830
FXUS63 KLMK 261411
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1011 AM EDT Wed Jun 26 2024

.KEY MESSAGES...

*   Showers and storms will move through the region along a
    cold front this afternoon. Some storms may be strong
    bringing gusty to damaging winds and heavy rain.

*   Shower and storm chances return Saturday through early Sunday.
    Locally heavy rain and gusty winds will be the main threats.
    Above normal temperatures return by early/mid next week.

&&

.UPDATE...
Issued at 1010 AM EDT Wed Jun 26 2024

SPC mesoanalysis and SDF ACARS exhibit stable conditions across the
forecast area after overnight convection, related to a weakening
MCV, has moved away towards the Ohio. Current temperature readings
are heavy influenced by the ongoing thick cloud coverage and as a
result, surface-base instability will take a few more hours to
develop leaving the morning forecast mostly dry. Convective
initiation will take place this afternoon with best storm coverage
after 4pm given the combination of building BL instability and
timing of upstream convectively-generated vorticity wave. This
scenario agrees fairly well with latest HRRR and NAM hi-res
output. Rest of the forecast remains on track.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 306 AM EDT Wed Jun 26 2024

Currently...

A weak MCV over western Kentucky, a weak 25-30kt LLJ, and weak
instability is allowing for showers and storms to persist while
moving southeastward. Showers and storms are expected to continue
this morning and begin to dissipate in the next few hours.
Confidence in this is quite low given marginal characteristics and
poor model initialization.

Today...

Troughing will strengthen and swing through the Great Lakes and Ohio
Valley today, sending a cold front south through the region. Along
and ahead of this front, showers and storms are expected. As the
front approaches the region and troughing aligns, providing lift to
present moisture. In the afternoon, a 35-40kt LLJ will help to
increase shear and storm organization. Will likely see enough
instability and organization of storms for scattered strong to
severe storms. Main threats will be cold pool driven convection
leading to gusty or damaging winds and heavy rain. Greater threat
will be over the eastern half of the region where less precip fell
yesterday and will have more time to destabilize. PWATs will be in
the 2.0-2.2 inch range. Will see a widespread 0.25-0.5 inches of
rain with near 1.0 inch totals with storms.

Tonight...

Showers and storms will push out of the region with the cold front.
Winds will veer to a northerly direction and skies will begin to
thin. Much drier and near normal conditions will build into the
region. Low temperatures on Thursday morning are expected to be
mostly in the mid 60s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 306 AM EDT Wed Jun 26 2024

Thursday - Friday Night...

Looks to be a fairly quiet end to the work week as the upper trough
responsible for an active mid week pattern will be pushing east.
This will leave our region in a low amplitude and dry NW flow aloft,
transitioning to more zonal flow by Friday. At the surface, high
pressure will center over the Great Lakes on Thursday, and then
slowly push east by Friday.

Can`t rule out a few lingering showers across our SE on Thursday
morning, however expecting dry conditions thereafter. The post-
frontal airmass will bring high temperatures for Thursday back
around normal values for this time of year, which is mid to upper
80s. Thursday night brings comfortable lows mostly in the mid 60s,
and may present a good radiational cooling/fog setup. Pressure
gradient should be calm to light with high pressure centered just to
our north, and overall upper sky cover should be on the lower end.
As a result, may end up with some patchy fog, most likely in the
river valleys. High temps rise back above normal by Friday with
values mostly in the low 90s. Friday night brings much milder lows
back into the low and mid 70s for most.

Saturday - Sunday Morning...

A seasonably strong shortwave will scoot across the far northern
Plains, into the upper Midwest, and across the Great Lakes Saturday
morning through Sunday morning. An associated surface low will
follow this similar path, and drag a trailing cold front toward our
region on Saturday. This feature will then sink slowly southward of
our area on Sunday morning.

Ahead of the cold front on Saturday into early Sunday, we expect to
get quite warm, moist, and unstable. Despite expected convective
activity on Saturday, temps are still forecast to reach the mid 90s
for most, and these values coupled with dew points in the low 70s
could yield max heat index values around our 105 degree Heat
Advisory criteria. Something to watch for. In addition to the heat
and humidity at the surface, an overall very moist atmospheric
column looks to set up as forecast soundings show a taller/skinnier
type of CAPE profile, and forecasts show PWATs could be up around
2.25" through the column. Deep moisture content combined with high
freezing levels and relatively slow storm movement will all provide
a recipe for localized intense/torrential rainers. In addition to a
localized flash flood threat, we will likely have an isolated wet
microburst/damaging wind threat with tall storms (ETs 45-50 K feet)
and water loaded downdrafts. Overall, deep layer shear is expected
to stay in the 20-25 knot range for the 0-8 km range, which is a bit
too low for more organized updrafts, and overall instability will
likely fall into the moderate range. Could see us eventually added
to a Marginal type of risk, but overall expect most of the severe
threat would be very localized and mainly pulse in nature. Think the
threat of some localized flash flood instances/heavy rain is the
slightly bigger concern at this point.

Once convective activity starts on Saturday, we will likely see
intermittent rounds of convection through Sunday morning before the
surface cold front sinks south. This will be due to "chain reaction"
types of evolution, and subtle mid/upper impulses propagating
through the zonal flow aloft and adding a bit of a kick/trigger at
times. As a result, will carry at least some chances even through
the night, despite the diurnal minimum.

Sunday Afternoon - Tuesday...

Shower and storm chances are expected to diminish across our south
through Sunday morning, with dry conditions taking hold thereafter.
Dry NW flow aloft once again takes hold of our area, along with
surface high pressure in the post-frontal regime. This leads to a
dry early week time frame, with temperatures steadily climbing back
well into the 90s by Tuesday.

&&

.AVIATION /12Z TAFS THROUGH 18Z THURSDAY/...
Issued at 652 AM EDT Wed Jun 26 2024

Weakening convection is moving through the region currently and
likely will not impact the terminals. The remainder of the day will
consist of a cold front dropping south through the region. Along and
ahead of the front, showers and storms will move through. Confidence
is low on timing due to poor model initialization and
environmental recovery timing. Best chance to showers and storms
will be in the afternoon through midnight. Strong storms could lead
to heavy rain and gusty winds.

In the overnight hours, the cold front will push showers and storms
out of the region and clouds will begin to thin. As the front moves
through the terminals, winds will veer to a northerly direction.

&&

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

&&

$$

UPDATE...ALL
SHORT TERM...SRM
LONG TERM...BJS
AVIATION...SRM