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000
FXUS63 KLMK 130028
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
828 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.

&&

.MESOSCALE...
Issued at 536 PM EDT Fri Apr 12 2024

WSR-88D KLVX shows scattered weak convection forming along and west
of I-65 just behind the main cloud shield where some clearing was
able to take place this afternoon. This allowed for some additional
daytime heating which increased SBCAPE to around 100-250 J/Kg
combine that with steep mid-low level lapse rates and we have the
environment for isolated convection with the threat of some
lightning, small sub-severe hail and with storm motion to the
southeast at around 40kts, some gusty winds. The best chance for
slightly stronger convection appears to be across northern KY and
coming out of southern IN where we have better instability. We`ve
already seen a few isolated cells with pea size hail and gusty
winds. Activity is expected for the next couple of hours then
diminish with the setting sun.

&&

.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 /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 827 PM EDT Fri Apr 12 2024

Other than a few isolated showers and storms that are moving out of
the area and weakening, VFR flight categories will be in place for
the forecast period tonight. Skies will clear out and winds will
remain out of the west through most of the period. Winds may pick up
slightly again during the day tomorrow with gusts of 15-20kts other
than that it remains clear and VFR.

&&

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

&&

$$

MESOSCALE...BTN
SHORT TERM...CSG
LONG TERM...BJS
AVIATION...BTN