614
FXUS62 KFFC 121759
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
159 PM EDT Sun May 12 2024

...New 18Z Aviation Discussion...

.SHORT TERM...
(Today through Monday)
Issued at 345 AM EDT Sun May 12 2024

Key Messages:

 - Fair weather will prevail in the region today.

 - Cloudy skies, cooler temperatures and scattered light rain
   showers are expected Monday.

Today & Monday:

Upper level ridging and a surface high will bring benign weather to
the region today. The core of the surface high will be closer to us
today (compared to Saturday) and this will result in lighter winds
this afternoon. Northwest winds between 4 and 8 mph can be expected.
Light and variable winds will develop tonight as the boundary layer
decouples and the surface high settles over Georgia.

An approaching trough will bring significant changes to Georgia`s
weather on Monday. Cloud cover will return in force tonight as
southwesterly follow in the mid and upper levels brings a surge of
moisture northward. By Monday morning isentropic lift associated with
a weak mid level trough (ahead of the larger shortwave in the
Plains) could produce light rain showers. Any accumulations through
Monday morning should be less than 0.25 inches. A relative minimum in
precipitation potential is expected Monday afternoon before
widespread rain showers and thunderstorm build back in Monday
evening/night (associated with lift from the parent trough and a low
level jet). Shifts in the forecast towards greater rain chances and
more cloud cover have introduced a significant amount of uncertainty
into the high temperature forecast for Monday afternoon. Below
average high temperatures are likely (>90% chance), but the spread in
the NBM guidance is quite large. For the Atlanta area the spread
between the 25th and 75th percentile MaxT`s is 7 degrees (69 to 76
degrees). Similar large spreads exist for the rest of northern and
central Georgia. Our deterministic forecast remains close the the 50
percentile of the NBM and favors a highs in the lower 70s for most of
northern and central Georgia.

Albright

&&

.LONG TERM...
(Monday night through Saturday)
Issued at 345 AM EDT Sun May 12 2024

The long term forecast looks quite wet overall with a parade of lows
within the southern branch of the jet moving past the CWA through
the end of the week (and possibly even into early next week, but that
is beyond the scope of this forecast). The forecast picks up Monday
night with rain likely ongoing across the CWA. Upper level cut off
low with begin to progress eastward, albeit slowly, and initial upper
level divergence will have overspread the CWA. Isentropic lift over
a theta-e gradient should provide for widespread rain showers through
the night, though some elevated instability may provide for a few
rumbles of thunder.

As the low progresses east, but upper level support will arrive with
moderate jet streak overspreading the CWA on Tuesday. Ensemble
guidance paints a decent probability space for the intersection of
instability, shear, and precipitation over the CWA, with highest
probabilities in central GA, decreasing as you move into north GA.
This feels appropriate, and the northward extent may be overdone
overall. Models will typically struggle with the rain based
reinforcement of the surface boundary attempting to lift north as a
mass response to the surface low, and generally these boundaries will
remain further south than forecast. In simpler terms, the further
south the surface based warm, moist air from the Gulf remains, the
lower the overall severe threat for our area. Looking at hodographs
and overall model forecast soundings, primary threat would likely be
wind and maybe hail. SW surface winds will make ingestion of
streamwise vorticity a bit more challenging, keeping tornado threat
low for now. Better examination will be had in the short term
guidance as Tuesday evening comes into range.

The trade off of a lower severe threat may be an elevated
flooding/flash flooding risk, especially if that boundary sits in the
same location further south and provides a source for repeated
lifting of air parcels. Central Georgia would once again be the
primary candidate for this, though the sandy soils can take a bit
more rain before it becomes a problem. Current forecast QPF over this
time period is 2- 4" with locally higher amounts in central GA, and
1-2" across north GA including metro Atlanta. 6 hr flash flood
guidance is generally 4" or higher across much of central GA, so any
threat may be driven by more convective elements and/or training of
cells over the area.

The system clears out through Wednesday morning, and we should see
some clearing through Thursday before the next system approaches the
area. Model trends seem to be slowing this system a bit, pushing the
overall timing of rain into Friday. This is another slower moving
system, and both the GEFS and EPS probabilities of rain are
relatively high through the weekend. Details of what exactly this
looks like are bit more fuzzy, though the deterministic suite shows a
stalled boundary over the CWA that appears to be the focus of most
of the rainfall. This is a bit of a concerning signal given we may
have some heavier rainfall on the front end of the week, but
certainly too early with too much uncertainty to ring any flooding
alarm bells just yet.

Lusk

&&

.AVIATION...
(18Z TAFS)
Issued at 150 PM EDT Sun May 12 2024

VFR conditions will continue through the evening, with gradually
deteriorating conditions from the W after midnight tonight.
Showers will spread into CSG by daybreak, with rain spreading
across the remainder of the terminals through Mon morning. Have
opted for lower ceilings (IFR) in rain as model soundings look to
be nearly saturated in the lower levels at the expected onset of
precipitation. Rainfall is not expected to be too heavy through
the end of the forecast period other than at CSG. However, due to
the expected moisture levels in the boundary layer, vsbys may be
further limited by fog. Winds will be very light, although SE
winds will begin to increase at the end of the period.

//ATL Confidence...18Z Update...
Medium for timing of rain onset along with cig heights and vsbys
in rain, high for other elements.

SEC

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          56  73  60  75 /   0  70 100 100
Atlanta         60  70  62  77 /  10  70  90 100
Blairsville     52  68  56  70 /   0  60  90 100
Cartersville    57  71  60  77 /  10  80  90  90
Columbus        63  76  66  80 /  30  70  90 100
Gainesville     57  70  61  73 /   0  60  90 100
Macon           61  75  64  78 /  20  70  90 100
Rome            57  71  62  78 /  10  70  90 100
Peachtree City  59  71  62  79 /  20  80  90 100
Vidalia         64  80  67  80 /  10  60  90 100

&&

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

$$

SHORT TERM...SEC
LONG TERM....Lusk
AVIATION...SEC