774
FXUS63 KIND 040657
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
257 AM EDT Tue Jun 4 2024

.KEY MESSAGES...

- Warmer today and humid.

- Best chances for showers and thunderstorms Wed.

- Possible brief downpours will accompany thunderstorms Wed morning.

- Below normal temperatures in the 70s late week into the weekend

&&

.SHORT TERM (Today and tonight)...
Issued at 257 AM EDT Tue Jun 4 2024

Early this morning remnant cirrus and some mid-deck clouds were
approaching the far Southwest Indiana counties, while further
upstream a large area of cloud cover was nearly stationary. Despite
the lack of cloud cover, winds remain elevated in the 1-3km layer,
helping to produce some friction in the boundary layer and inhibit
the ability for the surface to easily decouple. Expect temps to
slowly radiate into mid 60s but could take until just prior to dawn
for this to occur.

After sunrise expect the upstream cirrus from overnight convection
to be arriving from the southwest. With cirrus overhead, expect the
depth to the mixing layer to be likely remain within the first
couple thousand feet of the surface. This should keep the boundary
from seeing any robust subsidence and maintain dewpoints in the
upper 50s to lower 60s. While there does appear to be some filtering
to the daytime heating, surface parcels should readily climb given
the slightly drier boundary layer conditions and change to heat
capacity. But if clouds become thicker earlier in the day this could
play a role in keeping temps in the lower 80s longer. Still appears
set that mid/upr 80s is in store for the afternoon, but with some
increased mid-lvl instability beginning to approach from the
west/southwest this could introduce additional cloud cover along
with an isolated showers/thunderstorm late in the afternoon.


Broad trough continues to slowly slide east, but appears for much of
the evening to remain displaced to the west. The southerly flow
moist layer will be advecting north across the Ohio Valley. Then the
question becomes when will precip overspread the area and what will
the precip footprint look like. Strong ascent to parcels upstream
this evening still looks to be probable, coupled with collision to
parcels as they steadily moisten and should help increase precip
shield late tonight. Guidance differs on coverage as well as timing,
so have not made many changes to the prior forecast of low chance
pops this evening, then increase in coverage and chances overnight.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 257 AM EDT Tue Jun 4 2024

Wednesday...

Main concern for the day will revolve around the convective
footprint and timing. The longwave pattern suggests a broad area of
southerly flow from the GOMEX streaming north through the Tenn
Valley into Ohio Valley. This allows the moist channel to stream
moist/ascending parcels through this area, continuing further
north/northwest with the low-lvl shortwave displaced across the
Upper Midwest. Upstream a 500mb trough will be sliding into the
Northern Plains, which should assist the ascending parcels further
in the downstream zones of the Ohio Valley. The question on whether
the surface will become unstable in the morning hours remains, but
the setup would suggest cloud cover shielding much of the solar
energy thus helping to limit how unstable the atmosphere becomes.

There does appear to be some organized convection developing
upstream early in the day and would further reinforce the northern
stream of cloud cover and eventual precip into Central Indiana by
midday/afternoon, but it is conceivable that some of this could get
more organized around daybreak. The trough axis will quickly pivot
east through Indiana in the afternoon, which should also push the
deeper layered moisture to the east along with convective elements.
But overall with lengthy ascent to already moist parcels what precip
that does fall will likely be from better collision coalescence of
parcels, coupled with the higher water content to the atmosphere and
any precip could easily produce more efficient downpours or pockets
of heavier rainfall.

Guidance has continued a progressive approach to the moist channel
steadily pushing east by the evening hours. It appears a secondary
trailing moist boundary will lag late Wed across the Western Great
Lakes stretching southwest through Iowa, and should push through
during the nocturnal hours. But there has been good agreement that
mid-lvl heights are leaning towards some weak diffluent flow which
should be enough subsidence to erode any lagging moisture. So feel
confident that precip will be done in the evening hours, then a dry
overnight progged for Indiana.

Thursday through Sunday... Generally the several days following Wed
appear primed to be incredible. Northwest flow will be the main
player, ushering in much cooler air to the region. Thur/Fri will
observe a pleasant thermal trough digging south that should help
keep afternoon temps in the 70s and overnight lows in the 50s. Sat
could feature enough mid-lvl moisture that some diurnally induced
sprinkles may develop. The steep lapse rates and perhaps some
surface destabilization during the afternoon could aid in an isolated
thunderstorm as well.

Sun guidance begins to deviate amongst ensembles members, as a
tropical remnant enters the far Southwest CONUS and appears to
introduce moisture to the southern Rockies. The deep trough should
be starting to relax marginally Sun, which likely will allow any
system to traverse the CONUS efficiently. While guidance is hinting
that a central CONUS precip footprint could develop, it would not
take much to introduce clouds and perhaps low chance precip to
Indiana by late Sun.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 205 AM EDT Tue Jun 4 2024

Impacts:

- TSRA with possible MVFR conditions associated after 22Z.

Discussion:

VFR conditions overnight will likely persist through much of the
day. Some diurnally driven cumulus should develop midday, but expect
this to remain VFR conds. Isolated showers and thunderstorms are
possible after 22z. Should a shower/storm pass over a terminal a
brief reduction to MVFR conditions could be expected.

South winds should diminish this evening to 5kt or even lower.
Direction could become more southeasterly but should return to
southerly during the day Tuesday. Speeds are expected to increase as
well to around 10kt after 21z or so.


&&

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

$$

SHORT TERM...Beach
LONG TERM...Beach
AVIATION...Beach