019
FXUS63 KJKL 011948
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
348 PM EDT Wed May 1 2024

.KEY MESSAGES...

- Very warm this afternoon, followed by near-record highs on
  Thursday.

- Shower and thunderstorm chances return to the forecast Friday
  through Tuesday.

&&

.UPDATE...
Issued at 1220 PM EDT WED MAY 1 2024

Hourly grids were freshened up based on recent observations and
trends. Sfc and upper level high pressure will lead to warmer and
drier weather compared to Tuesday with a few passing cirrus and
fair weather diurnally driven cumulus.

&&

.SHORT TERM...(Today through Thursday)
Issued at 308 AM EDT WED MAY 1 2024

A very foggy start this morning for most of the forecast area; areas
along the escarpment are the exception as of this writing. However,
satellite trends show some subtle westward expansion of fog.
Therefore, there is still time for the likes of Somerset and
Morehead to experience fog. Conditions were ripe for fog given
rainfall that occurred during the day followed by clearing skies
and calm wind. While we will mix out nicely this afternoon
(temperatures soaring well into the 80s with dew points in the
50s), ensemble forecast soundings indicate the low-level
inversion will come roaring back overnight. Due to the anticipated
daytime mixing, we think the fog will be less widespread.
Therefore, we`ve introduced fog to the river valleys tonight to
start. This can be finessed further by day shift.

An upper-level ridge in place over the Southeast US amplifies on
Thursday, resulting in a hot afternoon. High temperatures will be
close to records. Jackson`s record is 87 set in 2012 while London`s
is 88 set in 1959. Relative humidities will plummet in the
afternoon which raises a non-zero fire weather concern (similar
conditions today, though RH value will be slightly higher). Of
course, recent rain will squelch the concern overall, as will
light wind.

One last item to consider on Thursday is a non-zero chance of an
isolated pop-up thunderstorm. The forecast remains dry at this time,
but this possibility was noted in the CAMs. Dew points in the 50s
will result in significant dew point depressions which will be
challenging to overcome. Ensemble soundings indicate marginal
instability of about 500j/kg and virtually no shear. However,
convective temperatures will likely be met which could afford at
least some cumulus clouds attempting to bubble up. Forcing may come
in the form of a weak perturbation rippling atop the ridge, ahead of
an incoming trough digging in over the lower Mississippi River
Valley.

.LONG TERM...(Friday through Wednesday)
Issued at 348 PM EDT WED MAY 1 2024

Core of westerlies remain to our north through the bulk of the
extended time frame, through the Upper Midwest and Great Lakes.
That leaves our area within weak flow aloft, with subtle
disturbances passing through the region at times during the
extended portion of the forecast. Low pressure drops out of the
northern Pacific and into the West Coast by this weekend. This
system then slides eastward over the Central Plains and eventually
noses its way into the Upper Midwest and Great Lakes regions by
the end of the forecast window. This will bring stronger winds
(core westerlies) across our region by the end of the period as a
broad trough is carved out over the lower forty-eight. In general
this will keep eastern Kentucky within the warm sector (south of
the polar jet) through the period. At the surface, and with little
or no support aloft, a cold frontal boundary appears to drop
southeast to the Ohio River by late Sunday, then stalls briefly
before retreating northward in quick fashion Monday. A cold
frontal system then approaches from the west by the end of the
extended. Several of the aforementioned disturbances will tend to
keep the threat of showers and thunderstorms in the forecast
during much of the extended, with a diurnal flavor to the
activity.

Sensible weather features seasonably warm temperatures running as
much as 5 to 10 degrees above normal. There will be at least a
chance of rain, or at least a climatological 30% or higher PoP
each day of the extended. A series of disturbances will pass
through the Ohio Valley during the period, the first roughly late
Friday into Saturday, with a second late Sunday into Monday and
then a third late Tuesday into Wednesday. The last disturbance at
the end of the period will be more closely associated with the
storm system approaching from the west. Other than thunderstorms,
not seeing much in the way of hazards through the period. QPF for
the extended does not exceed 1-1.5 inches in total, hardly enough
to be of concern at this time. We could experience some strong
thunderstorms, perhaps an increased potential for some severe
storms towards the end of the forecast window. Afternoon
instability increases each day, Monday through Wednesday, with
MLCAPES climbing from around 500 J/kg on Monday to close to 2000
J/kg by Wednesday. Only seeing marginal shear Monday at around 25
kts effective shear. That increases to around 30 kts by Tuesday
and then between 30 and 40 kts by Wednesday. Consequently,
thinking at this time is that a strong storm or two could not be
ruled out Tuesday, then some strong to a couple severe storm would
be possible by Wednesday with the approach of the storm system
from our west if current model solutions hold. Confidence is not
high due to the fact that this is still a week away. But NCAR
Ensemble C-Shield forecast would tend to support this line of
thinking.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 1245 PM EDT WED MAY 1 2024

VFR will largely prevail through the period with sfc and upper
level ridging dominating. The exception will be fog potential
between about 05Z and 14Z again tonight though as noted by the
previous forecaster, this should be more confined to the river
valleys and along some of the larger creeks and lakes. Some MVFR
fog could still develop at some of the TAF sites, with LAMP
suggesting IFR or lower potential at KSJS and KSYM. Any fog should
lift and dissipate by 14Z, with VFR returning to all areas at
that time.

&&

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

$$

UPDATE...JP
SHORT TERM...BROWN
LONG TERM...RAY
AVIATION...JP