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658
FXUS62 KFFC 251410
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
1010 AM EDT Wed Sep 25 2024

...Morning Update...

.UPDATE...
-- Changed Discussion --
Issued at 1004 AM EDT Wed Sep 25 2024

Latest radar imagery shows light rain showers spreading over
portions of North GA (as far south as I-20) this morning. This
activity is in association with a surface trough situated across
northwest GA and a frontal boundary a little further back to the
west. We are expecting rain showers and thunderstorms to overspread
the region through the day today as the frontal boundary sags south
and east. Thunderstorm chances look to peak during the afternoon and
an isolated strong or severe storm cannot be ruled out as heating
will be greatest around this time along with ample shear. With
increasing clouds and rain in the area, temperatures should not be
oppressive today -- current temperatures are in the 70s and for
most of the area today these shouldn`t fluctuate too much.
Southeast GA, where there are slightly less clouds and lower rain
chances, temperatures will once again climb into the 80s this
afternoon. The forecast largely remains on track and only a few
updates were made to reflect current trends.
-- End Changed Discussion --

&&

.SHORT TERM...
(Today through Thursday)
Issued at 330 AM EDT Wed Sep 25 2024

A weak trough is situated across NW GA early this morning. The
trough is fairly well depicted on the regional radar pictures,
where convection has formed. A weak frontal boundary is situated a
little further west and should continue to push eastward through
the period. Tropical moisture will continue to interact with the
boundaries and is expected to bring locally heavy rainfall to
portions of north and central GA through tonight.

Copious amounts of moisture/rainfall will begin to overspread the
CWA tonight and continue through Thursday ahead of Helene. For
the short term period, the axis of heaviest rainfall will be in
the vicinity of the surface trough/front. For now, that looks like
it should roughly set up along the I-85 corridor or a little
westward. Storm total QPF through Thursday afternoon of 3 to 5
inches is likely with some locally higher amounts possible. Will
make no changes to the Flood Watch. Winds should become breezy
late in the period, but the strongest winds should begin to
overspread the area later Thursday.

With all the rain and clouds, temperatures near normal are
anticipated and the record setting max temps look to be over for
now.

A few strong storms or an isolated severe storm will be possible
today, especially during the afternoon when heating has the best
chance. CAPE values will be marginal but good shear will be
present. An isolated tornado cannot be ruled out, even when much
of the surface instability is lost. The potential for tropical
tornadoes will increase on Thursday as Helene approaches the Gulf
Coast and the outer rainbands impact the CWA.

NListemaa

&&

.LONG TERM...
(Thursday night through Tuesday)
Issued at 330 AM EDT Wed Sep 25 2024

Tropical Storm Helene is currently positioned east of the Yucatan
Peninsula and is forecast to track northward over the eastern
Gulf of Mexico through today and Thursday. Helene is forecast to
become a major hurricane shortly before making landfall along the
Big Bend of Florida on Thursday evening. Significant impacts are
expected across the forecast area Thursday and Friday as Helene
tracks northward between a mid/upper-level trough to the west and
a mid/upper-level ridge to the east. Some degree of uncertainty
remains regarding the exact track of the center of the storm
across the forecast area, but again, substantial impacts are
expected across north and central Georgia. Details follow...

Rainfall: As mentioned in the short term discussion, a
significant rainfall event is expected today (Wednesday) and will
be followed by the expansive rain shield of Helene on Thursday,
setting the stage for what may be substantial flash flooding and
localized river flooding. Additional rainfall of 2.5 to 3.5 inches
is expected Thursday night through Friday night with isolated
areas of 4-5 inches. Given the heavy rainfall expected atop
saturated soils, there is a Moderate Risk (level 3 of 4) across
essentially all of the forecast area Thursday night into early
Friday morning. There is a Slight Risk (level 2 of 4) for
excessive rainfall along and north of I-20 on Friday. A Flood
Watch remains in effect across the entire forecast area until 18z
Friday.

Winds: The strong winds associated with the inner portion of
Helene are not forecast to arrive until Thursday afternoon and
evening. Winds will increase from south to north late Thursday
through Friday morning, with sustained winds at 25-35 mph and
gusts of 35-50 mph. Gusty conditions are expected essentially
area-wide given the size of the system. Even stronger sustained
winds and gusts are expected for areas closest to the center of
Helene. Where exactly these strongest winds occur will depend on
the track of the center. Given the moisture-laden soils by this
time, areas of tree damage and power line damage are likely.
Discussion has begun regarding issuance and coverage area of a
Tropical Storm Watch.

Tornadoes: There is a Slight Risk (level 2 of 5) across our far
southeastern counties and a Marginal Risk (level 1 of 5) across
much of east-central Georgia for tropical cyclone tornadoes
Thursday night into early Friday morning. The potential for low-
topped supercells and thus short-lived tornadoes will be maximized
for areas east of the center of Helene.

Fortunately, Helene will move at a fast pace, exiting the
forecast area on Friday morning. The system will be absorbed into
the mid-latitude flow and enhance the mid/upper-level troughing
over the Southeast. Maintaining a mention of isolated to scattered
showers and storms this weekend through early next week as
ensemble guidance depicts continued upper-level troughing and
decent moisture.

Martin

&&

.AVIATION...
(12Z TAFS)
Issued at 649 AM EDT Wed Sep 25 2024

Messy forecast on tap for the next several days. MVFR cigs should
begin to move in during the mid morning. Some isold/sct shra
become more likely around that time too. The widespread shra/tsra
expected by early afternoon and affecting vsbys. Embedded TSRA
becomes likely by the late afternoon. On and off shra/sct TSRA for
the remainder of the period. Winds should remain on the east
side. IFR cigs expected overnight. Winds should become gusty by
early tomorrow morning.

//ATL Confidence...12Z Update...
Med confidence all elements.

NListemaa

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          67  74  67  78 / 100 100 100  50
Atlanta         67  72  67  75 / 100 100 100  40
Blairsville     62  69  62  72 / 100 100 100  80
Cartersville    65  73  65  76 /  90 100 100  50
Columbus        70  75  67  79 / 100 100 100  20
Gainesville     66  72  67  75 / 100 100 100  50
Macon           69  76  68  80 / 100 100 100  20
Rome            65  72  67  77 /  90 100  90  60
Peachtree City  67  73  65  76 / 100 100 100  30
Vidalia         73  80  72  85 /  90 100 100  20

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 2 PM EDT this afternoon through Friday
afternoon for GAZ001>009-011>016-019>025-027-030>039-041>062-
066>076-078>086-089>098-102>113.

Tropical Storm Watch for GAZ069-071-072-079>086-089>098-102>113.

&&

$$

SHORT TERM...NListemaa
LONG TERM....Martin
AVIATION...NListemaa