534
FXUS63 KIND 171903
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
303 PM EDT Tue Jun 17 2025

.KEY MESSAGES...

- Humid today with scattered showers and storms possible, especially
  southeast, with briefly heavy downpours possible.

- Severe weather possible Wednesday afternoon into Wednesday night

- Much warmer this weekend with near Heat Advisory conditions by
  Sunday

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 303 PM EDT Tue Jun 17 2025

...SEVERE WEATHER POSSIBLE ON WEDNESDAY...

A rather complicated forecast ahead of us as a short-wave approaches
from the west. There are a lot of moving parts with the upcoming
system, and multiple convective scenarios are currently in play.

Beginning with today, weak troughing aloft and some modest
instability will lead to a few showers and thunderstorms mainly
south of I-70. These are not expected to be severe, but may produce
locally heavy rainfall at times.

Isolated showers and storms may persist into the overnight hours as
weak large-scale forcing remains in place. Again, severe weather is
not anticipated during the overnight hours with locally heavy
rainfall being the primary threat.

WEDNESDAY

A shortwave trough ejecting into the Great Plains today will be the
primary factor leading to Wednesday`s severe weather threat. Most
guidance shows substantial convective development this afternoon
over Kansas as this feature advances into the Plains. The resulting
convective complex then moves eastward tonight and into Wednesday
morning, interacting with a developing surface low over northern
Missouri. Beyond that point is where things get a bit murky, and
possible scenarios will be discussed below.

1. A strong convectively-enhanced surface low lifts northeast into
the Great Lakes, currently shown by the ECMWF. Increased mass
response and a stronger and more backed low-level wind field, and
thus a higher tornado potential (especially closer to the low
itself). This scenario would lead to a greater overall severe wind
threat as well, due to a stronger low-level jet and thus longer
hodographs. Greater overall shear would act to increase storm-scale
organization and the risk for bowing line segments. Members of
guidance depicting this scenario tend to have slower storm arrival
times as well, with activity peaking in the late afternoon and
evening hours.

2. MCV-like enhancement does not occur and a weak surface low passes
to our north. This scenario is currently shown on the GFS, and would
lead to less backing within the wind field and an overall lower
tornado threat. However, a tornado threat could still exist as there
remains fairly strong shear within the 0-1km layer (albeit with less
curvature in the hodograph). Early storm arrival times tend to be
shown by guidance depicting this scenario, with activity as early as
18z.

Regardless of which scenario plays out, plenty of instability and
wind shear will be present for severe weather. Severe straight-line
winds and large hail are the primary hazards. The tornado threat is
conditional on the points mentioned above. Furthermore, there are
hints within guidance that the primary trough could lag behind the
surface low allowing thunderstorms to linger into the night, leading
to a heavy rain and flooding threat.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 303 PM EDT Tue Jun 17 2025

Ensemble guidance shows anomalous ridging developing over the Ohio
River Valley by this weekend. Deterministic guidance shows 500mb
heights as high as 5965m which is 1-2 sigma above the mean. Intense
ridging, reinforced by strong warm air advection, would lead to
well-above normal temperatures as we head into next week.

The strongest warm air advection, and therefore the warmest surface
temperatures, looks to set up to our northwest and not directly
overhead. Additionally, the ground is quite wet from the abundant
rainfall we`ve recently seen. Therefore, despite the strength of the
anticipated ridge, we may reach temperatures as warm as one might
expect. Still, readings near 90 or into the low 90s are certainly
possible.

Though the ground moisture mentioned above may limit the ambient air
temperature somewhat, it may be a double-edged sword in the sense
that it will increase the overall humidity...leading to high
apparent temperatures. Heat indices exceeding 100 degrees are
probable late this weekend and into next week.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 140 PM EDT Tue Jun 17 2025

Impacts:

- MVFR ceilings at times this afternoon and evening, possibly into
  the overnight

- Showers and thunderstorms near BMG this afternoon, low chance near
  IND

- Greater chance of showers and storms at all terminals on
  Wednesday, with severe weather possible.

Discussion:

Low-level moisture and weak forcing has lead to MVFR ceilings this
morning and afternoon with some scattered showers. A few heavier
showers as well as some embedded thunder are noted near BMG. These
should continue on and off into the afternoon hours.

Shower activity largely dies down overnight, though an isolated
shower may still occur. Clouds may alternate between SCT and BKN at
times leading to period MVFR ceilings.

Stronger forcing arrives on Wednesday with increased chances for
scattered showers and thunderstorms after 18z. Some of these may be
strong to severe with MVFR conditions or worse.

Surface winds, not associated with storms, look to climb to between
10-15kt with gusts to 25kt at times Wednesday afternoon.


&&

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

$$

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