000
FXUS63 KIND 161825
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
225 PM EDT Tue Apr 16 2024

.KEY MESSAGES...

- Isolated showers and thundershowers though morning.
- Gusty winds between 20 and 30 mph today.
- Showers and thundershowers expected overnight. A few strong storms
  possible.
- Severe storms possible on Wednesday
- More rain around Thursday night, then dry and turning colder

&&

.FORECAST UPDATE...
Issued at 959 AM EDT Tue Apr 16 2024

A few changes made to the forecast  with this morning`s update.
Temperatures and winds look good with highs on track to be near 80
today and wind gusts of 20-25 mph possible this afternoon. Did drop
PoPs over the next couple of hours based on current radar. Models
runs for PoPs during the day today are still over estimating rain
for central Indiana but given current observations can`t rule out a
few showers later today with diurnal heating so have kept slight
PoPs midday to afternoon. The better chances for rain remain late
this evening into the overnight ahead of an approaching low and cold
front.

&&

.SHORT TERM (Today and tonight)...
Issued at 300 AM EDT Tue Apr 16 2024

A cold front currently resides over southern portions of Indiana
near the Ohio River. This boundary has triggered a few showers and
thunderstorms, but these have been very isolated and short-lived.
High-res guidance shows occasional convective development along this
boundary as it lifts northward through the morning. However, models
have been a bit bullish regarding activity thus far compared to
reality. Will keep PoPs quite low through morning.

Besides precip chances, winds behind the retreating cold front are
expected to gain a more southerly component with time. The air mass
south of the boundary is currently quite moist, but guidance shows
drier air becoming entrained from a decaying continental air mass
over the southeast. This may allow boundary layer mixing to be more
efficient today, so despite thicker cloud cover another day with
highs near 80 appears likely. A deepening surface low to our west
will allow the MSLP gradient to tighten during the late morning and
afternoon hours. Combined with efficient mixing, winds are expected
to increase with a few gusts between 20-30mph possible.

By evening, the aforementioned surface low will be approaching the
region. Showers and storms are currently firing up over the Great
Plains and should progress eastward with time while the parent
system slowly occludes. Guidance is in good agreement that these
showers and storms outpace the system`s narrow warm sector by the
time they reach Indiana. Given that the primary axis of instability
should be further west and that lapse rates appear marginal at
best...severe weather is looking less likely, but a strong storm
with gusty winds could still be possible. Timing-wise, look for this
activity to spread into Indiana around 00z and continue into the
night.

Low temperatures tonight are expected to be warm, given strong warm
air advection and cloud cover. Expect lows to only drop back into
the 60s by Wednesday morning.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 300 AM EDT Tue Apr 16 2024

Wednesday...

An upper level trough will move through during the day, with a cold
front at the surface. Some questions remain with the timing of the
surface cold front, which would have impacts on the severe weather
threat across central Indiana.

There will be additional forcing from an upper trough, and the area
will be near the left exit region of an upper level jet. However, an
inversion will likely help inhibit any convection until the front
itself can provide enough forcing to overcome it. Thus, convection
will likely be confined to a thin line along the front as it moves
across central Indiana.

Colder air aloft moving in with the trough will provide steeper
lapse rates, and there will be some shear as well. The front`s
timing will impact the available CAPE, with later arrival of the
front leading to better instability to work with.

Given all the above, a conditional threat for severe weather exists,
with large hail looking like the primary threat given the parameter
space. Damaging winds and isolated tornadoes are also possible along
the potential line of storms, but these have lower probability.

Again, the later arrival of the front would lead to higher CAPE and
better chances for severe, while an earlier arrival will lead to
lower CAPE and lower odds.

One interesting thing to note is that many CAMs keep the stronger
cells out of central Indiana, keeping them east and north of the
area. These are due in part to an earlier frontal passage.

Will go with likely PoPs most areas as a thin line is expected to
move through with the front, regardless of strength of the
convection.

Thursday and Friday...

A larger upper level system will move into the northern USA. At the
surface, a cold front will move through the area with a surface wave
riding along it. Forcing and moisture look adequate for high PoPs by
Thursday night.

Rain chances will diminish on Friday. However, with the front
stalling out not too far south of the area, some additional rain may
sneak in on Friday night, mainly south. Will go with some low PoPs
then.

Saturday and beyond...

Cooler weather will rule as the area is under a broad upper trough
for much of the period. High pressure will be in control at the
surface, keeping the area dry through Monday.

Low temperatures will dip into the middle and upper 30s for parts of
the area Saturday and Sunday nights. If winds become low enough,
frost can`t be ruled out in the north, especially Sunday night.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 224 PM EDT Tue Apr 16 2024

Impacts:

- Low probability of showers and thunderstorms before 00z.

- Southerly winds, gusting to a little over 30kts through the period.

- Numerous showers and thunderstorms from after 00z to early
morning. Showers possible through end of period.

- MVFR ceilings with overnight storms

Discussion:

VFR conditions to start but MVFR ceilings will move in overnight
with expected showers and thunderstorms ahead of a cold front. The
best chances for storms will be from after 00z through around 10z.
There will then be additional chances through the day Wednesday as
the front itself moves through but ceilings are expected to
return to VFR mid-morning to midday.

Winds will be southerly for much of the time but will shift more
southwesterly by midday tomorrow. Expect sustained winds of 15 to 20
kts and gusts up to 30-35 kts.

&&

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

$$

UPDATE...KF
SHORT TERM...Eckhoff
LONG TERM...50
AVIATION...KF