Scientific Forecaster Discussion
fxus62 kffc 230027
Area forecast discussion
National Weather Service Peachtree City Georgia
827 PM EDT Thu Jun 22 2017
Previous discussion... /issued 320 PM EDT Thu Jun 22 2017/
Short term /tonight through Friday night/...
main forecast concern will be initially here in the near term as the
environment has shown some rapid destabilization with the extremely
tropical airmass in place as the low cloud deck has been scattering
quickly from the south given being in the warm sector of Cindy's
remnants. Convective bands streaming in from the south fueled by a
steady strong moisture advection off the Gulf will have about 2000-
3000 j/kg of SBCAPE to attain, albeit tall/skinny in profile. The
issue will be with both the pwats being close to 2 inches and
enhanced area of helicity rich low levels just starting to impinge
upon the western border of the County Warning Area. Some 250 m2/s2 of 0-1 km srh
will be bothersome for isolated quick spin-up tornado potential in
our western tier from late afternoon here into the evening. Also
given the aforementioned pwats, any stronger convection will have
high precip efficiency and training of cells could bring flash flood
potential. It's not a welcomed sight to see temps of upper 80s/low
90s over dewpts in the mid to upper 70s advecting into the area.
The deeper moisture field and orientation of Cindy's dynamics should
continue to phase with an upper shortwave more to the northwest by late
tonight into Friday. Expecting a lull in shower/storm coverage
mainly after midnight tonight as chance to likely pops stay more
orientated to the far northwest and Tennessee Valley. Could have a similar type of
convective threat for northern portions of the area by Friday
afternoon (given progged instability/low level shear parameters) and
then be more progressive to the southeast with the evolution of the
shortwave and translated sfc front late Friday night into Saturday.
Tailored likely to categorical pops with this feature accordingly
across north Georgia. Will be rather gusty out of the SW ahead of this as
Temp wise, a bit more diurnal range expected Friday with more areas
reaching highs close to climo in the upper 80s to low 90s (less
morning cloud coverage expected).
Long term /Saturday through Thursday/...
the remnants of Tropical Storm Cindy will finally be out of our hair
at the beginning of the long term forecast period on Saturday
morning. However there will be a cold frontal boundary moving south
across the area. Rain and thunderstorms will be ongoing along the
front...enhanced by diurnal heating in the afternoon. There looks to
be enough deep layer shear /0-6km of 20-30kts/ as a broad trough
deepens across the eastern 2/3rds of the US to work in conjunction
with instability invof the front. This should allow for some
organization of thunderstorm clusters along the front. The main
threat will be damaging wind gusts. Storm Prediction Center has a large majority of
central and eastern Georgia in a marginal risk.
The front will make slow progress into central Georgia Saturday
evening into the overnight hours but the loss of daytime heating and
rather poor forcing should allow most activity to gradually
dissipate. Front looks to linger across far southern zones on Sunday
where again diurnal heating should allow for a gradual increase in
thunderstorm activity through the afternoon. Shear appears to be
displaced too far north to pose a notable severe threat by this
time. Can't rule out isolated stronger storms...but think Saturday
has better parameters than Sunday.
Front should clear the County Warning Area by Monday. A rather unseasonably
strong area of sfc high pressure will gradually build into the
region from the north in the wake of the front...which will make
for a dry day. A strong shortwave rotating around the broad scale
trough over the eastern US will likely bring some clouds to area
on Tuesday...but thinking large dome of sfc high pressure will
keep things dry. Height rises in the mid level behind this
shortwave combined with sfc high pressure should make for a very
pleasant Wednesday. Will see moisture gradually return outside of
the extended as the sfc high begins to scoot off the Atlantic
Main cluster of rain showers/thunderstorms and rain now shifting east of all the terminals
except ahn where activity will persist just a little longer.
Model guidance actually much more optimistic wrt cigs overnight in
both coverage and cloud heights. However...with such saturated
conditions of late...will lean toward persistence and previous
forecast of some developing MVFR cigs tonight. Otherwise...drier
air working in for Friday but still enough moisture to warrant
continued prob30 for most sites.
//Atl confidence...00z update...
Medium for cigs tonight.
High for remaining elements.
Preliminary point temps/pops...
Athens 71 90 73 85 / 60 30 60 70
Atlanta 72 87 73 83 / 60 40 70 70
Blairsville 67 83 68 79 / 70 60 80 70
Cartersville 72 87 72 83 / 60 60 80 70
Columbus 74 90 75 86 / 20 20 40 60
Gainesville 70 86 72 82 / 60 40 80 70
Macon 73 91 74 88 / 30 20 30 40
Rome 72 87 72 84 / 60 70 80 70
Peachtree City 71 88 72 84 / 50 30 60 60
Vidalia 75 91 75 91 / 40 20 20 30