268
FXUS62 KCAE 261618
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
1218 PM EDT Thu Sep 26 2024

.SYNOPSIS...
Hurricane Helene is forecast strengthen into a major hurricane
in the eastern Gulf of Mexico as it approaches the Florida
Panhandle region. Widespread rain and severe weather will become
increasingly likely across the area by tonight. Uncertainty
remains in the exact track and impacts of the system. However,
confidence in impacts is increasing with tropical storm force
winds as the primary threat. A few tornadoes will be possible
through Friday morning along with flash flooding. The storm is
expected to move west and north of the area Friday with
diminishing winds.

&&

.NEAR TERM /TONIGHT THROUGH FRIDAY/...
Key Messages:
- Conditions deteriorate through the daytime hours as Hurricane Helene
  moves north, passing to our west tonight.
- Tropical Storm Warning in effect for the entire CWA. Potential
  for gusty winds in excess of 40 mph, especially tonight.
- Tornado threat increases, peaking this evening into tonight.
- Flood Watch in effect this morning through Friday afternoon
  for the CSRA and southwestern Midlands. Areas of heavy
  rainfall could result in flash flooding, especially south and
  west of I-26.

This afternoon through Friday Morning:

As of the 11am NHC advisory, Hurricane Helene has maximum
sustained winds of 105 mph and continues to strengthen in the
southeastern Gulf of Mexico. Not much change with the latest
forecast track brings the hurricane ashore this evening in the
Florida Panhandle, rapidly moving northward through Western
Georgia tonight. Rain chances will continue to rise ahead of the
cyclone as tropical moisture and isentropic lift increase
across the region. The most significant impacts are expected
this evening continuing through the overnight hours. Potential
hazards from Helene include strong wind gusts, isolated
tornadoes, heavy rainfall, and localized flooding.

Wind: A Tropical Storm Warning is in effect for the entire CWA. The
hurricane has an unusually large wind field for a tropical
cyclone in the lower latitudes and will be transitioning to an
extra-tropical cyclone after landfall resulting in a tricky
wind forecast for the Midlands and CSRA. What we can say with
higher confidence is that the strongest winds are likely across
the CSRA and Southwestern Midlands which will be closer to the
cyclone center. There will be a potential for the stronger winds
to cause localized wind damage including isolated to scattered
power outages.

Tornadoes: With Helene forecast to pass to our west, this places the
FA in the right-front quadrant of the cyclone which is a favorable
location for tropical tornadoes. The combination of strong 0-6
km wind shear and increasing helicity will support tornado
development in any thunderstorms that develop. The greatest risk
will come tonight in rainbands associated with Helene. It is
important to note that many, but not all, tropical tornadoes
develop quickly and are short lived resulting in limited lead
time. This threat is compounded by the timing of greatest risk
which is during the overnight hours.

Heavy Rainfall and Flash Flooding: Rainfall chances basically
categorical or close to if not 100 percent overnight into Friday
morning.  A Flood Watch in effect this morning through Friday
afternoon for portions of the forecast area. Rainfall amounts
are likely to be highest closest to the track. Forecast rainfall
amounts vary greatly from east to west with the potential for
2-5" inches of rainfall with locally higher amounts in the watch
area.

Outside of the tropical hazards, small diurnal drop off overnight
with lows expected to fall into the low to middle 70s.

Friday late morning through Friday afternoon:
The remains of Helene will rapidly track off to the northwest of
the area, towards central TN and KY through the day. Rainfall
will be ending towards noon time, and conditions will improve
through the afternoon. Afternoon highs will moderate somewhat
with the return of some sunshine.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
Key messages:
- A closed upper low over the Ohio River Valley this weekend
  with a chance of showers mainly north of I-20.
- River Flooding expected to be occurring.

A closed upper level low pressure system over the Ohio River Valley
absorbs TC Helene Friday Night and then crawls eastward toward the
Mid Atlantic States this weekend. The best chance for showers
appears to be on Sunday with the upper low directly to the north of
the Carolinas. Temperatures are expected to be slightly above normal
for the end of September.

The excessive amount of rainfall which will continue to fall in
Upstate SC during the passage of TC Helene is expected to increase
river flows to minor to moderate flood stage this weekend.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Key Messages:
- Drier and continued warm conditions expected next week.

A pesky closed upper level low pressure system moves offshore and
begins to open up on Monday and is gradually replaced by above normal
H5 heights. This should result in dry weather and temperatures
3 to 5 degrees above climatology for early October. Some river
levels should drop below flood stage by mid week.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Conditions expected to continue to deteriorate at the Terminals
through tonight. Some improvement possible late in the taf
period on Friday.

Rain and embedded thunderstorms continue to increase in
coverage while ceilings continue to fall. Although there may be
brief periods of vfr between rain bands, majority of taf
locations will be mvfr/ifr into Friday morning. East to
southeast winds will generally be between 5 and 10 knots for
much of the day, increasing this evening as Helene approaches
the region. Restrictions are expected to be widespread and
persistent tonight with low ceilings, isolated to scattered
thunderstorms, heavy rainfall, and strong winds both aloft and
at the surface.

EXTENDED AVIATION OUTLOOK... Restrictions are possible into Friday
morning as Helene passes west of the forecast area. Low ceilings,
heavy rainfall, and strong winds are possible.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...Flood Watch through Friday afternoon for SCZ016-018-020>022-
     025>028-030-035-037-041-115-116-135-136.
     Tropical Storm Warning for SCZ016-018-020>022-025>031-035-037-
     038-041-115-116-135>137.
GA...Flood Watch through Friday afternoon for GAZ040-063>065-077.
     Tropical Storm Warning for GAZ040-063>065-077.
&&

$$