381
FXUS63 KJKL 180042 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
842 PM EDT Fri May 17 2024

.KEY MESSAGES...

- An upper level trough advancing slowly toward us from the west
  will continue to support showers and thunderstorms into Sunday,
  with the focus shifting southeastward in our area with time.

- Upper level ridging moves into the area from the northwest
  Saturday night and Sunday bringing drying, with dry weather
  expected area wide from Sunday night through Tuesday night.

- The upper level ridge shifts to our southeast by Wednesday. A
  series of upper level waves and an approaching cold front will
  bring the potential for rain back Wednesday into Thursday.

- The upper level ridge passing over will result in warmer
  weather, with above to well above normal temperatures forecast
  Sunday through Wednesday.

&&

.UPDATE...
Issued at 841 PM EDT FRI MAY 17 2024

Hourly grids were updated based on recent observation trends.
Lightning activity has not been detected recently and with sunset
approaching, thunder will be removed from the forecast grids
within the next hour. Partial clearing or breaks in the clouds
could set the stage for fog formation tonight and this potential
will continue to be monitored for possible inclusion in the HWO
and or SPS. The previous forecast already hit fog rather hard in
the weather and visibility grids.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 501 PM EDT FRI MAY 17 2024

A split flow pattern aloft persisted over the central and eastern
CONUS late today, with a trough from northern TX northeastward
over the Midwest. The trough continues to shift very slowly
eastward, with plenty of moisture available ahead of it for
precip. Light rain and showers continue to move across the JKL
forecast area, but thunder has been very limited due to lack of
sun and destabilization. With the opportunity for heating waning,
have not used anything more than a slight chance of thunder into
tonight. A model blend suggests a likelihood of precip over the
region this evening, with the 12Z NAM being wettest. However,
this was due to the NAM generating more significant convection,
which is appearing less likely (in fact, the 18Z run has now
backed off).

The trough continues to approach on Saturday, and with even very
modest warming it looks like there will be enough destabilization
for more showers and thunderstorms to develop. The greatest deep
moisture is expected over our southern counties, with models
showing drying (especially aloft) beginning to make its way into
our northern counties as the trough axis begins to cross our area.
The deep moisture would make it easier for convective columns to
persist in our south and support more widespread precip, but
better heating could lead to more instability north and a better
chance of thunder there where precip does occur.

As the trough continues slowly eastward, its axis should be to our
southeast late Saturday night. With drying aloft and loss of
heating, remaining precip will taper off and clouds should also
break up.

MOS guidance is hitting fog fairly hard tonight. With light winds
and moist air, this makes sense should breaks in the clouds begin
to appear. The GFS forecast sounding suggest this, with the NAM
as well (mainly over our northern counties). Fog can also be
expected Saturday night as clouds decrease further and light winds
persist, but minimal change in low level air mass occurs.

.LONG TERM...(Sunday night through Thursday)
Issued at 501 PM EDT FRI MAY 17 2024

High pressure at the surface and aloft builds into the Ohio Valley
and Appalachia regions for the start of the extended, through
Tuesday. Western CONUS trough then gets booted to the east through
the Plains and into the Great Lakes and Ohio Valley by the end of
the period. At the surface, storm system located over the
southeastern CONUS will continue to push out into the Atlantic at
the start of the extended. High pressure resides over our area as
our next weather maker gradually organizes and strengthens over the
Upper Midwest during the start of next week. Eventually this system
pulls a surface cold front into the Commonwealth by Thursday and
through eastern Kentucky by the end of the forecast window,
Friday.

Sensible weather features a warm start to the extended. Afternoon
highs will be in the lower 80s Sunday and mid 80s from Monday
through Wednesday. With surface dew points right around 60,
conditions will just begin to feel a bit uncomfortable through the
morning and early afternoon. But RH values should drop back down and
be a bit more comfortable through the mid afternoon and early
evening. Overnight lows will be cool, mid 50s to around 60 Monday
and Tuesday morning. Overnight lows moderate from there as moisture
is lifted into the area and the threat of rain begins to increase.

With respect to rain, we will have a low chance (20-30% PoPs) of
rain Sunday as the system over the southeastern CONUS moves out into
the Atlantic. After a couple days of dry, warm weather Monday and
Tuesday, the storm system to our west becomes close enough to bring
the threat of showers and thunderstorms to our area. PoPs as high as
60-70% will bring another roughly one-third to three-quarters of an
inch of rainfall to the area from Wednesday through Thursday. At
this point we are still running behind climatological normals by
around one inch, so this will help but in general additional rain
would be helpful. There is enough instability for thunderstorms
about any time there is a threat of rain. However, at this time the
best combination of instability (1500-2500 J/kg) and effective shear
(30-40 kts) will come Wednesday. Consequently, a few strong storms
or even a severe storm or two could not be ruled out on Wednesday.
For now we just monitor trends and update accordingly.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 835 PM EDT FRI MAY 17 2024

Conditions at TAF issuance again ranged from LIFR to VFR across
the JKL forecast area, with MVFR being the most prevalent. Showers
or light rain was also affecting many places.

Showers should decrease in coverage through 06Z, with some breaks
in the clouds and or partial clearing anticipated by that point.
In general, this should result in deteriorating conditions by that
time for areas currently VFR with deterioration possible
elsewhere as well. IFR or worse conditions are forecast to develop
in most places from 03-07Z and then persist into the 12Z to 15Z
period, with though most precipitation will taper off by 09Z. The
exact category and timing of the lowest conditions for each of
the TAF sites are uncertain due to the timing and and areal extent
of any partial clearing or breaks in the clouds overnight.
Improvement is expected to VFR or MVFR for most areas by 18Z with
VFR forecast to end the period.


&&

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

$$

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