Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 231908
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
308 PM EDT Sun Jul 23 2017

.SHORT TERM /Tonight through Monday Night/...
Recent analysis of afternoon water vapor imagery reveals a mid level
synoptic pattern over the CONUS characterized by a persistent ridge
over the western US...and an amplifying cyclonic flow regime over
the eastern US. The most notable feature east of the Rockies is a
southeastward moving shortwave trough over the western Great Lakes.
MEanwhile at the sfc...a weak sfc front extended roughly from the
Great Lakes S/SW through IN,IL, MO, and AR...with a weak trough
extending down the Piedmont of the Carolinas into Georgia.

Rest of today and tonight: Forecast is complicated by numerous
outflow boundaries and convectively induced perturbations in the
mean flow. This morning`s MCS over KY has diminished...although
its outflow boundary has helped several complexes develop over
eastern TN and western NC. Think highest concentration of
convective coverage will be across north Georgia where any larger
scale outflow could be influenced by orographic processes and
perhaps the weak sfc trough. Nonetheless...with MLCAPE between
2000-3000J/Kg across the entire CWA...storms could pop up
anywhere. Downburst winds the main threat with low level lapse
rates over 7C/km and PWs near 2 inches. The HRRR has been
consistent in showing redevelopment across KY/TN towards sunset
tonight /likely influenced by morning MCS and the weak front/. It
is possible some of this convection could impact far north Georgia
after midnight...though confidence is low given time of day and
weak flow. Showing slight POPs for now to reflect this
possibility...with a diminishing trend towards sunrise.

Much of the same story for Monday as sfc troughing continues and
Great Lakes shortwave moves into New England. Aforementioned weak
front will likely be closer to the state...but still far enough away
to not have a profound impact on convective initiation. Forecast
will be complicated again by outflow boundaries and convectively
induced perturbations in the mid levels. All things
considered...trend should still remain largely diurnally driven.

Temps will be hot...and it will be humid.

Kovacik


.LONG TERM /Tuesday through Sunday/...
No major changes to the long term from the previous forecast. A weak
trough of low pressure will remain over the CWA early in the long
term. This will develop into a closed low over Georgia by Wednesday
and as the H5 ridge builds over the middle of the country, this will
push the low out of Georgia however there are discrepancies in the
models as to how much moisture will be pushed out as well. Due to
this will maintain pops across the CWA for the latter half of the
week. The next short wave will move out of the upper plains and
toward the CWA toward next weekend increasing the chances of precip
late in the week and next weekend. Temperatures will remain at or
near climate norms through the long term.

17


&&

.AVIATION...
18Z Update...
Typical summertime trends expected through this TAF cycle.
Convection has developed over the large majority of the CWA...with
either -SHRA or -TSRA in the general vicinity of all sites.
Expect coverage of storms to increase over the next several hours
before dissipating...with the threat for several strong wet
microbursts through sunset. Some mid level convective debris may
linger through the overnight hours before gradual clearing
commences and the diurnally driven cu field develops mid Monday
morning. Some fog could be possible Monday morning should heavy
downpours occur towards sunset...but coverage nor confidence high
enough to mention in TAFs. Storms will develop again Monday
afternoon. Opted to keep winds almost due west to perhaps slightly
northwest generally less than 10kts.

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

Kovacik

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          75  91  73  91 /  40  50  40  40
Atlanta         75  89  74  89 /  40  50  40  50
Blairsville     69  85  67  87 /  50  50  40  40
Cartersville    73  88  72  89 /  40  50  40  40
Columbus        75  92  75  88 /  40  50  40  60
Gainesville     74  88  73  89 /  40  50  40  40
Macon           75  92  74  90 /  40  50  40  50
Rome            72  89  73  90 /  40  50  40  40
Peachtree City  73  90  72  88 /  40  50  40  50
Vidalia         76  92  74  90 /  40  50  40  60

&&

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

$$

SHORT TERM...Kovacik
LONG TERM....17
AVIATION...Kovacik



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