Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
309 PM EDT Monday Aug 3 2015
Short term /tonight through Tuesday night/...
Pretty quiet forecast period continues with largely dry and weak northwest
flow aloft serving to inhibit the typical summertime convection.
Aside from a weakening low pressure system moving slowly across
northern Florida into far southeast Georgia and some orographic enhancement in the
far NE mountains...probability of precipitation are limited mainly to these areas for any
shower and isolated thunderstorm development. The low level
moisture advection off the Atlantic coast has proven to bring
patchy early morning fog in portions of the east and south...which
again looks to be the case for Tuesday morning. An approaching
weak disturbance in the upper flow should raise some precipitation
potential just beyond the short term.
Temperatures again look reasonable based on blend of recent guidance though
will need to watch how much cloud coverage could limit diurnal range
in portions of east central Georgia with aforementioned weak coastal low.
Long term /Wednesday through Monday/...
no major changes to the long term portion of the forecast.
Longwave trough will be digging across the eastern Seaboard by early
Wednesday. Models are progging a fairly potent shortwave to round
the base of the trough on Friday. The County warning forecast area will remain in northwest flow
through the weekend. High pressure aloft will build back across the
area for the first of next week.
A cold front will begin to approach the County warning forecast area late Thursday. The
front will eventually stall across portions of the County warning forecast area for the
weekend...before dissipating by early next week.
Previous discussion below...
Long term period begins with upper level westerlies dropping
slightly south into the area while surface trough develops further
north. The combination of these looks to increase thunderstorm
chances into Wednesday afternoon. Models insisting that there will be a
residual layer of dry air in place across the atl metropolitan to limit
rain chances but thinking this will be overcome late in the day as
upstream activity moves in. Have therefore gone above guidance
numbers with Middle Range chance for all locations.
Thursday continues to look like the most active day for US this
week with strong upper trough axis sweeping across the Tennessee
Valley and into north Georgia during time of maximum heating. Would expect
activity to be non diurnal in nature for the most part given the
large scale forcing. Shear values are not all that impressive
despite the strength of the upper system with only a slight
uptick in 0-1km bulk shear values noted. Despite this...would
expect severe potential to increase through Thursday afternoon
with damaging winds the main concern.
Transition to northwest flow by Friday and into the weekend with
strong impulses moving through the mean flow. Although drier air
will certainly move in the fronts wake over north
Georgia...thinking strong disturbances will be able to overcome
this. Probability of precipitation during this time period reflect this thinking with grid
values higher than that of model projections.
mainly VFR conditions expected through period with some early morning
MVFR visibility or possibly IFR/MVFR ceiling reductions for the eastern
sites kahn and kmcn. Otherwise expect scattered to few cumulus field in 4-6
kft range for afternoons and higher overnight with mostly clear
skies. Winds are tricky for late afternoon into overnight around
katl...could see wavering between north-northwest and NE though should become
mainly north-northwest overnight and light with calm winds at other sites.
Tuesday looks to have light northwest winds for near katl and more west
for other sites. Precipitation chances too low both this afternoon and
Tuesday for any mention in taf but cannot rule out isolated
activity into this evening.
//Atl confidence...18z update...
medium on winds for katl and early morning visibility/ceilings for
High on all else.
Preliminary point temps/pops...
Athens 72 96 73 96 / 10 10 10 30
Atlanta 73 94 75 94 / 10 10 10 30
Blairsville 62 89 65 87 / 10 20 10 40
Cartersville 68 94 71 94 / 10 10 10 40
Columbus 74 97 75 93 / 10 10 10 30
Gainesville 72 93 74 92 / 10 10 10 30
Macon 72 97 74 96 / 10 10 10 30
Rome 68 95 70 94 / 10 10 10 30
Peachtree City 70 95 72 94 / 10 10 10 30
Vidalia 74 95 75 96 / 20 20 10 40