174 
FXUS62 KFFC 191150
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
750 AM EDT Sun Apr 19 2020

.PREV DISCUSSION... /issued 400 AM EDT Sun Apr 19 2020/ 

..Another Significant Severe Event Anticipated Today...

SHORT TERM /Today through Monday/...
Would definitely classify the current state as the calm before the 
storm across the area as high pressure remains in control over the 
Carolinas with influence over the local area resulting in a 
continued dry northerly flow. Dewpoints hardly of the severe variety 
thus far with upper 30s and lower 40s the rule. All this points to a 
scenario in which area will be on the edge of surging moisture and 
energy but also means demarcation of these 2 zones later today will 
be an area primed for severe storms including tornadoes and damaging 
winds. 

Initially, it will be just an isentropic lift scenario with S to SW 
flow of 50 kts at 5k ft stream over the relatively cold dome 
mentioned above. All CAPE will be of the elevated variety but still 
sufficient for some thunder for Central portions. Things will change 
very quickly however through the early afternoon hours with a very 
sharp gradient of energy developing. Although surface based CAPE 
will remain near zero all the way down to the southern metro, we 
will see values in excess of 2000 J/KG approaching our far SW zones. 
The STP will be increasing to around 5 during this time as well 
allowing for a start to the tornado threat as well as damaging 
winds. 

Further north of this, up to I20, the pure dynamics of this system 
may be enough to overcome the relative lack of instability. Shear 
may prove to be too high the further north you go as updrafts will 
simply not be able to support. However, damaging winds will remain a 
likely component for the Atlanta metro and other areas along the I20 
corridor.

Main event looks to be along the front later in the evening for 
Central GA as instability and corresponding STP surges northward 
briefly. Although overall geographic footprint of this system may be 
smaller than last system, this one is not to be taken lightly by any 
means as tornadoes look likely along and south of a Columbus to 
Macon line. In addition, a few strong and long track tornadoes will 
be possible given sigtor ramping up during this timeframe and 
updraft helicities represented by most of the hi res guidance. Rapidly 
improving conditions for late Sunday night into Monday although 
winds will be gusty in cooler NW flow. 

Deese

LONG TERM /Monday Night through Saturday/...
Tuesday will be dry and somewhat windy favoring N GA with some areas
close to wind advisory criteria(20 mph sustained).

The next system of concern will be on Thursday as surface low pressure
and associated short wave approach the area. There looks to be 
a sharp gradient of instability as the warm front gets stuck over
central GA. This system will need to be monitored for severe weather 
potential as we get closer. Either way, another period of wet weather
can be expected starting Wednesday night and maximizing Thursday
into Thursdsay night with just small chances for lingering light showers
briefly on Friday. 

Models are inconsistent with another system approaching on Saturday
and precip currently favoring n GA is very much a compromise.

BDL

HYDROLOGY...
The Flash Flood watch will be continued due to the potential
for heavy rainfall over central and portions of n GA. 2 to 5 inches
of rain can be expected with locally higher amounts. Some of the rain
could occur in a short period of time. Heavy rainfall will likely lead
to localized flooding. Flooding of low-lying areas, creeks and streams
can be expected with additional larger river rises anticipated as well,
well after the rain ends.

.AVIATION...
12Z UPDATE... 
A challenging forecast to say the least with 
multiple waves of SHRA and TSRA likely across the terminals today.
Anticipate the first of these to accompany lowering cigs this 
morning with MVFR developing. Will be some TSRA with this first 
wave for sure and will include in TEMPO group. Will handle most 
of the TSRA in Prob30 group and utilize 2 Prob30 groups for MCN 
and CSG to account for severe line of storms late this evening and
potential gusts to 45kts. If anything, cigs go down even further 
later Sun evening as some LIFR potential will accompany the final 
wave of SHRA/TSRA.

//ATL CONFIDENCE...12Z UPDATE... 
Medium on TSRA timing. 
High on remaining elements.

Deese

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          61  55  72  49 /  90 100  70   0 
Atlanta         63  56  70  50 / 100 100  60   0 
Blairsville     59  49  65  44 /  80 100  70   0 
Cartersville    62  53  70  47 / 100 100  60   0 
Columbus        71  61  76  51 / 100 100  50   0 
Gainesville     58  53  71  48 /  90 100  70   0 
Macon           68  60  76  51 / 100  90  60   0 
Rome            62  53  71  47 /  90 100  60   0 
Peachtree City  65  57  72  48 / 100 100  60   0 
Vidalia         73  65  77  56 / 100  90  70   5 

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 11 AM EDT this morning through Monday 
morning for the following zones: Baldwin...Barrow...Bibb...
Bleckley...Butts...Carroll...Chattahoochee...Clarke...Clayton...
Cobb...Coweta...Crawford...Crisp...DeKalb...Dodge...Dooly...
Douglas...Emanuel...Fayette...Glascock...Greene...Gwinnett...
Hancock...Haralson...Harris...Heard...Henry...Houston...Jasper...
Jefferson...Johnson...Jones...Lamar...Laurens...Macon...Marion...
Meriwether...Monroe...Montgomery...Morgan...Muscogee...Newton...
North Fulton...Oconee...Oglethorpe...Paulding...Peach...Pike...
Polk...Pulaski...Putnam...Rockdale...Schley...South Fulton...
Spalding...Stewart...Sumter...Talbot...Taliaferro...Taylor...
Telfair...Toombs...Treutlen...Troup...Twiggs...Upson...Walton...
Warren...Washington...Webster...Wheeler...Wilcox...Wilkes...
Wilkinson.

&&

$$

SHORT TERM...Deese
LONG TERM....BDL
AVIATION...Deese