334
FXUS62 KFFC 171148 AAA
AFDFFC

Area Forecast Discussion...UPDATED
National Weather Service Peachtree City GA
748 AM EDT Fri May 17 2024



...New 12Z Aviation Discussion...

.SHORT TERM...
(Today through Saturday)
Issued at 504 AM EDT Fri May 17 2024

As the morning begins, the upper level ridge responsible for
yesterday`s dry and sunny conditions is moving eastward towards
the Atlantic coast. Meanwhile, positively-tilted troughing is
positioned over Texas. Southwesterly flow aloft will set up
between these two features, which will allow for steady advection
of deep moisture into the forecast area. A shortwave disturbance
traversing this southwesterly flow, has triggered an MCS, which is
currently centered to the south of Mobile Bay and will continue
to move eastward over the northern Gulf of Mexico. High clouds on
the northeast side of this complex have been spreading over the
forecast area in the early morning hours, which will be followed
by showers moving from west to east into the area this morning.

The axis of the aforementioned trough and an upper level speed
max will advance towards the area over the course of the day. With
increasing deep moisture, dewpoints are forecast to increase into
the mod to upper 60s across north and central Georgia.
Furthermore, precipitable water values will rise to between 1.6
and 1.9 inches by this afternoon. After the coverage of showers
increases through the morning, scattered convective activity is
expected to become more likely by mid afternoon and into the
evening hours. As warm air works its way northward from the Gulf,
temperatures in south-central Georgia will warm into the low to
mid 80s, while only rising into the 70s elsewhere across the area
under persistent cloud cover and showers. The influence of the
aforementioned speed max will contribute to 0-1 km shear values of
20-25 kts and deep layer bulk shear values of 40-50 kts this
afternoon and evening. The warmest, most humid areas in south-
central Georgia will also see the greatest surface-based
instability, with SBCAPE values progged to range from 1000-1500
J/kg. This environment will be supportive of severe thunderstorm
development in south-central Georgia, while thunderstorms are
expected to remain elevated in north Georgia.

The SPC has diagnosed a Slight Risk (level 2 out of 5) of severe
thunderstorms in west-central Georgia, including Columbus, and a
Marginal Risk (1 out of 5) elsewhere across central Georgia. To
begin in the early afternoon and early evening, thunderstorms are
anticipated to be discrete and potentially supercellular, and
severe storms that occur will be capable of producing large hail,
damaging wind gusts, and possibly a couple of tornadoes. In the
late evening into the overnight hours, the upscale growth of
storms will become outflow driven, potentially evolving into an
MCS. In this phase, damaging wind gusts will be the primary hazard
with any severe storms that develop. It is worth noting that the
severe weather threat will be conditional. It will ultimately be
contingent upon how far north warm air from the Gulf is able to
advance and the behavior of outflow boundaries from upstream
convection.

Considering the high PWATs and deep atmospheric moisture,
stronger storms could produce locally heavy rain, particularly in
the mid afternoon to early evening where the potential for deep
convection and training motion look most likely. With soils across
much of the area being saturated from recent rainfall, if storms
move in a training motion over common locations, it could lead to
increased runoff and localized flooding concerns.

As the trough axis moves into the Lower Mississippi River Valley
region, the warm front is expected to continue to work its way
northward into Georgia through Saturday morning. At this time,
dewpoints will increase into the upper 60s in north Georgia and
low to mid 70s in central Georgia. At this time, low temperatures
are forecast to start off in the low to mid 60s in north Georgia,
and upper 60s to low 70s in central Georgia (south of the warm
front). Temperatures are then expected to warm into the upper 70s
to low 80s ahead of an cold front moving eastward from Alabama.
During the peak heating hours, SBCAPE values could increase to as
high as 2500 J/kg in portions of east-central Georgia. Enhanced
southwesterly flow ahead of the shortwave will also contribute to
deep layer bulk shear values of up to 40 kt. While conditions on
Saturday will be heavily dependent on the evolution of the
overnight and early morning MCS, convection is expected to develop
in the afternoon ahead of the advancing cold front, and the
environment and parameters mentioned above will be sufficient to
support the development of some strong to severe thunderstorms.
The primary hazards with any severe storms that form will be
damaging winds, although hail and a brief tornado or two cannot be
ruled out.

King


&&

.LONG TERM...
(Saturday night through Thursday)
Issued at 504 AM EDT Fri May 17 2024

The long term forecast picks up with the low pressure system and
attendant cold front over the forecast area slowly progressing
eastward as the upper level wave dives across the southeast.
Ongoing showers and thunderstorms in the early evening hours
Saturday will be in a favorable environment to become strong to
severe. Undeterred by the appreciable loss of diurnal heating
after sunset, thunderstorms are expected to persist through the
early morning hours on Sunday as they are able to tap into an
unstable (MUCAPE ranging from 500-1000+ J/kg) and dynamically
supportive environment (bulk shear +/- 40kts). Despite the
elevated nature of thunderstorms, a few could become strong to
severe with the greatest hazard being damaging wind gusts. Hail up
to 1 inch and a brief tornado (primarily across southeastern
Georgia where 0-3km SRH is sufficient) will also be possible,
though the probabilities are relatively low. SPC currently has a
Slight Risk (level 2 out of 5) for severe weather progged for
areas along and south of a line from roughly Columbus to Macon to
Washington that is valid through the 12Z time frame on Sunday. As
moisture wraps around the backside of the low as the system pushes
eastward, another round of scattered to numerous showers is
expected with locations across eastern Georgia Sunday forecast to
see the best rain and thunderstorm chances. At this time, no
severe weather is expected on Sunday with storm chances tapering
off by Sunday night, but can`t rule out a strong storm.

The other notable hazard through the weekend is the rainfall
associated with the active weather in the short term and the
weekend system. Some locations across central Georgia could
receive around 2.0" of rain with a decreasing gradient to ~0.75"
to the north. This forecast cycle has backed off a bit with
respect to the rainfall totals through the weekend. Despite this,
will need to keep an eye on any locations that see repeated
instances of heavy rainfall in strong storms and/or training
storms through the weekend where locally higher amounts may be
possible. PWATs are running between 1.5-2.0+" across much of
central Georgia, and while the sandier soils of the coastal Plain
can handle more rainfall than their northern counterparts across
the Piedmont, a few isolated instances of nuisance flooding will
be possible.

Beyond the busy start to the long term forecast period, high
pressure aloft and at the surface returns to kick off the work
week. A weak wedge will set up shop through the first half of the
week bringing dry conditions to the area. PoPs return to the
forecast with a chance of showers and thunderstorms for north
Georgia Wednesday as a cold front approaches the area. As the
frontal boundary sags south Thursday, chances for showers and
thunderstorms will be on the table through the day Thursday.
Temperatures in the upper 70s and low 80s at the start of the
forecast period will begin a warming trend through the end of the
extended with highs topping out in the upper 80s (with a few
locations hitting the 90 degree mark across south central
Georgia).

KAL


&&

.AVIATION...
(12Z TAFS)
Issued at 733 AM EDT Fri May 17 2024

Ceilings will lower to MVFR by 15z, in addition to showers
becoming more widespread. Chances for thunderstorms appear to be
greatest this afternoon with forcing from a disturbance aloft
combined with diurnal instability. As such, TEMPOs have been
introduced for TSRA at all sites for either 17z-21z or 18z-22z.
Winds will be E to SE at 4-8 kts. Winds may briefly shift to SW
this afternoon in portions of central Georgia. Ceilings are
forecast to lower to IFR after 00z at the northern TAF sites.

//ATL Confidence...12Z Update...
Medium confidence on progression of ceilings and convection.
High confidence on all other elements.

Martin/King


&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          64  80  63  80 /  70  60  50  60
Atlanta         66  79  65  81 /  70  70  50  50
Blairsville     60  75  59  76 /  80  70  50  60
Cartersville    63  80  62  81 /  70  70  50  50
Columbus        70  81  65  84 /  70  80  40  30
Gainesville     64  78  64  79 /  80  70  50  60
Macon           69  81  65  83 /  60  80  40  50
Rome            64  79  62  83 /  70  70  50  40
Peachtree City  66  80  63  82 /  70  70  40  40
Vidalia         72  84  68  83 /  40  80  60  60

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...King
LONG TERM....KAL
AVIATION...King