Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 282351

Area Forecast Discussion
National Weather Service Peachtree City GA
751 PM EDT Wed Jun 28 2017

.PREV DISCUSSION... /Issued 348 PM EDT Wed Jun 28 2017/

SHORT TERM /Tonight through Thursday Night/...

Moisture return has begun in earnest. Model precipitable water
values approaching 2" in the southwest by 12Z, and are 2"+ across
the forecast area by 00Z tomorrow evening. Weak mid/upper-level
wave is progged to be a little slower lifting out of the northern
gulf into the region and I have slowed the spread of higher POPs
into and across the forecast area accordingly. Still looking at
Chance POPs spreading up the western edge of the area by 12Z but
likely POPs lag until we approach afternoon. Mid-level lapse rates
are weak, as is the upper wave, so chances for severe thunderstorms
still look to be minimal, however chances for locally heavy rain
are looking pretty good.


LONG TERM /Friday through Wednesday/...

Primary concern in the long term period is timing and likelihood
of mostly diurnally driven convection. Shortwave trough over MS/AL
on Friday progged to weaken and fill as it moves slowly east over
the southeast while front lifts north. By Saturday, what`s left
of wave will be east of GA but not likely to see much subsidence
unless large MCS moves over the state Fri afternoon or overnight.
12Z models somewhat different on strength and timing with CMC
having more well defined wave and EC/GFS muddier/weaker. WPC
favoring non CMC blend which agrees with local office consensus.

Translation from above paragraph means that convection will
become widespread on Friday afternoon and evening and may continue
overnight. Too soon to say whether severe storms are likely but
GFS/NAM are showing increasing low level moisture and instability
during the day (MLCAPE ~2000 J/kg) as front lifts north and east
as a warm front. Vertical wind shear quite weak with ~10kts 0-1k
bulk shear and 10-20kts 0-6km shear. Could see heavy rain if one
place could see more than 2 inches which could be possible based
on latest QPF.

After wave passes Sat, more broad wave moves east from lower MS
valley into eastern CONUS Sunday. Lift not as well defined with
this system and appears associated front may never make much
progress into the state. Again, only CMC showing stronger wave and
more southward progress and as before, favoring non-CMC blend
with rest of long term forecast. Diurnal PoPs expected in this
pattern with 30-40 during the day and at most 20 during the night.
Attm, holiday forecast for the 4th appears to show this
lower/climatological normal tstm chcs. Will continue to monitor,
but for now will take that as good news as recent 4th July events
have been very stormy.

Prev long term discussion follows.


PREV DISCUSSION... /Issued 342 AM EDT Wed Jun 28 2017/

LONG TERM /Thursday Night through Tuesday/...

Day to day forecast still consistent for the long term period. By
Thursday night the return flow has been established and we remain
under a south to southeast low level flow. Models still hint at a
short wave moving across central or south GA Thursday or Friday.
An upper trough deepening over the Great Lakes and into the OH
Valley over the weekend may help push a front into TN/KY.
So...likely pops look reasonable for north GA on Saturday and have
stayed with that. Into the first of the week the pattern is
unsettled and we remain in an unstable airmass. However there
looks like there may be some brief drying for the end of the
period but not enough to remove pops. Have lowered pops a bit for
Monday and Tuesday.



00Z Update...

Through the remainder of the evening, VFR ceilings will prevail
before MVFR ceilings/vsbys begin to move in through the early
morning areas, primarily for CSG, MCN, and ATL area sites by the
12z time frame. MVFR ceilings will predominate through the day
Thursday. Scattered showers and isolated thunderstorms will
increase through the morning and become more widespread on
Thursday afternoon. Winds will remain east to southeast through
the period generally less than 10 kts.

//ATL Confidence...00Z Update...

Medium confidence on lower ceiling and precip onset. High
confidence on winds.



Athens          66  81  70  82 /  10  50  50  60
Atlanta         70  81  71  82 /  20  60  50  70
Blairsville     60  79  66  77 /  10  40  50  70
Cartersville    67  80  70  82 /  30  60  50  70
Columbus        73  83  73  86 /  30  70  50  60
Gainesville     68  80  68  79 /  10  50  50  70
Macon           70  84  71  86 /  20  60  50  60
Rome            68  81  70  83 /  30  60  50  70
Peachtree City  68  81  70  82 /  30  60  50  70
Vidalia         72  85  72  87 /  10  60  50  50




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