Special Weather Statement, NWS Atlanta, GA

Area Forecast Discussion
National Weather Service Peachtree City GA
646 AM EST Fri Jan 3 2020

.UPDATE...

Updated to include areas of dense fog across the wedged zone of
north Georgia and have advisory out until 10am. Also adjusted some
pop trends this morning given more convective banding occurring
in western portions of the area that could have some embedded
isolated lightning. Previous discussion follows.

Also 12z Aviation update below.

Baker

&&

.PREV DISCUSSION... /Issued 330 AM EST Fri Jan 3 2020/

SHORT TERM /Today through Saturday/...

Complex fcst continues today into Saturday given multiple forcing
features. Warm front associated with developing sfc low to the west
is progressing northward this morning while a lingering wedge keeps
a rather tight thermal gradient across the eastern Atlanta metro
back toward Athens and farther north. More stratiform precip has
been rather light back in the northwestern tier of the CWA, though
there is more indication of convective banding further south - see
Hydrology section below for more details.

Aside from the heavy rain/flooding threats, there is enough progged
instability today generally south of the I-85 corridor to have
thunderstorm potential with strong wind threat from enhanced
downdrafts aided by hydrometeor loading. SPC Day 1 Outlook continues
to have a Marginal risk across this portion of our CWA as well.

Somewhat occluded fropa looks to occur late today across the NW,
then exit the SE by late this evening/early Saturday, though the
amplified upper trough axis won't swing across the region until late
Saturday/early sunday. Have therefore continued chance pops for
showers across most of the area in the morning and then have a
gradual decrease to be more confined to north GA by the afternoon.
With the cold core advecting into the north and some lingering low
level moisture, thermal profiles still support some brief rain
shower to snow shower transition and by Saturday late afternoon into
evening, some light snow accumulations under half an inch cannot be
ruled out in the higher peaks of northeast GA.

Temps look to make it into the 60s across most of north GA today and
even the low to mid 70s in portions of central GA in the warm sector
of the aforementioned frontal system. Saturday looks a bit cooler
but still above climo prior to the trough axis passing through and
the expected CAA just beyond the short term.

Baker

&&

.LONG TERM /Saturday Night through Thursday/...

Progressive pattern continues through the extended forecast period.
Still looking at the potential for some lingering light rain/snow
showers across the far north Saturday evening in the moderate to
strong cold advection behind the exiting short wave. Chances for any
significant accumulations remain low at this time, however some light
amounts are possible, especially along the ridges and peaks of the
north Georgia mountains. Cold and dry Sunday/Sunday night before
warming returns ahead of the next system approaching Monday night.
Looks like temperatures rebound enough for precipitation to be liquid
from the onset late Monday night/early Tuesday. Tuesday night we
will need to watch for the potential of a brief wintry mix across the
far north once again if the colder air is able to catch up with the
exiting precipitation. Dry and cool Wednesday through Wednesday
night before another warmup ahead of the next system moving in for
the end of the week.

20

&&

.HYDROLOGY...

While the upper forcing and more enhanced deep layer moisture axis
still supports likely showers or light to moderate rain in the
northwestern CWA, we will hold onto the current Flood Watch, though
not confident in higher amounts for any expansion north of the I-85
corridor. QPF has now had more consistency with honing in on
convective banding potential generally along and southeast of the I-
85 corridor through today, which is already occurring at the time of
this discussion in the SW near Columbus. Storm totals are looking to
be near 1.5 inches in this SW to NE swath, with isolated higher
amounts likely given the unseasonably precip efficient environment
with PWATs 1.5-1.75 inches, mostly unidirectional wind field, and
increased CAPE. Feel the flooding threat with any convective banding
is more of an isolated "flashy" type and not high enough progged
rainfall amounts in this area to warrant another watch, but will
definitely need close monitor today.

Baker

&&

.AVIATION...
12Z Update...
LIFR/VLIFR cigs and some dense fog across northern sites this
morning with higher near the southern sites. A warm front moving
northward could have some slight improvements to the northern
sites by 14/15z. Expect more widespread precip development during
the day today and possible banding of heavier showers or
thunderstorms. Kept TSRA mention to the southern sites though
cannot rule out farther north later. Winds east to NE for the
northern sites shifting SSW close to 14z this morning then west
by this afternoon.

//ATL Confidence...12Z Update...
Medium on all elements.

Baker

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          67  53  59  34 /  90  70  50   5
Atlanta         66  52  56  33 /  90  70  40  10
Blairsville     60  46  51  28 /  80  80  60  20
Cartersville    62  49  55  31 /  80  80  50  10
Columbus        73  54  60  35 /  90  70  40   5
Gainesville     62  51  55  33 /  80  70  50  10
Macon           75  56  63  34 /  90  80  50   5
Rome            61  49  54  31 /  80  70  50  10
Peachtree City  68  52  57  33 /  90  70  40  10
Vidalia         78  61  67  36 /  50  80  70   5

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM EST this morning for the
following zones: Banks...Barrow...Bartow...Cherokee...Clarke...
Cobb...Dawson...DeKalb...Douglas...Forsyth...Gwinnett...Hall...
Jackson...Lumpkin...Madison...Morgan...Newton...North Fulton...
Oconee...Oglethorpe...Paulding...Pickens...Rockdale...South
Fulton...Walton...White.

Flood Watch through this evening for the following zones:
Catoosa...Chattooga...Dade...Floyd...Gordon...Murray...Walker...
Whitfield.

&&

SHORT TERM...Baker
LONG TERM....20
AVIATION...Baker

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Special Weather Statement
National Weather Service Peachtree City GA
838 AM EST Fri Jan 3 2020

GAZ066-067-078-031415-
Harris GA-Troup GA-Meriwether GA-
838 AM EST Fri Jan 3 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN HARRIS...SOUTHERN
TROUP AND SOUTHWESTERN MERIWETHER COUNTIES UNTIL 915 AM EST...

At 838 AM EST...a strong thunderstorm was near Whitesville-Pine Lake,
or near Valley...moving northeast at 60 mph.

  HAZARD...40 mph wind and heavy rain.

  IMPACT...Expect minor damage to tree limbs and blowing around of
           light...unsecured objects. Heavy rain may cause temporary
           street flooding especially in poor drainage areas.

Some locations in the path of this storm include
LaGrange, Greenville, West Point, Hogansville, Pine Mountain, Saint
Marks, Mountville, Cannonville, Louise, Odessadale, Stovall, Big
Springs, Jones Crossroads, Baughs Crossroads, Smiths Crossroad,
Whitesville-Pine Lake, Lake Harding and Long Cane.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

People outdoors should seek shelter immediately. Motorists should
slow down and be prepared for possible loss of control due to
hydroplaning.

LAT...LON 3318 8491 3304 8464 3266 8509 3267 8509
      3269 8512 3272 8512 3274 8511 3274 8513
      3276 8514 3278 8512 3281 8517 3283 8517
      3285 8515 3286 8519 3291 8519
TIME...MOT...LOC 1338Z 225DEG 53KT 3283 8510

WIND...40MPH

Special Weather Statement
National Weather Service Peachtree City GA
845 AM EST Fri Jan 3 2020

GAZ032-033-044-045-053>057-067-068-031415-
Fayette GA-North Fulton GA-Cobb GA-Clayton GA-Coweta GA-DeKalb GA-
Spalding GA-Meriwether GA-Pike GA-Henry GA-South Fulton GA-
845 AM EST Fri Jan 3 2020

...SIGNIFICANT WEATHER ADVISORY FOR FAYETTE...NORTH FULTON...SOUTHERN
COBB...CLAYTON...EASTERN COWETA...SOUTHWESTERN DEKALB...WESTERN
SPALDING...NORTHERN MERIWETHER...NORTHWESTERN PIKE...NORTHWESTERN
HENRY AND SOUTH FULTON COUNTIES UNTIL 915 AM EST...

At 845 AM EST...a line of strong thunderstorms was along a line
extending from Cascade Heights to near Luthersville...and moving east
at 40 mph.

  HAZARD...Heavy rain.

  IMPACT...Heavy rain may cause temporary street flooding especially
           in poor drainage areas.

Some locations in the path of these storms include
Atlanta, Newnan, Decatur, Fayetteville, Jonesboro, Smyrna, Peachtree
City, East Point, Stockbridge, Union City, Forest Park, Riverdale,
College Park, Fairburn, Clarkston, Tyrone, Morrow, Lovejoy, Hapeville
and Stone Mountain.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Motorists should slow down and be prepared for possible loss of
control due to hydroplaning.

LAT...LON 3334 8472 3382 8454 3382 8416 3321 8440
      3304 8465 3315 8485
TIME...MOT...LOC 1345Z 253DEG 34KT 3372 8450 3324 8470