374
FXUS63 KIND 090953
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
553 AM EDT Thu May 9 2024

.KEY MESSAGES...

- Another round of thunderstorms this afternoon, with an isolated
  severe hail and wind threat

- Periodic chances for showers and a few storms this weekend into
  early next week.

- Normal to slightly below normal temperatures Friday through
  Saturday with warmer temperatures next week.

&&

.SHORT TERM (Today and tonight)...
Issued at 248 AM EDT Thu May 9 2024

Rest of the night...

A secondary frontal boundary has now developed over northern
portions of central Indiana, allowing for continue lift with
moderate theta-e advection. This has led to a slowly propagating
convective line. Within this line, thunderstorms are expected to
remain sub severe, but steep mid level lapse rates and strong mid
level flow may be enough for isolated small hail reports. The other
concern is for localized flooding. Due to the slow propagation
vectors on these storms, narrow corridors could see a quick 0.5-1.5"
over the next few hours. Luckily, this area has been mostly spared
from prior day rainfall, but any areas with poor draining could
become inundated fairly quickly, along with some ponding on
roadways.

Otherwise, the focus will be on continued development of southern IL
pushing into south central Indiana. Once again, these storms are
expected to remain sub-severe, but isolated small hail and localized
flooding are potential hazards. This time, the flooding is would
mostly be due to a quick 0.5" passing over already saturated
grounds.

Thursday and Thursday Night...

For Thursday, central Indiana will be between two frontal
boundaries. A warm front to the east, and an eventual cool front to
the N/W. Although, surface temperatures will not be quite as high
today (upper 60s to mid 70s), dew points will remain elevated,
providing modest instability in the presence of 7-7.5 C/km low level
lapse rates.

Thermodynamic parameter spacing for today should be more subdued
with the EL down near 300mb, and mid level lapse rates near 6.5
C/km. Thus providing CAPE values between 1000-2000 J/kg this
afternoon. Most of this CAPE will be along and south of the I-70
corridor by the mid afternoon when CI is expected to begin. Dynamic
forcing aloft will still be rather robust. Current expectation is
for a mid level jet around 60kts and an upper level jet around 90-
100kts overhead, providing an effective shear of 40-50kts this
afternoon and evening. Even though instability will be subdued
compared to previous days, if will likely still be sufficient enough
in the presence of strong dynamics for thunderstorms to organize
into clusters this afternoon, and provide a non-zero severe threat
for damaging winds and hail. Luckily, low level shear values will be
far too weak for a tornadic threat for central Indiana.

Given the slow progression of the aforementioned cool front, storms
clusters may begin to train over similar areas, leading to a
localized flood threat as well today.

By late this evening, the cool front should be south of central
Indiana, finally proving the region with a reprieve from
thunderstorms and showers. The only threat for Thursday night will
be some low lying ground for over southern Indiana, where the front
could remain close enough to keep surface winds light.

&&

.LONG TERM (Friday through Wednesday)...
Issued at 248 AM EDT Thu May 9 2024

Friday through Sunday...

The long term will start off cooler and drier as an upper trough
moves through early Friday in northwest flow aloft and low level
winds blow from the northwest in between the departing low pressure
system and broad high pressure over the Plains and Rockies. However,
shower chances will return Friday night and Saturday as a broad
trough of low pressure rotates southeast across the lower Great
Lakes. Deeper moisture. The best chances of convection will be over
northern and eastern sections, closer to the trough. Instability
progs are only indicating enough available instability for brief
thunder mention over northeastern counties Saturday afternoon as the
system starts moving off into the eastern Great Lakes and northern
Appalachia. With BUFKIT soundings showing very limited moisture,
even northern and eastern sections will see less than 50% coverage.

With limited cloud cover, very steep 0-3km low level lapse rates and
deep mixing layer below an elevated EML per BUFKIT soundings
supports Saturday afternoon wind gusts to near 30 knots. So, along
with it being cooler, with slightly below normal temperatures in the
middle 60s to lower 70s, it will also be a windy day.

As instability quickly disappears after sunset and the trough moves
away, so to will any lingering showers. In addition, winds will also
drop off allowing for good radiation cooling. Dry air in place with
dew points in the 40s suggests, overnight lows will also get down
into the 40s Saturday night.

Temperatures will warm up a bit on Saturday as low level winds shift
to the southwest and a mostly dry column and upper ridge just to our
west suggest mainly just some high clouds moving in ahead of the
next low pressure system taking shape over the High Plains. Good
confidence that most locales will return to the 70s.

Sunday night through Wednesday night...

Confidence decreases late this weekend and next week regarding
timing and coverage of convection as models are all over the place
on the timing of the High Plains system into the Ohio Valley.
Generally through, southerly flow ahead of the system is expected to
support above or at least normal temperatures for this time of year
which means highs in the lower to middle 70s or warmer.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 553 AM EDT Thu May 9 2024

Impacts:

- MVFR and worse ceilings at times with convection through 03z
  Friday

- MVFR and worse conditions to linger after 03z Friday

Discussion:

More convection will arrive from Iowa this morning as an upper wave
approaches tonight. Moderate instability will support thunder
except perhaps at KLAF, north of a secondary warm front, where
instability will be markedly weaker. Hi-Res soundings are indicating
a saturated boundary layer which will support MVFR and worse flying
conditions much of the TAF period. The convection should mostly be
over late this evening as instability wanes.

Winds will be mostly NE and N at KLAF, north of the warm front and
mostly have a southerly component over the other sites at least
through this evening before winds shift to the north.

&&

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

$$

SHORT TERM...Updike
LONG TERM...MK
AVIATION...MK