-- Discussion containing changed information from previous version are highlighted. --
885
FXUS63 KIND 170243
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1043 PM EDT Sun Jun 16 2024

.KEY MESSAGES...

- Extended period of hot and humid conditions through next
  weekend, lower humidity expected late this week.

- Afternoon heat indices approaching 100 this week may be hazardous
  to sensitive and vulnerable groups.

- Isolated to scattered storms Monday and Tuesday afternoon,
  additional precipitation chances over the weekend.

&&

.FORECAST UPDATE...
Issued at 650 PM EDT Sun Jun 16 2024

A model blend has been sufficient for overnight temperature forecast
in this current pattern. Thus, predictability for tonight is high and
no changes are needed.

A meridional surge of subtropical moisture is expected tomorrow.
Moisture magnitude in the middle troposphere varies among the model
suite. Some show some dry midlevel air preceding the deeper
moisture surge, and thus fairly large vertical theta-e differential
due to this contrasting with a warm moist PBL. This scenario would
lead to brief strong wind gusts with any thunderstorms that form.
Little organization is expected given weak deep layer shear, and
cloud bearing wind suggests that short-lived single cells should
move northeastward at around 25 mph.

&&

.SHORT TERM (This evening through Monday)...
Issued at 241 PM EDT Sun Jun 16 2024

Rest of This Afternoon...

Very warm to hot conditions will continue this afternoon. Dewpoints
will continue to climb in the central and eastern portions of the
forecast area, making it feel even warmer. Apparent temperatures may
reach the upper 90s for a period in the southwest forecast area.

A few CAMs show convection firing in southwest Indiana and moving
into central Indiana late this afternoon, but without much of a
trigger and best instability southwest of central Indiana, feel that
the odds are too low to mention. Any convection from the MCV moving
through northern Illinois should remain northwest of the area.

Tonight...

Quiet weather is expected tonight. Cumulus will dissipate leaving
some passing high clouds.

Humid conditions will lead to lows only in the lower 70s.

Monday...

With a warm start and sunshine in the morning, temperatures will
rise quickly. Dewpoints will remain high and around 70 degrees.

These conditions will produce some cumulus by the afternoon.
Meanwhile, some weak energy will ride around the upper high to the
east and bring some forcing to the area. Mid level temperatures do
not look to produce a cap, so the weak forcing should interact with
the instability to produce isolated to scattered showers and
thunderstorms.

The clouds and convection will help keep temperatures cooler than
the highest guidance forecast. However, highs will still reach the
lower and middle 90s. Heat indices may approach 100 degrees,
especially in the southwest.

&&

.LONG TERM (Monday night through Sunday)...
Issued at 241 PM EDT Sun Jun 16 2024

Monday night through Wednesday...

The main story in the extended period will be the abnormally hot
conditions which are expected to persist. Upper ridging centered
near the Northeast is expected to amplify resulting in increasing
heights over the Ohio Valley. At the surface, high pressure also
centered across the Northeast should promote southerly flow back
across the Ohio Valley early in the period. This will help to
increase moisture which combined with daytime heating supports at
least low end chances for showers and storms Tuesday.

Increasing heights aloft combined with southerly flow will keep
temperatures abnormally hot. In addition, look for humidity to
remain elevated at least to start the period. Overnight temperatures
should remain in the 70s.

Wednesday night onward...

Upper ridging is expected to retrograde late in the week and build
back west which will bring even warmer 850mb temperatures towards
central Indiana compared to earlier in the week. This could result
in hotter temperatures Thursday/Friday. The slight good news is
humidity should be lower late week as surface high pressure also
builds west helping to advect drier air into the area. The extended
stretch of heat this early in the season is abnormal so make sure to
stay hydrated and take frequent breaks in air conditioning if you
are outdoors. Sensitive and vulnerable groups should especially take
the necessary precautions to avoid the potentially hazardous
temperatures.

Most guidance shows upper ridging breaking down into the weekend
allowing for a system to move in. While there is a good signal the
ridge will break down, there is disagreement between models in how
quickly this occurs which limits confidence on exact details such as
precipitation chances or timing. The best chance for rain at this
time appears to be on Sunday once a shortwave trough moves into the
region. Increasing rain chances and clouds should bring some relief
to the heat, but there is uncertainty in how much this will help.

&&

.AVIATION (06Z TAF Issuance)...
-- Changed Discussion --
Issued at 1043 PM EDT Sun Jun 16 2024

Impacts:

- Isolated thunderstorms Monday afternoon

Discussion:

Moisture advection will bring a more robust cumulus field, and
isolated showers and thunderstorms. Coverage is limited and thus
probability of impact is too low for inclusion in the TAFs at this
time. Mixing will again be enough for at least sporadic wind gusts
up around 15-17 knots during the warmest part of the day.
-- End Changed Discussion --

&&

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

$$

UPDATE...BRB
SHORT TERM...50
LONG TERM...Melo
AVIATION...BRB