474
FXUS63 KIND 230143
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
943 PM EDT Wed May 22 2024

.KEY MESSAGES...

- Isolated strong/severe storms are possible tonight, mainly south
  and southeast of Indianapolis. Damaging winds and localized
  flooding are the most likely hazards

- Rain and thunderstorms possible on Friday, and again on Sunday.

- Cooling trend possible next week.

&&

.FORECAST UPDATE...
Issued at 943 PM EDT Wed May 22 2024

Radar, satellite and CAMS trends support dry weather through at
least the early overnight. Although, boundary has stalled over our
far southeastern sections, so the plan is to lower the cloud cover
through the early overnight but keep small thunderstorm chances in
overnight over south central sections or closer to this boundary.
CAMS hint at convection devloping and moving along this boundary
toward daybreak. Otherwise, light northeast winds north of the
boundary and a very dry boundary suggest any fog will be very
localized and over areas to the south of the front.

The lack of cloud cover and drier air supports temperatures getting
down to as low as the middle 50s over nortwestern sections while
southeastern sections closer to the front and convective cloud cover
will likely only bottom out in the lower to middle 60s.

&&

.SHORT TERM (This evening through Thursday)...
Issued at 258 PM EDT Wed May 22 2024

Synoptic Pattern:

Broad troughing continues over the Upper Rockies, ejecting a
succession of waves eastward into the Great lakes region. Today is
no different, as a compressed short wave axis is moving through
aloft this afternoon and evening along with a deep surface low to
the north. This low has gone through occlusion processes, with dry
air cutting off the cold front from the trough aloft. This should
leave a weak stationary front across central Indiana over the next
24 hours providing a dichotomy of impacts across the region.

Also of note is a developing weak surface high over the southern
Great Lakes region in the presence of confluence and AVA aloft. This
will help reinforce dry air north of the stationary boundary tonight
into tomorrow.

Weather Conditions:

South of the Boundary (Mainly south of the I-70 corridor)

Within this area, surface moisture will remain elevated in the
presence of broad SSW flow. This, along with modest mid level lapse
rates will keep the atmosphere unstable and primed for convection
with any source of lift. However, lift will remain weak through the
afternoon and evening keeping conditions mainly dry outside of a
rogue isolated thunderstorm within weak lift along the boundary.
Late tonight greater lift along the mid level trough axis could be
enough for isolated to scattered showers and thunderstorms. Even
though most storms should remain weak due to the lack of substantial
shear, high storm tops and precip loading could be enough for a few
strong to severe storms. These scattered showers/storms may continue
through portions of the day on Thursday before increased subsidence
ends the threat in the evening.

Temperatures will remain slightly higher today/tonight in this
region with highs in the mid 80s this afternoon and lows in the mid
60s overnight. However, temperatures tomorrow may have a harder time
climbing south of the boundary due to greater cloud coverage.
Currently, temperatures tomorrow are expected to remain in the upper
70s for southern central Indiana.

North of the Boundary (Generally along and north of the I-70
corridor)

Much of this area will remain rather mundane over the next 24-36
hours. Dry air attached with increasing heights to the north will
decrease instability and lift substantially leading to near zero
rain chances this afternoon through early tonight. A slight
resurgence of moisture overnight attached with a weak shortwave may
be enough for a weak isolated thunderstorm to lift over the boundary
overnight, but most areas north of the boundary should remain dry.

For tomorrow, high pressure and associated subsidence should keep
and showers/storms contained over south-central Indiana.
Temperatures tomorrow will have an easier time increasing within
deep PBLs and partly sunny skies; expect highs near to just above
80.

&&

.LONG TERM (Thursday night through Wednesday)...
Issued at 258 PM EDT Wed May 22 2024

A progressive and fairly active weather pattern looks to continue
through the weekend.

SYNOPTIC OVERVIEW

The large-scale upper-level flow pattern across the CONUS can be
described as western troughing with split flow over the east coast.
While smaller-scale features ebb and flow through the overall
pattern described above, the larger picture should mostly remain the
same through the week into the weekend. By next week, guidance shows
a bit of a reversal with troughing taking hold over the east coast
and a split flow / ridge pattern over the western states.

In terms of sensible weather here in Indiana, it will be the smaller-
scale features that we`ll need to keep tabs on. The first of these
is a potent vort max passing well to our northwest Thursday into
Friday. Despite how far it is from Indiana it may still provide
enough forcing for showers and thunderstorms on Friday. Guidance
shows a few other smaller vorticity filaments passing nearby on
Friday as well. These may be convectively induced by earlier
convection upstream...so there is inherent uncertainty here, given
how chaotic convection is and how difficult a time models have with
it. Aside from convection, if low-level moisture return is quick
enough there may be a chance of some patchy fog Friday morning.
Probability appears low, however.

Enough model agreement exists for likely PoPs later on Friday. Model
soundings show little flow aloft so organized convection is not as
likely. Nevertheless, a quick downburst and/or small hail is
possible given a rather deep CAPE profile amid steep lapse rates.
Additionally, profiles contain abundant moisture and so a locally
heavy rain threat may present itself as well.

After a bit of a break, the next vort max emerges from the western
trough late Saturday. Guidance is generally in agreement showing
surface cyclogenesis across the Plains overnight into Sunday. The
resulting surface low then looks to pass over or just to the north
of Indiana. In terms of rain and storms, we may end up seeing two
rounds...one in the morning, and one later in the afternoon/evening.
The morning round is associated with the system`s warm front and
remnant upstream convection. The second round occurs in the system`s
open warm sector and along the attendant cold front. Unlike Friday`s
system, there is decently fast upper-level flow which may support
more organized convection and therefore a severe weather threat. It
is too soon to talk specifics, but the potential is there over a
broad area. The eventual outcome will come down to placement and
timing of key features (the low itself, the warm front and cold
front, and any remnant cold pools from previous convection).

Beyond that, next week appears less active due to broad troughing
overhead. Even so, a few waves embedded within northwesterly flow
may provide a chance for precip on Monday or Tuesday. Temperature-
wise, a return to near or even slightly below normal temperatures is
possible.

FORECAST CONFIDENCE

Overall confidence in the forecast is good. Ensemble guidance is in
agreement through Friday with large-scale features. In fact,
agreement within guidance is fairly good through much of next week
as well. There is a strong signal for prolonged troughing through
the end of May. Generally negative teleconnections (AO/NAO) add
weight to this idea. Confidence decreases for finer scale features,
such as convective timing and hazards. This is primarily due to the
chaotic nature of convective patterns where features can interact
and affect their evolution and subsequent days evolution.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 709 PM EDT Wed May 22 2024

Impacts:

- Small chance for brief MVFR and worse conditions at KBMG
  after 06z and KIND and KHUF after 12z.

Discussion:

VFR conditions are expected through most of the TAF period with a
small chance for thunderstorms and brief MVFR and worse conditions
at all but KLAF starting overnight and into Thursday.

Winds will be shifting to the WNW but then back to SSE Thursday and
less than 10 knots.


&&

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

$$

UPDATE...MK
SHORT TERM...Updike
LONG TERM...Eckhoff
AVIATION...MK