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Area Forecast Discussion (AFD)

Issued by Peachtree City, GA (FFC)

                            
005 
FXUS62 KFFC 260220
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
1020 PM EDT Fri May 25 2018


.UPDATE...
Convection has been redeveloping over western GA over the last 1
to 2 hours. Latest hi-res models indicate this will continue
through 08Z, lifting northward and dissipating afterwards. Have
increased pops to likely over western GA for the next several
hours. Due to the redevelopment, will maintain the current Flash
Flood Watch.

No other changes planned.

&&

.PREV DISCUSSION... /Issued 349 PM EDT Fri May 25 2018/ 

SHORT TERM /Tonight through Saturday Night/...

With Subtropical Storm Alberto off the Yucatan Peninsula and high 
pressure off the southeast coast, this has allowed abnormally high 
moisture flux to increase across the southeast.  Therefore we have 
widespread showers and isolated thunderstorms continuing across east 
central GA this afternoon.  This activity will continue through 
early evening, eventually diminishing while it lifts north with some 
precipitation (likely in the form of showers) moving into the metro. 
The coverage will be limited, but a better chance for the metro to 
see precipitation, especially between 20Z and 04Z. Activity should 
diminish later tonight. Patchy fog is possible during the morning 
hours. With the mid-level ridge trying to build in a bit across SE 
GA, this will likely limit the coverage of showers/thunderstorms 
tomorrow. However, looking aloft, best vorticity will be across 
north GA. Therefore, we expect this area to be the axis by which we 
see better coverage of showers/thunderstorms, likely later 
afternoon/evening Saturday. This activity should diminish after 
midnight Sunday. 

The main impact with any showers/thunderstorms will be heavy rain.
Expect high rainfall rates given the high PWATs and efficient 
saturation in the atmospheric column. Minor flooding could occur 
quickly with these heavy downpours. 

Precipitation totals through the short-term will be around a half an 
inch areawide with locally higher amounts possible associated with 
those heavier showers/storms.  

Temperatures will be slightly below normal.

26

LONG TERM /Sunday through Friday/...

The main concerns through the long term period will centered around 
precipitation from what is now Subtropical Storm Alberto, as of the 
11 AM EST update from NHC. As of the most recent forecast 
package, NHC has Alberto reaching land sometime on Monday near the
AL/MS border. Models start to diverge after reaching land, but 
the overall trend in the models is a generally east track towards
our area. The GFS brings Alberto through our northwest corner late
Wednesday, while ECMWF keeps Alberto further north and west of 
our area completely. Regardless of the model differences and the 
exact track/intensity of Subtropical Storm Alberto, heavy rain 
will be a continued threat in our area through the long term 
period as PWATs rise to 1.5 to 2+ inches.

For our area, Alberto will bring heavy rainfall and the potential
for flooding. Although winds should not be a major issue with 
Alberto, with already wet soils it will be relatively easy for 
trees to fall. Current QPF associated with Alberto is about 3-6 
inches with locally higher amounts possible, especially in 
northeast GA and east central GA. Flash flooding will also become 
a problem as well as river flooding. With the above-normal 
rainfall that most areas have seen over the past few days, soils 
are already saturated and additional precip would be expected to 
cause problems. Make sure to be aware of any forecast 
changes/watches/warnings, as well as updates from NHC, as there is
still uncertainty within the track of Alberto. The need for any 
flood-related watches will continue to be monitored. 

Decided to go with a blend for precip for most of the long term as 
models diverge shortly after Alberto reaches land. Regardless, 
chances for showers and thunderstorms exist daily and any day
could see a strong thunderstorm. High temps through the long term
are generally in the upper 70s and 80s, with low temps in the 60s
and 70s. 

Reaves

&&

.AVIATION...
00Z Update...
Convection will continue for the next several hours and then
diminish rapidly. Expect convection to develop by Saturday
afternoon although coverage should be less than today. Cigs will
become MVFR after 06Z tonight with a slow improvement Saturday
morning to VFR. 

//ATL Confidence...00Z Update... 
Medium on timing of convection
Medium on cigs late tonight
High on remaining elements.

17

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          66  84  67  80 /  60  40  40  60 
Atlanta         68  83  69  78 /  60  50  40  60 
Blairsville     63  78  63  77 /  60  60  60  60 
Cartersville    67  83  67  80 /  60  60  50  60 
Columbus        69  85  69  80 /  60  50  40  70 
Gainesville     67  81  67  78 /  60  60  50  60 
Macon           68  84  68  80 /  60  50  40  70 
Rome            68  84  67  82 /  60  60  50  60 
Peachtree City  67  84  67  79 /  60  50  40  60 
Vidalia         70  86  70  81 /  50  40  40  70 

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 8 AM EDT Saturday for the following 
zones: Baldwin...Banks...Barrow...Bibb...Bleckley...Butts...
Carroll...Chattahoochee...Cherokee...Clarke...Clayton...Cobb...
Coweta...Crawford...Crisp...Dawson...DeKalb...Dodge...Dooly...
Douglas...Emanuel...Fayette...Forsyth...Glascock...Greene...
Gwinnett...Hall...Hancock...Harris...Heard...Henry...Houston...
Jackson...Jasper...Jefferson...Johnson...Jones...Lamar...
Laurens...Lumpkin...Macon...Madison...Marion...Meriwether...
Monroe...Montgomery...Morgan...Muscogee...Newton...North 
Fulton...Oconee...Oglethorpe...Paulding...Peach...Pickens...
Pike...Pulaski...Putnam...Rockdale...Schley...South Fulton...
Spalding...Stewart...Sumter...Talbot...Taliaferro...Taylor...
Telfair...Toombs...Treutlen...Troup...Twiggs...Upson...Walton...
Warren...Washington...Webster...Wheeler...White...Wilcox...
Wilkes...Wilkinson.

&&

$$

SHORT TERM...17
LONG TERM....RW
AVIATION...17