779
FXUS63 KIND 072340
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
740 PM EDT Sat Jun 7 2025

.KEY MESSAGES...

- Showers and thunderstorms likely this evening into tonight

- Locally heavy rainfall and flash flooding possible tonight

- Cooler than normal with periodic rain early next week

- Warming trend midweek

&&

.SHORT TERM (This evening through Sunday)...
Issued at 303 PM EDT Sat Jun 7 2025

Northeasterly flow earlier today brought a round of wildfire smoke
which lead to hazy skies and reduced visibility. The haze has
thinned some as winds are beginning to take on a southerly component
ahead of a developing low to our west. Any thicker haze should be
confined to our northeast this afternoon.

The aforementioned low developing to our west is being driven by a
weak mid to upper-level wave, which is in the process of gradually
de-amplifying. Guidance is mixed on how strong of a surface low
makes it to our area, with the higher-resoluation / CAM guidance
generally showing a weaker solution versus the global models showing
a stronger solution.

Regardless, abundant cloud cover along with scattered showers and
thunderstorms is expected this afternoon into tonight. Model
soundings show tall and skinny CAPE profiles, moist adiabatic lapse
rates through the column, and weak shear (under 30 knots). Severe
weather is not expected, but with high freezing levels and a very
moist column rainfall production could be quite efficient. A flash
flooding threat may materialize overnight as convection could be
slow-moving and/or repetitive.

The best timing of heavy rain looks to be after 00z this evening and
into the overnight. Spatially it is a bit less certain, as
convection looks to be quite random and slow-moving. However, if we
end up with a stronger low there could be a bit more forcing
available to help concentrate convection. Mid-level frontogenetical
forcing associated with the 700mb low center may be the most likely
spot for this. Based on latest model trends, the most likely path of
the mid-level low looks to be across the northern half of our CWA.

Temperatures shouldn`t drop too much tonight with thick cloud cover.
A diurnal swing of only 10 degrees appears likely, which places lows
only into the mid 60s by Sunday morning. Low clouds are expected to
decrease during the day Sunday as today`s low exits off to the east.
Temperatures should rebound into the mid to upper 70s except over
our northeast where low clouds could persist a bit longer.

&&

.LONG TERM (Sunday night through Saturday)...
Issued at 303 PM EDT Sat Jun 7 2025

Strong vorticity advection on the SE side of an upper level trough
will aid in southward progression, eventually putting the trough
axis just north of Indiana Late Sunday into Monday. Confluence along
the leading edge of the 850-500mb low will aid in a narrow corridor
of moisture convergence and lift. Prior to the corridors arrival,
the antecedent airmass will likely be rather dry on Sunday, of which
should keep precipitation from falling until after 00Z Monday. Lapse
rates within this confluence zone on Sunday night are marginal (just
above 6 C/km), of which will limit instability and updraft growth.
This should lead to scattered showers with isolated thunderstorms,
all of which will likely remain sub-severe.

Latest trends have been delaying the boundary passage until
additional low level pressure depletion during the day on Monday. If
this does occur, another round of thunderstorms is possible Monday
afternoon and evening, this time with some severe risk given a
locally enhanced area of shear. There is still a lot of uncertainty
for Monday`s synoptic pattern, but this should be monitored closely
given the potential severe threat.

After this frontal passage, shortwave ridging will move into central
Indiana, leading to a dry period Monday night through Wednesday next
week. Temperatures will moderate but likely remain near seasonal
without strong WAA or upper level ridging. Later in the week,
combating dynamics will likely lead to an unorganized upper level
pattern, with a tendency towards broad upper level riding, but with
a developing mid level low. The current expectation is for this to
lead to hot, humid weather, but with temperatures subdued slightly
due to increases in cloud cover and precipitation. There is still
high uncertainty on any rain timing, but the general pattern should
support periods of rain Thursday through the weekend. Expect highs
to be above seasonal averages, likely in the low to mid 80s with
elevated dew points.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 739 PM EDT Sat Jun 7 2025

Impacts:

- Widespread showers and scattered storms tonight ending by 10Z.

- VFR conditions becoming MVFR in heavier precipitation with IFR
ceilings late tonight

-Showers and isolated TS developing around/after 09/00Z.

Discussion:

Earlier wildfire smoke has moved out of the area being replaced by
convective showers and scattered TS which will continue to increase
the rest of the evening lasting into the early morning hours on
Sunday. Although TS coverage at the moment is fairly benign, there
still appears to be an marked increase in the low level mass
convergence fields this evening to warrant scattered TS coverage and
VCTS in the terminals with modest instability around. These TS should
begin to wane and move east after 05Z, with -SHRA expected to
gradually end between 06-10Z.

In the wake of the precipitation with temperature/dewpoint
depressions near zero, ceilings will gradually fall through the MVFR
category into the IFR category by 10Z. As winds in the boundary
layer begin to increase tomorrow mid morning, ceilings will improve
most areas and become scattered by early afternoon. The next storm
system will approach the area late tomorrow afternoon and I have
introduced VCSH for KLAF/KHUF at 23Z. Thunderstorm activity should
be lower in coverage than today but opted to add VCTS for KIND
after 09/02Z.

&&

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

$$

SHORT TERM...Eckhoff
LONG TERM...Updike
AVIATION...Crosbie