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874
FXUS63 KJKL 251031
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
631 AM EDT Sat May 25 2024

.KEY MESSAGES...

- Showers and thunderstorms are expected from time to time through
  the middle of next week, especially during the afternoon and
  early evening hours.

- There is a potential for severe thunderstorms on Sunday and
  Sunday night, with damaging winds and tornadoes being the
  primary threats.

&&

.UPDATE...
-- Changed Discussion --
Issued at 631 AM EDT SAT MAY 25 2024

We continue to see showers and a few thunderstorms roll across
parts of the Cumberland Valley this morning. This activity
continues to decrease in intensity given lack of better
instability that is more focused across the Tennessee Valley this
morning. Updated PoPs to better handle the morning convection,
but otherwise just blended in latest obs and trends.
-- End Changed Discussion --

&&

.SHORT TERM...(Today through Sunday)
Issued at 413 AM EDT SAT MAY 25 2024

The morning surface analysis shows a diffuse cold front is placed
across the Middle and Upper Mississippi River Valley and parent low
is along the Canadian border of Minnesota. In the mid-levels, a
shortwave embedded in the flow is pushing across parts of the
Ohio and Tennessee Valley. This boundary will push slowly east
today, as it puts the breaks on right around the Ohio River. The
previously mentioned wave has contributed to overnight convection
that continues to track across parts of eastern Kentucky this
morning. Also, additional convection seems to be developing in
the wake of the cluster of storms we saw through the night and
ahead of another line of storms across central Kentucky this
morning. That said, a fair amount of uncertainty exist for how
convection will evolve through the day and therefore have
generally capped PoPs in the 30-50 percent range through the day.
The CAMs are portraying varying coverage for for showers and
thunderstorms today leading to the uncertainty through the day and
will likely depend on how this morning activity pans out. There
is also height rises noted in the mid-levels that could limit
activity as well. The more organized convection will be in the
Upper parts of the Ohio Valley. This is where effective shear
values could increase into the 30-40 knot range. Here in eastern
Kentucky the convection that can develop today will be more
unorganized lacking shear, but ample instability will be in place,
with MUCAPE values in the 2000-3000 J/kg range. Sunday night, any
storm activity that develops will relent in the evening, with
loss of daytime heating. This as height rises noted earlier continue
into the evening. The only thing that could change this would be
more robust convection developing upstream that could take
advantage of left over instability.

Sunday, all eyes will turn toward convection that develops across
the Central Plains today and pushes toward the Ohio Valley by Sunday
afternoon. This as a shortwave trough axis pushes toward the Ohio
Valley at the same time. There remains a fair amount of uncertainty
as to how this convection will evolve as it tracks east given the
mesoscale nature. The CAMs are showing differing timing on this line
of thunderstorms, but generally suggest after 19Z (3 PM). The
various CAMs are also showing the potential for bowing segments
within the line of convection that pushes across the area. There
would be the potential for ample MUCAPE values in the 1000-2000 J/kg
range combined with effective shear of 40-50 knots to develop ahead
of this initial line of convection. Given the initial more line
normal shear the threat of damaging wind gusts and even a QLCS
tornado can`t be ruled out. This will have to be watched closely
in forecast updates later today. SPC did increase a portion of the
area to an enhanced risk mainly for wind and tornado risk as
mentioned above. The other risk would be for instances of Flash
Flooding where convection tracks over the same areas under ample
moisture profiles and deep convection.

.LONG TERM...(Sunday night through Friday)
Issued at 400 AM EDT SAT MAY 25 2024

Analysis and Discussion:

The extended period will start off with an upper level pattern
featuring ridging in place over New England and southeastern Canada,
with a flat ridge over the Gulf of Mexico, northern Mexico, and off
the southeast CONUS coast, with a subtropical surface ridge in place
over the west-central Atlantic. A fairly well developed trough aloft
will be pushing out of the central and northern Plains Sunday night
into Monday and into the Great Lakes and upper Ohio Valley regions.
Another ridge is forecast to be in place over the west coast to
start things. The midwest trough, along with its attendant surface
low and cold front, will be our weather maker in the extended. This
system is expected to deepen as it moves eastward through the Great
Lakes and Ohio Valley and into New England Monday and Monday night.
As this area of low pressure moves our way, the warm sector will
feature a steady influx of warm, moist air off the Gulf of Mexico
northward into the Tennessee and Ohio Valleys on persistent and
strengthening southerly or southwesterly flow. This influx of air
will allow the atmosphere to juice up and destabilize during the day
on Sunday especially late. There will also be decent wind shear
occurring, with southerly to southwesterly flow at the surface
veering to westerly aloft. There will also be an element of speed
shear, especially late Sunday night into early Monday, as winds
increase in the forecast soundings from 20 to 25 kts near the
surface, to between 50 and 65 kts aloft. The confluence of lift from
an approaching cold front, instability associated with moisture
advection at low levels, and wind shear, will set the stage for
severe weather across eastern Kentucky heading into Memorial Day. At
this time, it appears that the most favorable time for severe
weather in eastern Kentucky will be Sunday night into Monday, as the
cold front moves through. We should see precipitation steadily
tapering off Monday evening, after the cold front has moved through
and the upper level trough moves off further to our east. We could
see a few showers or storm pop up over some of our eastern counties
from late Tuesday through Wednesday, as a couple of shortwaves
rotate around the backside of the much larger departed trough and
through Great Lakes and Ohio Valley. After that, a ridge of high
pressure should settle over the region for the rest of the week.
This ridge will bring dry weather back to the area, along with
warming temperatures.

The storm prediction center recently upgraded severe weather
probabilities across eastern Kentucky from slight and marginal to
mainly enhanced, so we will be closely monitoring this situation, as
severe weather appears more and more likely. Temperatures will
continue to run above normal to begin the new work week, with highs
ranging topping out in the lower 80s for most locations on Monday.
After that, we should see a steady cool down for a couple of days,
as additional disturbances aloft pass through the region, and allow
cooler to filter in for a bit. This will also be a side affect of
the initial large trough aloft intensifying further and near
stalling out near the mid-Atlantic region.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 203 AM EDT SAT MAY 25 2024

Most sites are beginning the period VFR at this late night hour.
We have been tracking a cluster of convection across portions of
eastern Kentucky this evening and overnight. This is leading to
VCTS at LOZ and JKL. Outside this other sites should remain out of
the thunderstorm activity early in the period. There is some
concern for low VIS for fog in the usual river valleys, but also
at SME and LOZ which both got rainfall from the cluster of storms.
Mainly handled this idea with TEMPO group for now. This should
lift as we move toward the dawn hours as additional convection
pushes into the region. The winds will remain light and variable
through the period, but if you experience a thunderstorm expect
more erratic wind gusts.

&&

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

$$

UPDATE...DJ
SHORT TERM...DJ
LONG TERM...AR
AVIATION...DJ