for now.

&&

.AVIATION (18Z TAF Issuance)...
-- Changed Discussion --
Issued at 107 PM EDT Sat Jun 22 2024

Impacts:

 - Wind gusts subside this evening

 - Showers and low probability of thunder late tonight

 - Brief MVFR stratus Sunday morning

Discussion:

As mixing decreases this evening, gusts are expected to end. Mid
level cloud cover will slowly increase, but VFR conditions will
prevail. Weakening convection will move east-southeast across
Indiana later tonight, with some thunder possible, especially at
KLAF. Otherwise rain showers may impact TAF sites in the time window
indicated. Timing is fairly high confidence at this time. A band of
stratus within the MVFR category is possible behind the convection
during the morning, but confidence is low-moderate. Wind gusts will
return with winds more west-northwesterly midday tomorrow.
-- End Changed Discussion --

&&

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

$$

UPDATE...BRB
SHORT TERM...50
LONG TERM...Nield/KF
AVIATION...BRB