131
FXUS63 KJKL 270015
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
815 PM EDT Thu Sep 26 2024

.KEY MESSAGES...

- The remnants of tropical system Helene will bring a widespread,
  soaking rain event into Friday.

- Flash flooding could result from the remnants of Helene, but the
  overall potential may be limited by its quick movement.

- Wind gusts of generally 40 to 60 mph are expected at times from
  late tonight into Fri as the remnants of Helene pass by.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 455 PM EDT THU SEP 26 2024

Late this afternoon, an upper level ridge was centered to the
west of Bermuda with another upper level ridge extending from the
Southern Rockies to the upper MS Valley. An upper level low was
centered near the confluence of the MS and OH Rivers while Major
Hurricane Helene continues to move north in the northeastern Gulf
of Mexico and headed toward northwest portions of FL. A nearly
stationary frontal zone remains from low pressure in Quebec to
the upper OH Valley to eastern KY to northwest FL to the
northwestern Gulf of Mexico. The upper level low continues to
interact with the boundary and moisture transported into the
region for a continued precursor rain event (PRE). Rain continues
to move from eastern TN north into much of eastern KY at this
time.

Tonight and Friday, the upper level low is expected to move south
to northeastern MS/northwest AL with this upper low and Hurricane
Helene more or less moving into Fujiwhara fashion with Helene
tracking quickly across northwest and FL and southern and central
GA. This will then move across the Southern Appalachian region
and then to the Cumberland Plateau through early to mid afternoon
on Friday, gradually weakening and becoming extratropical. Bands
of rain more closely associated with Helene are expected to cross
the region tonight through Friday morning as the pressure
gradient also increases between Helene and high pressure north of
the eastern Great Lakes vicinity. These winds will have a
downslope component a times, but PW will rise near or in excess of
2 inches tonight remain at those levels into the morning before
dry slotting works northwest on Friday afternoon. As Helene nears,
a general additional soaking rainfall should occur areawide. Some
locally more intense rain of 3 or more inches could occur in a
band somewhere across eastern KY per some CAM runs, though a
general 1 to 2.5 inches of rain expected through Friday evening.
Winds and wind gusts are also a concern and in addition to a flood
watch in effect generally south of the Mtn Pkwy. Areas generally
south of the Mtn Pkwy have either had more rain over the past 3
days and/or are expected to have the highest totals on average.

12Z HREF mean wind gusts increase to 40 mph or higher across the
highest terrain along the VA border toward midnight with the
stronger gusts progression to the north and northeast through the
remainder of the night. Some of this is not expected to be realized
in the deeper valleys before sunrise. However, 12Z HREF mean
brings wind gusts to near or in some instances than 60 mph
northwest across much of the area Friday morning to early Friday
afternoon, before gradually slackening. Momentum is likely to mix
down as a dry slot moves in behind a morning band of rainfall.
Higher elevation locations will experience a longer period where
stronger wind gusts are possible from late tonight into early
Friday afternoon. A High Wind Warning was issued for Bell, Harlan,
and Letcher County from 11 PM tonight to 8 PM on Friday with
another tier of High Wind Warnings to the north and west 2 AM on
Friday to 8 PM on Friday which generally has elevations of 1500
feet or higher or where soil moisture is highest/heavier rain has
fallen over the past 3 days or so. A Wind Advisory was issued for
areas further northwest, but gusts to around 60 mph area possible
especially in the eastern Bluegrass region and on ridges and
further adjustments to headlines may be needed. 12Z HREF
probabilties of 60 mph gusts or higher are significant over much
of the area at 50 to 100 percent. The 18Z HRRR wind gusts are in
general agreement with the HREF values. So in summary, tonight,
the strongest wind gusts of 40 mph or more are expected in the
High Wind Warning area later tonight, especially on ridges, with
wind gusts peaking across the region during Friday morning to mid
afternoon on Friday.

From late Friday into Friday night, the upper level low and Helene
will gradually merge with the combined low meandering over the
Lower OH Valley region. Following a relative lull in chances for
showers on Friday afternoon and evening with the dry slotting,
moisture is progged to increase from west to east late Friday
night with an associated increase in shower chances from west to
east.

.LONG TERM...(Saturday through Thursday)
Issued at 225 PM EDT THU SEP 26 2024

The forecast period begins with the area still largely under the
impacts of the remnants of Hurricane Helene. At upper-levels, the
remnants of Helene will begin to merge with a largely stationary cut-
off circulation that`s been situated over western Kentucky through
much of this week. As the two systems merge into one circulation,
shower and storm chances will persist through the day Saturday and
linger through the weekend. Models continue to remain in rather good
agreement going into next week with the circulation getting picked
up by the mean flow and ejecting out of the area by Monday morning
but lingering PoP chances will exist through the end of the period
as an upper-level trough, moving through southern Canada, drags a
cold front through the region Tuesday afternoon which will then
usher in cooler and drier weather for the middle of next week.

Overall, the forecast period will be highlighted by multiple rounds
showers and storms. Shower and thunderstorm chances drop a little
bit with the merging of the closed circulation and the remnants of
Helene but chances (40-70%) exist through the weekend. Temperatures
through the period will remain rather seasonal as highs are forecast
to in the upper-60s to upper-70s. Overnight lows, will be warmer
with the insulation of the system overhead but with the approach of
a cold front on Tuesday, cooler temperatures and fall-like weather
will be in place for the end of the period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 815 PM EDT THU SEP 26 2024

Variable aviation conditions were observed at TAF issuance time as
areas of low clouds and showers continued impact eastern
Kentucky. Conditions range generally between IFR and VFR on
average, but localized LIFR was present at a few terminals closer
to the Virginia border. A rumble of thunder is possible overnight,
but confidence in any affecting a particular TAF site remains too
low the mention. An uptick in the rainfall rates should occur in
bands ahead of Helene tonight as well as on Friday morning. Winds
will average from the east at 5 to 10 KT to begin the period and
then become east and northeast at 10 to 20 KT, with gusts up to
around 30KT by 12Z. Winds should increase from the northeast
between 12Z to 18Z to as high as 15 to 25KT and begin to trend to
the southeast for southern locations to end the with gusts up up
into the 35 to 50KT range through at least 19Z. LLWS will also be
a threat later tonight into Friday morning, as well, with winds
as high as 50 KT a thousand feet off the sfc generally blowing
from the east or northeast and then trending toward southeast
after 18Z.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 5 AM to 8 PM EDT Friday for KYZ044-050>052-
058>060-068-069-079-083-104-106>109-111-112-114-119.

Flood Watch through Friday evening for KYZ058-068-069-079-080-
083>088-107>120.

High Wind Warning from 2 AM to 8 PM EDT Friday for KYZ080-
084>086-110-113-115>117-120.

High Wind Warning from 11 PM this evening to 8 PM EDT Friday for
KYZ087-088-118.

&&

$$

SHORT TERM...JP
LONG TERM...VORST
AVIATION...GEERTSON/JP