143
FXUS62 KFFC 171322 AAA
AFDFFC

Area Forecast Discussion...UPDATED
National Weather Service Peachtree City GA
922 AM EDT Sat May 17 2025

...Morning Update...

.UPDATE...
Issued at 905 AM EDT Sat May 17 2025

A line of thunderstorms has pushed through north Georgia this
morning, with a few embedded strong storms producing straight-
line winds, small hail, and frequent lightning. At the time of
this writing, the line has largely weakened with the exception of
a bowing segment south of I-20 that is surging due east over the
I-75 corridor. The larger scale line of storms is slowly sinking
southeastward. An overcast sky and a capping inversion should --
for the most part -- keep deep convection at bay through the
morning hours. Still, gusty winds (up to around 40 mph) and
occasional CG lightning will be possible as the line marches into
central Georgia.

Martin


&&

.SHORT TERM...
(Today through Sunday)
Issued at 322 AM EDT Sat May 17 2025

Key Messages:

 - A line of thunderstorms will advance through far north Georgia
   during the early morning hours ahead of a cold front. A few
   storms within this line could become severe.

 - Scattered thunderstorms are expected this afternoon and evening
   in portions of central Georgia in a warm/humid environment and
   along the stalled frontal boundary.

 - Showers and thunderstorms return on Sunday, with isolated
   strong to severe storms possible. The possibility of an MCS
   entering the area will need to be monitored.

As the morning begins, a line of thunderstorms is advancing
southward through middle Tennessee ahead of a cold front. The
progression of the line has slowed a little bit compared to the
previous forecast, though a few isolated storms have begun to
enter the far northwestern corner of the forecast area. By the
time storm arrive in the far northern tier by around 4 AM EDT,
SBCAPE and MUCAPE values around 1000-1500 J/kg will still be
present. Furthermore, 0-1 km shear ahead of the cold front will
range from 30- 35 kts and 0-1 km storm relative helicity values
will range from 150 to as high as 250 m2/s2. Considering these
factors, isolated storms ahead of the line may become
supercellular, capable of producing a brief tornado and strong
wind gusts. It will also be likely to see a few stronger storms
embedded within the greater line, with bowing segments capable of
producing damaging wind gusts and brief tornadoes, as well. By
sunrise, the line is anticipated to be roughly parallel to the
north ATL metro. At this point, the cold front will become more
elongated from west to east, at which point it will begin to stall
and storms will steadily weaken. Showers and thunderstorms will
work their way southward through the metro area during the early
and mid morning hours.

By the early afternoon, the front is expected to stall in an area
between the metro area and a line from Columbus to Macon. The
passage of the cold front will only have a minor impact on high
temperatures this afternoon. Highs in north Georgia are forecast
to rise into the mid to upper 80s in all but the far northeastern
mountains (which will be slightly cooler). To the south of the
front, highs in central Georgia will rise into the low to mid 90s
once again today. These highs will range from about 5-9 degrees
above daily averages. The frontal boundary is expected to provide
a focus for convective development during the afternoon and
evening hours. While may hi-res solutions keep convective
development sparse in the vicinity of the front, this very well
may be underdone given strong destabilization to the south of the
front. SBCAPE values between 2000-3000 J/kg will still allow for
the development of isolated to scattered thunderstorms in the
afternoon hours. With deep layer bulk shear of 45-55 kts, some of
the storms that develop will have the potential to become
supercellular and produce damaging wind gusts and hail. Because of
this, the SPC has maintained a Day 1 Marginal Risk (level 1 of 5)
for severe weather. Precipitation is expected to gradually come
to an end in the hours following sunset with the loss of diurnal
heating.

The frontal boundary will still be in place across central
Georgia on Sunday morning. At this time, a 500 mb ridge will
advance across the Great Plains. A quickly moving shortwave will
move across the Southeast on the eastern side of the ridge
pattern, where it will then overrun the front on Sunday morning
into the afternoon. Chances for showers and thunderstorms will
increase accordingly, with scattered showers and a few isolated
thunderstorms during the morning and more numerous showers and
thunderstorms in the afternoon. The greatest chances for showers
and thunderstorms are forecast to be in the far west/northwest
portions of the forecast area where isentropic lift will be most
aligned with the stalled surface boundary. Forcing along the front
will be weak at this point, but SBCAPE values ranging from around
1000 J/kg in far north Georgia to 2000 J/kg in south-central
Georgia and a moderately sheared environment will allow for
isolated thunderstorms to become strong to severe in the afternoon
and capable of producing strong wind gusts.

Another variable that will warrant monitoring as we get closer in
time is the formation and evolution of any MCSs that develop
upstream overnight into Sunday morning. An MCS entering central
Georgia during the afternoon could find itself in a highly
favorable environment for downstream growth and propagation, which
would lead to a more widespread wind threat. Ample uncertainty
remains in this scenario at this time.

King


&&

.LONG TERM...
(Sunday night through Friday)
Issued at 322 AM EDT Sat May 17 2025

Key Messages:

  - Warm to hot. Highs in the upper 80s and low 90s, with a
    potential cool down around mid-week.

  - Small chance of severe weather Sunday afternoon. Main hazard
    is damaging winds. There is a marginal (level 1 of 5) risk of
    severe. Risk tappers off into the evening.

Thunderstorms may continue into the evening hours on Sunday with
whatever instability may remain through central Georgia. Entering
the overnight hours, the subtropical ridge rebounds northward as
the upper level shortwave moves out of the area. Thunderstorm
activity should shift northward through this timeframe, though
overall activity will be significantly reduced. With the terminus
of the subtropical thermal ridge across north Georgia, diurnal
thunderstorms activity can be expected each afternoon Mon and
Tuesday ahead of our next system.

As we get into the Wednesday timeframe, a more robust upper level
trough will descend into the area bringing a cold front and more
widespread showers and thunderstorms. Currently limited to no
severe weather is anticipated with this due to the strength of the
thermal ridge, however will definitely keep an eye on it as we
get into the near term. Temperatures behind the front will be cool
for this time of year with highs in the 70s and (hopefully) drier
conditions.

SM


&&

.AVIATION...
(12Z TAFS)
Issued at 707 AM EDT Sat May 17 2025

A line of SHRA/TSRA is advancing southeastward through north
Georgia and approaching the northern metro area. Prevailing -SHRA,
along with a TEMPO for TSRA, is being carried at ATL from 12-15Z
this morning. MVFR ceilings are also expected in the vicinity of
the line of precip through 17Z at ATL. Ceilings will then improve
to VFR and scatter out during the late afternoon. As the frontal
boundary stalls in central Georgia, scattered TSRA will be
possible near CSG/MCN this afternoon, warranting a TEMPO from
18-22Z. Winds through the daytime will be SW to W, at 8-12 kts and
occasional gusts up to 18-22 kts. Winds will diminish after
sunset. MVFR level clouds will be possible once again in the early
morning on Sunday, most likely in west-central Georgia.

//ATL Confidence...12Z Update...
Medium confidence on ceiling trends.
High confidence on all other elements.

King


&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          86  66  85  65 /  50   0  30  10
Atlanta         87  68  85  68 /  70  10  50  10
Blairsville     81  59  79  59 /  60  10  30  20
Cartersville    87  64  85  65 /  70  10  50  20
Columbus        89  69  90  68 /  40  10  40   0
Gainesville     85  66  84  66 /  70   0  40  10
Macon           90  68  90  68 /  50  10  40   0
Rome            88  64  85  65 /  60  10  50  20
Peachtree City  87  66  87  66 /  60  10  50  10
Vidalia         92  72  91  70 /  30  20  30  10

&&

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

$$

SHORT TERM...King
LONG TERM....SM
AVIATION...King