Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
739 am EDT Sat Sep 20 2014
Previous discussion... /issued 312 am EDT Sat Sep 20 2014/
Short term /today through Sunday/...
latest regional surface analysis shows high pressure centered off
the New England coast with wedging down the eastern Seaboard and
into the Carolinas and north Georgia. Meanwhile...also monitoring
surface low developing off the central Florida coast which thus
far remains a weak feature but could play a significant role in
the local sensible weather the next 24 hours. Already seeing some
influence...mainly outside of our area...with coastal convergence
on the north side of low allowing for good coverage of showers
along the Golden Isles of Georgia. Expect this activity to remain
well east of the area through daybreak.
Should be a cloudy start for most as low clouds over NE Georgia
fill in as well as advect west. Feel these clouds will be with US
for longer than models project within developing wedge but should
not have too much influence on expected maximum temperatures. As clouds erode
for southern sections...instability will increase modestly with
local WRF indicating cape values between 500 j/kg and 1000 j/kg
along and south of a mcn to csg line. This combined with
precipitable water around 1.5 and convergence created by wedge/low
combination should allow for low end scattered coverage of showers
with isolated thunderstorms possible as well.
As low lifts quickly NE on Sunday...drier air will be tugged in on
the backside with precipitable water dropping below one inch for
most locations and resulting in less than mentionable probability of precipitation through
Sunday afternoon. A late arriving cold front will be moisture
starved but actually have a healthy amount of cape (1500 j/kg to
2000 j/kg) along with some subtle shortwave energy to produce low
end probability of precipitation by 00z. Should moisture values increase in future model
runs...these probability of precipitation will likely need to be increased further.
Long term /Sunday night through Friday/...
a cold front is forecast to move across the area Sunday night and
Monday with limited moisture and only weak instability associated.
A drier airmass moves over much of the area for Tuesday with
moisture returning Wednesday through Friday with the GFS and
European models differing on how much and when. With the easterly
flow in place no instability is forecast. For now small precipitation
chances will be confined to the southeast County Warning Area Thursday through Friday.
Forecast temperatures close to normal through Monday then below
normal into Friday.
main low cloud shield that had been confined to far NE Georgia
with just spotty formation further west has now infiltrated most
of the area including the Atlanta terminals. Model guidance in
agreement this should continue through middle morning and will keep
MVFR advertised at all sites with the exception of ahn where
higher ceilings should prevail. Continued previous forecast of keeping ceilings
in a little longer and scattering out to a VFR deck by early
//Atl confidence...06z update...
medium on low ceiling duration.
High on remaining elements.
Preliminary point temps/pops...
Athens 80 59 86 66 / 10 0 5 10
Atlanta 80 64 85 66 / 10 5 5 20
Blairsville 78 55 80 56 / 5 5 10 30
Cartersville 81 59 85 61 / 5 5 5 30
Columbus 81 64 88 68 / 10 5 0 5
Gainesville 78 62 82 65 / 5 5 5 20
Macon 81 60 86 64 / 20 5 0 5
Rome 84 60 85 61 / 5 5 10 30
Peachtree City 80 58 86 64 / 10 5 0 10
Vidalia 81 65 88 67 / 40 20 0 5