904 
FXUS63 KIND 210659
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
259 AM EDT Sun Jul 21 2024

.KEY MESSAGES...

- Dry and seasonable today

- Scattered showers possible tonight focused over the southeast half 
  of the area

- Chances for rain/t-storms and increasing clouds through at 
  least mid-week may help keep temperatures slightly below normal

&&

.SHORT TERM (Today and Tonight)...
Issued at 259 AM EDT Sun Jul 21 2024

Mid and high level clouds continue to increase in coverage over the 
region early this morning as moisture aloft gradually advects in 
from the southwest. The remnants of high pressure at the surface and 
ridging aloft keeping an overall dry airmass across central Indiana. 
06Z temperatures were primarily in the 60s.

A slow moving upper level low over the Missouri Valley this morning 
will pivot east into the region by early Monday...picking up 
progressively deeper moisture from the southwest by late tonight. 
This will bring at least an isolated to scattered risk for showers 
and a few rumbles of thunder into the southeast half of the forecast 
area overnight ahead of the weakening upper wave.

Despite the noted increase in moisture aloft...dry air and 
subsidence lingers below 500mb this morning. While moisture will 
gradually infiltrate lower through the column...it will take all day 
and likely some of tonight to effectively eradicate the layer of dry 
air above the boundary layer with little forcing aloft ahead of the 
upper wave. Cloud coverage will be prevalent today focused largely 
above 10-15kft with at least some scattered cu development for the 
afternoon courtesy of diurnal heating. 

Light showers will likely remain south of the forecast area through 
early evening with any precip chances holding off until tonight. 
Despite the weakening of the upper wave...a subtle increase in 
forcing aloft ahead of the feature and broader moisture advecting 
into the region will likely be enough to enable scattered showers to 
move into the southeast half of the forecast area overnight with a 
lower threat further northwest across the region. Cannot entirely 
rule out a few rumbles of thunder with the showers but instability 
is limited and overall moisture profiles via model soundings are not 
particularly impressive.

Temps...even with increase cloud cover today...low level thermals 
are supportive of highs rising into the low and mid 80s. Lows 
tonight will largely be in the mid 60s.

&&

.LONG TERM (Monday through Saturday)...
Issued at 259 AM EDT Sun Jul 21 2024

A more unsettled pattern is expected through at least 
midweek as guidance shows upper troughing persisting across the 
eastern CONUS with gulf moisture advecting northward. This will lead 
to increasing humidity and chances for precipitation. Daytime 
heating over sufficient lower tropospheric moisture should support 
scattered diurnal convection. There will be a weakening upper low 
moving across the area though forcing from the feature looks to be 
negligible. 

An upper wave approaching the region late Tuesday was expected to 
provide stronger synoptic forcing for precipitation. Latest guidance 
has trended south with the greatest forcing for ascent from the wave 
now likely to remain closer to the Ohio River. This has resulted in 
lower chances for rain/storms though scattered diurnal convection is 
still possible. 

The best chance for precipitation now appears to be late in the day 
Wednesday as a deeper trough diving south helps to push a frontal 
boundary across Indiana. Confidence in the forecast for Thursday is 
lower due to diverging model regarding the timing of the 
aforementioned front and how quickly dry air moves in behind it. If 
drier air quickly moves in early Thursday quiet weather conditions 
would be expected during the day. A slower frontal passage could 
potentially keep sufficient PBL moisture in place for scattered 
showers or storms, especially in the afternoon as destabilization 
from daytime heating occurs. 

The front will likely move out by Thursday night allowing for dry 
conditions to return late this week. Look for temperatures to remain 
slightly below normal for much of the extended period.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1240 AM EDT Sun Jul 21 2024

Impacts

- No impacts expected

Discussion: 

VFR conditions will continue throughout the forecast period. 
Moisture aloft will gradually increase across the area as a broad 
weak upper wave approaches from the west. Dry air will linger above 
the boundary layer before diminishing tonight. This will lead to an 
increase in mid and high level clouds throughout the day with 
diurnal cu developing for the afternoon again. Light northeast winds 
are expected.

As the upper wave arrives this evening and sharpens...potential for 
isolated showers will increase across the southeast half of
central Indiana. At this point...coverage is likely to remain low
enough to keep out of the forecast.

&&

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

&&

$$

SHORT TERM...Ryan
LONG TERM...Melo
AVIATION...Ryan