101
FXUS63 KJKL 270950
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
550 AM EDT Fri Sep 27 2024

.KEY MESSAGES...

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

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

- Wind gusts of generally 40 to 60 mph are expected at times today
  as the remnants of Helene pass. Locally higher wind gusts are
  possible.

&&

.SHORT TERM...(Today through Saturday)
Issued at 545 AM EDT FRI SEP 27 2024

09Z sfc analysis shows the quickly tightening pressure gradient
approaching Kentucky as, still a hurricane, Helene lifts toward
Kentucky. This system has spread copious amounts of rain over the
area through the night helping to saturate the soils. It is also
starting to push the higher winds into the this part of the state
with the highest elevations affected first but some stronger gusts
are starting to make it into the lower lands. Currently, under
cloudy skies, temperatures and dewpoints are well mixed and
uniform in the middle to upper 60s. Easterly winds are gusting to
30 mph on the higher observation sites with those values expected
to climb towards dawn.

The models, and their individual ensemble suites, remain in
pretty good agreement aloft through the short term portion of the
forecast despite a highly anomalous situation involving the
landfalling hurricane intertwining with the persistent 5h low to
the west of the area. This dance brings the remnant core of Helene
to our doorstep just after sunrise with ample mid level energy
wrapping around the reinvigorated upper low. This synoptic
pattern will help to keep the system stronger than normal for
these situations with all the attendant sensible weather concerns
through the day, today. These concerns start to diminish this
evening as the remnants transitions to extratropical and we deal
with a deep 5h low meandering over the state generally holding to
our west through Saturday. While the model spread is small for
this situation, the NBM appears to be struggling in comparison to
the higher resolution CAMs through the short term with respect to
key details such as wind speeds, gusts, and rainfall. Adjustments
were made to the forecast for these elements into Saturday.

Sensible weather features a very active and concerning weather
day across eastern Kentucky as the remnants of Helene lift through
the area with high winds and excessive rains the primary threats.
For the rain, bands of tropical moisture and efficient warm rain
processes will wring out between 2 and 3 inches of rainfall with
locally higher amounts through the early evening hours. For this
reason, along with the antecedent rains of the past week, we have
extended the flood watch for the almost the entire area - pushing
the boundaries north on account of the last couple of the Helene
rainbands modeled to pivot through that part of the area as it
retrogrades to the west.

Winds are the other big concern with definitive mid level drying
arriving from the east by midday and likely prompting the high
winds aloft to mix to the sfc for a time later this morning into
the afternoon. Accordingly, in addition to the higher winds above
1500 and 2000 feet in the southeast this morning we look for winds
in excess of 60 mph to reach the sfc on account of the drying and
a building - again anomalous - easterly jet at 925 mb. The HREF
and the individual CAMs show this threat clearly so we have
upgraded the existing Wind Advisory for much of the area outside
of the southeast to a High Wind Warning. Of greatest concerns will
be the trees still flush with leaves and certain to be heavier as
they are wet along with soaked soil around their rootballs
leading to them being more easily toppled. Finally, pointing out
the anomalous high wind direction for a third time, these trees
probably have not been stressed from that direction too much
through their life-cycle. The strong wind gusts will also be a
threat to high profile vehicles - especially those on north to
south oriented roads such as I-75. The winds should maximize in
the Bluegrass and I-64 corridor from around noon through 4 pm before
they gradually start to settle into the evening hours.

Otherwise, temperatures will be warmer than normal in the east
today, on account of the afternoon drying, and seasonable on
Saturday though high dewpoints will keep the humidity up and make
for another mild night. Patchy fog will be around through the day
with the rain - and tonight with any temporary clearing. The
stacked low overhead will then slowly move east on Saturday
bringing high chances of showers back into the area along with
more cloud-filled dreariness.

The changes to the NBM starting point mainly consisted of again
increasing winds and winds gusts per the CAMs today into tonight,
as well as adding in more details from those higher resolution
models for PoPs and QPF through the afternoon and again on
Saturday.

.LONG TERM...(Saturday night through Thursday)
Issued at 327 AM EDT FRI SEP 27 2024

After the remnants of the Helene fujiwara with the mid-level low
in parts of West Tennessee, it will become vertically stacked
Friday night and this mid-level low will slowly meander eastward
through early next week. This will keep the weather active with
periods of showers and at times a few thunderstorms through
Tuesday and there seems to be good agreement on this in the
deterministic and ensemble outputs. The rain chances will
generally peak in the afternoon hours each day. WPC does keep a
small risk of flooding Sunday given the rainfall expected with the
remnants of Helene, but this will be highly dependent on how the
activity pans out today.

There is good agreement in the ensembles and deterministic guidance
on a northern stream trough axis pushing toward the Great Lakes and
helping push the mid-level low and opening it up as it heads east.
This northern stream trough will also usher a cold front eastward
across the Ohio Valley. This will aid in bringing in a drier weather
pattern and cooler morning starts eastern Kentucky by mid and late
week. Given this opted to decrease valley lows closer to the tenth
percentile of the NBM, with valleys dropping into the mid and upper
40s Wednesday and Thursday mornings.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 155 AM EDT FRI SEP 27 2024

Generally MVFR to IFR conditions were observed at TAF issuance
time as areas of low clouds, fog, and widespread showers continued
to impact eastern Kentucky. A rumble of thunder remains possible
into Friday morning, but confidence in any affecting a particular
TAF site remains too low to mention. An uptick in the rainfall
rates is underway as the bands ahead of Helene push into the area.
Winds will average from the east to northeast at 5 to 10 kts,
with some higher gusts, to begin the period increasing quickly to
10 to 20 kts sustained, with gusts up to around 30 kts by 12Z.
Winds will then continue to increase from the northeast between
12Z to 18Z to as high as 20 to 30 kts and begin to trend to the
southeast for southern locations to end up with gusts in the 35
to 50 kts range through at least 20Z. LLWS will also be a threat
later this night into Friday morning, with winds as high as 60 kts
a thousand feet or so off the sfc generally blowing from the east
to northeast initially - trending toward southeast after 18Z.
Things start to settle toward the end of the aviation period, but
low clouds will likely remain in place for most locations.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 10 AM this morning to 8 PM EDT this
evening for KYZ044-050>052-058>060-068-069-079-104-106-108-111.

Flood Watch through this evening for KYZ050>052-058>060-068-069-
079-080-083>088-104-106>120.

High Wind Warning until 8 PM EDT this evening for KYZ080-084>088-
110-113-115>118-120.

Wind Advisory until 8 PM EDT this evening for KYZ083-107-109-112-
114-119.

&&

$$

SHORT TERM...GREIF
LONG TERM...DJ
AVIATION...GEERTSON/GREIF