203
FXUS62 KFFC 141758
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
158 PM EDT Tue May 14 2024



...New 18Z Aviation Discussion...

.UPDATE...
Issued at 1149 AM EDT Tue May 14 2024

Wind and hail driven severe probabilities have increased across
north Georgia for locations north of the I-20 corridor this
afternoon and evening. Some uncertainty remains in how the current
isentropically forced light rain across these areas will
influence the overall severe threat this afternoon. However, if
the warm front is able to lift further northward and clouds clear
enough for sunshine to destabilize the surface as the upper level
shortwave passes, could see strong to severe storms this afternoon
and evening. The short term forecast otherwise remains on track.

&&

.SHORT TERM...
(Today through Wednesday)
Issued at 406 AM EDT Tue May 14 2024

Key Messages:

 - A couple of strong or severe storms could develop between 4 PM
   and 10 PM today, especially in central Georgia.

 - Scattered sub severe storms are possible in northern Georgia
   Wednesday afternoon.

Today and Wednesday:

An upper level trough moving at a snails pace through the Tennessee
Valley will be the primary player in our weather over the next 36
hours. Southerly flow ahead of the trough will continue to advect
moisture northward, allowing low clouds, haze and light rain showers
to continue in the region this morning. Later this afternoon it will
draw a warm front northward into central Georgia. This front should
serve as a focal point for thunderstorms between 4 PM and 10 PM.
Though additional elevated thunderstorms may form north of the warm
front in northern Georgia. Diurnal heating and rising surface
dewpoints (peaking near 70 degrees) behind the warm front should
allow SBCAPE values to peak in the 1000 to 2000 J/kg range this
afternoon. This instability should be coupled with adequate shear
values (0 to 6 km values between 25 and 40 kt) for isolated
supercell development near the warm front. Note the mean STP values
in the 1 to 3 range in the 00Z HREF guidance. Mid level lapse rates
have also improved in the CAM guidance compared to what was
projected yesterday (mean values are now in the 6.0 to 7.0 C/km
range). Given these considerations today`s Marginal Risk (Level 1 of
5) appears to be a higher end Marginal. This is especially true
along a line from Columbus to Macon to Augusta, where proximity to
the warm front will elevate the severe potential. Along this line
damaging winds are the main concern, but large hail or a brief
tornado are possible. Further north the elevated nature of the
storms should lead to a lower potential for damaging winds or hail.

Patchy fog could occur tonight along and north of Interstate 20. Any
fog should dissipate quickly Wednesday morning as a weak cold front
pushes through the state. Diurnal heating and proximity to the core
of the upper level trough should promote scattered showers and
thunderstorms over the terrain of northern Georgia Wednesday
afternoon and evening. Weak shear (0-6 km values between 10 and 20
kt) and limited instability (500-1000 J/kg) should generally keep
these storms sub severe. A couple isolated showers or storms could
occur over central Georgia, but narrow CAPE profiles, weak mid level
capping and lower surface dewpoints should limit the potential. More
sunshine should allow temperatures to increase Tuesday (compared to
today) despite the passage of a cold front in the morning. Look for
afternoon highs in the upper 70s in northern Georgia and lower 80s
in central Georgia.

Albright

&&

.LONG TERM...
(Wednesday night through Monday)
Issued at 406 AM EDT Tue May 14 2024

Long term picks up Wednesday evening/overnight, where some lingering
showers and isolated thunderstorms may be ongoing across northern
GA, but should quickly come to an end. Thursday continues to look
dry as it has all week, with rain beginning to spread into the area
Friday morning into the day. There is some signs of complications
for rain spreading in - ensembles are showing slower solutions yet
again tonight, with 00Z guidance pushing best probabilities into
later Friday evening and into the day on Saturday. Deterministic
guidance provides some insight into what seems to be happening -
models seem to like keeping the upper level low moving across the
south mostly detached from the northern branch of the jet, allowing
it to continue to slowly lumber its way across the region into
Saturday. Another potential complication to precipitation chances
would be convective evolution on the previous day into Friday
afternoon, similar to what we`ve seen play out with events
yesterday (Monday), where a strong MCS cuts off the Gulf and
prevents much of the potential rainfall from impacting the area.
This seems plausible given that the current system has pushed the
theta-e gradient well into the Gulf and the developing sfc low
that will drive Friday and Saturday`s rainfall won`t be anything
spectacular. The mass response to the sfc low will be modest as a
result, so we certainly won`t see that theta-e gradient lift
rapidly, and it is likely to be somewhat reinforced by some
isentropic lift to the north of it. That gradient would likely be
the focus of an organized convective system. All this rambling is
to say that uncertainty still remains regarding overall rainfall
and storm chances on Friday and Saturday, and while current
rainfall amounts are in the 1-2" range, there is a large range of
what may occur that will be highly dependent on several critical
points this forecaster doesn`t trust the models to handle well.

After that, there is decent signal in the ensembles that the upper
level low will slip to the SE, allowing for a sfc low to form off
the GA/Carolina coastlines. This could throw back some cloud cover
and moisture on Sunday which will need to be monitored, but
currently keeping low end PoPs in the forecast to account for
uncertainty. Low off the coast could also create some sudo-wedge
conditions that would impact temps across parts of GA, but too much
uncertainty again to really deviate from the NBM guidance on this.

Lusk

&&

.AVIATION...
(18Z TAFS)
Issued at 155 PM EDT Tue May 14 2024

MVFR/IFR cigs at most TAF terminals with VFR at CSG. Cigs
expected to improve to low end MVFR at most locations through the
afternoon before deteriorating to IFR/LIFR 15Z Wednesday. KATL/metro
could see LIFR cigs but will depend largely on how much rainfall
these locations receive this afternoon/evening. Isolated to
scattered SHRA and TSRA for most locations during the late afternoon
and evening hours with VCSH through the early morning. PROB30 for
SHRA/TSRA returns on Wednesday afternoon for northern TAF sites. SE
winds will shift to the SW by ~21Z and will continue to turn W
through TAF cycle at 5-10KT.

//ATL Confidence...18Z Update...
High confidence on winds. Medium confidence on all other elements.

KAL

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          62  80  61  86 /  70  30  20   0
Atlanta         64  80  62  85 /  60  30  20   0
Blairsville     58  73  57  78 /  80  70  50   0
Cartersville    61  79  59  84 /  70  40  30   0
Columbus        66  83  62  88 /  50  10   0   0
Gainesville     63  77  62  84 /  80  50  30   0
Macon           65  83  62  88 /  50  10  10   0
Rome            61  79  59  85 /  70  50  30   0
Peachtree City  63  81  61  86 /  60  20  10   0
Vidalia         69  86  66  88 /  50  10  10   0

&&

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

$$

SHORT TERM...KAL
LONG TERM....Lusk
AVIATION...KAL