039
FXUS63 KLMK 161422
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1022 AM EDT Thu May 16 2024

.KEY MESSAGES...

*   Widespread showers and storms Friday into Saturday, with gusty
    winds and heavy rain possible in the stronger storms Friday
    afternoon and Friday night.

*   Drier and warm Sunday and Monday.

*   Showers and storms return Tuesday and Wednesday.

&&

.UPDATE...
Issued at 1022 AM EDT Thu May 16 2024

Low stratus continues to hang on a little longer than expected
across southern and central KY but current visible satellite imagery
shows clouds beginning to break and mix out. As the low stratus
clears high clouds associated with the next approaching system will
increase high clouds over the are start around midday into the
afternoon. Only updated the sky grids to reflect the current cloud
cover and the increase of clouds later this afternoon. The rest of
the forecast remains on track. Product updates coming shortly.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 305 AM EDT Thu May 16 2024

Synopsis...Split flow pattern will continue during the next 24 to 36
hours with weak mid-level ridge transitioning through the lower Ohio
Valley today ahead of a southern-stream shortwave trough over Texas.
At the surface, subtle high pressure will stretch from the lower MS
Valley to the Southeast while a tenuous stalled boundary dissipates
along the OH river.

This morning...As expected, satellite and surface observations show
fog/stratus developing across most of the forecast area. As of this
moment, lowest visibilities are concentrated across southern Indiana
and north-central Kentucky where clearing was evident earlier
tonight. Further south, visibilities are still slightly higher and
stratus dominate over a more surface-based event. This could be
explained, in part, by the continuous action of gravity waves
generated from upstream convection which might be promoting boundary
layer mixing. Overall, HREF guidance supports visibilities falling
through sunrise leaving the possibility of issuing a Dense Fog
Advisory for parts of the forecast area. Expect any fog/stratus to
start lifting by 14Z as daytime mixing kicks in.

Afternoon/Evening...The weak mid-level ridge will continue moving
eastward and vorticity energy from the southern-stream shortwave
trough will approach the area. As a result, anticipate a slight
uptick from west to east in light shower activity during the late
afternoon and evening hours. Otherwise, winds will remain light and
shifting from the west in the early afternoon to the south-southwest
in the evening.

Tonight...Better rain and storm chances are forecast for the
overnight hours as isentropic lifting and moisture advection support
brief moderate rainfall and a few lightning strikes. GFS forecast
soundings and CAM guidance indicate best storm chances towards
sunrise on Friday given better lapse rates and saturated profile.
Widespread flooding or severe weather is not expected with this
activity.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 305 AM EDT Thu May 16 2024

A 500mb trough over the southern Plains Friday morning will advance
to the Ohio and Tennessee Valleys by Saturday night. The main 5H
wind energy will stay to our south from Texas to Georgia, and this
is where CIPS analogs and CSU-ML prog the best chances of severe
storms. GFS shows the best water vapor transport concentrated over
the Gulf Coast states as well. Still, precipitable water values
around 1.5" are expected in southern Indiana and central Kentucky
Friday and Saturday as long as robust convection to our south
doesn`t steal the moisture. As a result, widespread showers and
storms are in the forecast. Can`t completely rule out a few strong
storms, especially in southern Kentucky Friday evening, beneath the
left exit region of the upper jet and on the nose of a LLJ coming up
from Alabama and Tennessee, but right now it looks like instability
will be weak and deep layer shear marginal. With deep moisture and K
Index of 30-35, efficient rainers and locally heavy downpours and
flooding appear to be the main threat.

Showers may linger east of Interstate 65 Sunday as the system slowly
pulls away, but overall it`s looking drier for Sunday-Monday in our
position between systems to our east and west.

Confidence decreases for Tuesday-Wednesday as models grapple with a
pattern change from split flow this week/weekend to more of a trough
west/ridge east early next week and then more quasi-zonal by mid-
week. But, the general consensus is that our next weather-maker will
move through the region during this time period, accompanied by more
showers and storms. The chance for severe storms in on the table as
surface low pressure moves from the central Plains to the Great
Lakes, interacting with an open western Gulf. This idea is further
supported by ECMWF CAPE-Shear EFI and CSU-ML progs, especially
Tuesday night into Wednesday.

Temperatures will be on a moderating trend once the rainy system
Friday-Saturday starts to move off to the east. By Monday and
Tuesday highs in the middle and upper 80s can be expected with dew
points in the 60s.

&&

.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 644 AM EDT Thu May 16 2024

Impacts/Confidence:
- High confidence in VFR conditions returning late this morning
- Medium confidence in deteriorating conditions tonight with wave of
showers and storms

Discussion...A mix of fog and stratus have kept most of the
terminals under visibility and/or ceiling restrictions this morning.
Such conditions will continue at least until 14Z when daytime
heating starts to mix the surface layer, dissipating the fog and
lifting the cloud base. Rest of the day will feature Visual Flight
Rules and light winds slowly shifting to the west-southwest. Shower
and thunderstorm activity will increase late this evening and
tonight while winds remain light and from the south. Best chance of
at least MVFR impacts should arrive after 17/6Z.

&&

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

&&

$$

UPDATE...BTN
SHORT TERM...ALL
LONG TERM...13
AVIATION...ALL