675
FXUS63 KIND 130638
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
238 AM EDT Mon May 13 2024

.KEY MESSAGES...

- Showers and a few thunderstorms expected beginning late today
  into Tuesday

- Up to around one inch of rain expected

- Rain chances return Thursday into Friday

&&

.SHORT TERM (Today and Tonight)...
Issued at 238 AM EDT Mon May 13 2024

Skies have remained mostly clear so far early this morning as the
broad surface ridge across the eastern part of the country maintains
a strong influence over the Ohio Valley. Temperatures have remained
mild overnight with light southerly flow. 06Z readings were in the
60s.

There has been a noted trend to slow down the arrival of impacts
from the upper low and associated surface wave currently moving
across the central Plains. Residual dry air and subsidence lingers
over the region and the ACARS soundings early this morning at KIND
depict that very nicely. Even as the upper low and surface wave
approach the forecast area from the west...onset of rainfall and
convection will be delayed until this evening for much of the region
due to the presence of the dry air mentioned.

High clouds are slowly expanding into the Ohio Valley early this
morning and will gradually increase in coverage into the early
afternoon as progressively deeper moisture advects into the region.
But with that being said...expect a modest amount of sunshine
through the first half of the day with more substantial cloud cover
holding off until the afternoon. Most of the convection will remain
to the west and northwest of the forecast area today but likely to
see the initial surge of scattered showers into the Wabash Valley by
late day.

Model soundings highlight the drier air present through much of the
lowest 10kft will be the last to moisten...likely not fully
saturating until this evening as a deeper surge of isentropic lift
depicted at 300K spreads into the area from the southwest. The
arrival of slightly stronger flow at 850mb in advance of the upper
low and surface wave will also aid in an uptick in moisture
advection this evening with showers increasing in coverage and
becoming numerous tonight. Thunder will be mitigated by minimal
instability aloft remaining scattered at best through the night.
Brief and locally heavy rainfall will be possible late tonight...
focused especially south of I-70 as precip water values rise to near
1.25 inches. Much of the forecast area will see around a quarter
inch by daybreak Tuesday with pockets of higher amounts over the
southern half of the forecast area.

Temps...considering the later onset to showers today...nudged temps
up a bit from previous forecasts as upper 70s will be common by this
afternoon. Lows will largely hold in the lower 60s tonight.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 238 AM EDT Mon May 13 2024

Tuesday Through Thursday.

By Tuesday morning the low pressure system associated with the rain
at the end of the short term period 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 the frontogenesis within this band looking weaker
compared to earlier model runs with the warm conveyor belt more cut
off by heavier precipitation across the Gulf states inhibiting the
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 total rain amounts around 0.5-1.25 inches
with the heaviest rain Tuesday afternoon.

Model soundings show some instability during the daytime hours on
Tuesday, but the thermal profiles show near moist adiabatic
temperatures which will limit the thunder coverage and keep the
severe threat to essentially zero. There will be additional
precipitation Tuesday night on the backend of the system, but expect
that coverage will gradually lessen after midnight going into
Wednesday as the better forcing pushes into the East Coast.
Conditions look much quieter going into the middle of the week as
high pressure builds in the aftermath of the early week system.
Temperatures will remain near normal with little flow at the surface
and aloft to advect warmer air into the area.

Friday Through Sunday.

Another upper level low is expected to take a similar track to the
system earlier in the week Thursday night into Friday with another
round of sub-severe showers and thunderstorms. The exact track with
this system remains much more uncertain with the recent Euro model
runs sticking out as significant outliers compared to most other
deterministic and ensemble guidance which keeps precipitation across
Indiana well into the weekend as the system slows and deepens vs the
more progressive track of most other guidance.  Will keep low POPs
into Saturday to account for this potential, but think that
precipitation should exit the area by Saturday morning. Dry weather
is also then expected for Sunday with the low potential for rain if
the Euro model run verifies.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1228 AM EDT Mon May 13 2024

Impacts:

- Showers and embedded storms arrive late this afternoon into tonight
- IFR conditions developing late tonight

Discussion:

Skies remain mostly clear early this morning as the Ohio Valley
continues under the influence of departing high pressure. High
clouds are slowly expanding towards the region and that will
continue through daybreak. Ceilings will gradually lower during the
afternoon with scattered convection expanding into the Wabash Valley
late day. S/SW winds are expected through late today peaking at 10-
15kts this afternoon with sporadic higher gusts.

Showers will become widespread this evening across central Indiana
with the approach of low pressure from the west. Weak elevated
instability supports embedded thunder tonight but coverage alone
will not warrant introducing a VCTS at the terminals at this time.
Lower ceilings will arrive through the evening...dropping to MVFR
and eventually IFR overnight with lower visibilities in rain.

&&

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

&&

$$

SHORT TERM...Ryan
LONG TERM...White
AVIATION...Ryan