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