931
FXUS63 KJKL 110905
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
505 AM EDT Sat May 11 2024

.KEY MESSAGES...

- Some showers and perhaps a storm or two are possible, at times,
  this afternoon.

- Precipitation free weather is anticipated from Saturday night
  into Monday morning, before more unsettled weather returns.

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

&&

.SHORT TERM...(Today through Sunday)
Issued at 505 AM EDT SAT MAY 11 2024

08Z sfc analysis shows low pressure and a cold front approaching
the area from the northwest. Ahead of this, a bubble of high
pressure has been enough to keep the skies mostly clear and winds
light through the bulk of the night. As a result, fog formed
rather quickly in the valleys and has become thick. Now, a
smattering of low clouds is moving through the area during these
early morning hours and that should limit the expanse of the fog.
An SPS is in effect for most of the area for areas of dense valley
fog through 9 am. Otherwise, the conditions with this high has
allowed for a small ridge to valley difference to set up.
Specifically, readings vary from around 50 on the hilltops to
near 40 in the more sheltered spots of the east. Meanwhile,
dewpoints are within a degree or two of temperatures at most
observation sites.

The models, and their individual ensemble suites, are in excellent
agreement aloft through the short term portion of the forecast.
They all depict a clipper trough dropping into the Ohio Valley
this morning and passing by to the northeast of Kentucky through
the afternoon in northwest mid level flow. Slight 5h height falls
and a brush by of the shortwave`s energy will affect eastern
Kentucky into the evening. Heights will then slowly rebound
tonight with ridging starting to push into the region from the
west and practically overhead during the day, Sunday. The model
spread remains quite small with these key features so the NBM was
used as the starting point for the short term grids along with the
incorporation of the CAMs details for PoPs and timing through
this afternoon.

Sensible weather features another day on the cool side with a
passing threat for some showers as a result of an arriving cold
front. While showers will be the predominate form of precipitation
today - a few cells may find enough instability to break a cap
just above 700 mb and grow deep enough for some fleeting thunder.
Just a small amount of QPF are expected from the rainfall today -
around a tenth of an inch or less for most places. Post frontal,
the convection pulls out to east the tonight with clearing
conditions and another bout of ridge to valley temperature
differences developing along with some more limited valley fog as
the winds stay up better than this night. High pressure builds
back into the area on Sunday coincident with the rising heights of
the upper level ridge. This will mean a mostly sunny day with
temperatures a notch warmer than those of today - closer to normal
in the mid 70s.

The main adjustments to the NBM starting point consisted of adding
in some terrain details to the hourly temperatures and lows
both this morning and again tonight. As for PoPs - the NBM values
were adjusted to include some CAMs details for the shower and
scant thunder chances through the afternoon hours with the passing
cold front.

.LONG TERM...(Sunday night through Friday)
Issued at 433 AM EDT SAT MAY 11 2024

Operational models are in good agreement through the first half
of the extended with synoptic features, and diverge from there. In
general, eastern Kentucky resides in a split flow pattern through
the period, with stronger wind fields (westerlies) across the
Deep South and to our north along the Northern Tier and Great
Lakes. Because of the weaker wind fields aloft, one main trough
only manages to crawl through the OH/TN valley regions from late
Monday through Wednesday. A second southern stream trough tracks
through the region late in the period, Dy7...or Friday. At the
surface, low pressure lifts out of the Great Plains and through
eastern Kentucky Tuesday into Wednesday, then a second low
pressure system moves into the TN valley by the end of the
forecast window.

Sensible weather features generally unsettled weather through the
extended with two main rounds of weather to deal with, the first
from late Monday through Wednesday, then a second round from
Thursday night through Friday. There are two periods of dry
weather, or at least a lull in shower activity, at the start of
the extended...Sunday night into Monday and then again Wednesday
night into Thursday. Due to a general lack of instability and
shear across the area through the period...and relatively weak
flow aloft, thunderstorm activity will likely be limited and occur
primarily during peak heating, or during the afternoon and early
evening time frame. Not seeing signals that would suggest much
hazardous weather through the period, though WPC does have eastern
Kentucky within a marginal risk for excessive rainfall Tuesday
and Tuesday night. Thinking is that this risk is primarily due to
the slow speed of the first system`s progression through the Ohio
and Tenn valleys. With limited instability and shear, and by
extension a lower risk of strong and/or severe thunderstorms over
our forecast area, it is difficult to see convection being a
primary ingredient to an overall hydro risk. Freezing levels are
not particularly high, generally below 11 kft through that portion
of the forecast. Wind fields are on the lighter side, but storm
motion is still greater than 10 kts until Tuesday night. By late
Tuesday night steering winds do drop to between 5-10 kts. PWATS
are up close to 1.4 inches, or 75th percentile of climatology.
Thus, while the threat of hydro issues is low at this time, it
would appear that if there were any problems, a Tuesday through
Tuesday night window of time would be most likely time frame of
concern.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 220 AM EDT SAT MAY 11 2024

VFR conditions are still holding at all sites at the start of the
forecast period. With mostly clear skies and light winds, though,
valley fog formation is kicking into overdrive, some of which
may impact the TAF sites with IFR or lower conditions for a time.
To account for this, a TEMPO group for fog down as low as 1SM
visibility was kept in the forecast along with low CIGs. Expect
west to west-southwest winds to increase through the morning
ahead of a cold front and upper disturbance that brings showers to
the area from late morning through much of the afternoon.
Sustained winds up to 12 kts will transition to a more
northwesterly direction with passage of that boundary in late
morning and afternoon - then diminishing after dark.

&&

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

$$

SHORT TERM...GREIF
LONG TERM...RAY
AVIATION...CMC/GREIF