Area Forecast Discussion
Issued by NWS Atlanta, GA

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489
FXUS62 KFFC 232329
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
729 PM EDT Sun Apr 23 2017



.UPDATE...
Update for the 00Z Aviation Discussion.

&&

.PREV DISCUSSION... /Issued 320 PM EDT Sun Apr 23 2017/

SHORT TERM /Tonight through Monday Night/...

A complicated synoptic system is currently impacting the CWFA
bringing widespread beneficial rainfall to the area...plus a few
thunderstorms to portions of central Georgia. A cold front is
currently moving across western GA, while a warm front is situated
right across the Interstate 20 corridor. A weak wedge has developed
across NE GA this morning and has been re-enforced by the widespread
rainfall.

Locations east of the cold front and south of the warm front have
been in the warm sector for most of the day. This area roughly
corresponds to east of Interstate 85 and south of Interstate 20.
Less cloud cover and good heating have allowed for decent
destabilization to occur. Lapse rates remain marginal, but shear
values remain favorable. Have seen one rotating thunderstorm this
afternoon already...wouldn`t rule out additional ones. Scattered
strong thunderstorms will be likely, with isolated severe
thunderstorms possible through the remainder of the afternoon. The
primary mode of severe weather should be wind gusts up to 60mph.
Localized flooding is also possible, as the potential for heavy
rainfall continues.

Luckily, surface instability begins to wane a bit as the coldest
temps aloft, associated with the mid level low, move in overnight.
Even so, lapse rates steepen to impressive values. Wouldn`t be
surprised to get a few reports of small hail, even within the
showers this evening.

The mid level low pressure system will continue to slowly move
across the CWFA through Sunday. The mid level forcing will continue
the potential for isolated/scattered showers through the remainder
of the period.

NListemaa

LONG TERM /Tuesday through Sunday/...

Extended forecast period still expected to start out quiet and mild
through mid-week followed by warmer and a bit more unsettled weather
for the latter portions. Upper-level energy with the mid to late
workweek system lifts well north of the area, but loss of upper-
level ridging and the proximity of a dying frontal boundary still
merits a chance for convection Thursday through Friday, especially
across the north. Little forcing aside from diurnal heating through
the majority of the remainder of the forecast period until late.
Overall, little change made to the long-term forecast grids with
this cycle. Please see the previous Long Term Forecast discussion
below.

20

Previous LONG TERM Forecast Discussion/Monday Night through
Saturday/...

All of the activity during the short term period will be pushing
east out of the CWA by the beginning of the long term forecast
period on Monday night. The slow moving closed H5 low will be
centered in the vicinity of Georgia and SC coastline...with
associated sfc low centered just downstream off the NC/SC coastline.
Wrap-around shower activity associated with this system will be
mainly confined to eastern counties and should gradually push east
through the overnight hours...leaving the CWA dry with mid level
heights beginning to rise.

Tuesday and Wednesday look to be very dry and pleasant as a weak mid
level shortwave ridge builds in and weak high pressure takes over at
the surface. Could see some lingering lower level cloud cover
Tuesday...but temps should begin to rebound with highs upper 70s to
low 80s Tues and mid-upper 80s Wednesday.

The weak shortwave ridge will begin to shift to the east of the
region late Wednesday into Thursday. Upstream pattern shows an
elongated trough building into the Western and Central US...with
several notable embedded shortwave troughs responsible for the
development of numerous sfc waves along a frontal boundary. This
frontal boundary will push toward the CWA early Thursday.
Deterministic models begin to diverge somewhat around this
time...but both agree the front will stall across the state by
Thursday night...which makes sense given large displacement from
parent system. Plenty of instability should allow for thunderstorm
development in the vicinity of this boundary...but weak shear argues
against robust organization at this time.

00z EC came more in line with 00z GFS tonight with a broad mid level
closed low developing within the broad cyclonic flow across the
Western/Central US...which is also now being reflected in the
ensemble data. Given this solution...strong cyclogenesis should take
place in the lee of the Rockies next weekend. This should kick the
stalled boundary across our area north as a warm front as it moves
east into the Midwest/Great Lakes... with the associated cold
front expected to approach the area at the end of the long term.

Kovacik

&&

.AVIATION...
00Z Update...
Backdoor "wedge" front is moving across the ATL area but should
stall just after passing through Atlanta. Winds will be northeast
for a good part of the evening then become northwest as the upper
low moves into the area. IFR cigs behind the front and vfr/mvfr
cigs ahead of the "wedge" front. MVFR/IFR cigs tonight should
become MVFR/VFR Monday. Showers ahead of the cold front will move
east of the forecast area early this evening with drizzle and
isolated showers developing across the forecast area tonight and
into Monday morning.

//ATL Confidence...00Z Update...
Low to Medium on cigs tonight.
Low to medium on winds this evening.
High on remaining elements.

17

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          55  66  54  78 /  90  50  30  10
Atlanta         53  67  55  78 /  40  30  10   5
Blairsville     51  65  52  76 /  80  50  20  10
Cartersville    52  66  51  79 /  30  20  10   5
Columbus        53  70  54  82 /  20  10   5   5
Gainesville     52  65  55  77 /  80  50  20  10
Macon           52  71  54  81 /  70  20  10   5
Rome            51  67  52  80 /  40  20   5   5
Peachtree City  52  68  54  79 /  30  20   5   5
Vidalia         60  74  57  80 /  80  40  20  10

&&

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

$$

SHORT TERM...17
LONG TERM....RW
AVIATION...17



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