-- Discussion containing changed information from previous version are highlighted. --
780
FXUS63 KJKL 210019 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
819 PM EDT Mon May 20 2024

.KEY MESSAGES...

- Dry weather is expected area wide through Wednesday morning.

- There is a potential for showers and thunderstorms at times from
  Wednesday afternoon through Sunday.

- Very warm temperatures will persist through Wednesday. An
  increase in clouds and the possibility of rain will bring
  somewhat lower temperature after that, especially Thursday and
  Friday.

&&

.UPDATE...
-- Changed Discussion --
Issued at 819 PM EDT MON MAY 20 2024

The axis of upper level ridging will shift east tonight with a
weak shortwave moving into the OH Valley later tonight. A ridge of
sfc high pressure will remain centered to the east and southeast
of eastern KY. The pattern is conducive to the continued
decoupling of deeper valleys and development of at least a
moderately strong temperature inversion from the valley to ridges
or ridge/valley split. Valley fog should develop around or shortly
after midnight with the high leading to light winds and not much
cloud cover. The areal extent of this and intensity should be
less than the past couple of nights, however, and more typical of
this time of year.

Hourly grids were adjusted based on recent observation trends, but
this led to no substantial changes at this time.
-- End Changed Discussion --

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 522 PM EDT MON MAY 20 2024

The latest upper level map features a ridge axis aligned southwest
from the western Atlantic through the central Appalachians into
the Tennessee Valley. A trough is positioned from central Canada
through portions of the Great Basin and eastern Pacific. This is
allowing for southwest flow through the Rockies, Plains, and the
middle and upper Mississippi Valley. At the surface, high
pressure is seen from New England through the southeastern CONUS.
A quasi-stationary boundary is aligned from near the Saint
Lawrence River Valley through the lower Great Lakes, and into the
Midwest, before turning more southwest across the central/southern
Plains. Despite seeing a decent amount of cumulus today, drier
air mixed down from aloft, allowing for dew points in the lower to
middle 50s at most locations. Temperatures peaked in the mid 80s.

The models are in good agreement aloft through the short term,
with a vigorous short wave trough to travel from the Desert
Southwest to the central Plains by early Tuesday, before curling
and deepening as it makes its way over the Midwest and then the
Great Lakes Tuesday afternoon and night. 500 mb heights will be
on the rise for the Ohio and Tennessee valleys through Tuesday
night, while the surface high gradually pivots southeast with
time, allowing for slightly better return flow across eastern
Kentucky towards the end of the period.

Dry and warm weather will continue through the short term. Besides
some passing thinner high clouds tonight thanks to a dampening
short wave trough transiting to our north, skies will be mostly
clear. This should allow temperatures to dip close to readings
seen early this morning, with mid to upper 50s in valleys, and
lower 60s on ridges. It is conceivable that a few spots could get
slightly colder than this morning, given the drier air in place
and a slower developing and somewhat less extensive round of river
valley fog. Tuesday will feature another mostly sunny day, but
cumulus should be as prevalent to slightly more so compared to
today, as a bit more moisture will be in place. Highs will be
similar to around a degree or so warmer, with mid to upper 80s
common. One more night of mostly clear skies will be on tap
Tuesday night, with low temperatures modifying up a few degrees.
Still, some of the colder valleys in the east should still be able
to achieve mid to upper 50s, with low to mid 60s elsewhere.

.LONG TERM...(Wednesday through Monday)
Issued at 522 PM EDT MON MAY 20 2024

There is decent enough agreement with respect to the pattern aloft
among the operational models through Dy5, Saturday, then solutions
diverge from there with some of the more significant synoptic
features. Pattern is best described as being a broad zonal flow
across the eastern CONUS. Further west a few lows rotate in a circle
the wagons fashion across the northern Rockies and Canada`s BC with
a mean trough stretching down to the Baja. On occasion, short wave
energy shoots eastward from out of the mean trough sitting over the
West Coast and Rockies. Main challenge is the timing and strength of
each of the short wave disturbance as it tracks across the country
and into the Ohio Valley, or Commonwealth, particularly after Dy5
where there is less agreement in solutions. At the surface, a weak
frontal zone will sag southward across the region by Wednesday
night, providing a focus for mainly afternoon and evening diurnal
convection from late Wednesday through to the end of the forecast
window as a series of disturbances travel through the region.

Sensible weather generally features a warm and unsettled extended,
with daily high temperatures ranging from around 80 into the mid
80s, approximately 5 degrees above normal on average. Thursday and
Friday are our two coolest days with clouds and rain keeping
temperatures around 80 for highs each day. With extra cloud cover
overnight lows are expected to run generally in the 60s, though
guidance suggests some mid to upper 50s will be possible if there is
enough clearing that takes place on any given night. Should temps
dip into the 50s, one could expect valley fog to be a good bet,
similar to what we have experienced over the past week. Not seeing
much in the way of obvious hazardous weather threats. There are
periods of time where there is some marginal effective shear 30-35
kts to deal with. However, at this time not seeing any periods of
time where ample instability matches up with the necessary shear for
the more robust and/or organized convection. Overall this aspect of
the forecast is of a lower confidence with respect to the potential
of hazardous weather. Total rainfall expected through the period
from late Wednesday through Monday is generally around 1.5 inches or
less. The Weather Prediction Center does include portions of eastern
Kentucky in a Marginal risk of excessive rainfall for Day 5, Friday.

&&

.AVIATION...
-- Changed Discussion --
(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 815 PM EDT MON MAY 20 2024

VFR conditions will continue to prevail through the majority of
the period. The only exception will be some MVFR or lower fog that
will occur in the river valleys between 05 and 13z. Crossover
temperatures are a bit lower this afternoon overall, which should
keep the fog a bit more confined late tonight into early Tuesday
morning compared to the past couple of nights. KSME and perhaps
KLOZ have a chance to dip into the MVFR range at least briefly
between about 09Z and 12Z and included a couple of hours of MVFR
at both locations. Winds will average around 5KT or less through
14Z, before becoming south to southwest at less than 10Kt to end
the period.
-- End Changed Discussion --

&&

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

$$

UPDATE...JP
SHORT TERM...GEOGERIAN
LONG TERM...RAY
AVIATION...GEOGERIAN/JP