541
FXUS63 KIND 250701
AFDIND

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

.KEY MESSAGES...

- Scattered to numerous thunderstorms through the early overnight,
  isolated severe threat
- 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. Some supercells are possible as well
with all convective hazards on the table. 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...

Strong ridging aloft is expected to build across the plains in the
wake of the front. This will allow an area of cool, Canadian high
pressure to settle across Indiana on Tuesday through Wednesday.
Forecast soundings on these days show a dry column with little to no
instability present. Thus will trend toward a dry forecast, partly
cloudy days and mostly clear nights with seasonable temperatures.

Thursday and Friday...

Models suggest the strong ridging looks to remain over the mid
section of the CONUS, but this will allow for the development of a
weak Omega block, with the front end low setting up over the middle
Atlantis States. This will bring cyclonic flow aloft over Indiana,
influenced by the upper low to the east. Meanwhile at the surface,
strong surface high pressure centered over the Great Lakes with cool
easterly flow will be present across Central Indiana. The lower
levels are not a favorable set-up for precipitation, but the
cyclonic flow aloft cannot rule precipitation out. Thus it is likely
that at least some small chance pops will be included at that time
for now.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1238 AM EDT Sat May 25 2024

Impacts:

- Brief MVFR stratus possible early-mid morning

- Wind shift to northwesterly midday Saturday

Discussion:

Some variability in wind direction will occur around the beginning
of the TAF period due to recent diminishing convection and its
augmentation of the low-level pressure field. Winds should stabilize
to southerly toward morning and then veer as a front moves through.
A band of stratus will accompany the front and could result in brief
MVFR ceilings. Post-frontal winds will be northwesterly.
Probabilities of showers will be 20-30 percent at TAF sites until
the front passes.


&&

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

$$

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