Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
1025 am EDT Thursday Jul 30 2015
quiet weather so far this morning...but showers and thunderstorms
will begin to develop by midday ahead of the cold front pushing
into north Georgia and in association with the weak surface trough
in central Georgia. Hi- res models indicate convective
development by around noon or shortly before...and this seems
reasonable. Made minor changes to probability of precipitation to better follow this
Previous discussion... /issued 730 am EDT Thursday Jul 30 2015/
Short term /today through Friday/...
Weak...ongoing convection across our central Georgia counties
overnight appears to be associated with the weak surface trough that
has set up across that region. Will likely see isolated to scattered
showers through the morning hours down there...with better chances
for more widespread coverage later in the day as heating helps to
provide further destabilization. Big question is how much convective
development do we see across the far north ahead of the approaching
frontal boundary. Hi-res models seem to be spreading sufficient dry
air into that area before too much activity develops. This seems a
bit premature. I will be carrying a gradient in my pop grids from
north to south...but I am going to include low chance probability of precipitation all the
way to the Tennessee line. As the front sinks south across the area
today scattered convection is expected to increase. I have kept probability of precipitation
below likely even across central Georgia as the region remains under
the weak eastern periphery of the upper ridge. Instability is not
overly impressive today...but should be sufficient for a few strong
to marginally severe storms by the afternoon... mainly across the
southern 2/3 of the area. How far south the much drier airmass
settles by Friday remains a bit uncertain...I have kept chance
afternoon probability of precipitation across the area roughly from Columbus to Macon
Afternoon highs will remain above seasonal normals through today as
well. Forecast heat index values approach 105 across some of our
central Georgia counties today...however I believe sufficient cloud
cover will keep temperatures a few degrees cooler than yesterday
keeping the area just below advisory criteria.
Long term /Friday night through Wednesday/...
Models continue to agree on a weak cold front remaining stalled
across central Georgia over the weekend and possibly providing a
focus for isolated to scattered showers and thunderstorms there
during the afternoon and evening. Then an upper disturbance pushes
the front south and east of the area by Monday... with a drier
northwest middle and upper flow reducing rain chances across the
entire area by Monday and possibly even Tuesday of next week. The
GFS is showing a mostly dry... reinforcing cold front pushing into
north Georgia on Wednesday with a persistent northwest flow aloft. This
would continue to hold rain chances down through at least middle
week. At the same time... the European model (ecmwf) is showing a moist south to
southwest surface to middle level flow setting up by Wednesday with
an upper disturbance approaching from the west by Wednesday
afternoon. This would suggest increasing rain chances for middle to
late next week. Will lean toward the drier GFS solution for now...
but still show a slight to low chance of afternoon convection for
Tuesday and Wednesday. Moderate instability... along with weak
wind shear suggest any afternoon storms should remain below severe
Behind the front... a brief relief from the heat is expected as
slightly cooler than normal temperatures gradually spread from
north Georgia Friday night into central Georgia over the weekend.
This relief may persist through Monday... but appears above
normal temperatures and near critically high heat indices will
likely return to much of the area by Tuesday and Wednesday of
VFR conditions expected to predominate through the period outside of
convection. Scattered MVFR or lower visibilities expected through
14z...may have brief impacts at the kahn/kmcn/kfty/kpdk taf sites.
Winds will remain light and variable in direction through the
period...but will favor northwesterly most areas after 14z.
Scattered convection is expected once again. Best coverage will be
between 16z-00z...although isolated showers and thunderstorms will
be possible at any time. Will tempo thunder at the taf sites during
the 18z-21z time frame when best chances are anticipated.
//Atl confidence...12z update...
Confidence medium to high on all elements.
Preliminary point temps/pops...
Athens 93 73 91 69 / 40 30 20 10
Atlanta 92 72 90 71 / 40 30 20 10
Blairsville 88 64 87 61 / 40 20 10 5
Cartersville 92 70 91 67 / 40 20 10 10
Columbus 94 75 93 73 / 50 30 40 30
Gainesville 92 72 90 70 / 40 30 10 10
Macon 94 74 93 72 / 50 40 40 30
Rome 92 69 91 66 / 30 20 10 10
Peachtree City 93 72 91 68 / 50 30 20 10
Vidalia 95 76 93 74 / 50 40 50 40
Short term...rain shower