641
FXUS63 KIND 271029
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
629 AM EDT Mon Apr 27 2026

.KEY MESSAGES...

- Multiple rounds of thunderstorms expected today, severe weather is
  possible this afternoon into tonight.

- Isolated Showers and thunderstorms possible on Tuesday, mainly
  across southern Indiana.

- Cooler temperatures expected Wednesday through Sunday.

&&

.DISCUSSION (Today through Sunday)...
Issued at 330 AM EDT Mon Apr 27 2026

TODAY`S SEVERE WEATHER POTENTIAL

A potent vort max is ejecting out of the Rockies as of this writing.
Lee cyclogenesis is ongoing over the high plains, with the resulting
cyclone expected to move northeastward through sunrise. The system
passes to our northwest this afternoon. Strong mass response should
drive a potent southerly low-level jet (LLJ), which increases into
the evening hours.

Flow at the surface may still be out of the east-southeast through
this morning, as surface high pressure slides eastward. This may
limit moisture return over Indiana, with some CAMs showing
relatively dry conditions into this afternoon (RH as low as 45
percent). Winds gradually become more southerly through the day,
allowing dew points to increase through the evening hours.

Two scenarios exist for convective evolution today. First,
convection developing over Kansas (as of 3am) grows upscale into an
MCS and propagates eastward through the night into the strengthening
LLJ. Some CAM guidance like the HRRR show such a scenario, with the
MCS arriving around 19z. Of particular interest is the relatively
dry air mass over Indiana and whether this causes the approaching
MCS to weaken. Also of interest is strong wind gusts shown by some
CAMs within the anvil region of the MCS. This appears to be driven
by strong evaporational cooling as rain falls into the dry low-level
air mass. Momentum from the strengthening LLJ is then mixed
downward, allowing for the strong wind gusts. Guidance also hints at
a flooding threat on the southern margin of the MCS where training
cell motions are most favored.

The second scenario is that there is no MCS, or it passes to our
north, and thunderstorm development occurs over Illinois along the
systems`s trailing cold front. Such a scenario would allow
instability to build up until explosive convective development
occurs. Shear vectors slightly off boundary should allow for
initially discrete convection, with shear magnitudes favoring
supercells over Illinois. Upscale growth into a line then appears
likely with eastward extent. Moisture advection ahead of the front
should allow convection to sustain through Indiana and into Ohio. It
is possible that the MCS from the first scenario does arrive and
affects only part of our CWA with the cold frontal convection
arriving later for those that did not see the MCS.

Given the potential for multiple rounds of convection, pin-pointing
exact timing remains tricky. Additionally, keying in on which
hazards are most likely and where is a challenge as each round of
convection alters the environment ahead of the next round. That
being said, all hazards are possible with today`s severe weather
given the amount of shear (40-60kt) and instability (1500-2500 J/Kg
MLCAPE) expected. All hazards are possible especially with any
supercell that develops. Supercells are most likely over Illinois,
however, with upscale growth increasingly likely by the time things
reach Indiana. Strong to damaging winds are favored with upscale
growth or in scenarios that result in an dominant MCS. Given the
strong LLJ and high amounts of SRH (200-300 m2s2) present within the
warm sector, a QLCS tornado threat is possible as well.

TUESDAY ONWARD

A second shortwave ejecting from the Rockies closely behind Monday`s
may provide another chance at showers and storms. However, given the
potency of Monday`s system, much of the moist unstable air will have
been swept away by the time the second system arrives. Sufficient
moisture return may be possible for storms over the southern half of
Indiana late Tuesday. Severe weather may again be possible should
this occur, especially further south, but this depends on how
quickly moisture and instability can advect back northward.

After Tuesday, persistent troughing aloft takes hold and cooler than
average conditions are favored for the second half of the week and
into the weekend. High temperatures in the 60s and lows in the 40s
appear likely Wednesday through Saturday. Guidance is hinting at
some lows into the 30s possible this weekend, which could mean frost
potential.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 627 AM EDT Mon Apr 27 2026

Impacts:

- S-SE wind gusts 20 to 30 kt today
- Scattered to numerous convection, mainly afternoon into evening
- LLWS around 45kt this evening/tonight
- MVFR ceilings this evening into early Tuesday

Discussion:

VFR conditions start the day with a gradual lowering of ceilings
occurring. Winds will increase later this morning, with frequent
gusts to around 25kt, with a potential for a few gusts near 30kt
in the afternoon.

Uncertainty ramps up quickly today in terms of rain. There could
be some weakening convection in the morning hours. Some convection
may develop after 18Z depending on mesoscale features, but better
odds of thunderstorms will occur after 22Z. Will use PROB30s, but
when details become clearer, TEMPOs will be needed in later
issuances.

Otherwise, MVFR ceilings are expected to develop as rain becomes
more widespread and low-level moisture increases. These ceilings may
persist into Tuesday morning. Additionally, a cold front is
anticipated late tonight with a wind shift to westerly behind the
front. A period of low-level wind shear is likely ahead of the
front as southerly flow increases.

&&

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

$$

AVIATION...50/Eckhoff
DISCUSSION...Eckhoff