Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 220103

Area Forecast Discussion
National Weather Service Peachtree City GA
903 PM EDT Fri Jun 21 2024

...Evening Update...

Issued at 848 PM EDT Fri Jun 21 2024

The tropical moisture has brought a few light showers to our far
southeastern counties this evening. These showers have remained
fairly light with updrafts encountering dry air aloft and should
be coming to an end. Have made a few adjustments, but the short
term forecast otherwise remains on track.


(This afternoon through Saturday)
Issued at 254 PM EDT Fri Jun 21 2024

500 mb analysis shows a stout upper-level ridge positioned over the
eastern CONUS while high pressure prevails at the surface. A
relatively disorganized area of showers and thunderstorms currently
offshore about 80 miles ESE of Brunswick, Georgia will continue its
WNW track toward the Georgia and northeastern Florida coasts today.
Per the NHC, there is a 60% chance that this system could briefly
become a tropical depression before it reaches the coast.

Currently, a Cu field has developed across much of the area with
enough insolation to drive temperatures into the lower 90s to mid-
90s outside of the mountains. Isolated showers (and possibly a
thunderstorm) associated with the aforementioned system could clip
the far southeastern portion of the forecast area. While marginal
instability is progged across said area, would not be surprised if
no thunderstorms occur as little to no lightning is depicted via GLM
(Geostationary Lightning Mapper) with the system right now. A slight
chance (up to around 20% PoPs) for showers is expected overnight
across said area. Overnight lows will range from the upper 60s to
mid-70s (with slightly cooler conditions in the mountains).

As the tropical moisture associated with the system pushes farther
into central Georgia amid the prevailing easterly synoptic flow,
PWAT will climb to 1.5" to 2.0". As a result, expecting much of east-
central Georgia to have at least a slight chance (~20%) to a chance
(up to ~50%) for showers and thunderstorms tomorrow afternoon. The
HREF is progging 1000-1500 J/kg of MUCAPE, but the hi-res guidance
reveals abysmal lapse rates, so the potential for strong/severe
storms is low. The increasing moisture will contribute to increasing
heat index values (nearing 100 degrees across much of the area).
Highs will be in the mid-90s outside of the mountains.



(Sunday morning through next Thursday)
Issued at 254 PM EDT Fri Jun 21 2024

On Sunday, subtropical high begins to shift west as trough begins to
form and dig into the NE going into Monday. Shortwave within the
upper level flow will amplify this trough on Monday and help push a
front towards the area. Front can be noted on the 925 mb surface, as
the surface reflection is heavily modified by the afternoon sun.
This front will likely stall and not do much other than push some
lower humidities at the surface into the area Monday evening into
overnight, before a surface high builds in and moisture returns by
Tuesday. Diurnally driven convection looks to be possible for most
days given moisture and strong daytime heating that will allow us to
hit convective temperatures.

Heat will be the primary weather story in the long term. 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

At the tail end of the long term, uncertainty is a bit higher. Model
ensembles show a system approaching the eastern CONUS, but their is
decent amount of uncertainty around timing and strength. Should a
front move through, PoPs will certainly increase, but current PoPs
reflect better the uncertainty around the situation.



(00Z TAFS)
Issued at 739 PM EDT Fri Jun 21 2024

VFR conditions expected throughout TAF period. SCT030-060 Cu
field will return again during the late morning hours tomorrow.
FEW IFR cigs may encroach on the MCN airfield from the SE during
the morning hours. Easterly winds at 5-6KT this afternoon will
become light and VRB overnight. Easterly winds pick up again at
5-6KT tomorrow morning. MCN could see VCSH during the afternoon
but the bulk of the SHRA/TSRA should remain to the SE.

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



Athens          69  93  72  96 /   0  10  10  20
Atlanta         72  95  75  96 /   0   0  10  10
Blairsville     64  88  67  89 /  10  10  10  20
Cartersville    69  95  72  96 /   0   0   0  10
Columbus        72  97  75  99 /   0  10  10  10
Gainesville     69  92  73  94 /   0  10  10  20
Macon           72  95  73  99 /   0  20  10  20
Rome            71  96  72  97 /   0   0   0  10
Peachtree City  69  96  72  98 /   0   0   0  10
Vidalia         74  92  73  96 /  20  60  20  50