809
FXUS63 KPAH 270928
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
428 AM CDT Fri Sep 27 2024

.KEY MESSAGES...

- Widespread showers with heavy rain will continue through this
  evening as the remnants of Hurricane Helene interact with an
  upper-level storm system near the Quad State. Forecast
  rainfall in this period currently ranges from around 2 to 4
  inches across the area with locally higher amounts possible.

- A Flood Watch and Wind Advisory have been issued due to
  conditions from the remnants of Hurricane Helene with the
  Flood Watch now expanded to include all but the western four
  counties of Southeast Missouri.

- The rains will become lighter and more isolated through the
  weekend, while winds remain breezy Saturday then become light
  on Sunday.

- The Quad State will begin to dry out on Tuesday as a cold
  front passes.

&&

.DISCUSSION...
Issued at 428 AM CDT Fri Sep 27 2024

Hurricane Helene barreled into the Big Bend region of Florida as
a Category 4. A fast forward motion (30 mph at the 4AM CDT
update) has taken the center of the storm to east-central
Georgia, heading northward. The storm center is east of the
prior forecast track, likely a complication due to the messy
interaction with a cutoff low near the Quad State. While Helene
appears to be taking a wider turn than originally anticipated,
it is expected to shift northwestward to the Tennessee River
Valley and approach Central KY/TN border this evening. From
there, the storm stalls out and gets wrapped up into the upper-
low through the weekend.

Two primary hazards are expected with Hermine. The first is
heavy rainfall and potential for flooding. Rainbands ahead of
Hermine are already being steered into the Quad State due to the
influence of the upper low. With the storm center moving closer
through the day today, moderate to heavy showers will continue
to be widespread. WPC QPF is generally around 2-5 inches of
additional rainfall to go with the inch or so that has already
fallen in eastern and northern portions of the Quad State.
Much of the Quad State have been very dry of late, though some
spots received decent rainfall yesterday, and portions of
Southern Illinois faced torrential rainfall Monday evening, so
a few spots are a bit more primed for flooding issues.
Precipitable water rises to 2 to 2.25 inches today, especially
high for this time of year. Instability is poor and the
Appalachians may hinder some moisture transport, but the storm
should be able to overcome that for now. The key to flooding
development will be whether 1 to 3 hr rainfall rates can get
high enough, likely leaving flooding issues localized. The Flood
Watch has been expanded northward to include the entire CWA
except for the western four counties of SEMO. The expansion
territory may not receive as much rain on average, but includes
some of the more primed areas. The upper low continues absorbing
much of the remnants of Helene through the weekend, but
rainfall rates will diminish, ending the flood threat. A few
showers may remain in the east Monday as the system finally
departs.

The second primary hazard is gusty winds that could be damaging.
The fast forward motion and rapid intensification before
landfall brought stronger tropical storm force wind gusts
further inland than is typical, and models suggest a slow
increase in pressure. HREF winds are overestimating winds at
this time with gusts closer to 20 mph instead of a modeled 30
mph. This isn`t surprising due to the tendency towards
decoupling overnight in the Quad State. Late afternoon to early
evening wind gusts in the HREF are concerning with mean gusts
of 50-55 mph in the north and 40-50 mph elsewhere. The 75th
percentile flirts with High Wind Warning criteria. The focus for
the stronger gusts is positioned northeast of the Quad State,
prompting a High Wind Warning issuance by the Indianapolis and
Louisville offices. Global models have lower gusts, and
negligible thunderstorm potential will prevent full mixing of
winds aloft. However, those winds aloft are howling with HREF
mean 850mb wind gusts around 70 mph in the north during the
afternoon. With the strongest gust potential northeast of the
Quad State (and perhaps becoming more likely to stay there if
the storm takes a wider turn before heading northwest), we will
stick with a Wind Advisory for now. Winds noted in the product
have been increased to 20-30 mph sustained with gusts of 45-50
mph broadly and gusts to 55 mph in the Evansville Tri-State and
I-64 corridor. Wind gusts will need monitoring today to
determine whether an upgrade to a High Wind Warning is needed.
Either way, soggy soils as rainfall continues to occur will make
trees susceptible to wind damage.

The system lingers through the weekend, with breezy winds
Saturday gusting to 30 mph. Rainfall amounts will be much
lighter, ending flood potential. Winds finally become light
Sunday as the system weakens. Shower activity ends Monday with
the departure of the upper low. A cold frontal passage Tuesday
brings in cooler and drier air as high pressure moves eastward
into the Quad State.

Highs near 70 today and tomorrow trend warmer as skies become
more clear, topping out in the upper 70s to lower 80s Tuesday
before the cold front drops highs to the 70s again. Lows in the
mid-60s this morning remain elevated as long as Gulf moisture
streams in, then fall to the lower 50s following the Tuesday
cold front.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1123 PM CDT Thu Sep 26 2024

Rain is steadily increasing across the area and will become even
more widespread overnight through Friday. This will lead to IFR
conditions and possibly lower will through much of the rest of
the TAF issuance. The very heavy tropical downpours will also
lead to reduced visibilities as low as 2 miles or less at times.
Winds are expected to become gusty from the northeast Friday
with gusts reaching into the 25 to 35 kt range.


&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Flood Watch through Saturday morning for ILZ075>078-080>094.
     Wind Advisory from 7 AM this morning to 1 AM CDT Saturday for
     ILZ075>078-080>094.
MO...Flood Watch through Saturday morning for MOZ076-086-087-
     110>112-114.
     Wind Advisory from 7 AM this morning to 1 AM CDT Saturday for
     MOZ076-086-087-100-107>112-114.
IN...Flood Watch through Saturday morning for INZ081-082-085>088.
     Wind Advisory from 7 AM CDT /8 AM EDT/ this morning to 1 AM
     CDT /2 AM EDT/ Saturday for INZ081-082-085>088.
KY...Flood Watch through Saturday morning for KYZ001>022.
     Wind Advisory from 7 AM this morning to 1 AM CDT Saturday for
     KYZ001>022.

&&

$$

DISCUSSION...ATL
AVIATION...KC