981
FXUS63 KLMK 260152
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
952 PM EDT Wed Sep 25 2024

.KEY MESSAGES...

*  Widespread moderate to heavy rain and windy conditions on Friday
   as the remnants of Hurricane Helene move through the Lower Ohio
   Valley.

*  Potential for 2 to 4 inches of rain from late Thursday night to
   early Saturday morning. Locally higher amounts are possible.

*  Wind gusts of 35 to 45 mph are possible during the day Friday as
   the center of Helene works into KY and the Ohio Valley.

&&

.UPDATE...
Issued at 951 PM EDT Wed Sep 25 2024

Earlier showers along the I-75 corridor have dissipated as the
better moisture feed is now shunted well to the east, more along the
spine of the Appalachians.  Sfc cold front still analyzed over
eastern Kentucky and mid-level flow is still out of the south, so
not out of the question that we could still get a stray shower
overnight. Have cut POPs back slightly but still in the 20-40% range
along/east of Highway 127.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 336 PM EDT Wed Sep 25 2024

A weak north-south oriented cold front will remain over eastern
Kentucky tonight as its parent low moves NNE through western Quebec
and a 5H low spins in place near the confluence of the Ohio and
Mississippi rivers. Moisture ahead of the front and the upper low
will bring widespread clouds to the region, along with some
scattered light rain showers east of I-65 closer to the surface
boundary. Any rain tonight would be very light.

The upper low will sink slightly south toward Memphis tomorrow as
the surface boundary to our east remains roughly in place and
continues to weaken. Similar to today, widespread clouds and
scattered light rain showers can be expected, with only light
precipitation amounts while breezes come in from the east around 5
to 10 mph. The effects from Helene`s remnants will hold off until
just after the Short Term period.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 336 PM EDT Wed Sep 25 2024

The main focus in the long term will be Helene and how it impacts
our region for the end of the week and into the weekend. Main
impacts continue to be the potential rainfall as well as strong
gusty winds associated with the system as it moves into the Ohio
Valley.

As of the 11am EDT update, Helene had become a category 1 hurricane
with the National Hurricane Center forecast anticipating Helene to
rapidly intensify into a potential category 4 hurricane over the
next 36 to 48 hours before making landfall along the FL Panhandle
Thursday evening. The current NHC track for Helene appears to be a
bit further west and south compared to the 12z run of the
deterministic models, which brings the center of the storm northward
through GA then more into eastern KY before hooking it to the west
and meandering over the area into the weekend as it weakens further.

Our first impacts from Helene will be felt Thursday night into early
Friday morning as moderate to potentially heavy rain work in from
the south as the system quickly works through GA as it slowly
weakens. Rainfall amounts could range from a quarter of an inch near
and just south of the Parkways to nearly an inch along the KY/TN
border. Rain will continue during the day on Friday as Helene works
into the Ohio Valley then starts to hook and loop back to the west
Friday night into Saturday. An additional 1 to 2 inches will be
possible across our CWA from 12z Friday to 12z Saturday. Total
rainfall from Helene is still anticipated to range between 2 to 4
inches with locally higher amounts possible.

The second impact will be the potential for strong advisory criteria
wind speeds and gusts during the day on Friday. NBM has continued to
trend too low on its wind values for Friday and with the 12z HREF
Ensemble probability of wind gusts equal or greater than 40 mph by
12z Friday is between 80-100% with EURO Ensemble showing the same
during the day on Friday. While confidence is becoming high we will
likely need a wind headline in the form of a Wind Advisory on
Friday, locations needed in the advisory remain in doubt. Like the
rain mentioned above, the wind forecast will be determined on how
much Helene weakens as it works northward through GA and where the
center of the storm will be located as it reaches KY and the Ohio
Valley on Friday. Given this uncertainty, opted not to issue any
weather headlines at this time.

As Helene transitions into a post-tropical cyclone over the weekend,
showery weather will linger as it merges with the upper low over the
Ohio Valley. It will then open up and exit off to the east northeast
as we start next week.

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 743 PM EDT Wed Sep 25 2024

Upper low over southern Illinois, with moist southerly flow bringing
plenty of cloud cover northward across Kentucky. Low clouds are just
scattering out of LEX and RGA, while SDF, BWG, and HNB are now VFR.
Expect light/variable winds overnight with a mid-level ceiling. With
LEX and RGA being the last to scatter out, some MVFR fog isn`t out
of the question toward daybreak Thursday.

E-NE winds will gradually pick up to around 10 kt through the day,
with lowering cigs as moisture advection increases ahead of Helene.
Not confident enough that rain will arrive during the TAF period,
but did include PROB30 for late afternoon activity in the east and
south.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

UPDATE...RAS
SHORT TERM...13
LONG TERM...BTN
AVIATION...RAS