Severe Weather Potential Update

285
FXUS63 KJKL 012001
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
401 PM EDT Thu May 1 2025

.KEY MESSAGES...

- Some of the storms late this afternoon through mid-evening could
be strong to severe, with gusty to damaging winds and heavy rain
the primary threats. An instance of large hail or a brief, spin-up
tornado can`t be ruled out.

- The potential for showers and thunderstorms continues at times
into Sunday.

- Some of the storms Friday and Saturday could be strong to
severe, with gusty to damaging winds and heavy rain the primary
threats.

- Above normal temperatures will persist through Friday, followed
by below normal temperatures from Saturday into early next week.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 400 PM EDT THU MAY 1 2025

A warm and rather humid afternoon is underway in eastern Kentucky as
a weak boundary/surface trough approaches from the west. The surface
boundary is supported by a 500H shortwave ejecting out of a large
scale trough over the Central CONUS. Out ahead of this feature,
widely scattered light showers and areas of thicker mid-level cloud
cover have limited destabilization, particular for the southeastern
half of the JKL forecast area. Temperatures range from the mid 70s
in the southeastern portions of the CWA up to the upper 70s/lower
80s along/west of the Pottsville Escarpment. Sunshine has likely led
to the best destabilization in the warmer locations. Upstream, a
line of showers and thunderstorms has developed along the surface
trough and just ahead of an 500H vort max. This line has largely
behaved so far this afternoon, though a few segments have been
strong with gusts up to around 40 mph.

Through the remainder of the afternoon through mid-evening, the
shortwave trough and the attendant line of convection will pass from
west to east over eastern Kentucky, largely exiting through Pike
County by about 9 PM. The combination of weak-moderate instability
(~1000 J/kg of MLCAPE) and modest shear (30-40 kts EBWD) under a
passing 40-50+ kt 500mb jet will support a severe thunderstorm
threat, especially over the northwestern portions of the JKL CWA
through, at least early evening. The primary severe threat appears
to be damaging wind gusts with linear convective segments.
Supercellular structures are also possible, but weaker winds toward
the equilibrium level should limit cell intensity and longevity. If
a supercell structure develops, an isolated instance of large hail
or a brief isolated tornado cannot be ruled out. The counties of
greatest concern has been placed under a Severe Thunderstorm Watch
through 7 PM. Further south and east, the shear and instability will
be weaker, limiting or inhibiting the severe threat.

A few showers could linger overnight but forcing will be limited to
just a few passing subtle disturbances in the southwest flow aloft.
However, plenty of low-level moisture should support abundant low
clouds and perhaps some fog in places. Overnight temperatures will
be mild, generally settling into the lower 60s. Looking ahead to
Friday, weak height rises in the morning/midday should favor mainly
rain-free conditions for most. However, another upper-level
disturbance ejects out of the large scale trough to our west and
lifts across the Lower Ohio Valley during the late afternoon and
evening. The 15z RAP is supportive of up to 2,000 J/kg of MUCAPE
building ahead of the disturbance, fueling the potential for
additional showers and thunderstorms, primarily Friday evening;
however, the shear for overall storm organization remains weak
(generally under 30 knots). Linear shower/thunderstorm
clusters/segments are possible with damaging winds again the primary
concern. Expect another warm day with high temperatures in the upper
70s to lower 80s.

.LONG TERM...(Friday night through Wednesday)
Issued at 420 AM EDT THU MAY 1 2025

The period is expected to begin with upper level ridging extending
from the Caribbean into portions of the western Atlantic and
centered near Bermuda, upper level troughing from Canada to Lake
Huron to the upper MS Valley to sections of the Central to Southern
Plains, with another ridge over portions of the western Conus, and
another upper level trough over the eastern Pacific nearing the west
coast of Conus. At the surface, as the period begins, an initial
area of low pressure associated with a shortwave moving across
Canada is expected to beg nearing the St Lawrence Valley with a
frontal zone trailing into the eastern Great Lakes to OH valley to
Southern Plains. A secondary cold front in advance of the 500 mb
trough axis should extend from the Central Great lakes to mid MS
Valley to Central Plains as the period begins with surface high
pressure centered in the Northern Plains/Dakotas.

Friday night to Saturday night, the northern portion of the upper
level trough initially extending from Canada into the Central Conus
is expected to shear to the east and northeast across Hudson Bay and
into Quebec while the southern portion in the central Conus shifts
to the MS Valley and east of the MS River with a closed low forming
in the OH Valley vicinity with upper level ridging building east into
the Central Conus/Plains. Further west the upper trough is expected
to move into the western Conus/western Canada with the southern
portion of it also closing off over the southwest Conus/Canada.
Meanwhile the first surface front should move into eastern KY and
the Appalachians and become diffuse on Friday night with the next
upstream frontal zone becoming more significant as it enters the OH
Valley on Friday night. As the upper level low develops, a sfc low
should develop along this boundary is expected to track from the
Lower OH Valley to east of the Appalachians from Saturday through
Saturday night with the trailing cold front likely crossing central
and eastern KY later Saturday into Saturday night downstream of the
developing upper level low. Across eastern KY ahead of the more
significant boundary crossing the area later Saturday into Saturday
night, moisture transport back into the region is expected to yield
values in the 1.1 to 1.3 inch range per 0Z GEFS and 0Z ENS ensemble
means. PW values are expected to decrease below 1 inch in all areas
on Saturday night as the deeper moisture departs to the east.
Although convection is possible to begin the period, the approaching
sfc front and low pressure system as well as the upper level system
should result in more widespread coverage of showers and some
thunderstorms across the entire region from later Friday night into
Saturday evening. Areawide average rain totals during this time are
expected to generally range from about 0.8 to 1.5 inches though
locally higher totals may occur in locations impacted by multiple
thunderstorms. In any locations impacted by significant rainfall later
today and Friday, there remains some concern for localized instances
of mainly urban and small stream flooding and the region has a
marginal Excessive Rainfall Outlook for Friday night into Saturday.
A stronger storm or two is also not out of the question on
Saturday. With anticipated clouds and showers in the area, highs
for Saturday are expected to be in the mid 60s to low 70s, or
below normals which are in mainly the low to mid 70s.

Sunday to Monday night, the upper level low is expected to meander
in the vicinity of the OH Valley per the consensus of guidance while
upper ridging shifts east to the Gulf and over the Central Conus and
the western Conus upper low meanders over the Southwest Conus and
toward the Four Corners region. With deeper moisture having
departed, concerns for heavy rain end though with the upper low in
the vicinity periods of clouds and chances for showers linger
especially on Sunday with a general minimum in chances both Sunday
and Monday nights. Temperatures should average 5 to 10 degrees below
normal mainly for highs for both Sunday and Monday.

Tuesday to Wednesday, the upper level low initially over the OH
Valley to Southern Great Lakes region is expected to gradually
depart to the east and northeast through midweek with increases in
mid level heights at that point. Small chances for showers will
linger, especially during both Tuesday and Wednesday afternoons with
temperatures moderating to around normal at midweek.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 208 PM EDT THU MAY 1 2025

VFR conditions prevail at TAF sites and issuance time. However, a
boundary approaching from the west will bring the increasing
threat for showers and thunderstorms later this afternoon into
this evening. Ahead of front, southwesterly winds of 7 to 13 kts
with gusts up to 25 kts are anticipated. Once showers and storms
arrive, expect temporary reductions in flight categories as well
as well as gusty and erratic winds. Some of the storms could be
strong to severe, especially toward the I-64 corridor with
damaging wind gusts the primary threat. An isolated instance of
large hail cannot be ruled out. A lull in the activity is
expected tonight, though additional rounds of showers and storms
are likely later Friday on into Saturday.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...GEERTSON
LONG TERM...JP
AVIATION...GEERTSON