641
FXUS63 KLMK 220740
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
340 AM EDT Wed May 22 2024

.KEY MESSAGES...

*   Scattered storms expected this morning across southern IN and
    far northern KY.

*   Strong/severe storms possible region wide this afternoon with
    damaging winds, hail, and very heavy rainfall being the main
    threats.

*   Stormy pattern with a risk for localized flooding Thursday
    through Tuesday with strong/severe storms possible Sunday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 340 AM EDT Wed May 22 2024

Early morning satellite imagery shows partly to mostly cloudy skies
across the region.  Temperatures were very mild with readings in the
upper 60s to around 70 in the I-75 corridor, but west of I-65, temps
were in the lower to mid 70s.  Area radars were lit up with
convection mainly over northwest KY into portions of southern IN.
Mesoscale analysis shows a plume of steep mid-level lapse rates
across western KY into southern IN resulting in elevated
instability.  Ongoing convection in the vicinity of Owensboro looks
to be forced by a small perturbation coming through the region. This
activity looks to move off to the east-northeast and will affect
areas along and north of the Ohio River through sunrise.  These
storms will be capable of producing frequent lightning, gusty winds,
heavy rainfall, and perhaps some marginally severe hail within the
strongest cores.  The downstream environment toward the I-65
corridor is a bit more stable, so much of this activity should
diminish in intensity with eastward extent.

For the daytime hours, some ongoing convection may still be in
progress across southern/southeast IN and into northern KY with the
aforementioned perturbation heading east-northeast.  In the wake of
this perturbation, some subsidence looks to push into the region
which should keep much of the area dry from the mid-late morning
through the mid-late afternoon.  Increasing insolation will lead to
destabilization during the afternoon as the HREF suggests that 1500-
2500 J/kg of MLCAPE will develop.  Weak surface front will continue
to drop in from the northwest while an upper level shortwave trough
axis pushes in from the southwest.  Convection looks to redevelop
across south-central KY this afternoon and then other scattered
convection is likely to fire across the remainder of the region.
Model proximity soundings agree with the HREF showing about 1500-
2500 J/kg of MLCAPE with 0-6km shear values in the 35-45kt range. It
would appear that based on soundings that we could have some
supercells within this environment, though the overall flow may
become increasingly parallel to the convective axis.  In that case,
I could see more of a mixed mode environment with some supercellular
type structures growing upscale into some bowing segments.  Damaging
winds look to be the main severe threat.  Large hail may also be a
looming threat given that we`ll have a bit of CAPE in the hail
growth zone, but that may be offset by weaker mid-level shear.
Tornado threat appears to be quite low given the rather weak
synoptic scale forcing and the lack of curvature in the forecast
hodographs.  Very heavy rainfall will be likely with the storms
given that PWATs will be above 1.5 inches and slow storm motions are
expected.  Highs on the day will be in the lower to middle 80s.

For tonight, convection should be in progress this evening and will
continue as the mid-level perturbation coming out of the Ozarks
pushes through the region.  Some uncertainty remains on where the
highest coverage of convection will be.  Latest HRRR guidance
suggests that south-central KY may be at most risk for
showers/storms this evening with a gradual decrease in coverage by
mid-late evening.  There is a signal that another perturbation may
roll into the region late tonight spawning another round of
convection.  Overall severe threat going into the overnight looks to
diminish with the loss of heating/instability and rather weak shear.
However, slow moving storms training over the same areas could
result in an elevated flash flood risk across the southern half of
KY.  Overnight lows will be in the mid-upper 60s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 340 AM EDT Wed May 22 2024

Thursday through Wednesday...

A cold front will stall over the Ohio Valley, and coupled with
multiple shortwave troughs of low pressures and continued
southwesterly jetstream flow, will lead to increased chances for
showers and storms through Tuesday. Temperatures will warm each day
from near normal to slightly above normal. Dew points will also
remain in the mid-upper 60s, which will lead to warm and muggy
conditions through Tuesday.

Strong to severe storms are possible, however, this will likely be
determined on a day-by-day basis to assess mesoscale evolution and
recovery for convective initiation. Moisture is present through the
weekend and instability recovery looks possible each day, however,
shear remains weak-marginal. In this scenario, main hazards would be
locally gusty to damaging winds with heavy downbursts and lightning.

Sunday continues to trend as the best convectively organized day. A
low pressure system will likely move thorugh the mid-Mississippi
Valley and into the Ohio Valley, promoting stronger deep-layer
dynamics for strong storms organization. Model forecast soundings
suggest a very moist and unstable environment, with ample deep-layer
shear. Coupled with dynamic triggers at the surface and aloft will
likely allow for strong to severe storms. ECMWF EFI shows a signal
of 0.75-0.85 and a shift of tails of 1 on Sunday, which is a
generally significant signal given that most of M climate is within
severe weather season. CSU probabilities also shows a signal over
the region for Sunday. Over the next few forecast periods, trends
will be monitored closely.

Given multiple days of rain and possible training of cells, flooding
and flash flooding is possible. Current QPF for this timeframe is 2
to 4 inches, with locally higher amounts possible in the strongest
thunderstorms.

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 129 AM EDT Wed May 22 2024

Area radars this morning show scattered convection from KHUF down to
KCGI/KPAH and back to KMEM.  This convection will continue to move
eastward overnight and should weaken as it outruns instability.
Scattered showers will be possible at KSDF/KBWG overnight, probably
after 22/08Z or so, but this activity should not impact aviation
all that much. We will have the LLJ pick up around 2kft AGL and that
may result in marginal LLWS conditions between now and 11Z.

Moving into the morning hours, winds will pick up again out of the
southwest and shower chances look fairly low for the morning hours.
Latest convective allowing models suggest another wave of storms
starting up after 22/19Z or so.  Given the increased confidence will
go with VCTS mention at the terminals and attempt to refine that
with the 22/12Z TAF issuance.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...MJ
LONG TERM....SRM
AVIATION.....MJ