477
FXUS63 KIND 051325
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
925 AM EDT Sun May 5 2024

.KEY MESSAGES...

- Confidence continues to increase for severe weather potential both
  Tuesday and Wednesday. All hazards are possible, with damaging
  wind and large hail as the primary threat.

- Heavy rain threat Monday through Wednesday. Flooding possible due
  to multiple rounds of convection.

&&

.FORECAST UPDATE...
Issued at 925 AM EDT Sun May 5 2024

Lower stratus has expanded across much of the forecast area this
morning with broad cyclonic flow in place behind the front that
passed through overnight. 13Z temperatures ranged from the upper 50s
to the mid 60s with a steady N/NW wind.

The forecast is in very good shape for the rest of the day with the
primary focus for the update on the clouds and how quickly they mix
out. The current ACARS sounding for KIND shows moisture trapped
beneath an inversion between 900 and 850mb. As progressively drier
aloft associated with high pressure expands east into the region
over the next few hours...this will likely strengthen the inversion
for a short period of time before boundary layer mixing can overcome
it. Expect the lower stratus to linger in abundance as a result for
the next few hours with a trend towards increasing sunshine as the
clouds mix out into a cu field this afternoon.

Remain confident in a dry forecast for the entire area through late
day as the subsidence associated with the high pressure ridge should
aid in the deeper moisture remaining closer to the Ohio River and
points south. Northerly winds near 10mph are expected throughout the
day. Low level thermals support highs mainly in the low to mid 70s
for much of the forecast area .

Zone and grid updates out.

&&

.SHORT TERM (Today and tonight)...
Issued at 258 AM EDT Sun May 5 2024

Low cloud cover has begun to spread across central
Indiana early this morning mainly associated the remnants of a
decaying MCS. Within these low clouds, isolated weak showers are
possible, but most areas are expected to remain dry.

Behind this MCS, a NW shift in winds and modest AVA upstream of a
low level trough will be enough for low level height rises across
the region. This should eventually create enough subsidence and
mixing to erode the low level cloud cover. By the late morning,
pockets of sunshine are expected, slowly becoming partly cloudy by
the afternoon. The overall airmass is drier and cooler for Sunday,
leading to a slight dip in temperatures; back into the mid to upper
70s for highs.

During the day on Sunday, another shortwave is expected to develop
over the mid-Mississippi Valley, centered within the diffluent
region of the subtropical jet. This should push E/N into the Ohio
Valley late today. Confidence is increasing the the aforementioned
low level high will enough to suppress wave progression enough for
central Indiana to remain dry through the daytime hours and through
dusk. The greater source of lift within the wave looks tonight, with
showers quickly developing over KY/IN border around midnight. Dry
surface air will initially curtail precipitation onset, but
continued lift and saturation should be enough for scattered showers
prior to sunrise on Monday.

&&

.LONG TERM (Monday through Saturday)...
Issued at 258 AM EDT Sun May 5 2024

The main forecast concern in the extended is the potential for
severe weather Tuesday and Wednesday. However, rain chances persist
through most of the period due to the broad troughing aloft over the
eastern CONUS. Anomalous moisture combined with the potential for
multiple rounds of convection could also lead to heavy rainfall.

Monday through Wednesday night...

Showers and some thunderstorms will likely be ongoing at the
beginning of the period as a shortwave trough moves through the
region. Limited instability and deep-layer shear should inhibit any
severe weather potential for Monday. Multiple embedded shortwaves
within broad upper troughing are then expected to traverse the
region Tuesday/Wednesday. Models still show some discrepancies
regarding timing or location of any developing surface lows, but
generally have become better aligned.

The first potential round of severe weather looks to arrive sometime
Tuesday afternoon into the evening as a surface wave approaches.
Expect showers and storms to be ongoing early in the day within a
warm air advection regime. Cannot rule out severe potential in the
morning though the greatest threat should be later in the day as
increasing low-level theta-e advection leads to stronger
destabilization. In addition, guidance shows a mid-upper level jet
moving in during the latter half of the day. Moderate to strong
instability combined with increasing deep-layer shear supports the
potential for organized convection. All hazards could be on the
table for Tuesday though damaging winds and large hail appear to be
the greatest threat at this time.

Another round of severe weather is possible on Wednesday as a second
surface low moves towards the region. CSU machine learning and CIPS
analogs are more bullish with this setup, but uncertainties remain
in the forecast. An important factor to the severe weather threat on
Wednesday will depend on where the warm front associated with the
surface low sets up. Generally models show the frontal boundary set
up near central Indiana allowing for a moderate-strong unstable
airmass to develop late in the day for at least portions of the
area.

Subtle ridging may limit convective potential through portions
of the day, but increasing coverage of storms is expected late in
the day as large scale ascent and warm moist advection increases.
Strong deep-layer shear combined with the favorable unstable airmass
will likely support organized convection posing a threat for all
hazards. If the warm front sets up further south then the attendant
severe threat would shift further south due to less destabilization
so trends in the location of the low will have to be monitored
closely in the coming days. Prior day convection also limits
confidence some as this could impact the favorable parameter space.
Heavy rainfall is a concern both Tuesday and Wednesday given the
potential for multiple rounds of convection. Wednesday may have the
greatest threat though with the aforementioned warm front
potentially setting up west to east over central Indiana. This could
lead to training convection.

Thursday onward...

Rain chances persist through the long term period as broad troughing
remains aloft and broad cyclonic flow on the backside of the
departing low. Cold air advection within northwest flow will lead to
a cooler pattern heading into late week. By this point, it appears
the severe threat should shift out of the region.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 643 AM EDT Sun May 5 2024

Impacts:

-MVFR cigs thru 17Z
-Light Rain and MVFR Cigs Monday

Discussion:

Cloud cover will has increase with the arrival of MVFR cigs through
the western half of Indiana (all TAF sites). These clouds will
become scattered late this morning into the early afternoon,
eventually lifting out for VFR flight conditions through 12Z Monday.
Winds will generally be light and variable through the TAF period
with a predominately NW to N direction.

&&

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

&&

$$

UPDATE...Ryan
SHORT TERM...Updike
LONG TERM...Melo
AVIATION...Updike