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000
FXUS63 KLMK 170531
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
131 AM EDT Wed Apr 17 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Showers and thunderstorms are likely tonight through early
    Wednesday morning. The severe threat tonight into Wednesday
    morning looks low, with the greater threat being locally gusty
    winds, small hail, and heavy rain.

*   Confidence continues to decrease in the potential for severe
    storms tomorrow due to dry air sweeping into the region and the
    best upper air energy remaining to our north. Any thunderstorm
    development tomorrow should be isolated, though if any storms do
    develop they would have the potential to become severe.

*   Isolated strong to severe storms possible Thursday evening and
    overnight.

*   Much cooler weather this weekend.

&&

.UPDATE...
Issued at 950 PM EDT Tue Apr 16 2024

It`s a June-like night across the region, with mid to upper 70s
across the state. As of writing this at 9:35 PM EDT, it`s 79F at the
WFO. WAA regime due to low-level jetting will continue overnight,
with temps only expected to drop into the mid 60s for most. Forecast
remains in great shape, so no changes are planned other than
blending in some of the 00z data with the forecast.

Showers and thunderstorms currently to our west will make their
eastward progression into our forecast area tonight. However, the
guidance continues to support seeing these storms outrun the
instability axis, with most storms expected to become elevated.
Still expecting the most widespread coverage occurring after midnight
and before dawn. Similar to the afternoon discussion, can`t rule out
some stronger storms, with gusty winds, small hail, and locally
heavy rainfall. Will need to watch the western CWA a bit closer as
these storms begin arriving, as we could be on the eastern periphery
of a bulk shear gradient. Storms riding instability or shear
gradients often cause trouble, so it`ll be worth watching closely
later tonight. Storm motions will be much more progressive than last
night, so flooding concerns are not very high either. A few flood
advisories may be needed for any local spots that are hit by
multiple downpours.

With no major changes to the forecast, no need for updated forecast
products at this time.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 339 PM EDT Tue Apr 16 2024

Strong low pressure crossing the upper Midwest tonight will have a
cold front dropping south into the mid-Mississippi Valley by
morning. Showers and thunderstorms that are developing this
afternoon across Missouri and Arkansas will head east into the lower
Ohio Valley this evening and cross southern Indiana and central
Kentucky tonight, with the most widespread coverage occurring
between midnight and dawn. The storms to our west will remain robust
as they move into an axis of moisture and instability along the
Mississippi River in southeast Missouri, southern Illinois, and
western Kentucky. However as these storms move east overnight they
will outrun the instability and become slightly elevated as they
move into southern Indiana and central Kentucky, which has been a
consistent signal in the models recently. A few stronger storms will
be possible, with some gusty winds, small hail, and locally heavy
downpours. Unlike last night`s convection over Oldham County,
tonight`s storms will be more progressive with forward speeds of 30
to 40 mph, mitigating the flood threat. Any flooding problems should
be restricted to spots that collect water easily and are hit by
multiple heavy downpours.

Yet another unseasonably warm night tonight with lows generally in
the mid 60s. SDF has been at or above 60 degrees since 4:15am on the
14th (Sunday).

Wednesday the upper Midwest low will be occluding and weakening as
it travels well to our north from Wisconsin to the UP. The left exit
region of a straight upper jet streak will advance from Indiana to
Pennsylvania while a weakening 500mb speed max moves from Illinois
to Ohio. The pool of best precipitable waters will be found from
Michigan to Pennsylvania. Farther south in the Ohio Valley a dry
slot will sweep in, significantly limiting moisture supply. As a
result, model PoPs are consistently very low and NBM is printing out
PoPs in the single digits for much of the region. Looking upstream,
the dry slot today from eastern Kansas into western Iowa is free of
deep convection. As a result, the best chances for severe storms
tomorrow appear to be to our northeast, especially over northern and
eastern Ohio. This agrees with the latest SPC convective outlook`s
Slight Risk area to our north/northeast and the HRRR`s Convective
Hazard Forecast placing the best chances for severe weather over
Ohio. In agreement with neighboring offices, will hold on to a small
PoP in case any isolated storms can fire, especially since if any
storms do go up there will be plenty of instability and shear
available.

With dry air coming into the region tomorrow afternoon went on the
low side of guidance for dew points and the high side for afternoon
high temperatures (low-mid 80s). Southwest winds may gust to near
advisory criteria in the 25-35mph range, especially in southern
Indiana and north central Kentucky.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 339 PM EDT Tue Apr 16 2024

Dry weather is anticipated to begin the period Wednesday night. Weak
shortwave ridging builds into the region in the wake of the low
pressure system affecting our weather in the short term. This low
pressure system will continue to weaken as it lifts northeast across
the Great Lakes. Meanwhile, an upper level trough is forecast to dig
southeast over southern Canada and the northern Plains. This wave is
forecast to move eastward over portions of the Upper Midwest and
Great Lakes through Thursday night.

At the surface, low pressure organizes over the southern Plains
Wednesday night and is forecast to lift ENE across the Lower Ohio
Valley Thursday night. However, the low will only gradually weaken
with time due to its less than favorable position relative to the
stronger upper level dynamics to the north.

Wednesday night is shaping up to be dry and mild with lows ranging
from the mid 50s to lower 60s in most places. Thursday will
certainly start off dry and will likely remain dry until the evening
hours when low pressure approaches from the WSW. Expect partly to
mostly sunny skies and a south wind increasing to 10 mph by the
afternoon. Temperatures will likely peak in the low to mid 80s Thu
afternoon.

Shower and thunderstorm chances increase west of I-65 Thursday
evening and then across all of central KY and southern IN overnight.
Convection associated with the sfc low and associated cold front may
organize into a linear MCS, which the latest data suggest could
arrive in our western/northwestern CWA by 21-00Z Thu evening. These
storms could pose a risk for isolated damaging winds, depending on
sfc-based instability. The degree of destabilization is uncertain
and is a mesoscale detail that will need more time to become clear.
Deep-layer shear is adequate at around 35 kts, but will be limited
by only moderate W/SW flow aloft. As previously alluded to, the
stronger winds aloft will remain displaced to our northwest.

The best chance for strong to severe storms is from 21Z Thu through
06Z Fri, a time window that will likely be refined over the next day
or so. Waning instability overnight will allow convection to weaken
as it crosses KY. Low temperatures will range through the 50s (near
60 F at Lake Cumberland) Friday morning.

Showers may linger into Friday morning along and just behind the
cold front, especially east of I-65. However, expect a drying trend
from west to east on Friday. Low-level NW flow advects cooler air
into our region Friday through the weekend as strong sfc high
pressure noses southeast across the Plains and Midwest. Temperatures
should rebound into the mid 60s to near 70 F Friday afternoon, but
Saturday will be cooler with highs in the upper 50s to mid 60s.
Mornings will be chilly, especially Sunday and Monday, with lows in
the 30s to low 40s. At this point in time, the Saturday evening
forecast is looking somewhat cool (low to mid 50s) and dry.

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 130 AM EDT Wed Apr 17 2024

Impacts/Confidence:
- Medium confidence in isolated coverage of VCTS early this morning
as well as LLWS
- Medium to high confidence in MVFR ceilings this morning.
- High confidence in strong gusty winds today

Discussion...Current radar and satellite show isolated coverage of
storms across the forecast area. Current trends indicate that this
activity will continue to diminish as it moves to the east. As a
result, decided to leave the VCTS mention through sunrise and amend
if necessary. In addition, the presence of a decaying LLJ will
continue promoting LLWS conditions for a few more hours. As for
ceilings, an MVFR cloud layer should set in this morning in the wave
of precipitation and last until around 17Z. Otherwise, winds will
persistently gusts between 25 to 30 knots today with occasional
gusts of 30-35 knots in the afternoon. There is a conditional threat
of strong storms in the afternoon, but confidence in initiation and
coverage substantially limit predictability, so reflected dry
conditions.

Extended Outlook...Another round of storms (potentially strong) is
possible Thursday evening/night.

&&

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

&&

$$

UPDATE...CJP
SHORT TERM...13
LONG TERM...EBW
AVIATION...ALL