Area Forecast Discussion
Issued by NWS Atlanta, GA
FXUS62 KFFC 241909
Area Forecast Discussion
National Weather Service Peachtree City GA
309 PM EDT Fri Mar 24 2017
.SHORT TERM /Tonight through Saturday Night/...
No significant changes to the general trends we have been carrying
in the short term forecast period. Medium-range models continue to
show a deep, closed, upper low digging into the southern plains
tonight, then somewhat stalling briefly tomorrow over the mid/lower
Mississippi Valley before quickly beginning to fill and lift into
the Ohio Valley and Great Lakes region Saturday night. Best dynamics
and instability remain west and north of the area and the surface
front never approaches through this period. Should see some
instability and even a bit of shear into the west and north by late
in the day Saturday into the evening, but forecast numbers remain
unimpressive right now. This certainly supports the SPC Day2
Convective Outlook bringing Marginal/Slight risk to our doorstep but
keeping it west of the state for now.
.LONG TERM /Sunday through Friday/...
Very progressive/active long-term period in store for the local
area...as a Rex Block /evolving into an Omega Block and eventually
blocking ridge/ sets up shop over Western Europe and allows a series
of closed lows to traverse southern stream flow across the US.
The long-term period will begin with the short term`s strong closed
low pushing northeast into the Ohio Valley with trailing vort lobe
over the Southeast pushing into the Carolinas and allowing H5
heights to rise in its wake. Despite this leftover mid/upper level
support moving away from the local area...the sfc cold front will be
moving into the area from the west. Expecting this front to stall as
the parent sfc cyclone occludes...and models show a marked increase
in instability developing along and in the vicinity of front from
eastern KY through northern Ga and northern AL. SPC now highlighting
a marginal risk across this area for Sunday afternoon. Thinking
potential for isolated severe storms would be caused by moisture
convergence along the front as lee cyclone across Southern Plains
emerges into the TX/OK panhandle and provides a decent "push" of
Gulf moisture into frontal vicinity amidst southerly low-level flow
regime. Orographic lift will only help this process across north Ga.
But...all in all...lack of impressive dynamics will only keep severe
chances isolated at best. Front should fizzle by day`s end Sunday.
Will see a brief lull in activity Sunday night into Monday afternoon
before next system approaches. Open wave trough will migrate into
the area late Monday afternoon from the west...with track of both
upper level and sfc cyclone taking almost the exact same path as the
previous system. With no change in airmass from Sunday`s failed
attempt at fropa...low level airmass will only continue to increase
in moisture. This should allow for more instability with Monday`s
system...despite weaker DCVA from open wave trough. For now seeing
best destabilization across La/MS/AL...with a weakening trend as
things move towards Georgia. Can`t rule out strong-isolated severe
activity Monday night ahead of the front...but nothing is catching
the eye quite yet. Shear is sufficient for organization...yet not
overly impressive /less than 40kts 0-6km/ due to lack of stronger
mid/upper flow. Starting to notice timing differences in GFS/ECMWF
going into Tuesday in regards to frontal evolution. Given blocking
pattern... prefer the EC right now which stalls the next front
Monday into Tuesday...with possible reinforcing moisture along the
front allowing for showers and storms over north Georgia through the
afternoon on Tuesday. Confidence not high right now though. GFS
would argue we dry out Tuesday afternoon with an actual fropa.
Wednesday looks mainly dry at this point as a mid level ridge moves
over the Southeast...ahead of a strong closed low emerging from
Southwest US into Southern Plains. This system heads our way
Thursday. To be expected...GFS and EC continue to show differing
solutions. EC showing stronger system...becoming negatively tilted
as it moves into Midwest/OH Valley. This track would spare us
strongest dynamics Thursday night into Friday...however the track
of the weaker GFS system into the Southeast is a bit concerning.
Will have to wait on this system a few days. Evidence of continued
blocking pattern over Europe in hemispheric ensemble data may
favor the EC...as it seems to keep Rossby wave train more
representative of the block.
VFR conditions predominate through 06Z. Will see MVFR ceilings
developing 06-12Z, persisting through 14-18Z. Scattered showers/
thunderstorms move into far western portions of the area by 20Z
tomorrow, approaching the Atlanta Metro TAF sites 21-24Z. Southeast
winds 8-12kt w/ gusts 14-20kt through 22Z, diminishing to 3-7kt by
//ATL Confidence...18Z Update...
.PRELIMINARY POINT TEMPS/POPS...
Athens 55 74 58 76 / 5 20 60 60
Atlanta 57 73 59 75 / 0 30 60 60
Blairsville 51 68 54 66 / 5 30 80 70
Cartersville 55 74 57 74 / 0 40 80 60
Columbus 59 77 60 79 / 0 40 50 40
Gainesville 55 71 58 71 / 5 30 70 60
Macon 54 77 59 80 / 0 20 40 40
Rome 55 73 57 74 / 0 50 80 70
Peachtree City 54 74 58 76 / 0 40 60 50
Vidalia 57 76 60 81 / 0 10 20 20