602
FXUS63 KIND 141356
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
956 AM EDT Tue May 14 2024

.KEY MESSAGES...

- Showers and a few thunderstorms expected through Wednesday

- Up to around one inch of rain expected, highest across southwest
  Indiana

- Rain and storm chances return late Thursday through Friday

- Turning warmer this weekend

&&

.FORECAST UPDATE...
Issued at 956 AM EDT Tue May 14 2024

Made some minor adjustments to progression of PoPs and thunder
chances based on latest regional radar mosaic and observational
datasets - cannot rule out an isolated rumble through the morning
but what relatively low thunder threat there is will be highest
during and after peak heating in the afternoon and evening when what
minimal instability there will be (roughly 200-400 J/kg at best)
peaks across portions of the area, highest in the south. Marginal
risk clips the southern tier of the area this afternoon, but despite
the nearness of the slow-moving surface and upper low, a weak
parameter space in the form of modest shear and minimal instability
should severely hamper convective organization in the absence of
more significant destablization via either stronger than expected
advective processes or insolation via breaks in the low cloud cover.

Initial band of precip slowly making its way northward will hamper
heating today, especially across central portions of the area, and
adjusted highs down slightly to account for this.

&&

.SHORT TERM (Today and tonight)...
Issued at 239 AM EDT Tue May 14 2024

Through Daybreak.

Latest radar imagery shows the majority of the precipitation is
remaining to the west of the forecast area with ACARs soundings
showing a persistent dry layer below the cloud deck of 10kft. The
better isentropic lift associated with the approaching system
remains south of the Ohio River and across Illinois. Saturation
within the lower levels is expected to continue with the LLJ ramping
up through the rest of the overnight hours, but think precipitation
onset will generally be after 12Z for all but the furthest southwest
counties.

Today.

By daybreak this morning morning the low pressure system associated
the recent rain will be tracking through Missouri into the Ohio
Valley. A deformation zone to the northwest of the surface low looks
to clip the far northwestern counties, but models are showing only
weak frontogenesis within this band due to the  the warm conveyor
belt being somewhat cut off by heavier precipitation across the Gulf
states. This will inhibit the stronger moisture transfer needed to
bring the higher rain amounts to the banded area. That being said,
there still remains plenty of broad lift with the system with rain
coverage increasing through the day.

Model soundings show some instability during the mid to late
afternoon hours, but the thermal profiles show near moist adiabatic
temperatures which will limit the thunder coverage and keep the
severe threat to essentially zero. Will cap thunder mention to
isolated and confine it to the 21Z to 02Z timeframe. With abundant
cloud cover overhead through the day, expect that highs will only
reach to around the low 70s.

Tonight.

There will be additional precipitation tonight on the backend of the
system as the surface low passes overhead across the souther
counties, but expect that coverage will gradually lessen after
midnight going into Wednesday as the better forcing pushes into the
East Coast. With the surface low nearly overhead by 09Z, will lower
wind speeds during the mid to late overnight hours and will have to
keep an eye on the potential for some river valley fog. The
continued cloud cover tonight will also help insulate temperatures
with lows around 60.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 239 AM EDT Tue May 14 2024

A quasi-zonal flow aloft will dominate the lower 48 through the end
of the week...maintaining a pattern with periodic threats for
convection as storm systems pass through the area in the progressive
upper level regime. Model guidance continues to struggle further in
the extended this weekend into early next week...but there are hints
of a warmup as ridging aloft expands into the Ohio Valley by late
weekend.

Wednesday through Friday Night

The upper level low and associated surface wave that will be
catalysts in the rain chances and embedded convection today and
tonight will be sluggish in their departure to the east and this
will result in forcing aloft and moisture lingering back across
central Indiana into Wednesday with scattered convection focused
especially across the southeast half of the forecast area in closest
proximity to the upper low. Likely to see coverage gradually
diminish during the afternoon as upper ridging builds in from the
west but the lagging moisture through the boundary layer will keep
an abundance of clouds over the region for much of the day before
drier air arrives late day.

A surface ridge will sweep across the area Wednesday night with
clearing skies and a brief period of dry weather across the region
that will last into Thursday afternoon. The next surface wave
tracking east within the zonal regime aloft will move into the
Missouri Valley by Thursday afternoon then shift east into the Ohio
Valley Thursday night and Friday with widespread showers and
embedded thunderstorms returning. Precip water values will recover
quickly late Thursday and peak near 1.50 inches by early Friday...
supporting the potential for locally heavy rainfall within
convective cells. A trailing upper level wave will move across the
Ohio and Tennessee Valleys through early Saturday and serve to keep
showers across the forecast area through Friday night.

Temperatures will remain seasonable through the second half of the
work week with highs in the 70s. The coolest day is likely to be
Wednesday with rain and low clouds lingering over the region as the
upper low moves slowly away to the east.

Saturday through Monday

The model suite diverges beginning Saturday morning into early next
week...lowering confidence in the general forecast trends for the
weekend. Considering the progressive nature of the flow regime
aloft...prefer the solutions supporting convection diminishing on
Saturday as weak high pressure at the surface and ridging aloft
expands into the Ohio Valley. Cannot entirely rule out rain chances
Saturday and Sunday but expect much of the area will be dry for
large portions of both days. Highs will warm over the weekend with
the upper ridge building into the Ohio Valley. Low to mid 80s are
expected by Sunday.

Into early next week...a cold front will approach from the northwest
bringing an increase for convective potential Monday and Tuesday.
Further out next week...long range ensembles continue to hint at a
more robust surface low moving through the central Plains and upper
Midwest. While we remain well too far for specifics...this would
bring the potential for a more significant convective risk across
the eastern Midwest in the day 7 to 9 time period.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 558 AM EDT Tue May 14 2024

Impacts:

- MVFR cigs and occasional MVFR vsbys due to rain 14Z through 06Z
tonight.
- Brief TSRA possible 21Z to 03Z.
- Wind shift from south to east after 03Z tonight.

Discussion:

Occasional rain is expected through the day starting at around 14Z
at BMG. Vsbys will generally remain VFR but MVFR conditions are
possible in the heaviest showers of the day.  Highest rain coverage
currently is expected during the mid afternoon hours. There may be
some brief TSRA during the late afternoon and evening hours, but
confidence is low. Rain coverage will then be low enough to not
warrant a TAF mention after 06Z. Winds will generally be southerly
through the day today at 5-10kts with a wind shift to the east after
03Z.

&&

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

&&

$$

UPDATE...Nield
SHORT TERM...White
LONG TERM...Ryan
AVIATION...White