-- Discussion containing changed information from previous version are highlighted. --
550
FXUS63 KIND 080703
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
303 AM EDT Wed May 8 2024

.KEY MESSAGES...

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- Severe storms possible today, especially during the late afternoon
  and evening. Hail and wind are the primary threats.

- Heavy rain is possible at times through Wednesday night. Localized
  flooding will also be possible.

- Periodic chances for showers and a few storms late week into early
  next week.

- Normal to slightly below normal temperatures Thursday through
  Saturday with warmer temperatures next week.
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&&

.SHORT TERM (Today and tonight)...
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Issued at 303 AM EDT Wed May 8 2024

Synoptic Overview:

Central Indiana is now on the cool side of a warm front, which will
likely end up somewhere along a Kansas City to Paducah line later
this morning. For now, this frontal boundary is over southern IN,
and has suppressed surface winds, keeping a large portion of central
Indiana under light and variable conditions. On a separate, non
thunderstorm related note, these light winds in combination with
elevated surface moisture from prior rainfall will likely result in
patchy, dense ground fog over this area. As daybreak occurs, surface
heating should quickly mix out any fog, with 10mi or greater
visibility by 9AM.

For most of the day, central Indiana will be positioned within a
weak low level ridge, but also within strong upstream forcing and
moisture return. This ridge will act to suppress warm frontal
progression some, but high amounts of theta-e advection will
counteract this eventually lifting the warm front into central
Indiana. All CAMs have the warm front lifting northward throughout
the day, but even just 12-18 hours out, there is still significant
variability in placement. Generally, this frontal boundary is
expected to reach a Sullivan to Bloomington to Columbus line. This
is important as a majority of convective initiation is expected to
occur south of the front.

The aforementioned ridge will still have some influence on the
environment, keeping low level winds marginal and drying out the
near surface layer north of the front. Still, the impacts of the
upper level trough will allow for steep mid level lapse rates deep
instability profiles across much of the region. Theta-e advection
within the warm sector will also act as a lifting mechanism helping
establish CI later this afternoon.


Severe Weather Hazards and Timing:

As stated, CI is expected to occur continuously this evening south
of the warm front once convective temperatures are reached. There
will also be a convective threat overnight, but that will be highly
depending on the location of MCS development.

For today, the wind profile will look much differently than
yesterday, with winds in the lower 3km much weaker due to the
aforementioned ridge. However, winds aloft will remain rather robust
with a westerly 500mb to 300mb jet placed direction aloft. This will
likely lead to a variety of storm modes including multicell clusters
and lines as well as a few supercells. Any supercells that due
develop will have the tendency to split.

Within the initial evening threat. Tornadoes look unlikely given the
lack of low level winds, and high LCLs, but a strongly deviant right
movers in far southern central Indiana where dew points are elevated
could have enough streamwise vorticity ingestion for isolated
tornadoes. Hail and wind on the other hand will pose the main threat
for central Indiana. Deep CAPE profiles with strong flow through the
Hail Growth Zone will promote a large hail threat, and dry mid-level
air and DCAPE values over 1000J/kg should create a environment
capable of efficient downward momentum transfer and a damaging wind
threat. These threats will be greatest in any supercells that form
(especially hail within left movers).

The overnight threat will be primarily due to any MCS that
potentially forms west of central Indiana. This is currently highly
uncertain, due to substantial model inconsistency. However, if an
MCS does pass through overnight, a high wind threat will be
possible.  Given the west to east placement of the warm front and
the resulting upshear vectors, training thunderstorms will be
possible in this overnight regime. Because of this localized
flooding will be possible.
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&&

.LONG TERM (Thursday through Tuesday)...
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Issued at 303 AM EDT Wed May 8 2024

Thursday through Saturday...

A pair of upper waves and associated cold fronts in northwest flow
aloft will dive southeast across central Indiana and bring more
convection to mainly northeastern sections Thursday and again
Friday night and Saturday. Model agreement is good on the handling
of these features.

Temperatures will be noticeably cooler, especially Friday and
Saturday with below normal highs in the 60s.

Saturday night and Sunday...

Weak ridging and a fairly dry column will lead tranquil weather late
in the weekend along with temperatures moderating back to near
normal Sunday with afternoon highs in the upper 60s to middle 70s.

Sunday night through Wednesday...

Confidence is low on PoPs and temperatures next week as models agree
that split flow will develop over the Plains and a broad trough will
eventually move through the Ohio Valley. The question is when as
models and their ensembles are having trouble coming together with
big timing spreads. With these differences, did not make any changes
and left small convection chances in through the period along with a
warming trend due to the winds shifting to a southerly component.
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&&

.AVIATION (06Z TAF Issuance)...
Issued at 100 AM EDT Wed May 8 2024

Impacts:

- MVFR or brief IFR fog possible overnight

- More MVFR and briefly worse flying conditions in thunderstorms
  after 19z

- Wind gusts to 50+ knots and large hail possible at mainly
  KBMG and KHUF after 19z

Discussion:

The thunderstorms have moved away from the terminals leaving behind
mostly clear skies. The recent rain, light winds and dew points in
the 60s suggest MVFR and worse conditions in fog or stratus may
develop overnight. Most of the Hi-Res models and BUFKIT
soundings support this.

Flying conditions will return to VFR after daybreak and then an MCS
is likely to spread across the terminals from the west late this
afternoon and evening. This will bring more MVFR and briefly worse
conditions in the convection as well as a threat for damaging winds
and large hail, mainly at KHUF and KBMG.

Winds will be light to calm overnight and from the south to 10 knots
this afternoon.


&&

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

$$

SHORT TERM...Updike
LONG TERM...MK
AVIATION...MK