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000
FXUS63 KLMK 121928
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
328 PM EDT Fri Apr 12 2024

.KEY MESSAGES...

*  One more wave of scattered showers and embedded thunderstorms
   moves through this afternoon, clearing quickly after sunset this
   evening. Locally stronger wind gusts and small hail/graupel are
   possible in the strongest storms.

*  Above normal temperatures expected this weekend through much of
   next week. Strong to severe storm potential exists for the mid
   week time frame.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 328 PM EDT Fri Apr 12 2024

This Afternoon and Evening...

A shortwave trough can be seen on water vapor imagery diving
southeast toward the Tennessee Valley and southern Appalachian
Mountains this afternoon. An area of stratus clouds and rain showers
supported by the enhanced lift and moisture associated with this
trough is currently moving from our region into eastern KY and TN,
with clouds becoming more scattered to our north and west. Increased
sunshine, colder temperatures aloft, and a bit of residual low-level
moisture has allowed for the development of around 500 J/kg MLCAPE
across central IN this afternoon. This instability has contributed
to the development of isolated showers with a few rumbles of
thunder, and this area of showers will move south and east across
portions of southern IN and north central KY between now and sunset
this evening. Stronger showers/thunderstorms could bring down gusty
winds and small hail/graupel given stronger winds aloft and
relatively shallow freezing heights. These showers and storms should
subside quickly after sunset as we lose diurnal instability. Breezy
westerly winds will also continue through the evening hours,
gradually decreasing after sunset tonight as high pressure moves
closer to the area and the boundary layer stabilizes.

Tonight...

Drier air through the depth of the troposphere will work across the
Ohio Valley tonight, resulting in a gradual decrease in cloud cover.
Clear skies are expected by late evening, continuing through the
nighttime hours across the region. Temperatures should be able to
cool more efficiently tonight with limited cloud cover overhead;
however, persistent westerly winds on the order of 5-10 mph will
limit prime radiational cooling conditions. Still would expect lows
Saturday morning to fall into the low-to-mid 40s in most areas, with
upper 30s likely in the coldest valleys and other sheltered
locations.

Saturday...

Dry and pleasant weather is expected across southern IN and central
KY on Saturday as sfc high pressure passes just south of the region.
With the center of the high moving over the Gulf states, westerly
winds should continue into Saturday afternoon before gradually
backing to southwesterly Saturday evening. There will still be a WSW-
ENE gradient in 850 mb temperatures as the low-mid level ridge axis
won`t reach our area until Saturday night, so there should still be
a noticeable gradient in sfc temperatures from west to east (warmer
west) in spite of ample sunshine across the region. Highs Saturday
afternoon should range from the upper 60s along the I-75 corridor to
the low-to-mid 70s west of the I-65 corridor.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 328 PM EDT Fri Apr 12 2024

Saturday Night - Monday Night...

Dry conditions will be ongoing on Saturday night as benign NW flow
aloft and surface high pressure continue to control the area. There
does look to be a fairly tight pressure gradient across the area
between surface high over FL and and the surface low moving into the
Great Lakes. Surface winds will likely stay up around 10-15 mph
overnight helping to keep lows fairly mild and only in the low to
mid 50s. Sunday is still expected to be mostly dry, however a weak
frontal boundary extending from the surface low moving across the
eastern Great Lakes will impinge on our CWA. Models continue to hint
at a few light showers possible. Can`t rule it out so will continue
to carry a very small chance of a shower. The temperature trend
continues milder for Sunday with highs in the mid/upper 70s.

The weakly defined frontal boundary could hang up near or over our
region heading into Monday, but overall things look to stay mostly
dry. Wherever this boundary does end up, it will reinvent itself as
a warm front in response to cyclogenesis over the central High
Plains. Can`t completely rule out some light showers through Monday
night, however the confidence in timing placement as well as overall
amounts would all be pretty low.

At the moment, Tuesday looks to be dry as the warm front lifts
north, and upstream convection hasn`t yet arrived. Pretty good
consensus among deterministic data for the daytime hours at the
moment, so will go with dry and warm with highs around 80 degrees.

Tuesday Night - Friday...

We`ll have to pay attention to trends for the mid week time frame as
a couple of strong storm systems rotate through the central US. For
now, the Tuesday night system appears to weaken as it approaches our
area. The overall shear profile looks quite favorable for a severe
threat, however expecting that instability might be in question,
especially overnight when some sort of low level stability should be
in place. Still something to watch in case we do end up with some
instability to work with.

Depending on the exact timing of the lead system, there should be
some sort of a lull between Wednesday and Wednesday night as the
upstream pattern reloads and we sit in the subsident wake of the
first wave. If timing of that lead system ends up slower, then
Wednesday could end up wetter/stormier.

Another potent shortwave rotates through the central US by
Thursday/Thursday night, with strong cyclogenesis occurring ahead of
it. Looking for a strongly forced and widespread precipitation event
ahead of this trough axis at the very least. Depending on where the
surface low develops and tracks, we may be able to draw on enough
instability for some strong to severe storm concerns. That being
said, 12/12z runs of data seem to suggest that cyclogenesis happens
fairly late and mainly NE of our area, with a lot of the
precipitation shield occurring in the post-frontal regime. Not sure
how much of a severe threat that would yield, but things are a bit
too far out to speculate at this time. Bottom line is that the
period from Tuesday night through Thursday night needs to be watched
for potential for a round or two of stronger storms.

By Friday, we look to be post frontal and much cooler with highs
only in the upper 50s and low 60s after a mild/warm week. Expect
pretty strong and gusty WNW winds as high pressure builds into the
region.

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 144 PM EDT Fri Apr 12 2024

An area of MVFR stratus and scattered rain showers will continue to
move across the region this afternoon, quickly exiting by 19-20Z.
Another wave of isolated showers may develop later in the afternoon
and make a run at SDF/LEX/RGA through 23-00Z, but confidence and
coverage of these showers is low enough to leave out of the current
forecast. Later this afternoon, drier air will work in from the
north and west, gradually scattering out low clouds before skies
clear later this evening. Westerly winds will remain gusty through
sunset before gradually diminishing overnight tonight. After low
stratus scatters out this afternoon/evening, forecast confidence is
high in VFR conditions through the remainder of the current forecast
period.

&&

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

&&

$$

SHORT TERM...CSG
LONG TERM...BJS
AVIATION...CSG