591
FXUS63 KIND 241621
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1221 PM EDT Tue Sep 24 2024

.KEY MESSAGES...

- Showers and a few thunderstorms continue at times through today,
  with a low chance for an isolated strong to severe storm

- Seasonable temperatures for much of this week with highs in the
  70s and lower 80s and lows in the 50s and 60s

- Potential for more rain late week into the weekend from tropical
  remnants

&&

.FORECAST UPDATE...
Issued at 933 AM EDT Tue Sep 24 2024

- Scattered Rain showers this afternoon

Surface analysis late this morning shows low pressure in place over
east Central IL. This was resulting in cyclonic lower level flow
across Central Indiana and our forecast area resided within the warm
sector with south to southeast surface winds across the area. Radar
this morning shows a few scattered showers across the area, mainly
within the Wabash Valley. Dew points remained moist, in the mid 60s.
Aloft, a deep upper trough was in place over the northern plains,
extending south to the southern plains states. This was resulting in
southwest flow over Central Indiana.

Models today continue to suggest that the surface low to the west
will push northeast through the afternoon. This will keep Central
Indiana within the warm sector, Models suggest some CAPE available
this afternoon with any heating, also favorable shear is in place
with southeast winds at the surface and southwest flow aloft. This
will be a favorable environment for shower and thunderstorm
development through the afternoon. HRRR continues to suggest
scattered showers and storms across Central Indiana this afternoon.
Thus ongoing chances for rain appear warranted, and little change
will be needed. Given the expected clouds today and rain, highs in
the mid 70s appear on the mark.

&&

.SHORT TERM (Today and tonight)...
Issued at 311 AM EDT Tue Sep 24 2024

Bit of a messy situation today as weak low pressure over the lower
Ohio Valley is expected to lift north/northeastward through the
region today into tonight, aided by a lead shortwave/MCV and a
developing cutoff upper low moving into the area.

Disorganized convective complex is moving through southern Indiana
at this hour, with little activity upstream, though high resolution
models suggest some additional development later in the night and
into the morning hours as a broad southwesterly 20-25KT low level
jet interacts with the surface low and attendant boundaries, which
seems reasonable - but broadly speaking, late tonight into the
morning looks to be a relative lull in activity, with significant
uncertainty as to coverage and intensity of showers and
thunderstorms later in the day given limited insolation and
destabilization potential. Some modest deep layer shear is present,
and MCVs are well known to locally enhance low level shear, though
the bulk of the impact from this feature may be more to our south.
Given these factors, the marginal risk for severe over the east is
not unreasonable, but may be limited by weak instability unless
greater cloud breaks develop this afternoon than currently
anticipated.

Profiles will begin to dry rapidly from aloft as the system exits
the area to the east tonight, with perhaps some lingering showers in
the far east just after sunset. Low level moisture could potentially
produce a few spits of drizzle, but will more likely just keep cloud
cover in place across the area throughout the night.

Ensemble spread is relatively low on temps, though NBM appears too
warm today, particularly in the northwest where the cold front will
pass through earlier than elsewhere and cloud cover is likely to be
quite persistent. Have made adjustments in this regard. Lingering
cloud cover, low level moisture, and advection quickly becoming
neutral as the upper low stalls will prevent temperatures from
dropping too dramatically overnight, with mid 50s to low 60s
appearing likely.

&&

.LONG TERM (Wednesday through Monday)...
Issued at 311 AM EDT Tue Sep 24 2024

More rain is in store for the long term although confidence in
precise timing and coverage is low based on the still to be
determined evolution of Potential Tropical Storm Nine, seen on GOES-
16 IR satellite, well to the south of Cuba. There is growing
confidence that trough, currently over the eastern Dakotas, will
plunge southeast across the Ozarks on Wednesday before cutting off .
The strength and circulation of this is expected to hasten the
northward and northeastern progress of what will eventually, likely
become a Hurricane according to NHC. The official NHC track as the
remnants of this tropical cyclone reaching eastern Kentucky by 00z
Saturday and then wrapping around the Ozarks upper low in Fujiwhara
effect fashion. As it does so plenty of tropical moisture will
spread across the Ohio Valley. There is differences on how fast the
moisture and associated rain will get to central Indiana based
partially on the strength of a shaping Great Lakes ridge. That said,
most signs point to Friday as being the timing with the greatest
potential for rainfall. The upper low is expected to absorb the
tropical cyclone remnants this weekend, and then models and
ensembles suggest it will lift northeast across the Ohio Valley late
this weekend and early next week by getting kicked out by a strong
northern Plains and south central Canadian trough. All in all, this
supports PoPs lingering into the weekend and beyond.

There is some concern early this weekend for a few tropical storm
brief spin ups to the right of the storm path, which would favor more
eastern parts of central Indiana. Meanwhile, Friday looks like it
could get windy with the low pressure gradient tightening ahead of
the remnants.

The extensive cloud cover will limit temperatures with afternoon
highs mostly in the 70s and overnight lows in the 60s. These
high temperatures are near normal and lows above normal.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1221 PM EDT Tue Sep 24 2024

Impacts:

- VFR to MVFR Conditions expected this afternoon. MVFR conditions
expected with passing showers and storms.
- VFR this evening transitioning to MVFR/IFR overnight in Fog.

Discussion:

Low pressure over eastern Illinois will push northeast to Michigan
today while an upper trough remains across the region. A warm and
moist air mass across Central Indiana will allow for scattered
showers and storm development this afternoon. However, confidence
for specific timing remains low. Thus a large window of VCTS will be
used through the afternoon hours.

As the low passes to the north this evening, heating will be lost
and instability thunderstorm coverage is expected to decrease as the
lower level flow becomes westerly.

Overnight, weak lower level flow along with high dew points near 60
and low dew point depressions should lead to fog development. MVFR
to IFR fog will be expected during the overnight hours, with the
lowest visibilities expected at BMG/HUF and LAF. Fog will quickly
burn off as heating and mixing resumes after sunrise on Wednesday.

&&

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

$$

UPDATE...Puma
SHORT TERM...Nield
LONG TERM...MK
AVIATION...Puma