802
FXUS63 KJKL 120744
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
344 AM EDT Sun May 12 2024

.KEY MESSAGES...

- Precipitation free weather is anticipated through Monday
  morning, before more unsettled weather returns.

- Expect rather cool temperatures through the weekend, with
  milder weather then returning.

&&

.UPDATE...
Issued at 140 AM EDT SUN MAY 12 2024

Just a quick update to the forecast early this morning mainly to
add in the latest obs and trends for the T/Td/Sky grids. These
minor tweaks have been sent to the NDFD and web servers.

UPDATE Issued at 1133 PM EDT SAT MAY 11 2024

Updated the forecast package to emphasize tonight`s ridge valley
split just a bit better. Also beefed up fog across the area for the
remainder of the night. CAMs and ensemble data suggest surface dew
points should drop some through the overnight as drier air advects
into eastern Kentucky. Seeing a hint of that in the surface obs as
well. However, model guidance tends to keep Tds up through the
night. Seeing some fog formation in some of the more sheltered
valleys to our east. Forecast challenge is how much drier air will
be able to advect into the area versus surface dew points
leveling off or possible even rebounding a bit as the boundary
layer continues to decouple and grow in depth. As stated before,
surface dew points should rebound slightly or the drop should slow
and possibly level off. As temperatures continue to drop closer
to dew points, and we are beginning to see a more substantial drop
off now, believe conditions will become more favorable for some
fog development, particularly around or near sources of water.
Have made corresponding adjustments to the forecast package for
this latest line of thinking. Overnight lows looked on target for
our valley locations, however, raised the ridge top temps just a
couple degrees, which would be more in line with current
observations at our ridgetop sites. Updated zones and grids have
already been issued.

UPDATE Issued at 830 PM EDT SAT MAY 11 2024

Based on the current regional radar, the threat of any shower
activity over eastern Kentucky has waning quickly over the past
hour. Removed PoPs for the evening update and updated hourly T/Td
to capture the most recent hourly trends. With high pressure
moving into the area overnight, skies will continue to clear.
Difficult to say how much fog there will be overnight. With a
post frontal gradient wind am inclined to forego fog. But surface
dew points should rebound slightly with decoupling of the
boundary layer and expect winds will slacken enough for some
patchy valley fog to develop, particularly around or near sources
of water. Went ahead and freshened up the zones as well. No other
changes to the forecast package at this time. Updated zones and
grids will be issued shortly.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 322 PM EDT SAT MAY 11 2024

Last in a train of short-wave troughs has shifted just east of our
area this hour. This shift and more ridging building in should bring
a period of more tranquil weather for the short term. Skies should
become mostly clear tonight, allowing for another night of aurora
watching should those colors swing by here again. Similar to this
morning, temperatures by Sunday morning should fall into the 40s for
most locations in eastern KY. High pressure crossing overhead again
will mean some potential for valley fog formation.

Under more sunshine Sunday, highs should reach well into the 70s,
close to normal for mid May. Weak southerly flow Sunday night, as
that surface high shifts southeast of the region, will mean
temperatures a little warmer by Monday morning, with lows in the
mid 40s to low 50s.

.LONG TERM...(Monday night through Saturday)
Issued at 344 AM EDT SUN MAY 12 2024

The 12/0Z suite of model solutions appear to be in slightly
better agreement through the extended as compared to this time
yesterday. Plains low pressure and associated trough are poised to
enter the lower Ohio and Tennessee valley areas at the start of
the period. This system manages to get through our area during the
first 48 hours of the extended, weakening and opening up into a
trough as it tracks slowly eastward. Shortwave ridging will
transit the Ohio Valley late Wednesday through Thursday, providing
a brief lull in the unsettled weather pattern that will dominate
the extended. Phasing of northern and southern stream energy
result in a trough that moves through the Ohio Valley during the
last 24-36 hours of the forecast window (Fri- Sat). At the
surface, two low pressure systems at the start and end of the
extended will bookend surface high pressure that drifts eastward
across our area Thursday.

Sensible weather features generally unsettled weather through the
extended with a brief pause in the weather on Thursday. Thus the
extended begins with a round of rainy weather which persist
through Tuesday night and Wednesday, before slowly tapering off
from the northwest late Wednesday as a trailing cold front passes
through eastern Kentucky. Weak instability and shear will keep any
threat for severe storms in check with this first system. While
increasing PWATs of 1.2-1.4 inches aren`t spectacular, there does
appear to be a period elevated 850 mb moisture convergence under
notable upper level divergence by Tuesday afternoon and evening
just ahead of the surface low. This may lead to a period of more
steady moderate rainfall for portions of eastern Kentucky. WPC has
issued a Marginal risk ERO for this time frame as a result.

Further out in time, high pressure does exert its influence
briefly from Wednesday night into Thursday, providing a lull in
the threat of rain. Meanwhile, a northern Rockies trough and
Pacific low will translate eastward and phase into a deeper trough
that will eventually pivot across the eastern CONUS late in the
week. This second system will bring another round of showers and
thunderstorms to our area Friday through Saturday.

Temperatures will average above normal through the period, but
more as a result of overnight lows in the 60s running 5 to 10
degrees above normal. Exception will be Wednesday night into
Thursday morning as high pressure provides one night of lighter
winds, and at least partially clearing which will promote decent
radiative cooling, allowing temps to fall into the mid 50s across
most of the area. Tried to go with a muted diurnal range for the
remainder of the period because of added cloud cover and higher
PoPs. Afternoon highs will run about normal overall, mid 70s on
average.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 155 AM EDT SUN MAY 12 2024

VFR conditions will hold through the period with just a small
potential for some of the early morning river valley fog to impact
a terminal or two around dawn. Light and variable winds will pick
up later this morning from the west to northwest at 5 to 10 kts.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GREIF
SHORT TERM...SHARP
LONG TERM...GEERTSON/RAY
AVIATION...SHARP/GREIF