Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 170031
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
831 PM EDT Wed Aug 16 2017

.PREV DISCUSSION... /issued 320 PM EDT Wed Aug 16 2017/

SHORT TERM /Tonight through Thursday Night/...

A warm, moist airmass remains across the forecast area.  Convection
has been slow to develop this afternoon and expect mainly scattered
showers and isolated thunderstorms mainly this afternoon and early
evening.

Weak upper level ridging remains over the southeast through tomorrow
before building west over the northern Gulf of Mexico.  The flow
aloft flattens some by tomorrow evening with a weak disturbance
approaching north GA toward the end of the forecast period.  A weak
surface boundary will remain east of the area throughout the period
as well.  With upper level dynamics lacking, and only minimal
instability expect diurnally driven convection today and tomorrow,
with any development diminishing quickly with the loss of daytime
heating.

Guidance temperatures are in line, and continue to show overnight
lows mainly in the 70s with afternoon highs tomorrow once again in
the upper 80s to mid 90s.  Heat indices tomorrow will once again be
near 100.

Atwell

LONG TERM /Friday through Wednesday/...

Made very few changes to the extended forecast grids with this cycle
as medium-range models continue recent trends. Broad, weak mid/upper
ridging breaks down over the weekend in response to the sharpening
upper trough moving out of the northern/central plains into the Ohio
Valley and Great Lakes before beginning to re-establish itself early
next week. Please see the previous Long Term Forecast Discussion
below.

20

Previous LONG TERM Forecast Discussion /Thursday Night through
Tuesday/...

A fairly progressive pattern, especially noted by the northern
stream jet, will continue through the long term. Energy across
the NW Canadian provinces will dig down into the upper mid-west
and move eastward. While this energy does not sink too far south
into our region, we will get some residual mid and upper level
support, especially this weekend. Models are in disagreement with
how much interaction we will see with these features, especially
as it translates down to the surface. There are a couple key areas
to look at.

The first is the frontal passage progged to move through much of
the area by early Saturday morning. The GFS is a bit more robust
with this feature showing a lot more drying through the weekend
across north GA; the front becoming stalled in central GA. The
ECMWF shows a hint of the front moving through with some subtle
drying Saturday into Sunday, but has this boundary becoming
washed out/slipping north allowing moist/unstable airmass to surge
a bit further northward as compared to the GFS by Sunday afternoon.
Nevertheless, still feel better chances of convection will be
across central GA, collocated with the boundary.

All eyes are now on Monday, August 21st when the Eclipse is set to
cross the SE during the afternoon hours. As the surface high moves
off the mid-Atlantic, this will usher in moist southerly flow
across the region. This is not good for those hoping for clear
skies. Both models are still holding on to weak mid-level ridging,
although impulses moving NE from a wave of low pressure across the
GC region will aid in the formation of convection across the
region. The GFS illustrating a bit more upper level support as
opposed to the ECM. What does this mean in the end? Well, the
pattern is not conducive for mostly clear skies. However, this is
a typical summer time pattern across the region. So, viewing the
Eclipse is still a potential, between all the building
cumulonimbus and convection. One may just have to be at the right
place at the right time. There is still a lot of uncertainty at
this point. We will continue to update the forecast with new model
guidance and hope the mid-level ridge strengthens with surface
high pressure slowing its eastward progression.

Temperatures will be at or above normal and will be largely
dependent on overall cloud cover and convection. Temperatures
fluctuations during the eclipse (Monday afternoon between 1pm and
3pm) may drop a few degrees, but is largely correlated with cloud
cover and the path of totality.

26

&&

.AVIATION...
00Z UPDATE...

SHRA/TSRA has been flirting with the TAF sites, especially ATL,
PDK and MCN but thus far remained outside the 5 mile radii. Looks
like VCSH will suffice for the remainder of the evening and a
straight forward summertime forecast thereafter. Prob30 already
in there for Thu and looks on target.

//ATL CONFIDENCE...00Z UPDATE...
High on all elements.

Deese

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          74  92  74  92 /  20  30  20  40
Atlanta         75  91  75  91 /  20  30  20  40
Blairsville     69  86  69  86 /  20  40  20  40
Cartersville    74  91  74  89 /  20  30  20  40
Columbus        76  93  77  93 /  20  30  20  40
Gainesville     74  90  74  90 /  20  30  20  40
Macon           76  93  76  95 /  20  30  20  40
Rome            74  91  74  91 /  20  30  20  40
Peachtree City  74  91  74  91 /  20  30  20  40
Vidalia         77  94  77  94 /  20  30  20  50

&&

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

$$

SHORT TERM...Deese
LONG TERM....RW
AVIATION...Deese



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