Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 251713
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
113 PM EDT Thu May 25 2017



.PREV DISCUSSION... /Issued 1140 AM EDT Thu May 25 2017/

UPDATE...

Showers that moved across northern and eastern Georgia this
morning have since dwindled with only a few light returns noted
on radar. This precipitation activity is associated with an
anonymously deep upper level low tracking across the southern
Appalachians. Anticipate residual cloud cover this morning, which
should eventually clear out through the remainder of the afternoon
as the low pivots to the northeast. Gusty west winds will
continue through sunset.

PREV DISCUSSION... /Issued 732 AM EDT Thu May 25 2017/

PREV DISCUSSION... /Issued 509 AM EDT Thu May 25 2017/

SHORT TERM /Today through Friday/...
Cold front has finally pushed east of the CWFA early this morning.
However, a large upper low and trough will continue across the
eastern third of the country through today. Mid level energy rounding
the base of the trough will add just enough lift, to produce some
isold/sct shra today.

Shra coverage is expected to decrease through the day as the upper
low and trough pull off to the east. Steep lapse rates will be in
place this morning, but luckily surface instability will be at a
minimum. A rumble of thunder or two is not out of the question, but
do think that the chances of thunder are too low to mention at this
time. Dry conditions are expected overnight and on Friday.

Max temps today will be close to ten degrees below normal for this
time of year. However, tomorrows values will be near normal.

NListemaa

LONG TERM /Friday Night through Wednesday/...
Extended period begins with shortwave ridging building in in the
wake of the anomalous upper low exiting. ecmwf centers a weaker
ridge over the northern gulf while the gfs and sref slightly
stronger. All of the models put the TN Valley and north GA in a
slightly diffluent flow atop the ridge centered over the north
central gulf. Current consensus is to run low pops across the
north on Saturday...but a deeper look into the environment makes
one wonder if the atmosphere will behave. GFS...ECMWF...and NAM
all destabilizing the airmass across far north GA significantly
on Saturday. Lapse rates forecast to exceed 8.0 deg C/km and even
approach 8.5 depending on what model you look at. Combined with 0-
6km shear values 40 kts and SB Cape values AOA 2000 j/kg and even
more in the GFS mean that IF storms or an MCS develops further
north in the favored portion of the ridge...Saturday eve could be
interesting. Definitely something to watch for potential MCS
development across the central US on Friday can ride the ridge
southeast and re-ignite during the day Saturday. Hail and Wind
would certainly be a threat..but just don`t have a lot of
confidence . on coverage. Day 3 SPC outlook has the Slight Risk
coming into far NW GA which may have to expand a bit southward if
it looks like coverage could be higher further south.

Another significant vortex starts swinging south into the northern
Great lakes Saturday into Sunday forcing the ridge southeast and
pushing a frontal boundary into GA during the day on Sunday.  Models
in general agreement on the front working into north GA by late
Sunday into early Monday resulting in increase shower and
thunderstorm chances.  Once again...cannot rule out severe chances
given 40-50kts of 0-6km bulk shear and 7.0-7.5 deg c/km mid level
lapse rates forecast for sunday afternoon/evening across the
state...particularly north central. Will need to again see the
evolution of things on Saturday and the timing of the shortwave that
rotates through the broad trof digging over the great lakes region.

Sfc boundary sags south and hangs up across the state on Monday also
presenting an unfortunate increase in storm chances on our Memorial
Day.  Current parameters suggest there would be some severe chances
but too early to tell how it all plays out given the previous day
convection influence on the following day. Model consensus
running 50 to 60 pops on Monday attm and see now reason to
disagree.

Boundary sags south of the cwa on Tuesday and Wednesday giving the
region a shot of drier air and reprieve with a large trof taking
over the eastern half of the US.  Would expect below normal temps a
good portion of next week.

30

&&

.AVIATION...
18Z Update...
VFR conditions observed across the region and we anticipate this
to continue through the TAF period. A deep upper level low will
pivot northeast exiting the region with subsidence helping to dry
out the atmospheric column through the remainder of the
afternoon. This will result in BKN cigs eroding to SKC by around
sunset. Gusty west winds will diminish this evening. Pleasant
flying conditions through Friday. Clear skies and westerly wind
with the occasional gust possible.

//ATL Confidence...18Z Update...
High confidence on all elements.

26

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          74  55  84  65 /  30   0   0   0
Atlanta         73  58  84  67 /  30   0   0   0
Blairsville     68  51  79  60 /  30   5   0   5
Cartersville    73  54  84  65 /  30   0   0   0
Columbus        78  57  87  65 /  20   0   0   0
Gainesville     70  56  82  65 /  30   0   0   0
Macon           76  55  86  63 /  20   0   0   0
Rome            75  53  85  64 /  20   0   0   0
Peachtree City  74  53  84  63 /  20   0   0   0
Vidalia         78  60  86  66 /  20   0   0   0

&&

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

$$

SHORT TERM...NListemaa
LONG TERM....30
AVIATION...26



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