Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
345 PM EDT Tuesday Sep 30 2014
Short term /tonight through Wednesday night/...
latest regional surface analysis shows low pressure continuing to
move well off shore the southeast Atlantic coast with associated
trailing front trough Florida. Low level moisture exodus continues
to lag the front with considerable low clouds along and south of a
Columbus to Macon line. Well defined boundary is helping shunt this
moisture southward with just scattered middle level clouds in its wake
for the remainder of north and central Georgia.
For tonight...models show drying for all but the last 25mb to 50mb
of the atmosphere which leads ME to believe we may have more of a
fog problem than low clouds for tonight. Low level wind flow
confirms this and saturation pressure deficit forecasts indicate
two distinct areas...one over far north Georgia and another over
central Georgia. Will update severe weather potential statement to include possibility of some
patchy dense fog and add some mention to grids as well for the
Otherwise...locally developing zonal flow aloft combined with a
light southerly flow at the surface will lead to continued dry
conditions and increasing temperatures. Expecting a return to the
lower to middle 80s by Wednesday with just middle 80s on Thursday favoring a bias
By the end of the short term period we should see enough of a
return of deep layer moisture with precipitable water at 1.50
inches to warrant slight chance probability of precipitation for the far SW zones. Overall
coverage will be looted by the development of a subtle ridge aloft
in advance of strong shortwave over the Central Plains.
Long term /Thursday through Tuesday/...
models continue to be in good agreement with the cold front on
Friday and very little in terms of changes to timing and thinking.
Still the potential for some strong storms with 35kts of low level
shear Friday morning and up to 2000 j/kg of MUCAPE by the
afternoon. Cannot rule out a severe storm with this system.
Rainfall amounts appear to be 1.5 inches or less with the system
so no flooding concerns at this time.
Some uncertainty in the forecast Monday into Monday night. Both
GFS and European model (ecmwf) are bringing precipitation associated with a wave into
north Georgia...however timing is different. Have kept 10 percent
probability of precipitation in...but will likely need to add slight chance once there is
a bit more agreement in timing between models and runs.
Long term /Wednesday night through Monday/...
a cold front is expected to impact the County warning forecast area by the late week.
High pressure begins to shift offshore Wednesday night in advance of
an approaching cold front. The front should begin to cross the
Mississippi River by very early Friday morning and approach the northwest
corner of the County warning forecast area by midday Friday. Scattered thunderstorms are
expected along and ahead of the front. Since the main middle level
forcing gets shunted well north of the County warning forecast area...will keep out the
mention of severe at this time. However...since the front will be
coming through the area during peak heating and there will be some
good surface instability...do think a few of the storms could be
strong. The front should clear the County warning forecast area by early Saturday morning.
High pressure will build for the latter half of the weekend into the
early part of next week. Accompanying the high pressure will be
cooler temperatures and a drier airmass. Models have been consistent in
progging middle 50s across much of the County warning forecast area for lows Sunday
The cooler temperatures should not last too long. Return flow off of the
Gulf will bring increasing moisture and temperatures ahead of the next cold
front expected by the middle of the week.
stratus which has plagued the northern terminals the last several
days has finally lifted with a scattered deck prevailing for atl and
surrounding sites. Mcn and csg continue to have some low ceilings but
are rising with MVFR conditions now realized. Models show very low
level moisture coming in tonight which would be more indicative of
fog than low clouds. Not ready to jump on board all the way just
yet but will indicate some reduced visibility with greatest reductions
over ahn and southern terminals. Any fog that does develop should
burn off quickly on Wednesday with VFR conditions prevailing for the
remainder of the taf period.
//Atl confidence...18z update...
medium on reduced visibility potential.
High on remaining elements.
Preliminary point temps/pops...
Athens 60 84 63 85 / 5 5 5 5
Atlanta 65 83 67 84 / 5 5 10 10
Blairsville 54 79 56 80 / 5 5 5 10
Cartersville 58 84 60 85 / 5 5 5 10
Columbus 66 85 67 86 / 5 5 20 30
Gainesville 62 82 64 83 / 5 5 5 10
Macon 62 85 63 86 / 5 5 10 10
Rome 58 85 60 86 / 5 5 10 20
Peachtree City 60 84 62 85 / 5 5 10 20
Vidalia 64 84 64 85 / 0 0 5 5