992
FXUS63 KIND 061004
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
604 AM EDT Mon May 6 2024

.KEY MESSAGES...

- Showers likely with a few thunderstorms possible mainly near and
  south of I-70.

- There is a chance for severe storms Tuesday, especially during the
  afternoon and evening. All forms of severe hazards are possible.

- Additional strong to severe storms are possible Wednesday.

- Heavy rain is possible at times through Wednesday. Flooding   will
  also possible due, mainly Tuesday and Wednesday due to multiple
  rounds of convection.

&&

.SHORT TERM (Today and tonight)...
Issued at 318 AM EDT Mon May 6 2024

H20 vapor imagery was clearly showing an upper low spinning over the
Ozarks within a broad trough, underneath an upper Midwest ridge.
305K Isentropic lift ahead of this feature was leading to an area of
moderate showers that were lifting gradually northeast, north or a
stationary front over northern Kentucky. Isentropic analysis of
condensation pressure deficits suggest the showers will overspread
areas near and south of I-70 through the morning. With precipitable
water from an inch to 1.5 inches or up to the max moving average,
heavy rain will be possible at times. DESI 24 hour rainfall totals
near and south of I-70 range from around a quarter inch from the
25th percentile to three quarters of an inch from the 75th
percentile. With a sharp cut off expected due to more northeasterly
dry flow, precip amounts will drop-off a lot north of I-70 and some
spots may not see any shower activity today.

Model soundings and instability progs suggest only weak instability
will be realized today, so not expecting anymore than a few embedded
thunderstorms.

With deep moisture around, look for rather solid morning cloud cover
but some breaks this afternoon in the wake of the upper wave that
will swing in from Missouri. This and the northeast and east winds
should keep temperatures down. Northeastern sections may not even
see 70 degrees depending on cloud cover. Most locales will likely
see normal to slightly above temperatures in the 70s this afternoon.

Upper ridging will move across tonight in the wake of the upper
wave. This allow the stationary front to return northeast and winds
shift to the southeast. This in turn should result in little to no
convection until an approaching cold front gets closer Tuesday
morning per all of the CAMs. The southeast winds should also keep
temperatures from falling too much tonight with overnight lows in
the upper 50s to middle 60s looking good.

&&

.LONG TERM (Tuesday through Sunday)...
Issued at 318 AM EDT Mon May 6 2024

A challenging but potentially potent thunderstorm forecast will be
the main focus for the long term discussion. Details on the expected
conditions for Tuesday and Wednesday are below. For Thursday and
beyond expect near to below normal temperatures and cloudy
conditions. Light rain chances are possible Friday and Saturday.

Synoptic Overview:

A negatively tilted trough is currently nearing the Lower Rockies,
resulting in maximized CVA, collocated in the lee of the Rockies.
This will lead to rapid surface pressure depression and cyclogenesis
today. The low will then occlude later today as well, positioning
itself over the Dakotas. As the low becomes stationary, strong jet
dynamics will elongate the low, creating a succession of shortwaves.
It is these waves that will be our primary focus for severe
potential Tuesday and Wednesday.

Not only do we have the proper atmospheric disturbances for lift
across the Ohio Valley, we will also quickly destabilized as winds
veer towards southerly and push a warm, moist airmass over the
region. Temperatures should push back towards well above normal,
with highs in the upper 70s to low 80s Tuesday and Wednesday.

Tuesday Severe Threat:

As mentioned an initial wave on the eastern edge of an elongated low
will pass through the Midwest late Monday into Tuesday morning. Out
ahead of this wave, strong surface based lift should lead to the
development of an MCS over IA/MO late Monday. 50+kt deep layer sheer
and a deep EML should allow for quick propagation eastward, reaching
Indiana Tuesday morning. As the MCS moves eastward, it will
eventually become displaced from the greater mid to upper level
forcing resulting is strong but likely sub-severe convection by the
time in passes through Indiana.

Initially, this decaying MCS will act to stabilize the the lower
levels, but this should quickly be overcome as winds veer to the
south and push high theta-e values over central Indiana. The
greatest area of uncertainty for Tuesday will be where initiation
will occur, as it will largely be determined by upper level
diffluence. Once initiation does begin, Eff Bulk Shear of 50-60kts
and and a deep CAPE profile should allow for robust, organized
updrafts to form. A few CAMs are depicting a lingering boundary
formed by the prior MCS as the area of focus for CI. If this does
occur, this will likely reduce the overall severe threat for
northern portions of the area. Regardless, southern central Indiana
will likely still be in a threat for organized convection Tuesday
afternoon/evening.

Orthogonal shear vectors and mid level jet ventilation should allow
for discrete cells to develop. Some of them should be able to form a
sustained mesocyclone given SRH values greater than 150 m2/s2,
primarily over southern portions of the region. With that said, poor
precip dispersion aloft within weak anvil level flow, may lead to
precip loading in the updraft, and HP like supercells in those that
due end up sustaining them selves.

For now, the greatest risk looks to be damaging winds within
downbursts over northern central Indiana, and large hail over
southern Indiana. The atmosphere above 800mb looks rather dry and
precip loading in the updrafts of multicell clusters could lead to
lots of melting hail and dense cold pools. A few 70+ MPH gusts
cannot be ruled out. High EL and steep mid level lapse rates should
allow for some hail sorting. The biggest mitigating factor will be
the lack of anvil ventilation to the north. For this reason hail
could remain subsevere outside of any sustained rotating updrafts.
Over southern IN, upper level winds become stronger, making this
less of an issue.  Given the potential for sustained mesocyclones,
and low LCLs, tornadoes cannot be ruled out. Steamwise vorticity
will likely need to be enhanced by strong deviant motion or some
form of cell merging for tornadogenesis, but given how numerous CI
could be and the potential for a stagnant boundary, this is
definitely a possibility.

Wednesday Severe Threat:

Uncertainty increases for the severe threat on Wednesday, as a lot
of it will be predicated by Tuesday. A secondary wave, and forward
progression of the upper trough will help with creating a more
potent atmospheric profile for severe convection, but it will depend
on how far north the instability gradient will push northward ahead
of the short wave during the day on Wednesday. Wherever the CAPE
gradient does develop, robust, but mainly parallel shear profiles,
and strong CVA should allow for rapid CI and quick upscale growth.
There is still plenty of variability for timing of CI on Wednesday,
but the general expectation is for this potential MCS to follow the
CAPE gradient, pushing off to the east and eventually south through
Wednesday late afternoon and evening (+/- a few hours)

Once again, damaging wind gusts will likely be the greatest threat
on Wednesday. Effective shear will be plenty sufficient for
organized bowing segments. QLCS tornadoes will also be possible with
this event. A stronger LLJ, and high 0-1km SRH should allow for line
breaks and shallow mesocyclones to form within the MCS.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 603 AM EDT Mon May 6 2024

Impacts:

- With the exception of KLAF, MVFR flying conditions in showers
  are expected starting 16z or earlier

- Thunderstorms possible, especially after 18z at KHUF
  and KBMG

Discussion:

MVFR and possibly briefly worse flying conditions are possible this
this morning and afternoon as a stalled front retreats to the north.
However, KLAF should continue to see mainly VFR conditions with only
small chances for showers.

Winds will switch from mainly northeast to mainly east 10 knots and
less.

&&

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

$$

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