Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 140648
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
248 AM EDT Thu Mar 14 2024

.KEY MESSAGES...

- Multiple rounds of thunderstorms today/tonight. Severe
  potetial will be present for all rounds, but the best chance for
  severe potential will be between 8PM and 2AM.

- Breezy on Saturday with gusts over 30 mph

- Much colder around Monday, with a hard freeze expected Tuesday
  morning.

&&

.SHORT TERM (Today and tonight)...
Issued at 248 AM EDT Thu Mar 14 2024

Rest of Tonight...

A line of strong but sub-severe thunderstorms have developed across
western central Indiana tonight along a quasi-warm front.
Observations and sounding analysis show an increasing NW component
of the 850-700mb winds aiding a FGEN region and thus creating lift.
A nocturnal LLJ is providing the moisture and shear needed for
sustained updraft growth.

Surface dew points in the mid 40s and the development of a diurnal
temperature inversion should keep these thunderstorms elevated, and
the lack of a deep EL and steep ML lapse rates should keep hail
below severe criteria. The presence of the FGEN and a modest
nocturnal LLJ should maintain initiation as the boundary moves
northward, with increasing development NW of the currently like as
it reaches northern central Indiana. A quick 0.25"-0.50" and small
hail is possible in any storm.

As these storms move east, they should begin to weaken. This region
is further into a dry midlevel airmass, and removed from the
strengthening nocturnal LLJ.


Thursday Morning into Early Afternoon...

Another round of convection is likely later this morning into the
afternoon. CAM runs continue to show severe storms near Eastern KS
and northern MO growing upscale into a QLCS before propagating
eastward towards central IN sometime around mid-morning through mid-
afternoon. Continued low-level theta-e advection during the day and
favorable deep-layer shear supports the potential for this
convective system to maintain itself like most high-res models
suggest. This system should have a well establish RIJ given a dry
700-600mb layer and steepening mid level lapse rates. However, as it
moves into Indiana, a less favorable low level environment could
cause the QLCS to become outflow dominant leading to strong, but sub-
severe conditions. Still, there is a marginal threat for damaging
wind gusts and large hail as this line moves through, especially if
the UDCZ remains well organized. Most likely timing is between 11AM
and 3PM.


Thursday Evening into Thursday Night...

This warm sector will have multiple phases as a split low pressure
system develops. After the MCS passage in the earlier afternoon,
atmospheric recovery will likely produce strong ML-CIN as a deep EML
pushes over a near saturated surface layer. Initially, this should
limit convection for the mid to late afternoon hours, while allowing
for surface temperatures to recover. By around 6PM a channel of 60+
DP air will approach the region, moistening the 900-700mb column
and destabilizing the air. At this point, the environmental
conditions will become more favorable for convective
initiation/development, but will still need some from of forcing. The
most likely forcing mechanism will be a frontal boundary approaching
from the NW, but a left over outflow boundary from prior convection
could be enough.

Parameter spacing in this newly establish warm sector will be
sufficient for convective organization, with a deeply unstable
atmosphere and 50+ kts of effective bulk shear. Low level wind shear
will also be elevated especially along the frontal boundary and as
the LLJ strengthens near dusk. Any storm that initiates in this
environment will have the potential to produce severe weather, with
all thunderstorm hazards possible. Deep layer shear, and strong mid
level lapse rates promote hail growth, and the strong LL shear will
further lead to a hail risk, but also a tornado risk. The bigger
question on severe potential will be where the stalled boundary will
be positioned and if thunderstorms do in fact develop over central
Indiana. For this reason, the overall severe risk is lower, but
parameter spacing is plenty sufficient for a greater risk if
thunderstorms develop.

Another potential risk will be flash flooding along the
aforementioned stalled boundary. Depending on the timing of
thunderstorm initiation the evening, there could be a multiple hour
threat of successive high rain rate thunderstorms along the front
over northern IN. The main risk for this should remain north of
central Indiana, but could trickle into far northern portions of our
CWA if the front stalls further south.

As the front progresses eastward, a deeper low pressure will create
a better CAA regime upstream, eventually resulting in cold front
development and a push southward. When the front pushes southward
late this evening into the overnight, shear vectors will likely
promote more of a linear structure with the primary hazards being
damaging wind gusts and brief, weak tornadoes in any broken
segments.

&&

.LONG TERM (Friday through Wednesday)...
Issued at 248 AM EDT Thu Mar 14 2024

Friday...

The cold front will become closer aligned to the upper flow by the
start of Friday, and this will help slow its progress south. Thus,
rain chances will continue during the first half of the day, mainly
across the southeast half or so of the area. Will go no higher than
chance category. Drier air will work in behind the front and end
most chances for rain early in the afternoon.

Saturday and Sunday...

A cold front will move into the area late on Saturday and through
the area Saturday night. The front will not have much moisture to
work with, so will keep most areas dry.

Conditions will be breezy due to a tighter pressure gradient and
stronger winds mixing down. Wind gusts over 30 mph are likely for
parts of the area on Saturday, with gusts over 20 mph on Sunday.

Monday and beyond...

An upper trough and surge of cold air will move in for Monday. The
trough and cold advection might be enough to wring out some light
snow showers or flurries.

Sub-freezing temperatures will be around during the mornings
of Monday through Wednesday, with hard freeze readings in the
lower and middle 20s on Tuesday morning. Highs on Monday will be in
the mid 30s to lower 40s.

Some moderation will occur into mid-week next week, but uncertainty
remains on how fast it does.

Northwest flow may bring some weak upper energy at times, but
moisture will be lacking through Wednesday.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 100 AM EDT Thu Mar 14 2024

Impacts:

- Convection will impact KIND and may impact KLAF near start of
  valid time for an hour or two

- Additional convection will occur this afternoon and again
  this evening

- Outside of convection, winds will increase this afternoon
  with gusts around 25kt possible

Discussion:

A broken line of convection will move northeast past KIND and KLAF
early in the period. KIND is most likely to be impacted.

While some showers or isolated convection are possible afterward,
the next best chance of convection will come early this afternoon as
a potential line of storms moves west to east. Used PROB30s for now.
More widespread showers with embedded convection will move in 22Z-
01Z or thereabouts.

Outside of convection, VFR ceilings are expected through 06Z Friday.


&&

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

$$

SHORT TERM...Updike
LONG TERM...50
AVIATION...50


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