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Area Forecast Discussion (AFD)

Issued by Peachtree City, GA (FFC)

                            
000
FXUS62 KFFC 211138
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
738 AM EDT Thu Jun 21 2018



.PREV DISCUSSION... /Issued 353 AM EDT Thu Jun 21 2018/ 

SHORT TERM /Today through Friday/...
A more active short term period is expected as a glance at early 
morning water vapor imagery reveals a strong closed low centered 
roughly along the IA/MO border with associated weak shortwave 
ridging located just downstream. A glance at the remainder of the 
CONUS depicts a strong ridge across the lower 
California/Arizona/Baja region and a strong belt of cyclonic flow 
extending from eastern Canada into New England. Latest sfc analysis 
shows an occluded cyclone/front underneath the mid level low across 
the Midwest...with a cold front extending south from Missouri into 
the Southern Plains.

For today...aforementioned closed low will work in tandem with 
lingering trough across TX coast to pull some vorticity/embedded 
shortwaves northward and eastward across the Southeast. Associated 
lift provided by the lobe of vorticity will have the opportunity to 
work with deep tropical moisture advection across the Southeast this 
afternoon and evening as model projected PW values approach 2 inches 
or greater. This in conjunction with daytime heating /despite some 
SCT-BKN mid level cloud cover/ should allow the opportunity for 
decent convection this afternoon and evening. With the closed mid 
level low migrating closer to the area...flow in the mid levels 
should increase to at least 25-35kts across Georgia. This should 
allow for the potential of semi-organized updrafts and perhaps 
clustering of single cell convection carrying an isolated damaging 
wind threat along with heavy rainfall /given projected PW values/. 
Best chance for convection will exist across north Georgia into 
portions of central Georgia. Best 0-3km lapse rates should remain 
over central Georgia where less cloud cover exists...so if 
convection can make it into those areas the threat for wind could be 
slightly better.

Convection should wind down overnight Thursday...tho seeing some hi-
res guidance along with 00z ECMWF portraying an MCS developing 
across the TN Valley and moving southward. Will need to watch for 
this in later updates but for now will not overdo the POPs in this 
timeframe until things become a bit more clear. An early morning MCS 
could certainly impact the remainder of the forecast for Friday but 
for now will show another afternoon with decent chances for 
thunderstorms-especially across north Georgia as the mid level low 
moves into the OH Valley. Best jet support in the upper levels along 
with strongest H5 height falls remain just to the west over 
AL...which is where strongest convection will likely initiate. The 
closed low begins to pull northeast and starts to take the best 
energy and dynamics with it late in the day Friday. 
Nonetheless...convection across AL should advect into the area during 
the afternoon and evening posing a threat for strong to severe 
thunderstorms as shear supports even better  potential for multicell 
convection. SPC already indicating a Marginal Risk of severe weather 
across north Georgia Friday with the Slight Risk uncomfortably close 
across northern AL.

Kovacik

LONG TERM /Friday Night through Wednesday/...
Unsettled period remains in place for the extended period.
Aforementioned parent low will continue to lift northeastward into
the weekend, and with it the best rain chances. As zonal flow sets
up over the region it its wake, lingering surface moisture and
disturbances aloft will keep shower and thunderstorms chances over
the area Saturday. Riding aloft will build back into the area
Sunday and into early next week, but with moisture remaining
trapped under the high, diurnal convection is still expected each
day through the extended.

Temperatures remain warm through the weekend and into next week.
Increased cloud cover and precip activity could assist in keeping
temperatures a few degrees lower Saturday. With dewpoints in the
70s and above normal temperatures, heat index values will creep
into the low 100s several days, particularly over portions of
central and eastern Georgia. Although sub-criteria those spending 
prolonged periods outdoors should take frequent breaks and drink 
plenty of water.

31

&&

.AVIATION...
12Z Update...
Mid and high level clouds prevail across the TAF sites this
morning...with a glance upstream indicating that some lower VFR
cigs are approaching the state line. Do expect these clouds
/3-4kft/ to infiltrate the sites as the morning goes on and into
the afternoon. Cigs have the potential to top off between 4-6kft
so VFR should be the rule today. Convection is much more likely
than the previous few days so have added TEMPO in for now tho
should monitor cloud cover trends. BKN-OVC VFR should lower to
MVFR overnight and into Friday morning where they should remain
thru the rest of the cycle. West winds at 5-10kts expected with 
very isolated gusts 15-18kts not impossible.

//ATL Confidence...12Z Update...
Medium on ceiling trends.
Medium on convective coverage and timing.
High on all else.

Kovacik

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          91  71  89  70 /  70  50  60  40 
Atlanta         88  72  88  72 /  70  50  60  50 
Blairsville     82  66  82  64 /  80  50  60  60 
Cartersville    86  70  88  69 /  80  50  60  50 
Columbus        91  74  90  74 /  50  40  50  20 
Gainesville     86  70  86  70 /  70  50  60  50 
Macon           94  74  92  73 /  50  50  50  20 
Rome            85  70  87  70 /  80  50  60  50 
Peachtree City  89  71  89  71 /  60  50  50  40 
Vidalia         96  76  93  75 /  40  50  30  20 

&&

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

$$

SHORT TERM...Kovacik
LONG TERM....31
AVIATION...Kovacik