Special Weather Statement, NWS Atlanta, GA

Area Forecast Discussion
National Weather Service Peachtree City GA
332 PM EDT Thu Aug 20 2020

.SHORT TERM /Tonight through Friday Night/...
Primary concerns in the short term are heavy rain and
strong/severe storms. Unlike my thoughts yesterday at this time,
convection quite vigorous with isolated hail and damaging wind
threat over middle GA.  Mid and upper level vertical wind shear
not terrible for August with 500mb/300mb winds of 20kts/30kts.
Diffluent/divergent flow enhancing vertical motion over SW and
middle GA. SBCAPE around 3000 J/kg along and north of I-20 ahead
of developing line of storms, which is more than what I would have
guessed with temps in the mid 80s at best. Convection should
spread slowly north through the evening and will likely persist
past midnight.

Another round of convection expected starting mid-afternoon
Friday. Similar pattern with nearly stationary upper low to the
west and weak southerly flow. PoPs near categorical again and
expected to persist through much of the evening.

SNELSON

.LONG TERM /Saturday through Thursday/...
Saturday looks to be yet another wet day across the area, though it
is forecast to be the beginning of a pattern shift as the core of
the PV anomaly to our west lifts through the area during the day.
Forecast bulk shear is decent in the GFS/Euro, less so in the
NAM, and some instability will exist, especially as slightly
colder core of the 500 mb low moves past the CWA. Limiting factor
may actually be surface heating, though I'm surprised to be typing
that in Georgia in August, with forecast highs currently in the
low to mid 80s. Definitely not expecting any kind of widespread
severe coverage, but can't rule out an isolated severe storm on
this day that may be a bit more persistent than our typical summer
straight up, straight back down type of storms.

By Sunday the trough slower begins to dissipate as is gets
squeezed between western ridge and another ridge moving in from
the east Atlantic. Tropical airmass will still be in place, so
still expect to be able to squeeze some more moisture out of the
atmosphere these days with decent PoP chances each day. The lack
of any strong upper- level system coming in to replace our
departing trough will be an opportunity for the tropics to enter
the forecast on Tuesday.

Speaking of, if you had "dueling tropical systems in the Gulf of
Mexico" on your 2020 bingo card, the 12Z operational GFS says you
may be in luck! In all seriousness, the forecast beyond Monday is
fraught with uncertainty in part because of two different tropical
depressions, TD 13 in the MDR of the Atlantic, and TD 14 in the
Caribbean, both forecast to become named systems Laura and Marco
(order dependent on who wins the race). Both the track and intensity
of these systems will have large impacts on the overall forecast as
well as magnitude of any impacts, though given two potential systems
in the gulf, it is hard to argue any other scenario that doesn't
have some form of tropical moisture impacting the CWA through mid
next week. As for TD 13, current NHC forecast brings it the closest
to the CWA, and model consensus certainly favors a track near the
Keys/Everglades into the eastern Gulf before a more northward turn
around the edge of a high pressure over western Atlantic that has
been drifting west and will be a large portion of the steering
current for the system. TD 14 is expected to make a northward turn
soon, slow down a bit, and travel over the Yucatan, before moving
into the western Gulf, with the slower forward speed allowing TD 13
to catch up a bit. However, to emphasize for the 100th time in this
AFD, there is still substantial uncertainty this far out, amplified
by having two tropical systems potentially this close together.
Forecasted PoPs account for this by keeping out any likely chances
until more is known about the exact tracks. Please stayed tuned to
the latest forecasts for these via both us and our colleagues at
the National Hurricane Center.

Lusk

&&

.AVIATION...
18Z Update...
Scattered SHRA/TSRA again today with enough coverage to warrant
TEMPO 19-23Z then prevailing -SHRA 23Z-06Z. IFR stratus likely to
develop 10Z-13Z similar to this morning with another round of
SHRA/TSRA later in the afternoon Friday. Sfc winds remain light E
less than 6kts thru the forecast except gusty near TSRA.

//ATL Confidence...18Z Update...
Low-Medium confidence on IFR cig development
Medium confidence on SHRA/TSRA timing
High confidence on all other elements

SNELSON

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          69  82  68  82 /  70  80  70  60
Atlanta         69  81  69  81 /  80  70  70  60
Blairsville     65  75  64  76 /  60  80  70  70
Cartersville    69  83  68  83 /  70  80  70  60
Columbus        70  85  69  84 /  80  70  60  60
Gainesville     69  80  67  80 /  70  80  70  60
Macon           70  84  69  82 /  70  70  60  60
Rome            69  83  68  83 /  70  70  70  60
Peachtree City  69  82  68  81 /  80  70  70  60
Vidalia         72  85  71  83 /  50  70  60  70

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...SNELSON
LONG TERM....Lusk
AVIATION...SNELSON

Hazardous Weather Outlook
National Weather Service Peachtree City GA
1148 AM EDT Thu Aug 20 2020

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-211600-
Baldwin-Banks-Barrow-Bartow-Bibb-Bleckley-Butts-Carroll-Catoosa-
Chattahoochee-Chattooga-Cherokee-Clarke-Clayton-Cobb-Coweta-
Crawford-Crisp-Dade-Dawson-DeKalb-Dodge-Dooly-Douglas-Emanuel-
Fannin-Fayette-Floyd-Forsyth-Gilmer-Glascock-Gordon-Greene-
Gwinnett-Hall-Hancock-Haralson-Harris-Heard-Henry-Houston-Jackson-
Jasper-Jefferson-Johnson-Jones-Lamar-Laurens-Lumpkin-Macon-
Madison-Marion-Meriwether-Monroe-Montgomery-Morgan-Murray-
Muscogee-Newton-North Fulton-Oconee-Oglethorpe-Paulding-Peach-
Pickens-Pike-Polk-Pulaski-Putnam-Rockdale-Schley-South Fulton-
Spalding-Stewart-Sumter-Talbot-Taliaferro-Taylor-Telfair-Toombs-
Towns-Treutlen-Troup-Twiggs-Union-Upson-Walker-Walton-Warren-
Washington-Webster-Wheeler-White-Whitfield-Wilcox-Wilkes-
Wilkinson-
1148 AM EDT Thu Aug 20 2020

This Hazardous Weather Outlook is for portions of North and Central Georgia.

.DAY ONE...This Afternoon and Tonight...

Numerous to widespread thunderstorms are forecast this afternoon
and evening across north and central Georgia, and some
thunderstorms will persist overnight. A few storms could be
strong to severe. The main threats will be strong to damaging
winds, locally heavy rainfall, hail, and cloud-to-ground
lightning. There is also an increased risk of flash flooding,
mainly across north Georgia.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday...

Numerous thunderstorms are expected Friday and Saturday across
the forecast area. Scattered thunderstorms are forecast Sunday
through Wednesday. A few storms could be strong to severe each
day, with strong to damaging winds, locally heavy rainfall, hail,
and cloud-to-ground lightning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed through tonight.

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