-- Discussion containing changed information from previous version are highlighted. --
924
FXUS62 KFFC 201740 AAB
AFDFFC

Area Forecast Discussion...UPDATED
National Weather Service Peachtree City GA
140 PM EDT Mon May 20 2024



...New 18Z Aviation Discussion...

.UPDATE...
Issued at 1133 AM EDT Mon May 20 2024

Have made updates to the sky cover, wind/gust, T, and Td
forecasts for the next 24 hours or so. Otherwise, the forecast is
on track. See below for previous discussions.

Martin


&&

.SHORT TERM...
(Today through Tuesday)
Issued at 259 AM EDT Mon May 20 2024

As the shortwave to the east makes its grand entrance off the
eastern seaboard, a ridge is beginning to stretch across the Ohio
and Mississippi River Valleys. This ridge will continue to build
in along the spine of the Appalachians through today as a potent
negatively tilted shortwave over the Central Plains skirts off
over the Great Lakes Region. Surface pressure in the leeside of
the Appalachians is already evident in the surface analysis where
that is expected to strengthen thanks to the synoptic-scale
subsidence. Easterly flow will develop a southerly component
through the day, allowing the enhancement of the upslope winds
across the northeast Georgia mountains. With considerable moisture
remaining in the low levels of the atmosphere, SBCAPE between
500-1000 J/kg in northeast Georgia, and steep low level lapse
rates, a few orographically induced storms could initiate off of
mountainous terrain. The far northeast Georgia mountains are the
only locations in the CWA that are forecast to see any chance at
precipitation this afternoon as well as any meaningful cloud
coverage. Most locations today will see mostly sunny skies and
high temperatures topping out in the low to mid 80s with higher
elevations in the 70s. Overnight, enhanced cloud coverage from
modest moisture aloft across north Georgia will keep temperatures
from dropping much below the mid 60s, even in areas of higher
elevations where temperatures are forecast to bottom out in the
upper 50s. Areas further south across central Georgia will see low
temperatures closer to the 60 degree mark thanks to clear skies
allowing for longwave radiation to cool the surface more
efficiently.

Tuesday, a seasonably warm and sunny day is forecast for the
forecast area. Despite winds out of the southeast, surface
moisture is lacking, thus limiting chances for orographically
induced showers and thunderstorms across northeast Georgia again.
Have maintained a low end slight chance for precipitation across
extreme northeast Georgia as some moisture remains around the
850mb level. Otherwise, dry conditions are anticipated areawide.
Maximum daily temperatures will climb into the mid to upper 80s
areawide outside of elevated terrain, where temperatures will
remain in the 70s.

KAL


&&

.LONG TERM...
(Tuesday night through Sunday)
Issued at 259 AM EDT Mon May 20 2024

The long term period begins with a longwave ridge across much of
the eastern CONUS. This ridge will extend from the northwest Gulf
of Mexico into the Deep South and then northeastward towards New
England. Surface high pressure associated with this ridge will be
centered to the northeast of the forecast area. Subsidence
underneath this high will largely serve to inhibit precipitation
through Wednesday. With increasing 1000-500 mb thicknesses under
the ridge combined with plenty of sunshine, a warming trend will
continue on Wednesday. After starting the morning in the low to
mid 60s across the majority of the area, high temperatures on
Wednesday afternoon are forecast to rise into the upper 80s.
Temperatures will be locally cooler in the higher elevations of
far northeast Georgia.

While weather conditions will be benign across north and central
Georgia on Wednesday, a deepening upper low will be moving from
the upper Midwest towards the Great Lakes region. The axis of the
ridge will meanwhile clear Georgia to the east by late Wednesday,
at which point southwesterly upper flow between the low and the
ridge will enter north Georgia, leading to increasing atmospheric
moisture. As the low pressure system becomes occluded and moves
into southeast Canada, a cold front will advance slowly southward
into the Tennessee Valley region by Wednesday night. Isolated to
scattered showers and thunderstorms will begin to advance into far
north Georgia by early Thursday morning as a weak disturbance
traverses the upper-level flow and overruns the frontal boundary.
PoPs on Thursday and Thursday night will mostly be confined to far
north Georgia, with low-end chance PoPs in the far northern tier
and and progressively lower chances to the south. Even in spite of
increased cloud cover across far north Georgia near the front,
the warming trend will persist, with highs forecast to be in the
upper 80s in north Georgia and low 90s in central Georgia. These
high temperatures will be consistent with what can be expected for
the remainder of the week and into the weekend, which will run
about 4-8 degrees above climatological normals.

As the low continues to move away to the northeast, the frontal
boundary will become more elongated from west to east, and its
southward advance will begin to slow. By Friday morning, the
frontal boundary is forecast to stall near the Georgia/Tennessee
state line. A more robust shortwave will traverse the westerlies
and from the Lower Mississippi River Valley across the Southeast
on Friday into Friday night. This setup is likely to bring more
numerous showers and thunderstorms to the forecast area on Friday,
especially where wave overruns the stalled frontal boundary,
providing a focus for additional convection. Uncertainty still
remains in the model guidance with respect to the strength and
exact position of this disturbance, which will influence where the
most widespread precipitation will occur. While the frontal
boundary will begin to dissipate by early Saturday morning,
additional disturbances will continue to traverse the westerlies
and through the Southeast this weekend. Scattered showers and
thunderstorms are thus expected on both Saturday and Sunday, with
the highest chances during the afternoon each day where diurnal
instability will be greatest.

King


&&

.AVIATION...
-- Changed Discussion --
(18Z TAFS)
Issued at 128 PM EDT Mon May 20 2024

VFR conditions are expected to prevail through the TAF period at
all sites. FEW/SCT cumulus at 035 to 055 is expected through early
evening. Isolated, diurnally-driven -SHRA and -TSRA are expected
to remain north of the Atlanta area TAF sites and AHN. FEW/SCT
cloud cover between ~050 and ~100 is forecasted across northeast
GA and southward across the Atlanta metro overnight. Winds will be
E to SE at 3-8 kts today, becoming LGT to calm overnight. Another
Cu field will develop tomorrow (Tuesday) afternoon. Winds will be
E to SE at 3-8 kts again tomorrow.

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

Martin
-- End Changed Discussion --


&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          60  86  60  87 /   0   0   0   0
Atlanta         64  86  64  87 /   0   0   0   0
Blairsville     59  80  57  83 /  10  10   0   0
Cartersville    63  87  62  88 /   0   0   0   0
Columbus        63  86  63  88 /   0   0   0   0
Gainesville     63  85  62  86 /   0   0   0   0
Macon           60  85  61  88 /   0   0   0   0
Rome            62  87  62  88 /   0   0   0   0
Peachtree City  60  86  61  88 /   0   0   0   0
Vidalia         62  85  62  88 /   0   0   0   0

&&

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

$$

SHORT TERM...KAL
LONG TERM....King
AVIATION...Martin