Scientific Forecaster Discussion
Area forecast discussion...updated for aviation
National Weather Service Peachtree City Georgia
721 am EDT Sat Aug 23 2014
Short term /today through Sunday/...
/issued at 347 am EDT Sat Aug 23 2014/
big changes on tap through the short term period as models continue
to show just one more hot day before a welcomed back door cold front
sweeps across the area on Sunday. For today... the dominating upper
ridge begins to retreat westward as a series of disturbances track
down the eastern periphery and across the state during the afternoon
and overnight hours. This will warrant showing a better chance of
showers and thunderstorms across the north and east central portions
of the forecast area today... and holding onto a slight chance of
showers and thunderstorms for all areas tonight. The continued heat
and strong instability coupled with some upper support suggest the
potential for a few strong to possibly severe storms later this
afternoon and early evening... with strong to potentially damaging
winds being the main concern for later today. Nothing widespread is
expected... just cannot rule out this possibility as afternoon
SBCAPE values climb back into the 3000-4000 j/kg range...especially
across central Georgia.
As for the heat... area temperatures are expected to push well into the 90s
again today for most areas... especially across central Georgia where
near 100 degree temperatures will once again be felt during maximum daytime
heating. This will push heat index values near or above the critical
105 degree mark for areas generally along and south of Lumpkin to
Forsyth to Athens line where a heat advisory is currently in effect.
See no reason to change the advisory as currently posted.
The big change will come on Sunday as a cold front pushes down from
the northeast and pushes south of Columbus and Macon by Sunday
evening. This will spread clouds and increasing rain chances across
the area... but more importantly... bring much relief from the heat
as Sunday afternoon temperatures struggle to get into the 90s for most
areas. Although suspect the convection on Sunday will likely be
mostly showers... models continue to show 1000-2000 j/kg of cape
ahead and behind the front Sunday afternoon... so will continue to
word for a chance of thunderstorms as well. However... nothing
severe is expected at this time.
Long term /Sunday night through Friday/...
/issued at 347 am EDT Sat Aug 23 2014/
upper ridge continues to dominate at the beginning of the
extended...while surface ridge builds across the middle Atlantic and down
the Appalachians. With the pseudo wedge building in...winds become
easterly and cloud coverage remains broken at least initially. Cloud
coverage does help to keep temperatures on the cooler side on Monday.
Drier air moves in for the first half of the week /behind the
backdoor front/. With this...do not have moisture around for much
in terms of precipitation and thus have limited probability of precipitation to no mention or
slight chance. Differences exist between the GFS and European model (ecmwf) in the
second half the of the extended. GFS brings a cold front into the
area on Friday...while the European model (ecmwf) keeps an upper ridge across the
southeast. Have tended more towards the GFS and shown an increase
in clouds/precipitation for Friday associated with the front.
Differences also exist still with how the models are handling the
potential tropical system next week. GFS remains further west and
slower while the European model (ecmwf) is further east /although latest run is
west of previous run/ and faster. Neither 00z solution brings
impacts to the County Warning Area...but regardless...still far out in the
forecast and its something that needs to be watched as we head
into next week.
VFR conditions are expected through the forecast period despite a
big change in overall weather pattern. High pressure weakens its
grip today... allowing slightly better chance for scattered afternoon
thunderstorms. Then a backdoor cold front sweeps across the area
early on sun... bringing middle level ceilings and scattered to numerous showers
with some embedded thunderstorms to the area early on sun. Will show
tempo -tsra 19-23z today... then prob30 -shra 12-18z sun with the
front. Current northwest winds persist today around 8-11kts... then shift
NE around 08-10z sun with speeds around 10-12kts on sun.
//Atl confidence...12z update...
medium on all elements.
Preliminary point temps/pops...
Athens 97 73 88 70 / 30 30 60 30
Atlanta 93 75 90 72 / 30 20 60 40
Blairsville 88 69 83 67 / 30 30 60 40
Cartersville 94 71 89 72 / 30 20 60 40
Columbus 98 75 94 75 / 20 20 60 40
Gainesville 94 73 87 71 / 30 30 60 40
Macon 99 73 93 72 / 20 20 60 40
Rome 95 71 91 73 / 30 20 60 40
Peachtree City 94 71 90 72 / 20 20 60 40
Vidalia 99 75 94 74 / 20 20 60 40
heat advisory from noon today to 8 PM EDT this evening for the
following zones: Baldwin...Bibb...Bleckley...Clarke...Crawford...