039
FXUS62 KFFC 170907
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
507 AM EDT Fri May 17 2024

...Morning Area Forecast 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...
(06Z TAFS)
Issued at 206 AM EDT Fri May 17 2024

High clouds will continue to spread from west to east across the
forecast area over the next few hours. Ceilings will gradually lower
through the morning hours, down to 8-10 kft by 10-12Z and further to
MVFR by 15Z. Showers are forecast to spread into the area this
morning, with scattered showers moving into ATL by 12Z and becoming
more widespread around by 15Z. Chances for thunderstorms appear to
be greatest this afternoon with forcing from a disturbance aloft
combined with diurnal instability. As such, a PROB30 for TSRA has
been maintained from 18-00Z at all sites. Winds will be light, at 4
kts or less, and variable to start the period, coming up from E to
SE at 4-8 kts after sunrise. 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...06Z Update...
Medium confidence on the timing of ceiling lowering and precip
onset.
High confidence on all other elements.

King

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          75  64  80  63 /  70  70  60  50
Atlanta         73  66  79  65 /  80  70  70  50
Blairsville     69  60  75  59 /  80  80  70  50
Cartersville    73  63  80  62 /  80  70  70  50
Columbus        79  70  81  65 /  80  70  80  40
Gainesville     72  64  78  64 /  80  80  70  50
Macon           80  69  81  65 /  70  60  80  40
Rome            73  64  79  62 /  80  70  70  50
Peachtree City  75  66  80  63 /  80  70  70  40
Vidalia         86  72  84  68 /  40  40  80  60

&&

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

$$

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