429
FXUS63 KLMK 120715
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
315 AM EDT Mon May 12 2025

.KEY MESSAGES...

*  Scattered showers and possible thunderstorms will spread north
   across the area today.

*  Intervals of showers and scattered thunderstorms expected to
   continue through midweek.

*  Warming trend later in the week, with highs well into the 80s
   Thursday and Friday. However, unsettled weather likely to
   continue through this period as well.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 314 AM EDT Mon May 12 2025

The upper closed low pressure system is located over Louisiana this
morning, but we will see it begin to slowly drift northward
throughout today. The moisture transport axis is on the east side of
the low, stretching from central Florida up into Kentucky this
morning, which has supported a few showers and storms last evening,
and will continue to provide a moisture plume for shower and storm
development today. This moisture transport axis is driven by a 35-
40kt LLJ, which will stay east of the area today as the upper low
spins toward northern Alabama.

At the sfc, the associated sfc low will also be pushing northward,
but will likely follow the Mississippi River. The system is already
occluding this morning, and will expect the occluded front to push
into our forecast area later on today as it extends well north of
the center of the sfc low. With PWATs already 1.2-1.4" early this
morning, they will likely peak around 1.6" in an area of moisture
convergence along the frontal boundary. Per SPC Sounding database,
the expected PWATs today would be above the 90th percentile from
BNA. As a result of these high PWATs, numerous heavy rain showers
will be possible throughout today, pushing north-northwest through
the area. We do not see these cell motions often.

Additionally, isolated to scattered thunderstorms will be possible
this afternoon as daytime heating peaks. Despite plenty of morning
cloud cover and shower activity, guidance does suggest we could
break out of the cloud deck some this afternoon. If we are able to
do so, the peaks of sunshine would support differential heating and
stronger destabilization, leading to our environment becoming more
favorable for thunderstorms late in the afternoon. However, expected
effective bulk shear values around 20-25kts would be weak enough to
keep severe probs low for today. SPC does carry a general thunder
risk today, which agrees well with our thinking on storm chances
today. With any stronger storms, wind gusts and small hail could be
possible.

Hi-res data does support the idea of precip coverage becoming
more isolated this afternoon, with many locations possibly seeing
breaks in precip too. Due to this, forecast PoPs for this afternoon
could end up being somewhat overdone. Temps this afternoon range in
the 70s, with muggy sfc dewpoints in the mid-60s.

By this evening and into tonight, the loss of daytime heating will
lead to even less precip coverage. Some areas may end up being
completely dry this evening and tonight. However, will still hold on
to a low chance for most of the evening, but chances shift east of I-
65 for the overnight due to the closer proximity to the moisture
transport axis to the east. Temps will be mild once again tonight,
with lows in the lower 60s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 314 AM EDT Mon May 12 2025

===== Tuesday - Wednesday Night =====

By Tuesday morning, the upper low will be directly over the OH/TN
Valley. At the sfc, the associated sfc low should be located near
the Missouri Bootheel, extending an occluded front through southern
IL/IN and KY and supporting additional showers and storms throughout
the day. Daytime heating will likely enhance precip activity, though
severe probs will be even lower than Monday. PWATs may end up being
slightly lower tomorrow as the primary moisture transport axis
shifts even more east, though we may still end up with roughly 1.2-
1.3" values, which will be enough for widespread showers and storms
during the daytime.

As temperatures warm into the upper 70s, sfc dewpoints in the lower
60s will help us realize marginal instability. However, wind shear
parameters will be very weak tomorrow due to the proximity of the
stacked low pressure system. This will limit convection from
becoming organized enough to become severe. This will also have an
impact on storm motions, which may end up being very slow or even
stationary. Given the PWATs, heavy rain rates combined with the slow
storm motions could lead to some localized flooding issues,
especially in poor drainage or low-lying areas.

For Wednesday, the higher precip axis will shift to east-central
Kentucky as the upper low churns northeast of the area. Best chances
in our area will be east of I-65, with daytime enhancement of shower
activity possible again. Highs will reach the upper 70s and low 80s.
By Wednesday evening and night, upper level ridging will begin to
build into the region from the west, leading to drier conditions for
the entire area.


===== Thursday - Weekend =====

Thursday will be the warmest day of the week, and possibly of the
year so far. Upper ridging will be directly over the region, with
strong WAA regime in place due to breezy SW winds. Winds will be
elevated on Thursday due to a tighten sfc pressure gradient. Temps
are forecast to hit the upper 80s, though can`t rule out the urban
heat islands to come close to 90. However, saturated soils and green
vegetation will combat this possibility, so confidence in seeing 90
for the first time this year remains somewhat low. Regardless,
Thursday looks to be a pretty warm day, and also our one day of
completely dry conditions.


For Friday and Saturday the upper pattern flattens out
significantly, with precip chances driven by the interaction between
a slow-moving sfc front and subtle disturbances in the flow aloft.
Will keep it in the chance category given limited forecast
confidence, with highs slightly above normal and lows well above
normal as diurnal ranges will be smaller.

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 126 AM EDT Mon May 12 2025

Terminals are VFR early this morning, though as additional rain
showers push northward this morning, expect cigs to drop to MVFR and
possibly a brief period below the 2000ft fuel alternate threshold.
Cigs will lower from south to north this morning, with prevailing
-SHRA at all terminals. There will be a chance for a few
thunderstorms this afternoon, so decided to include -TSRA mention
with PROB30 groups. Otherwise, this afternoon could end up with some
breaks in precip.

&&

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

&&

$$

SHORT TERM...CJP
LONG TERM...CJP
AVIATION...CJP