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Area Forecast Discussion (AFD)

Issued by Peachtree City, GA (FFC)

FXUS62 KFFC 221903

Area Forecast Discussion
National Weather Service Peachtree City GA
303 PM EDT Sun Oct 22 2017

.SHORT TERM /Tonight through Monday Night/...
Cold front is currently moving across the Lower Mississippi River 
Valley with a pre-frontal trough analyzed just east of the 
Mississippi River. Surface high pressure has finally begun to push 
off the Mid Atlantic coast. The precipitation shield associated with 
the trough/front will continue to spread eastward overnight and 
approach far western GA during the early morning hours. 

The cold front should move through most of the CWFA by the late 
afternoon/early evening. The 12Z NAM, GFS and ECMWF all support a 
deep 500mb trough swinging through during the day...and all with a 
negative tilt and open wave by the time it reaches GA. All have 
varying strengths to the mid level system, with the GFS being the 
strongest and a little further south with the forcing. 

The ECMWF and the NAM take the best forcing just north of the CFWFA, 
with some marginally steep lapse rates across the far north. Surface 
instability values are a bit higher than they were yesterday, with 
all of the CAPE along and ahead of the frontal boundary. Surface 
instability across the north is slightly more concurrent with the 
marginal lapse rates than in previous model runs. The best CAPE 
values are expected across the southeast CWFA across areas that 
should receive the most sunshine. The best shear values are expected 
across the northern CWFA in the morning, but some marginal values 
are possible across the SE along the frontal boundary. 

Isolated to scattered thunderstorms are possible tomorrow beginning 
early in the morning in the west. Widespread severe weather is not 
anticipated but isolated severe thunderstorms will be possible as 
the system moves through. Locally heavy rainfall is also likely as 
the cold front moves through tomorrow. PWATS reach near 2" ahead of 
the boundary. FFG is rather high, so no widespread flooding is 
expected but localized flooding will definitely be possible. 
Rainfall amounts should average between 1" and 3", with locally 
higher amounts will be possible. 

Cooler temperatures and a drier airmass are expected behind the cold 
front Monday night. Lows in the 40s and 50s are possible, but the 
much cooler air will settle across the region into the long term 
portion of the forecast.


.LONG TERM /Tuesday through Sunday/...
Only tweaks to the long term based on the latest guidance.
Overall, much quieter weather expected.


Heavier precipitation should be sweeping east of the forecast area as
the period begins Monday night into early Tuesday. Right now it
appears that moisture will be too limited Wednesday for POPs as a
secondary upper trough and associated short wave move across. This
secondary system does push through another shot of good cold
advection with our coolest temperatures of the week expected
Wednesday and Wednesday night. Highly amplified and very progressive
upper pattern transitions the region back to southwesterly upper flow
quickly with a subsequent quick rebound in temperatures back toward
seasonal normals by the end of the week. The next upper trough/short
wave and the associated surface front sweep through next weekend. 



18Z Update...
Latest sat imagery shows lingering stratus from this morning has bkn 
up into a widespread cu field. Sct bkn sct025 will be possible for 
the next hour or two. IFR cigs are expected overnight, along with 
increasing chances for shra. Do think the best chances for thunder 
will be between 14z and 18Z tomorrow and think thunderstorms should 
remain isolated to scattered. Winds will remain on the east side 
through early tomorrow, but go to the west side behind any 
convection/the cold front. 

//ATL Confidence...18Z Update...
Medium to high confidence on thunder timing. Medium confidence on
cigs overnight. High confidence remaining elements. 


Athens          66  71  50  69 /  60  90  50  10 
Atlanta         68  71  51  66 /  80  90  30   5 
Blairsville     61  67  44  60 /  70  90  40  10 
Cartersville    67  71  48  64 /  90  90  30   5 
Columbus        71  75  54  70 /  80  90  30   5 
Gainesville     66  69  51  65 /  70  90  50  10 
Macon           70  75  51  71 /  50  90  50   5 
Rome            67  71  48  64 /  90  90  20  10 
Peachtree City  68  73  49  67 /  80  90  30   5 
Vidalia         72  79  57  74 /  40  90  80   5 




SHORT TERM...NListemaa