519
FXUS63 KIND 230230
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1030 PM EDT Sun Sep 22 2024

.KEY MESSAGES...

- Numerous showers with a few rumbles of thunder through this evening

- Additional rain likely late Monday into Tuesday

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

&&

.FORECAST UPDATE...
Issued at 1030 PM EDT Sun Sep 22 2024

No major updates needed to the forecast as of 10pm. A brief and weak
tornado formed earlier west of Muncie, which was associated with a
shallow convective shower (there was no lightning detected). This
shower was located along a subtle boundary, and the low-level
environment was conducive for the brief spin up (0-1km shear near
20kt, steep surface lapse rates, and very low LCLs). Additional weak
spin-ups are not expected tonight, as convection along the boundary
is diminishing and the low-levels are stabilizing. Any remaining
showers may produce very heavy downpours and perhaps a flash or two
of lightning.

&&

.SHORT TERM (This evening through Monday)...
Issued at 230 PM EDT Sun Sep 22 2024

It has been a while since we have experienced the afternoon
we have ongoing across central Indiana. Damp...cloudy and muggy with
numerous showers continue to press east across the forecast area.
18Z temperatures were primarily in the low and mid 70s.

Rainfall amounts have been light so far but welcomed with the
ongoing drought conditions across the Ohio Valley. While the initial
batch of showers has already shifted into the eastern half of the
forecast area...additional chances for rain will come late today
into the evening as a cold front sags south through the area. The
overall pattern will remain unsettled to begin the work week as the
front stalls near the Ohio River then lifts back north into the area
by Monday night.

Rest of This Afternoon and This Evening

Showers now focused over eastern counties will continue to push east
and should be largely out of the forecast area within the next
couple hours. Additional pockets of light showers persist further
west...but am more focused on whether any convective development can
organize ahead of the approaching cold front to the northwest. CAMs
continue to hint at showers and a few embedded rumbles of thunder
developing by late afternoon across the northern Wabash Valley then
tracking southeast across most of the forecast area into the
evening. Instability should be held in check with little to no
diurnal heating anticipated for the rest of the afternoon with a
thick cloud shield in place. This will however provide another
opportunity to receive some much needed rain.

Tonight and Monday

The frontal boundary will drift south to near the Ohio River before
stalling early Monday. Most of the rain should be out of the
forecast area by late evening with the bulk of the overnight
remaining dry. The focus will instead turn to lower clouds and
perhaps some fog as moisture within the boundary layer becomes
trapped beneath a strengthening inversion. A broad axis of low
stratus exists currently in the post-frontal environment and expect
this to settle across the forecast area from northwest to southeast
later this evening through the overnight.

Lower clouds will be slow to lift on Monday and will likely not mix
out at all as the inversion holds serve for much of the day. The
placement of the front to our south in tandem with subtle ridging
aloft will keep showers isolated to scattered at best and focused
primarily over southern counties into the afternoon. Will start to
see an uptick in rainfall coverage by Monday evening as the boundary
lifts back north into the southern forecast area and a surface wave
riding along it approaches from the southwest.

Temps...Lows will fall into the low and mid 60s tonight. The
extensive cloud cover Monday combined with light northerly flow will
actually keep temperatures slightly below average for late
September. Expect highs to top out in the low to mid 70s.

&&

.LONG TERM (Monday night through Sunday)...
Issued at 230 PM EDT Sun Sep 22 2024

Monday Night Through Thursday.

The next batch of precipitation is expected to move through Monday
night into Tuesday as a shortwave moves northeastward ahead of the
stronger upper level low which will be moving southward Tuesday.
Models are coming into better agreement in where the heavier axis of
precipitation looks to set up which doesn`t look favorable for much
of central Indiana with the LLJ enhanced precipitation likely closer
to the Ohio River into northern Kentucky while the TROWAL axis ends
up to the northwest of the forecast area.  Do think that most spots
see at least a quarter inch, but the chances for more than an inch
look isolated at best.

Focus then shifts to the low potential for more appreciable rainfall
towards the end of the work week with models showing there may be a
seasonably strong closed low to the west of Indiana and a tropical
system moving northward. Models tend to struggle to resolve these
strong interacting systems with ensembles showing a wide range of
outcomes with many being unreasonable in how they track both the
northern and southern systems.

Over the last day the general trend has been to push the northern
system through faster which will limit the ability to tap into the
tropical moisture which liens up with the probabilistic output
showing the potential for at least an inch about 20-25 percent lower
than how it looked this time yesterday.  At this time, dry weather
looks to be the most likely outcome through Thursday but rain may
move in Friday into the weekend. Temperatures will remain seasonable
with highs in the mid to upper 70s.

Friday Through Sunday.

As mentioned above, forecast confidence into the weekend is very
low, but current thoughts are that with the low pressure diving
further south that the chances for precipitation across much of
Indiana looks fairly low.  Strong pressure gradients associated with
the tropical remnants will create gusty gradient winds of 15-25 mph
Friday through Saturday. Will continue to track model trends but
without another larger shift, the earlier potential for 2+ inches of
rain looks much lower than earlier models showed.  Looking beyond
into the following work week, the pattern continues to remain active
but quite uncertain as to whether there this active weather will
impact central Indiana.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 744 PM EDT Sun Sep 22 2024

Impacts:

- Rain with embedded convection at times this evening
- Periodic MVFR ceilings this evening...dropping to widespread IFR
  ceilings tonight into Monday morning
- Patchy fog possible late tonight and early Monday

Discussion:

Showers, with a few embedded convective elements (no thunder as of
00z), will affect the terminals this evening. These should decrease
by around 03z as the system initiating them departs to the east.

Thereafter, northerly winds take hold, and lingering low-level
moisture should promote continued overcast skies with gradually
lowering ceilings. Widespread IFR ceilings are expected by morning.
Mist/fog is possible at times as well.

After daybreak, ceilings should lift but remains within MVFR
territory. A few showers are possible by the end of the TAF period
and beyond. Winds may become light and variable at times after 18z.


&&

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

&&

$$

UPDATE...Eckhoff
SHORT TERM...Ryan
LONG TERM...White
AVIATION...Eckhoff