677
FXUS62 KCAE 270612
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
212 AM EDT Fri Sep 27 2024

.SYNOPSIS...
Hurricane Helene has moved onshore and is currently moving into
south central GA. Widespread rain, flash flooding, very strong
and gusty winds along with isolated tornadoes remain possible
through late this morning. Confidence in impacts remains high
with tropical storm force winds as the primary threat. The
storm is expected to move west and north of the area Friday with
diminishing winds. Dry weather is expected Saturday into early
next week along with seasonal to slightly above normal
temperatures.

&&

.NEAR TERM /THROUGH TODAY/...
Key Messages:
- Hurricane Helene marching northward overnight and passing west
  of the area early this morning
- Tropical Storm Warning in effect for the entire CWA. Potential
  for gusty winds of 50-60 mph, especially in the CSRA.
- Tornado threat continues with a Tornado Watch in effect until
  8 AM Friday morning.
- Flood Watch in effect 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.

Overnight through Friday Morning:

Hurricane Helene has moved onshore and continues marching
rapidly northward into south central GA. CAE WSR-88D returns
show widespread rain across the area with regional network
showing rain blanketing the region. Hazards through this morning
continue to focus on the very strong and gusty winds isolated
tornadoes, heavy rainfall, and localized flooding.

Wind: A Tropical Storm Warning remains in effect for the entire
CWA. Hurricane Helene 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. Wind gusts up to 60 mph
are possible through this morning. 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. 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 this
morning. A Flood Watch is in effect through Friday afternoon for
portions of the forecast area. Rainfall thus far from Helene
shows numerous locations already in excess of 4 inches with
additional rain likely to result flooding issues.

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 ranging from around 80 in the
west to the mid 80s in the east.

&&

.SHORT TERM /TONIGHT 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 /06Z FRIDAY THROUGH TUESDAY/...
Restrictions to dominate the first half of the period with
conditions improving from mid morning through the end of the
period.

Hurricane Helene will be marching northward through the day and
pass west of the terminals. Numerous concerns through the period
with very strong and gusty winds topping the list. Sustained
speeds increasing to 35-40 kts and gusts of 50-60 kts at times,
particularly at AGS/DNL. Exceptionally strong winds will also be
present aloft. Rain will also continue and become heavy at times
with vsbys generally between 3 and 5 miles and cigs between 800
and 1500 feet. Conditions will begin improving during the late
morning hours as Helene passes to the west with winds slowly
subsiding through the day and clouds diminishing. Expect VFR
conditions from midday through the end of the period however
winds will remain a concern.

EXTENDED AVIATION OUTLOOK...No significant impacts to aviation
expected through Tuesday.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...Flood Watch through this 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 this afternoon for GAZ040-063>065-077.
     Tropical Storm Warning for GAZ040-063>065-077.
&&

$$