Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Peachtree City Georgia
729 am EDT Monday Aug 3 2015
Short term /today through Tuesday/...
/issued 239 am EDT Monday Aug 3 2015/
the boundary is still sitting across the County Warning Area and has moved a little
further north compared to yesterday. Based on the location of the
boundary...hi-res guidance and convection further north than
originally indicated by guidance yesterday...have included the
majority of the County Warning Area in a slight chance of showers and thunderstorms
today. Activity should be isolated but most of the area is fair game
for convection except for maybe far northwest Georgia. Instability is around
2000 j/kg of MUCAPE across east central Georgia and similar to
yesterday...not expecting severe storms.
Although the better moisture associated with the frontal boundary
shifts eastward over the Atlantic on Tuesday...and the GFS and European model (ecmwf)
are trying to keep the County Warning Area dry...the NAM and sref hint at some
precipitation across the far north. This is similar to what the hi-res
models are depicting...in addition to activity across central
Georgia. Forecast leans toward the wetter solutions but only a
slight chance of probability of precipitation mentioned. The northern activity is associated
with an upper level wave so may be slightly better organized than
what develops across the central part of the state.
Long term /Tuesday night through Sunday/...
/issued 239 am EDT Monday Aug 3 2015/
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.
winds again are the main forecast challenge at atl. Overall the
wind direction is not being handled well by the models. Winds
initially are easterly but should become northwest with mixing this
morning in the 13-15z time frame. Otherwise there are low clouds
across central and parts of northeast Georgia that should begin
to improve over the next two hours at mcn. The low clouds should
stay just south or on the edge of ahn.
//Atl confidence...12z update...
high confidence on ceilings and visibilities. Low on wind.
Preliminary point temps/pops...
Athens 95 70 98 73 / 20 20 5 10
Atlanta 94 73 95 75 / 20 20 5 10
Blairsville 90 61 91 66 / 10 10 20 20
Cartersville 94 66 96 71 / 10 10 5 10
Columbus 97 72 99 75 / 20 20 20 20
Gainesville 93 71 95 74 / 20 10 10 10
Macon 94 70 98 74 / 20 20 20 20
Rome 96 65 96 71 / 10 10 20 10
Peachtree City 94 65 96 71 / 20 20 5 10
Vidalia 92 74 97 75 / 20 20 20 20