276
FXUS63 KIND 231905
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
305 PM EDT Mon Sep 23 2024

.KEY MESSAGES...

- Widespread showers and a few thunderstorms through Tuesday

- Sneaky potential for a few severe storms Tuesday afternoon into
  the early evening

- Seasonable temperatures for much of this week with highs in the
  70s and lower 80s and lows in the 50s and 60s

- Potential for more rain late week into the weekend from tropical
  remnants

&&

.SHORT TERM (This Evening through Tuesday Night)...
Issued at 305 PM EDT Mon Sep 23 2024

Low stratus has been prevalent across central Indiana so far today
with a cool low level flow largely out of the northeast. A broad
area of rain continues its northeast expansion across the forecast
area this afternoon. Temperatures at 18Z ranged from the upper 60s to
the mid 70s.

The unsettled pattern that commenced on Sunday will persist through
Tuesday evening with additional opportunities for rain and storms.
The cold front that passed through the area Sunday evening now
resides near the Ohio River. The boundary will shift north back into
the forecast area tonight and Tuesday with a series of surface waves
traversing it. The final surface low will track through the region
Tuesday afternoon and evening...and presents a sneaky scenario for
isolated to scattered severe storms. Will discuss this in greater
detail below.

Rest of This Afternoon through Tonight

The area of rain draped across the southwest half of the forecast
area currently will continue press northeast...likely diminishing in
coverage slightly as it interacts with drier air above the boundary
layer inversion. There remains very weak instability aloft and have
seen periodic lightning strikes but for the most part...the bulk of
the storms should remain south of the boundary in Kentucky where
instability is greater.

The showers will continue into the evening with a gradual increase
in coverage developing near or just after sunset as 850mb winds
increase and nose into the region from the southwest. Model
soundings support a bump in instability as well that will likely
tend towards increased convection later this evening into the
overnight as the low level jet strengthens further. There is solid
potential to see a half inch to inch for much of the region with
locally higher amounts by Tuesday morning. These amounts alone
should not create any flood issues but will provide additional
relief from the ongoing drought conditions.

Tuesday and Tuesday Night

There may be a brief lull in convection Tuesday morning into the
early afternoon as the overnight convection shifts northeast with
the remnant boundary lifting north as a warm front. The focus will
shift to another round of scattered to numerous showers and storms
Tuesday afternoon and early evening as the main surface wave moves
into the area with some potential for a few severe storms.

The overall pattern on Tuesday is chaotic and messy as the
combination of saturated conditions within the boundary layer and
the early day convection leads to more questions regarding how much
destabilization can take place as storms fire in the vicinity of the
surface low Tuesday afternoon. That being said...there are
parameters in play that suggest a sneaky scenario for scattered
severe storms during the afternoon and early evening. The track of
the surface low and position of the warm front out ahead of the wave
will be key pieces in where this potential will best align...but
plenty of directional shear within the moist near surface layer will
exist and this shows up nicely in the hodographs up to 1-2km. Add in
the strong likelihood that LCLs will be generally under 2kft and 0-
3km CAPE values that will likely be near if not exceed 100 j/kg and
there is support for some mischief from showers and storms as the
low passes through in the form of either damaging winds and/or a
weak tornado threat. Afternoon and early evening would likely be the
primary timeframe for these concerns on Tuesday.

The low will move away to the northeast Tuesday evening with a
frontal boundary sweeping through the area. Drier air will advect in
behind the front but the lingering deep moisture within the boundary
layer will keep skies mostly cloudy all night Tuesday.

Temps...lows tonight will drop into the lower and mid 60s across the
forecast area. Expect another cooler day Tuesday with an abundance
of clouds and the scattered to numerous areas of convection. Low
level thermals support temperatures remaining in the 70s. Temps will
fall back into the mid and upper 50s behind the cold front Tuesday
night.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 305 PM EDT Mon Sep 23 2024

The long term period will have numerous chances for showers and
thunderstorms after a brief break in the rain to start off the
period.

Recent model runs, as well as the National Hurricane Center, are
leaning towards hurricane remnants reaching Central Indiana late
this week. Solutions are showing that the remnants may take on a
Fujiwara effect, interacting with an upper low that broke off of the
system bringing rain to the area today and tomorrow, which could
help to draw the remnants to our area. Confidence is still not very
high as solutions still aren`t quite in sync but they are starting
to agree better than before. Therefore, PoPs will be spread across
numerous days beginning early Thursday morning and lasting through
the end of the forecast period. Winds will be increasing Friday on
the leading edge of the remnants with non-thunderstorm gusts
potentially getting to 35-40 mph. When the center of the remnants
reaches the Ohio Valley, there is a potential for brief spin ups to
form as is somewhat common in these scenarios.

Temperatures will be more seasonable through the long term with
highs from the mid-70s to low 80s.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1248 PM EDT Mon Sep 23 2024

Impacts:

- Periodic MVFR ceilings through the afternoon then returning to
IFR conditions late tonight into Tuesday morning

- Rain showers at times through the forecast period with scattered
thunderstorms also possible this evening into the overnight

Discussion:

Showers will overspread central Indiana from the southwest through
the afternoon. Likely to see ceilings linger at MVFR in some
locations with occasional rises up to low VFR as well into the
evening. Winds will be light and variable for the most part into
this evening.

The frontal boundary stalled near the Ohio River will begin its trek
back north this evening into the overnight as a surface wave tracks
along it through the Ozarks. A subtle increase in instability across
the region will bring embedded convection with showers tonight.
Ceilings will fall back to IFR levels by the predawn hours with the
potential for brief lower restrictions within any heavier rainfall
or storms. The low will then lift up into the area Tuesday as winds
swing back around to southerly. Expect additional convection to
impact the terminals on Tuesday with ceilings likely to linger at
MVFR levels due to the deep moisture present through the boundary
layer.

&&

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

&&

$$

SHORT TERM...Ryan
LONG TERM...KF
AVIATION...Ryan