820
FXUS62 KFFC 191046
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
646 AM EDT Thu Sep 19 2024



...New 12Z Aviation Discussion...

.SHORT TERM...
(Today through Friday)
Issued at 411 AM EDT Thu Sep 19 2024

This morning, a low pressure system is sitting over South Carolina
with a stationary boundary over central Georgia. With upper level
ridging building in to the west over the Plains, the low will
eventually be shifted off the eastern seaboard today and the
stationary boundary will progress southward over northern Florida.
This afternoon and early evening, northeast Georgia could see a few
showers on the backside of the low before the system makes its exit
later. With SBCAPE between 500-1000 J/kg and bulk shear ~25KT, an
isolated rumble of thunder is possible, particularly over areas of
mountainous terrain.

The biggest story in the short term will be the high pressure
building in resulting in above average surface temperatures,
especially across north Georgia. Today, temperatures will reach the
mid to upper 80s with some locations across north Georgia seeing
temperatures top out 5 degrees warmer than climatology. Locations
further south will be closer to average. Temperatures today will be
moderated a bit by lingering cloud coverage due to the moisture
wrapping around low pressure system over South Carolina. Overnight
lows will be mild for this time of year, running in the mid to upper
60s (about 5 to 7 degrees above normal). Tomorrow, with the low well
to the east, a wedge begins to become established and will be
accompanied by mostly sunny skies. Temperatures tomorrow will be
warmer than today, with most locations in the upper 80s. A few
locations across the area will reach the 90 degree mark. Highs
tomorrow will be running as high as 10 degrees above normal for
areas across north Georgia and 5 degrees above normal for many
places across central Georgia.

KAB

&&

.LONG TERM...
(Friday night through Wednesday)
Issued at 411 AM EDT Thu Sep 19 2024

Key Messages:

  - Warm temperatures that will be 8-13 degrees above average in
    parts of north Georgia through the weekend.

  - Complex upper air pattern combined with tropical uncertainty
    make for a difficult mid to end of week forecast next week.

Forecast Discussion:

The main meteorological players at the beginning of the long term
will be a low pressure off the shore of New England that models
have settled in on forming, a mostly stagnant airmass over us, and
a developing surface high well to the north over the Canadian
maritime. Into Saturday, this low doesn`t look like it will have
pushed any cooler air into us, so our drier air will continue to
heat bringing temperatures into the 90s in some locations. This
low slowly slides to the south on Sunday as the surface high seeps
around it into the northeast. The models show signs of a surface
boundary push down the Appalachians, but for now do not bring it
in. This may be the first place where we can discuss a little
uncertainty, as models can struggle with the timing and strength
of these airmasses as they filter down the Appalachians, but given
the unusual location of the surface high, there are reasons to
believe CAD processes may not be as dominate yet.

More uncertainty introduces itself after this, with more players
entering the forecast. A cut off upper low currently over
California is expected to eject into the Plains developing an
attendant surface low. The exact timing, track, and even strength
of this low has decent uncertainty, and how close it gets to the
CWA will have implications for moisture draw from the Gulf and
potentially whether the wedge may run into additional challenges
moving into the area. The surface low off the coast is expected to
continue diving south, allowing the wedge to attempt to move into
the area, but the high pressure to the north of the low does
appear to begin to weaken a bit, decreasing the pressure gradient
and the potential strength of the CAD. So, this creates some
spread in the temperature forecast. NBM 10th and 90th percentiles are
about 5-7 degrees apart Monday and Tuesday across the CWA, higher
in the north and northeast.

Adding even more fuel to the fire by the end of the long term will
be the tropics. Generation of a broad low off central America
continues to look likely. While the probability that a tropical
system forms from this is increasing, there are still a wide
variety of possibilities ensembles continue to show in terms of
timing, strength, and position of any system, if one is even able
to form. Broad lows can help spark the formation of these systems
by providing a focus for convection and vorticity maxima, but
organization of these broader systems can sometimes be a struggle
for a variety of reasons. Once again, don`t pay attention to
single runs of models. Take clues from the broader ensemble, which
still highlights a wide range of possibilities.

Lusk

&&

.AVIATION...
(12Z TAFS)
Issued at 619 AM EDT Thu Sep 19 2024

VFR conditions for all terminals through TAF period. FEW/SCT IFR
from 12-13Z at metro sites. Will be scattering out not long after
sunrise to SCT 3-4kft through the day before becoming FEW250
overnight. FEW 4kft with cu field tomorrow after sunrise. Light
winds at 5KT or less will be out of the NE.

//ATL Confidence...12Z Update...
Low confidence on IFR. High confidence on remaining elements.

KAB

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          65  88  64  89 /  10   0   0   0
Atlanta         67  88  67  90 /   0   0   0   0
Blairsville     60  83  60  85 /  10   0   0  10
Cartersville    65  90  64  92 /   0   0   0   0
Columbus        69  90  68  91 /   0   0   0   0
Gainesville     65  87  65  89 /  10   0   0   0
Macon           66  88  66  90 /   0   0   0   0
Rome            64  91  63  92 /   0   0   0   0
Peachtree City  65  88  64  89 /   0   0   0   0
Vidalia         68  88  67  88 /   0   0   0   0

&&

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

$$

SHORT TERM...KAB
LONG TERM....Lusk
AVIATION...KAB