Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/14/23

Area Forecast Discussion

National Weather Service Indianapolis IN

 1001 PM EDT Sun Aug 13 2023

.Forecast Update...
Issued at 1000 PM EDT Sun Aug 13 2023

Much of central Indiana has remained dry this evening as dry air
remains in the low-levels, but showers are currently ongoing across
far southwestern counties. This is near a warm front which has
remained just south of central Indiana for much of the day. Expect
these showers to move out over the next hours. Additional isolated
convection will be possible through the night. Overall weak forcing
will limit greater coverage until the aforementioned warm front
begins to lift north towards daybreak Monday. Diurnal cooling will
be limited by extensive cloud cover and weak warm air advection.
Look for lows generally in the mid-upper 60s.

&&

.Short Term...(This evening through Monday)
Issued at 259 PM EDT Sun Aug 13 2023

A warm but pleasant afternoon continues across the area as weak high
pressure drifts through. Mid and high level clouds are slowly
increasing from weakening convection over the Missouri and mid
Mississippi Valleys with scattered diurnally driven cu as well. 18Z
temperatures were generally in the mid 80s.

After the brief respite from convection over the last few days...the
pattern will revert back to wet and unsettled as low pressure pivots
into the region from the upper Midwest late tonight into Monday.
While there remains some uncertainty in the details...the threat for
locally heavy rainfall increases late tonight and Monday morning
with a conditional threat for isolated severe weather Monday
afternoon with the approach and passage of a cold front.

Quiet weather will continue for the rest of the afternoon and
evening for much of the forecast area. Ongoing convective clusters
remain focused along the instability gradient currently focused over
the Tennessee and lower Ohio Valleys with additional storms across
western Missouri. The current KIND ACARS sounding shows very nicely
the presence of a subsidence inversion near 700mb. Some of this
drier air has made its way to the surface as well evidenced by
dewpoints that have dropped into the lower 60s. MOdel soundings show
the inversion holding firm over much of the region into the evening
which will significantly hamper any convection from making it into
the forecast area. Have held onto a small threat for rain over the
lower Wabash Valley for early evening where the inversion is weakest
and in closest proximity to the warm front draped to our southwest
but other than a sprinkle or light shower in the west...much of the
evening should remain dry.

The advection of deeper moisture will commence overnight as the warm
front lifts north into the forecast area in response to the primary
surface low dropping out of the northern Plains. The dry air and
subsident layer mentioned above though will be a bit stubborn to
dissipate as a predominant easterly flow develops north of the warm
front. May eventually see two axes of convection producing locally
heavier rainfall develop in the predawn hours...the first focused
over southern Indiana and our southern counties as the warm front
lifts into the area and in closer proximity to the nose of the low
level jet. Further north and closer to daybreak...there are hints of
a second axis of steadier to locally heavier rainfall develop within
the expanding baroclinic zone ahead of the boundary. This northern
area of precip looks to focus somewhere near the I-70 corridor
likely persisting through Monday morning as the warm front continues
to press north through the forecast area.

The expansion of rich moisture laden air highlighted by precip water
values hovering near 2 inches certainly supports the threat for
locally heavy rainfall but at this point it appears amounts will not
be necessarily uniform with the highest at 2 inches or greater being
isolated and most likely over southern portions of the forecast area.

The warm front will eventually lift to near the northern forecast
border if not just north over northern Indiana by Monday afternoon
with the primary low pivoting into the region. The presence of to
triple point moving across this area will provide a narrow band of
increased shear and helicity that will swing across the region
during the late afternoon in advance of the trailing cold front. The
dynamics listed above present a conditional severe weather risk but
the lack of significant heating/cloud breaks and subsequently
questionable levels of instability make this threat much less of a
certainty. Could see a plausible scenario play out if we can get
just enough instability to see low topped convection develop and
perhaps even a few low topped supercells within the tropical airmass
that could support an isolated severe weather risk. On the flip
side...could also see a scenario where clouds largely hold firm with
few if any breaks in the deck making for a messy convective mode
with multicellular activity producing brief downpours and perhaps
gusty winds. The main message at this point is that there remains a
potential for a few severe storms late Monday afternoon but it is a
conditional...low confidence threat based on our thoughts above.

The cold front will be east of the forecast area by early Monday
evening with a noticeably cooler airmass setting the stage for a
stretch of pleasant...early Fall like temperatures through midweek.
More on this in the Long Term section below.

Temps...lows tonight will fall into the mid and upper 60s. Clouds
and rain will hold temperatures down for Monday with highs holding
in the upper 70s and lower 80s over much of central Indiana.

&&

.Long Term...(Monday night through Sunday)
Issued at 259 PM EDT Sun Aug 13 2023

Quieter weather is expected through the long term period.
Temperatures will be below normal for most of the period but turning
warmer for the weekend with a couple chances for rain through the
week.

An upper short wave trough will be in the process of exiting the
Great Lakes region for the start of the long term. Lingering rain
will certainly be possible going into Monday night but as things
currently stand, most of the precipitation should move out by early
Tuesday morning. As the surface low slowly makes its was eastward
Tuesday, there will be a potential of light rain on the back side of
the low through the day, but confidence is low at the moment. How
quickly and the exact track of the surface low will be main factors
into how Monday night and Tuesday shake out. Overall, no major
impacts expected either way.

Behind this system, flow through the column will largely become
northerly which will advect in cooler air through mid to late work
week. Highs midweek are forecasted to be in the low to mid 70s
warming up to low 80s for the end of the work week. Lows during this
time will range from the 50s to 60s. The weather will be mostly
quiet as a surface high passes through allowing subsidence overhead.
Slight chance of rain will return Thursday as models indicate that
an upper will move through. The models are coming to more of an
agreement that this wave will form, but as not tons of moisture or
lift are evident, keeping PoPs low at this time with best chances
available for the northern half of the forecast period.

The pattern will shift again behind the late week wave, as upper
ridging and a surface high settle in. This will usher in warmer air
again and expected highs in the mid to upper 80s and even near 90
degrees will be possible. Other than some afternoon Cu, dry but
possibly humid conditions are likely for the weekend.

&&

.Aviation...(00Z TAF Issuance)
Issued at 743 PM EDT Sun Aug 13 2023

Impacts:

* VFR conditions expected through much of tonight, Rain chances
  increase towards daybreak Monday
* Ceiling restrictions developing as low as IFR near daybreak Monday
* Visibilities lower in rain and thunderstorms

Discussion:

VFR conditions are expected through much of tonight, but rain
chances begin to increase towards daybreak Monday as a low pressure
system approaches the region. Showers and embedded thunderstorms
will move in around 12-14Z as a warm front lifts north. A brief lull
is possible during the day, but additional convective development is
possible ahead of a cold front late Monday afternoon.

Ceilings will drop to MVFR as rain moves in towards daybreak Monday
and eventually as low as IFR during the mid-morning hours. Some
slight recovery is expected during the day, but MVFR ceilings should
remain through the mid afternoon hours.

Winds will flip around to easterly until the front lifts north of
the terminals during the morning. Winds will then veer to southerly
then southwest into the early afternoon.


&&

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

$$

Update...Melo
Short Term...Ryan
Long Term...KH
Aviation...Melo