026
FXUS63 KIND 221056
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
656 AM EDT Wed May 22 2024

.KEY MESSAGES...

- Not as warm, yet continued humid today as a weak cold front slowly
  crosses the region

- Isolated strong/severe storms are possible late today and tonight,
  mainly south and southeast of Indianapolis...damaging winds and
  isolated flooding are the most likely hazards

- Chances for rain continue through much of the holiday weekend into
  next week.

&&

.SHORT TERM (Today and tonight)...
Issued at 303 AM EDT Wed May 22 2024

Today...

A potent late spring storm system will cross Ontario today, dragging
its trailing cold front slowly across central Indiana from northwest
to southeast.  The boundary will make more progress across northern
counties per the departing cyclone`s eastward advancement...while
rather weak surface high pressure nudging east behind the boundary
tracking in a quasi-parallel path will slow the front as it
approaches the Ohio Valley.  Convection crossing the region early
this morning will weaken, due to better forcing departing north...
while mostly departing to our east, with scattered showers perhaps
lingering to the southeast of Indianapolis through daybreak.

The slowly-passing front will promote further rounds of mainly
isolated shower development...be it northern/central zones this
morning...southern counties through midday to early afternoon
hours...or perhaps a more favorable set-up for organized stronger
cells perhaps along our far south and more likely along the Ohio
Valley starting late today.  Southwesterly breezes gusting to at
least 15-20 mph will veer slightly as the front passes, but still
hold moderate humidity across the region...with dewpoints likely
reaching the upper 60s over southern zones.  Considerable cloudiness
ahead of the boundary should scatter out slowly from northwest to
southeast as the frontal zone arrives.  Despite starting out at near-
record-high mild levels this morning in the upper 60s...clouds will
promote a more reasonably mild day for late May with most locations
reaching the low 80s.

Tonight...

The frontal zone to the north-northwest of the lingering, quasi-
stationary boundary slowly passing the Ohio Valley will provide
modest lift and help to focus any next round of showers and
thunderstorms over southern portions of Indiana.  Convective
ingredients will be more favorable through evening hours...when both
instability and mid-level lapse rates will be adequate from far-
south to southeastern zones, while bulk shear of 40-50 kts slowly
decreases. Although latest guidance suggests numerous RW/TRW will
hold off until after 06Z - with this potential initiation from a
trailing vort max from the departed northern system sliding across
the northern Midwest.  Should these cells organize over our southern
counties, rain and a few strong storms could linger towards dawn
towards the I-70 corridor as shear values increase slightly pre-dawn.

All possibilities considered, expect scattered showers and a few
strong storms along the Ohio Valley and our far southern zones,
likely starting during the evening.  Cannot rule out isolated wind
damage, although widespread severe storms are not expected.  Likely
a greater threat will be flood potential with slower storm motion
and training/repeat cells over the same locations given the
boundary`s very slow motion.  A staunch precipitable water gradient
over southern central Indiana should limit flood threat to far
southern and southeastern counties.  Light winds will oversee
minimum temperatures ranging from mid 50s along the Upper Wabash
Valley to low 60s across the US-50 corridor.  Indianapolis will need
to drop below 70F by 05Z to avoid at least tying the record high
minimum for 5/22.

&&

.LONG TERM (Thursday through Tuesday)...
Issued at 304 AM EDT Wed May 22 2024

Thursday...

An upper level wave south of the area will interact with a lingering
surface front south of central Indiana on Thursday. Moisture will be
lingering near the surface front, and the upper system will have
some moisture with it. Across northern portions of the area, drier
air will be around along with some influence from surface high
pressure.

Thus, will go with some likely PoPs across the south, closest to the
wave and front, tapering down to dry PoPs across the far northwest,
deeper in the drier air.

Friday...

A more complicated pattern will be around for Friday. Another upper
wave to the south will bring another round of forcing to the area.
Meanwhile, an upper system well to the northwest will have an
accompany surface cold front approach the area during the day.

Questions remain on timing and location of best forcing during the
day. There could potentially be a split where highest PoPs are in
the northwest and southeast forecast area, with the middle part of
the area in a relative lull. However, confidence is too low to
differentiate at this time, so will keep broadbrushed likely PoPs
across the much of the area with lower confidence than usual.

As the front moves in Friday night, another round of rain will move
through, prompting likely PoPs again.

Saturday...

Generally quiet weather will rule on Saturday as high pressure
briefly builds in. There could be some lingering showers in the
morning, especially east. Blended guidance keeps low PoPs in the
afternoon east, but confidence is very low in this happening.

Sunday...

A more potent system will move into the area on Sunday. The system
will have good moisture with southerly flow in the warm sector of a
surface low pressure system. This combined with the expected forcing
from the upper wave should lead to rain across much of central
Indiana into Sunday night.

Of course, this far out, precise timing of the rain chances isn`t
possible, and current timing could shift. However, it does appear
that rain will fall at some point Sunday into Sunday night.

Depending on the timing and eventual path of the surface system,
strong to perhaps severe storms would be in the realm of
possibility. Will have to keep a close eye on it.

Memorial Day onward...

The Sunday system will be way out on Monday, but there could be some
lingering rain as the system exits. Will keep some low PoPs around.

Into mid-week next week, the eastern USA will be under a broad upper
trough with ridging across the western USA. Various waves moving
through the trough could bring some rain, but timing and strength of
these remains quite uncertain this far out. Will keep some low PoPs
around for now. Temperatures will be a little cooler than normal in
this setup.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 655 AM EDT Wed May 22 2024

Impacts:

- South-southwesterly wind gusts to 22-26KT at KIND thru 13Z
- MVFR CIG possible at times this morning
- Widely scattered SHRA/isolated TSRA near/south of KBMG after 21Z

Discussion:

MVFR ceilings are possible at times for a few hours this morning
ahead of a weak cold front slowly crossing the region from northwest
to southeast....with VFR otherwise expected into Wednesday night.
VCSH will otherwise be the rule through the TAF period, with
scattered SHRA/isolated TSRA possible near/south of KBMG after 21Z.

Southwesterly winds earlier this morning will diminish while slowly
veering to WSW/W today.  KIND may have robust gusts to 20-25KT
through 13Z.  More reasonable flow is otherwise expected today with
sustained winds around 9-13KT today...with winds diminishing early
this evening while veering to the north.

&&

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

$$

SHORT TERM...AGM
LONG TERM...50
AVIATION...AGM