Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 270756
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
356 AM EDT Sat May 27 2017


.SHORT TERM /Today through Sunday/...

Unsettled weather is expected across portions of northern GA through
the short term period.

Surface high pressure remains well to the south, while aloft the
CWFA will remain on the periphery of ridge. A couple of strong upper
level disturbances are progged to move across the top of the ridge,
one today and another during the first part of Sunday. The synoptic
and hi-res models do struggle with these types of systems,
especially with timing. Both of the locally run wrf models are
similar with trends for today`s system, a potential MCS. The HRRR
looks like it may be catching on, if the last frames are any
indication. There are still some timing issues, so have taken a
blend between the two locally run wrf`s and whatever frames of the
HRRR that are in.

The MCS is currently winding up across southern MO and northern AR.
The system should continue eastward in the flow for the next few
hours, then start to make a southeast dive during the late
morning/early afternoon...clipping northern GA. Have increased pops
to likely across those areas most likely impacted by the MCS. Do
think areas north of the Metro will have the best chances of
convection.

With very steep mid level lapse rates, good deep level shear and
very good surface instability present...storms will have the
potential to become severe. Isolated to scattered severe
thunderstorms will be possible across the north, with the primary
severe weathers modes begin large hail and damaging wind gusts.

The models are suggesting another round of convection during the
early part of Sunday...another potential MCS. Have taken a more
broadbrushed approach to pops for now...but it does look like areas
mainly north of Interstate 20 will be impacted. In addition, a few
of the storms could also be strong to severe.

NListemaa


.LONG TERM /Sunday Night through Friday/...

Main forecast concern in long term period is chance for
strong/severe convection on Monday. 00Z model guidance in pretty
good agreement with Monday forecast. Front progged to continue to
sag into the state Monday with above normal sfc temps and
dewpoints. SBCAPE rises to fairly high values even for late May,
GFS 2500-3500 J/kg. Deep layer shear should be sufficient for
severe convection, 0-6km bulk shear mags > 30kts over much of the
CWA, however low level shear quite weak with 0-1km bulk shear
around 5-10kts. In such environments, we typically see severe
storms with large hail and wind threats but very low risk of
tornadoes. PW will be fairly high but not too abnormally high for
this time of year (GFS values around 1.6 in). With large scale
lift not too high, QPF also less than 1 inch in most locations
Mon, so will likely see periods of heavy rain but flash flooding
risk somewhat low.

After front sags into middle or south GA, essentially washes out
Tuesday. Moisture remains plentiful but without any forcing, any
storms would be fairly isolated thru Thursday. Have kept PoPs
fairly low but unlikely we will see a dry period with weak SWly
flow aloft. By Thurs Night or Friday, warm advection should kick
in with increase in moisture as well. Have bumped up PoPs then.

SNELSON


&&

.AVIATION...
06Z Update...
Models still showing a disturbance dropping down across northern
GA today...accompanied by showers and thunderstorms. Not confident
that the isold/sct activity will make it as far south as ATL, so
have left out the mention of VCSH for now. Will probably have to
reconsider if the hi-res models come more into line and as the
actual cluster of storms continues to develop to the west. Winds
will remain on the west side, with some low end gusts during the
afternoon. There is some potential for bkn MVFR cigs overnight.

//ATL Confidence...06Z Update...
Medium confidence on any convective timing/coverage and MVFR cigs
early Sunday morning. Otherwise, high confidence.

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          88  69  89  70 /  20  20  20  30
Atlanta         87  71  87  70 /  10  10  10  40
Blairsville     82  63  82  63 /  60  50  40  60
Cartersville    86  69  88  68 /  30  20  20  50
Columbus        89  71  90  73 /   0   5  10  20
Gainesville     85  69  86  69 /  50  30  20  40
Macon           90  68  91  71 /   0   5  10  20
Rome            85  68  87  68 /  30  20  30  60
Peachtree City  87  68  88  69 /  10  10  10  30
Vidalia         91  70  94  73 /   0   0  10  10

&&

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

$$

SHORT TERM...NListemaa
LONG TERM....SNELSON
AVIATION...NListemaa


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