428
FXUS63 KIND 250935
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
535 AM EDT Sat May 25 2024

.KEY MESSAGES...

- Thunderstorms, possibly severe on Sunday/Sunday Night/Monday
- Shower chances and cooler temperatures Tuesday-Wednesday
- Dry and Seasonable Thursday and Friday

&&

.SHORT TERM (Today and tonight)...
Issued at 301 AM EDT Sat May 25 2024

A weakly baroclinic front tied to a deep occluding low near the
Manitoba/Ontario border will pass through this morning. Although we
will be at a diurnal minimum, warm/moist advection preceding the
front may be enough for isolated convection. With diurnal heating
and destabilization this afternoon, convection will redevelop but it
should be relegated to our far southeast counties by then (east of a
Seymour to Greensburg line).

The post frontal air mass will probably not be noticeably cooler
compared to yesterday, but drier continental air will feel less
humid by comparison. Mid to upper 70s for maximas are expected with
northwest winds 10 mph or less. Cirrus and an increasing MSLP
gradient with mixing toward dawn may interrupt radiative cooling
process to keep temperatures from falling substantially, but still 5-
7 degrees cooler than the previous couple of nights given dry air
mass and steeper diurnal curve early in the night when radiative
processes are more optimal.

&&

.LONG TERM (Sunday through Friday)...
Issued at 301 AM EDT Sat May 25 2024

Sunday through Monday...

Look for an active start to the extended period as severe weather is
likely Sunday and Sunday night as a mid-upper level trough with
multiple embedded impulses traverses the Great Lakes region. An MCS
is expected to be ongoing Sunday morning over portions of MO/IL
which should progress towards central IN around mid-morning to early
afternoon bringing the first potential round of strong to severe
storms. Latest models still show disagreement regarding timing of
the MCS due to uncertainty in how organized the line of storms or
cold pool will be. The MCS is likely going to gradually weaken upon
approach as it outpaces the stronger deep-layer shear further west.
Despite this, there is still the potential for severe weather with
this initial round of convection. The primary threat would be
damaging wind gusts, but embedded tornadoes cannot be ruled out if
the MCS remains organized. Mesoscale subsidence behind the line of
storms may allow for a brief break during the afternoon before
another round of severe storms moves in by the evening.

Guidance shows the upper trough becoming more negatively tilted and
amplified late Sunday resulting in a deepening surface low across
the Midwest. A strong LLJ associated with the system will advect
deeper moisture into central Indiana during the afternoon promoting
further destabilization despite early day convection. Scattered to
numerous storms are likely to develop ahead of a cold front over
MO/IL late in the afternoon. A strongly unstable airmass along with
strengthening deep-layer shear from increasing mid-upper level flow
will likely support severe thunderstorms. Shear vector orientations
and focus of low-level convergence suggest these storms should
quickly grow upscale and progress towards the area during the
evening and overnight hours. All convective hazards are on the table
with the primary threat being damaging wind gusts. In addition,
there is an elevated threat for localized flooding given anomalous
moisture return and the potential for training storms over saturated
grounds.

The aforementioned surface low should begin to move out early in the
day Monday. Rain chances remain in the forecast though with broad
cyclonic flow still in place.

Tuesday and  Wednesday...

Low POPs persist into Tuesday with another upper trough traversing
the Great Lakes Region. The best chance for showers is across far
northeast portions of central IN where better forcing is expected.
Locations further south and west should remain mostly dry. Strong
surface high pressure building across the region late Tuesday into
Wednesday will likely provide mundane weather conditions. Look for
relatively low cloud cover with highs in the 70s and lows in the 50s.

Thursday and Friday...

Models suggest the strong surface high pressure becomes centered
over the area with amplified upper ridging building in allowing for
mostly quiet weather conditions to continue. However, the
development of a weak Omega block is possible with an upper low
setting up over the middle Atlantic States. This will bring cyclonic
flow aloft over Indiana. The lower levels are not a favorable set-up
for precipitation, but the cyclonic flow aloft cannot rule
precipitation out. Temperatures are expected to gradually moderate
towards the end of the week.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 535 AM EDT Sat May 25 2024

Impacts:

- Brief MVFR stratus early-mid morning

- Wind shift to northwesterly midday

Discussion:

Light and variable winds will trend northwesterly as the front moves
through this morning. A band of stratus with MVFR ceilings is
expected to accompany the front. Ahead of the front, the probability
of showers is less than 20 percent.

&&

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

$$

SHORT TERM...BRB
LONG TERM...Melo
AVIATION...BRB