Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 152344

Area Forecast Discussion
National Weather Service Peachtree City GA
644 PM EST Fri Dec 15 2017

.PREV DISCUSSION... /Issued 231 PM EST Fri Dec 15 2017/

SHORT TERM /Tonight through Saturday Night/...

Fairly amplified large scale pattern will continue through the short
term. Currently...Ridging persists across the Rocky Mtn States while
broad troughing exits across the eastern 2/3rds of the country. As
faster mid level flow continues across northern latitudes...a slow
moving closed low is meandering across western Mexico. At the
sfc...high pressure is dominating most of the southern states in the
wake of a cold front draped from the Carolina Coast into the central

For the remainder of today and through tonight...Pacific
moisture along the subtropical jet will continue to stream into the
area through the afternoon and into the evening hours as the mid
level low continues to fumble around western Mexico. Most of this
will be in the form of mid and high clouds with some virga showing
up on local radar imagery. Consensus is that a vort ribbon stemming
from northern stream cyclonic energy will help push out the majority
of cloud cover through overnight as it passes from NW to SE. Sfc
high pressure will also continue to build into the region overnight
as the cold front continue south. Tight pressure gradient between
sfc high and baroclinic response of sfc low off the Carolina Coast
will keep breezy conditions into the first part of the evening
tonight before the center of the high moves closer to the CWA.

For Saturday...pesky Mexico closed low will be kicked into western
TX as a digging trough dives into the SoCal/Baja area. This will
induce a short wave/diabatic ridge across the Southeast and make for
fairly mild temps as H5 heights rise noticeably. Although moisture
will surge north into the Southern Plains and lower MS Valley...sfc
high pressure will not move offshore until the beginning of the long
term. Therefore...will stay dry and mild through Sat night with
lower level moisture gradually on the rise. A quiet short term then
gives way to an active long term.


LONG TERM /Sunday through Friday/...

The GFS and Euro continue to struggle on keeping run-to-run
consistency and consensus with each other from Monday onward with
extent of Gulf moisture axis and possible shortwave influences
through Wednesday. They at least both agree on some less
instability present Sunday so have taken thunder chance out then,
though include in portions of mainly central GA for Mon/Tue. Will
continue high end chance to likely chance for widespread showers starting
from the NW Sunday then other areas thru Tues, then limit to
slight chance pops Wed/Thu given uncertainty. Oddly enough they
both agree on the return of a broad SW Gulf moisture fetch by
Friday so have increased pops accordingly. Previous discussion


PREV DISCUSSION... /Issued 321 AM EST Fri Dec 15 2017/

LONG TERM /Saturday Night through Thursday/...

The long term period begins as a transition one as high pressure
continues to push offshore of the Carolinas and high amplitude mid
level trough begins to push east out of the 4 corners region.
Embedded shortwaves on the east side of this trough will move into
the Tennessee Valley Sat night and into Sunday. This will quickly
transition the nil pops early Sat night into likely rain chances
late Sunday. Given moisture and lift profile, would actually see a
large area of predominant showers but this is a good start this
far out. Given strength of the shortwave, it is likely we will see
some elevated thunder and perhaps even some surface based
instability. Will therefore continue to carry isolated thunder
chances in the grids.

With broad trough remaining west of the region through Wed, would
expect disturbed pattern to continue into mid week although models
differ on the details. Have utilized a blend for this forecast
which keeps a zone of likely pops in transitioning south of the
region by tue night into Wed.

Another storm system on tap into late next week as we approach the
holiday with models actually in good agreement this far out.
Despite good agreement, run to run consistency has been all over
the place and will therefore keep pops at chance for now.



00Z Update...
VFR conditions will prevail through the TAF period. BKN cirrus
will tend to scatter out through early Saturday morning. Winds
will remain largely NW through midday Saturday, shifting more SW
by evening at ATL area sites. MCN/CSG winds may trend NE on
Saturday. Wind speeds near 10kts this evening will taper to 3-6
knots for the remainder of the period.

//ATL Confidence...00Z Update...
High confidence all elements.



Athens          30  55  36  58 /   0   0   5  30
Atlanta         30  55  38  56 /   0   0   5  40
Blairsville     23  53  31  53 /   0   0  10  60
Cartersville    27  53  35  54 /   0   0  10  60
Columbus        31  58  39  64 /   0   0   5  30
Gainesville     30  54  37  53 /   0   0   5  40
Macon           30  57  36  63 /   0   0   5  10
Rome            26  54  34  52 /   0   0  10  60
Peachtree City  29  56  36  59 /   0   0   5  40
Vidalia         35  58  38  66 /   0   0   5   5




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