Special Weather Statement, NWS Atlanta, GA

Area Forecast Discussion
National Weather Service Peachtree City GA
657 AM EST Thu Dec 30 2021

.UPDATE...

Updated for the 12Z Aviation Discussion.

&&

.PREV DISCUSSION... /Issued 513 AM EST Thu Dec 30 2021/

..Update for cancellation of Tornado Watch 571...

UPDATE...

The overall severe threat has become more limited this morning as
cooler air surges southward and cuts off surface-rooted convection
across central portions of the CWA. Environmental parameters in
place still show at least an isolated threat for gusty winds,
small hail, and an outside chance for a weak tornado through the
late morning but  odds are too low to justify the continuation of
the Tornado Watch at this time. Warm, moist air overrunning the
outflow should continue south of the I-20 corridor,producing rain
rates around 1-2 in/hr in areas that have already seen 1-2 inches
of rainfall thus increasing the likelihood of isolated flash
flooding where training occurs.

Thiem

PREV DISCUSSION... /Issued 426 AM EST Thu Dec 30 2021/

.Morning Area Forecast Discussion...

SHORT TERM /Today through Friday/...

As has been the case for the last few days, upper ridging remains
centered over the Caribbean and extending roughly along the Atlantic
coast, and troughing remains in place over the western CONUS. This
persistent setup is keeping southwesterly upper level flow in place
over much of the eastern CONUS. At the surface, a stationary front
remains stalled to our north and stretching across the Tennessee
Valley. A strong surface high to the east of the Florida peninsula
is also maintaining southerly to southwesterly winds over Georgia.
As a result of these factors, north and central Georgia remains
within an unseasonably warm and moist airmass as the period begins.
Low temperatures this morning are expected to range from the low 60s
across far north Georgia to the upper 60s in east-central Georgia,
which will be between 28-32 degrees above climatological normals for
this time of the year. Perhaps "unseasonably warm" is a bit of an
understatement, as these lows could once again be near or above
records across the forecast area, once again.

Showers and thunderstorms are ongoing across portions of north
Georgia, roughly along and north of a line from Heard county to
Wilkes county. As the upper level shortwave traversing the upper
level flow and moving through the Tennessee Valley has moved
northeastward away from the forecast area, the line of showers and
thunderstorms has stalled across this area. Although minimal
instability remains across much of north Georgia, 0-1 km shear
values are still between 25-30 kts and deep layer bulk shear values
are between 50-60 kts. Although the marginal instability and the
lack of organized forcing are serving as limiting factors, it is
still possible that isolated stronger storms that develop this
morning could produce gusty and potentially damaging winds. With
deep moisture in place and precipitable values in excess of 1.5
inches across north Georgia, it is possible that stronger storms
could produce heavy rainfall. Localized flooding concerns are
therefore possible this morning, especially where training bands of
storms are able to set up.

The outlook for the daytime today remains a bit messy, and will be
contingent upon the evolution of the convection this morning and
where boundaries are able to set up in order to generate
convergence. Hi-res guidance continues to hint at the possibility of
a broken line of showers and thunderstorms pushing slowly southward
towards central Georgia late this morning and into the afternoon
hours, However, with non-existent synoptic scale forcing, there is
still much disagreement between model solutions on the timing and
evolution. In any case, high temperatures in the 70s and dewpoints
in the mid 60s will allow for sufficient instability for storm
maintenance, especially in central Georgia, where MUCAPE values
could range from 1200-1800 J/kg by this afternoon. Strong winds of
over 50 kts at 500 mb will also contribute to strong deep-layer bulk
shear co-located with the best instability. The combination of these
factors should be sufficient to support the development of a few
strong to severe thunderstorms. At this time, damaging wind gusts
appear to be the main threat with any severe storms that are able to
develop, as precipitation loading of downdrafts in stronger storms
could help transfer down the strong upper level winds. With low-
level shear values of 20-25 kts and 0-1 km SRH values of 100-150
m2/s2 in central Georgia, a brief tornado also cannot be ruled out,
as well. Aside from the lack of an organized forcing mechanism,
another limiting factor will be poor low and mid-level lapse rates.
As a result of these limitations, the SPC has kept the majority of
north and central Georgia in a Marginal Risk for severe weather in
their Day 1 outlook.

Storm total rainfall amounts throughout the remainder of the day are
currently forecast to be between 1-2 inches roughly along and south
of the I-20 corridor with progressively diminishing amounts to the
south. Given the aforementioned PWAT values over 1.5 inches,
stronger thunderstorms that develop could also produce locally
heavier rainfall. Fairly dry antecedent conditions remain in place
across central Georgia, which should help inhibit flooding concerns
in that area except for the possibility of heavy rain training over
a common location. On the other hand, observed rainfall in north
Georgia could increase the likelihood of flooding in areas that
receive additional heavy rain. In north Georgia, a couple of rivers
have moved to Minor Flood stage, with a handful of others near
bankfull.

Rain chances will steadily diminish this evening and tonight with
the loss of diurnal instability. With weak winds overnight and
saturated soils in locations that receive precipitation, it is
likely to see the development of fog across north and central
Georgia. The potential for dense fog development will furthermore
need to be monitored. The break from the rain during the overnight
hours into early Friday morning will be short-lived. As a surface
low strengthens over the Four Corners region and moves quickly
northeastward towards the Great Lakes region, another round of warm,
moist air will surge into the southeastern CONUS. Chances for
showers and thunderstorms will increase during the daytime on
Friday, with likely PoPs anticipated across north Georgia during the
afternoon hours. Modest instability, with SBCAPE values between 400-
800 J/kg, is possible in north Georgia in the afternoon. Deep layer
bulk shear values of 50+ kts and 0-1 km shear values of 20-25 kts
across the same location could lend itself to the possibility of
isolated severe thunderstorms capable of producing strong wind
gusts during the afternoon.

Considering the tropical airmass in place, both high and low
temperatures could match or exceed daily records through the short
term period, with lows in the 60s and highs in the 70s, and even
approaching the 80s in the far southern portions of the forecast
area.

King

LONG TERM /Friday Night through Wednesday/...

Looks like the new year may be headed in with a bit of a bang still.
Long term picks up Friday night, where shortwave over Ontario
rotating within the Arctic branch of the jet will have weak sfc low
to the north of the CWA over Ohio River Valley. Strong, Arctic high
and associated Arctic airmass will be sliding down the Rockies into
the Great Plains thanks to strong confluence aloft with the
leading edge stalling out over the central Great Plains. Southerly
to southwesterly flow will be in place across the CWA at the sfc
in part as a mass response to sfc low to the north, leading to
additional WAA and isentropic lift that will act both to keep our
warm, moist airmass locked in place and bring some chances of
showers and thunderstorms, especially across north GA, though
upper level forcing will certainly be lacking for anything more
than a low end severe threat and instability is somewhat lacking.

All of this will set the stage for Saturday. Two shortwaves will be
rotating through the base of the long wave trough positioned out
west that will also finally be getting a boot as rossby wave
breaking deteriorates the blocking high over the east Pacific. The
first of these will be a cut-off low that merges on Friday with
the larger trough and then ejects into the Plains on Saturday.
Sfc low pressure forms and moves along baroclinic/frontal zone
established by aforementioned system above. This begins the
process of driving the cold front towards the CWA.

It is at this point where things get interesting with regard to
model spread. Through the week we have been emphasizing how models
have handled the ejection of the second shortwave/PV anomaly within
the larger trough. The details of this have LARGE implications on
the overall timing of the cold front, the chances of seeing severe
weather in the area, and what, if any, winter wx may happen on the
backside of the system. Today the models of swung again toward
having a less phased solution of these systems. What this means is
that as the larger upper level wave progresses east, it pushes the
cold front toward the area, but not as quickly as it would if these
waves were in phase. With the lagging shortwave/bowling ball of PV
moving in a little bit later, we see another sfc low able to form
just to the north of the CWA along the front and move to the NE on
Sunday. The results of this are a delay of the cold front really
moving through the area until Sunday, potential for some severe wx
on Sunday in parts of central and east central GA, possibly in
addition to some initial severe wx on Saturday with the initial
frontal surge, and the possibility of some winter wx in the
mountains and parts of north GA on the backside of all of the Sunday
evening into early overnight.

As stated in previous AFDs, there will be some potent ingredients in
place, and we will finally be getting the upper level support that
has been lacking for other severe wx days this week. With models
still jumping around with the potential timing of everything, it's
hard to truly pin down an exact timing, but late Saturday still
shows the most consistent potential for having severe wx. The other
aspect of this will be the flooding potential, and we are already
seeing some heavy rainfall across parts of north GA this morning
that will only increase the potential by priming many of our rivers
and saturating soils. QPF values remain in the 1.5"-2.5" range
across north GA and isolated higher amounts will certainly be
possible. Isolated flash flooding and some flooding of creeks,
streams, and rivers seems likely.

After this, we finally get cold air into the CWA. The formation of a
sfc low may kick some snow showers back into north GA and especially
the mountains, though accumulations still don't seem likely at this
time. Track of the low would just be a bit too far north for
anything too significant in terms of accumulations (if that
solutions even plays out). Overnight lows look to be in the 20s and
30s across the area on Sunday night. Cool airmass moves into place
for a few days under sfc high that slowly slides to the east.
Temperatures will slowly increase as airmass modifies and
winds slowly turn back south through the end of the forecast
period.

Lusk

CLIMATE...

Records for 12-30

               Max Temperature         Min Temperature
  Station      High        Low         High        Low
  -------  ----------  ----------  ----------  ----------
   KAHN      76 1984     28 1909     60 1969      9 1917
   KATL      73 1984     26 1880     60 1996      1 1880
   KCSG      80 1984     34 1983     61 2015     15 1961
   KMCN      78 1984     27 1917     66 2015     13 1917

Records for 12-31

               Max Temperature         Min Temperature
  Station      High        Low         High        Low
  -------  ----------  ----------  ----------  ----------
   KAHN      76 1984     24 1917     58 1996     13 1917
   KATL      73 1984     26 1917     61 1996      4 1880
   KCSG      81 1923     34 1917     62 1936     18 1983
   KMCN      79 1923     28 1917     61 1973     14 1983

Records for 01-01

               Max Temperature         Min Temperature
  Station      High        Low         High        Low
  -------  ----------  ----------  ----------  ----------
   KAHN      76 1985     31 1936     59 1985      6 1918
                1952
   KATL      75 1952     25 1928     57 2019      7 1928
                                        1985
                                        1952
   KCSG      78 1952     32 1918     63 2019     18 1977
   KMCN      78 1985     32 1928     65 2019     17 1984
                                                    1928
                                                    1918

Records for 01-02

               Max Temperature         Min Temperature
  Station      High        Low         High        Low
  -------  ----------  ----------  ----------  ----------
   KAHN      73 1952     26 1928     57 1966     11 2018
                1930
   KATL      73 1952     17 1928     56 1997      1 1928
   KCSG      79 1909     30 1928     61 1966     11 1928
   KMCN      78 1952     23 1928     61 2017      8 1928

&&

.AVIATION...
12Z Update...
A line of SHRA, along with isolated TSRA, is currently extending
from roughly the ATL metro to AHN. Have carried prevailing SHRA
for ATL, with a TEMPO for TSRA from 12-16Z as convection is drawn
northward through the morning hours. SHRA/TSRA is anticipated to
move slowly southeast during the early afternoon, with chances
diminishing at ATL/AHN and increasing at CSG/MCN. A TEMPO for TSRA
has been introduced at 17-21Z at CSG and 19-23Z at MCN. Ceilings
will mainly be MVFR, with some isolated instances of IFR,
throughout much of the day.There will be a brief improvement to
in the late afternoon and early evening, when SHRA/TSRA coverage
diminishes. This improvement will be short- lived, as weak winds
and wet soils will contribute to a return to IFR ceilings after
02-03Z and possible fog development after 06Z. Winds will be
mainly SW to W at 7-12 kts, with isolated gusts with TSRA that
occurs, before decreasing to 6 kts or less overnight.

//ATL Confidence...12Z Update...
High confidence on winds.
Low to medium confidence on all elements.

King

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          72  57  71  63 /  80  40  60  60
Atlanta         72  59  72  64 /  80  30  70  50
Blairsville     68  50  69  59 /  50  20  70  80
Cartersville    72  56  72  63 /  70  20  70  60
Columbus        77  63  77  66 /  60  40  60  30
Gainesville     71  57  69  63 /  70  30  70  70
Macon           78  62  77  65 /  60  50  50  20
Rome            72  56  72  64 /  60  20  70  60
Peachtree City  73  58  74  64 /  80  30  70  40
Vidalia         79  66  79  66 /  30  30  30   5

&&

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

SHORT TERM...King
LONG TERM....Lusk
AVIATION...King

Hazardous Weather Outlook
National Weather Service Peachtree City GA
513 AM EST Thu Dec 30 2021

GAZ001>009-011>016-019>025-027-030>039-041>062-066>076-078>086-
089>098-102>113-311015-
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-
513 AM EST Thu Dec 30 2021

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

.DAY ONE...Today and Tonight...

Thunderstorms will be possible across north and central Georgia
through this evening. The primary threats will be gusty to
damaging winds, a brief tornado, periods of heavy rain, and
occasional cloud-to-ground lightning. Isolated flooding will be
possible where the heaviest rain occurs across north Georgia.

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

There is a chance for thunderstorms Friday for north Georgia. The
primary threats will be gusty to damaging winds, periods of heavy
rain, and occasional cloud-to-ground lightning.

Additional rounds of thunderstorms are possible Saturday and
Sunday. Some of these storms may be severe. There is also a
possibility for some mixed wintry precipitation in far northern
Georgia overnight Sunday evening into early Monday morning. Stay
tuned to the latest forecasts throughout the week for more
details.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not requested but spotters are encouraged
to submit reports of severe weather through the web by going to
weather.gov/atlanta.  Please relay any information about observed severe
weather to the NWS while following all local, state, and CDC
guidelines.

Special Weather Statement
National Weather Service Peachtree City GA
450 AM EST Thu Dec 30 2021

GAZ042>044-052>054-301030-
Fayette GA-Douglas GA-Coweta GA-Carroll GA-Heard GA-South Fulton GA-
450 AM EST Thu Dec 30 2021

...Strong thunderstorms will impact portions of Fayette, southern
Carroll, southwestern Douglas, Heard, Coweta and southwestern Fulton
Counties through 530 AM EST...

At 450 AM EST, a line of strong thunderstorms was along a line
extending from near Sandy Creek to Newell, and moving east at 15 mph.

HAZARD...Heavy rain.

SOURCE...Radar indicated.

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

Locations impacted include...
Newnan, Carrollton, Fayetteville, Franklin, Peachtree City, Union
City, College Park, Fairburn, Tyrone, Palmetto, Senoia, Grantville,
Bowdon, Whitesburg, Brooks, Ephesus, Centralhatchee, Moreland,
Sharpsburg and Turin.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

A Tornado Watch remains in effect until 500 AM EST for north central,
northwestern and west central Georgia.

&&

LAT...LON 3363 8446 3355 8446 3355 8444 3350 8442
      3348 8439 3346 8438 3344 8440 3341 8439
      3336 8440 3332 8439 3326 8443 3322 8486
      3322 8494 3321 8497 3319 8525 3354 8531
TIME...MOT...LOC 0950Z 260DEG 13KT 3351 8452 3341 8539

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH

Special Weather Statement
National Weather Service Peachtree City GA
538 AM EST Thu Dec 30 2021

GAZ042-044-052>055-057-301130-
Fayette GA-Clayton GA-Coweta GA-Carroll GA-Heard GA-Henry GA-
South Fulton GA-
538 AM EST Thu Dec 30 2021

...Strong thunderstorms will impact portions of Fayette, southern
Carroll, northwestern Henry, Heard, Coweta, southwestern Fulton and
Clayton Counties through 630 AM EST...

At 538 AM EST, a line of strong thunderstorms was along a line
extending from Kelleytown to near Corinth, and moving east at 25 mph.

HAZARD...Heavy rain.

SOURCE...Radar indicated.

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

Locations impacted include...
Newnan, Carrollton, Fayetteville, Jonesboro, Franklin, Peachtree
City, East Point, Stockbridge, Union City, Forest Park, Riverdale,
College Park, Fairburn, Tyrone, Morrow, Lovejoy, Hapeville, Palmetto,
Lake City and Whitesburg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3357 8490 3357 8481 3365 8446 3365 8425
      3363 8424 3365 8421 3356 8411 3344 8433
      3317 8524 3351 8531
TIME...MOT...LOC 1038Z 262DEG 23KT 3356 8410 3326 8498

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH

Special Weather Statement
National Weather Service Peachtree City GA
545 AM EST Thu Dec 30 2021

GAZ075-076-301115-
Jefferson GA-Glascock GA-
545 AM EST Thu Dec 30 2021

...A strong thunderstorm will impact portions of south central
Glascock and northern Jefferson Counties through 615 AM EST...

At 545 AM EST, National Weather Service doppler radar indicated a
strong thunderstorm over Edgehill, or near Gibson, moving east at 50
mph.

HAZARD...40 to 50 mph wind and increased chance of a brief tornado.

SOURCE...Radar indicated.

IMPACT...While winds should result in minor damage to tree limbs and
         blowing around of light, unsecured objects, this storm has
         also exhibited localized rotation. A brief tornado could
         quickly form.

Locations impacted include...
Wrens, Stapleton, Avera, Edge Hill, Edgehill, Matthews, Stellaville
and Stapletons Crossroads.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

People outdoors should seek shelter immediately.

&&

LAT...LON 3315 8227 3307 8229 3304 8229 3311 8265
      3321 8265 3325 8225 3323 8224 3323 8223
TIME...MOT...LOC 1045Z 272DEG 43KT 3316 8258

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

Special Weather Statement
National Weather Service Peachtree City GA
722 AM EST Thu Dec 30 2021

GAZ031>033-041>045-301300-
North Fulton GA-Douglas GA-Cobb GA-Haralson GA-Carroll GA-DeKalb GA-
Paulding GA-South Fulton GA-
722 AM EST Thu Dec 30 2021

...Strong thunderstorms will impact portions of southern Paulding,
western DeKalb, Haralson, southern Cobb, central Carroll, Douglas and
central Fulton Counties through 800 AM EST...

At 721 AM EST, a line of strong thunderstorms was along a line
extending from Powder Springs to near Tallapoosa, and moving east at
40 mph.

HAZARD...Heavy rain and increased chance for isolated flooding.

SOURCE...Radar indicated.

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

Locations impacted include...
Atlanta, Marietta, Douglasville, Carrollton, Decatur, Dallas,
Buchanan, Sandy Springs, Smyrna, East Point, Villa Rica, Powder
Springs, Chamblee, Doraville, Clarkston, Austell, Bremen, Temple,
Hiram and Tallapoosa.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3393 8450 3390 8423 3387 8420 3386 8417
      3369 8426 3358 8533 3389 8539
TIME...MOT...LOC 1221Z 274DEG 35KT 3387 8467 3371 8524

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...<30 MPH

Special Weather Statement
National Weather Service Peachtree City GA
852 AM EST Thu Dec 30 2021

GAZ044-053-054-301415-
Fayette GA-Coweta GA-South Fulton GA-
852 AM EST Thu Dec 30 2021

...A strong thunderstorm will impact portions of Fayette, Coweta and
south central Fulton Counties through 915 AM EST...

At 852 AM EST, a strong thunderstorm was over Handy, or near Newnan,
moving east at 45 mph.

HAZARD...40 mph wind and heavy rain.

SOURCE...Radar indicated.

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.

Locations impacted include...
Newnan, Fayetteville, Peachtree City, Union City, Fairburn, Tyrone,
Palmetto, Senoia, Brooks, Moreland, Sharpsburg, Turin, Woolsey, East
Newnan, Starrs Mill, Arnco-Sargent, Handy, Cannongate, Sandy Creek
and Lake Horton.

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 3344 8496 3344 8494 3345 8492 3357 8446
      3331 8440 3330 8441 3329 8496 3339 8500
      3343 8501
TIME...MOT...LOC 1352Z 259DEG 38KT 3337 8492

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH