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308
FXUS62 KFFC 210038
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
838 PM EDT Thu Jun 20 2024



...Evening Update...

.UPDATE...
-- Changed Discussion --
Issued at 829 PM EDT Thu Jun 20 2024

Slight adjustments have been made to the PoP grids to reflect the
latest trends with the surge of tropical moisture associated with
a low off the coast of Florida in the western Atlantic. The short
term forecast is otherwise on track.

.SHORT TERM...
(This afternoon through Friday)
Issued at 228 PM EDT Thu Jun 20 2024

Key Messages:

- Dry conditions will prevail for the rest of today and tonight.

- Isolated thunderstorms will be possible across east-central
Georgia tomorrow (Friday) afternoon.

500 mb analysis depicts an upper-level ridge and high pressure
extending from the Eastern Seaboard to the Mississippi River Valley.
The 12z sounding shows very dry air above ~850 mb and SPC
mesoanalysis depicts PWAT of 1.0" to 1.2". A Cu field envelopes much
of the area, but lack of appreciable moisture and abysmal
instability mean that convection is not expected, which makes sense
as Day Cloud Phase RGB satellite imagery reveals that no cloud tops
are tall enough to glaciate. The mostly to partly sunny sky will
allow insolation to drive temperatures into the lower 90s across
much of the area.

The ridge is expected to retrograde tonight into tomorrow (Friday)
while what is currently Disturbance 1 just northeast of the Bahamas
is steered west-northwestward by the flow around the ridge. The NHC
currently has a 40% chance of tropical development in the next 48
hours. Regardless of its tropical nomenclature, this feature will
bring with it an influx of moisture (characterized by PWAT greater
than 1.5" across portions of central Georgia) as it tracks inland
over the Georgia and Florida coasts tonight into tomorrow. The
tropical moisture and HREF-progged MUCAPE up to ~1000 J/kg across
east-central Georgia suggest the potential for isolated showers and
thunderstorms tomorrow afternoon. The SPC has a General Thunder risk
for this area, which makes sense, as a lack of 0-6 km bulk shear and
marginal instability suggest that the potential for strong/severe
storms is relatively low. Forecasted rainfall totals are not much to
talk about -- anywhere from a trace to around 0.10".

Martin
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&&

.LONG TERM...
(Saturday morning through next Wednesday)
Issued at 228 PM EDT Thu Jun 20 2024

Broad subtropical high will be in place across much of the southern
US to start the long term. Steering flow closer to the surface will
have pushed a tropical wave onshore Friday that should somewhere
near the FL/GA border starting Saturday. This feature will have
brought a good slug of moisture into the area and frictional
convergence around the system should provide for some rain and
thunderstorm development Saturday. Best chances will be down in
central GA, but could see some rain and storms pop up across much of
the CWA. This moisture remains in place into Sunday, allowing for
diurnally driven summer storms.

On Monday, models show upper level low swinging across NE CONUS.
This will drive a cold front toward the CWA, but it should lose much
of its momentum before arriving. Still, it may move through the area
on Monday, allowing for some enhancement of afternoon showers and
thunderstorms out ahead of it as moisture pools up a bit. Model
uncertainty expands a bit after this point, with position and depth
of the next trough across the northeast showing some meaningful
differences in the model ensembles. What is consistent is that we
will likely have plenty of moisture in place and a thermal
environment favorable for diurnally driven thunderstorm
development most days into the end of the week.

The potential bigger weather headline in all of this will be the
heat. NBM is showing temperatures in the mid to upper 90s, including
even a few triple digits, Sunday through Wednesday. Overnight lows
also would not provide for much relief falling into the low to mid
70s. Unlike our previous spell of heat, moisture looks to be a bit
more present, so heat indices creep up into the triple digits
again and heat products may be warranted. However. There is some
uncertainty around afternoon temperatures, especially given the
chances for diurnal convection. One bias we have noted in the
longer term guidance during our diurnal convection season is for
the blend to give an actual high that is a bit too high, as we
reach convective temperature and produce rain and cloud cover
across much of the area well before those highs can be realized.
You can see a reflection of this within the NBM percentiles, where
the NBM 90th and 10th percentile spread is 10 degrees or more at
many point locations, representative of models which are
convecting and cooling. The forecast will continue to reflect the
higher end heat chances, and once we have a better handle on what
type of coverage we may have on afternoon convection via short
term guidance, more concrete decisions can be made around heat
related products.

Lusk

&&

.AVIATION...
(00Z TAFS)
Issued at 728 PM EDT Thu Jun 20 2024

VFR conditions throughout TAF period. Winds will diminish overnight
to ~5KT or less with FEW250. Winds pick back up on the E/ENE side
tomorrow gradually increasing to between 8-10KT. FEW/SCT050-060
expected through the afternoon.

//ATL Confidence...00Z Update...
High confidence on all elements.

KAB

&&

.PRELIMINARY POINT TEMPS/POPS...
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Athens          65  93  69  93 /   0   0   0  20
Atlanta         69  94  72  95 /   0   0   0  10
Blairsville     63  87  65  89 /   0  10   0  20
Cartersville    67  94  69  95 /   0   0   0  10
Columbus        69  95  73  95 /   0   0   0  30
Gainesville     67  91  70  92 /   0   0   0  10
Macon           66  94  71  95 /   0   0   0  40
Rome            69  95  70  95 /   0   0   0  10
Peachtree City  66  94  69  95 /   0   0   0  20
Vidalia         68  92  73  92 /  10  40  20  70
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&&

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

$$

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