314 
FXUS62 KFFC 110932
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
432 AM EST Sat Dec 11 2021



.SHORT TERM /Today through Sunday/...

Throughout the night, we've watched from afar as a line of tornadic 
and damaging storms caused havoc across portions of the mid-
Mississippi River Valley and Midwest, reminding us just how 
dangerous and destructive the weather can be. Our thoughts go out to 
all those impacted by last night's historic severe weather event.

Closer to home, depending on your location you'd never expect to be 
in a pre-storm environment with the CAD wedge just now beginning to 
relinquish its hold across the forecast region. A Dense Fog Advisory 
has been issued and extended to 15Z across portions of the forecast 
area, although visibilities are beginning to improve for Central 
Georgia and portions of the far western CWA. Surface southerly flow 
will begin intensifying ahead of the incoming frontal system 
throughout the morning, forcing the wedge front back to the 
northeast as a moist airmass with 60+ degree dewpoints flood into 
the area and late morning and afternoon temps climb into the 70s.

This influx of warm, moist air will provide potential for a couple 
isolated severe storms this afternoon into the early evening as the 
cold front advances into Georgia. A line of storms has already 
formed along the frontal system and looks to move into far NW GA 
around 18Z this afternoon with a Slight Risk for severe storms for 
far NW and west central Georgia. The biggest limiting factor may be 
instability, with SBCAPE values progged to max out between 250-750 
J/kg in north and western Georgia just ahead of the incoming QLCS, 
while SFC-500 mb shear values should be excess of 50 kts. Storms in 
this environment should struggle to maintain vertical continuity and 
would more likely be sheared off, but momentum transfer and water 
loading within downdrafts could pose a threat for some isolated 
damaging winds gusts, especially where the QLCS bows toward the 
east. Additionally, a couple weak, brief tornadoes cannot be ruled 
out either within this environment. 0-1 km shear values are expected 
to be around 30-40 kt, with 0-1 km SRH values over 200 m2/s2, should 
create a strong zone of shear and vertical vorticity along the QLCS. 
However, weaker instability will struggle to take advantage of this 
potential, and lack of shear in the 2km-4km range will likely 
prevent any long-lived updrafts from sustaining themselves and 
instead regular cycling and collapsing of updrafts should be 
expected. All in all, the low-level shear is enough by itself for a 
couple tornadoes to develop, but any that do form should remain weak 
and short-lived. These chances will be mostly likely in far NW and 
west central GA, but limited chances are possible throughout the 
CWA. As the line of storms move through, looks for kinks within the 
line as evidence of enhanced vertical vorticity along the 
storm front. Rainfall accumulations on average should be under an 
inch.

However, it should be noted that these conditions are dependent on 
the wedge retreating from any particular area of interest. The wedge 
tends to hang around much longer that expected and has quashed 
severe potential in the past. While erosion is forecast, the 
location of the wedge front should be monitored as any areas in the 
cooler air would have very limited severe potential and areas along 
the wedge front could have an increased chance of tornado 
development.

Behind the cold front, temperatures should drop quickly with 
clearing skies. By Sunday morning most areas north and west of I-85 
will see morning temps in the 30s with areas in the higher 
elevations likely below freezing for a couple of hours. A sunny and 
calm Sunday will follow and highs rebound to very seasonal 50s to 
low 60s.


Thiem


.LONG TERM /Sunday Night through Friday/...

Looks like a quiet long term period with an upper ridge dominating
the area through the middle of the week. A short wave moves along
the northern Gulf and off the east coast of FL by the start of the
week. However...the effects of this system should remain south of
our area. So we can expect dry weather with a warming trend. The
upper flow becomes more west to southwest Thursday through Friday
as a frontal boundary sinks into the Southern Appalachians. Models
generally agree that the front may reach the TN/GA border by the
end of the period. Have continued with low pops for the far north
late Thursday into Friday.


41


&&

.AVIATION...
06Z Update...
LIFR conditions continue for majority of forecast area with all
area outside CSG showing CIGs between 200-400ft with dense fog
under 1SM along and north of I-20 around ATL/AHN, and patchy
LIFR/IFR in and around the MCN area. Improvement of VSBYs 
expected first, mostly between 12-15Z and winds shift from the SE
to SSW and strengthen ahead of the cold front. CIGs improvement
expected to be more gradual between 14-19Z from SW to NW. Line of
SHRA and possible TSRA then moving into are from NW. Potential
TSRA timing around ATL b/w 20-22Z, with lingering -SHRA and MVFR
cigs afterward and eventual improvement to VFR after 00Z.

//ATL Confidence...06Z Update...
Low-Medium on timing of VSBYs and CIGs improvement.
High on Precip timing, TSRA potential, and all other elements.

Thiem


&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          71  38  56  32 /  90  80   0   0 
Atlanta         71  37  55  36 / 100  80   0   0 
Blairsville     66  30  54  30 / 100  60   0   0 
Cartersville    72  33  55  35 / 100  70   0   0 
Columbus        75  42  60  39 /  90  90   0   0 
Gainesville     69  37  55  35 /  90  70   0   0 
Macon           76  43  62  35 /  70  80   5   0 
Rome            72  35  56  33 / 100  60   0   0 
Peachtree City  73  35  56  34 / 100  80   0   0 
Vidalia         78  52  63  41 /  40  70  20   0 

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM EST this morning for the 
following zones: Baldwin...Banks...Barrow...Bartow...Bibb...
Bleckley...Butts...Cherokee...Clarke...Clayton...Cobb...Dawson...
DeKalb...Dodge...Douglas...Fayette...Forsyth...Glascock...
Greene...Gwinnett...Hall...Hancock...Henry...Jackson...Jasper...
Jefferson...Johnson...Jones...Lamar...Laurens...Lumpkin...
Madison...Monroe...Morgan...Newton...North Fulton...Oconee...
Oglethorpe...Paulding...Pickens...Putnam...Rockdale...South 
Fulton...Spalding...Taliaferro...Telfair...Twiggs...Walton...
Warren...Washington...Wheeler...White...Wilkes...Wilkinson.

&&

$$

SHORT TERM...Thiem
LONG TERM....41
AVIATION...Thiem