Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Peachtree City Georgia
755 PM EDT Tuesday Sep 23 2014
Short term /tonight through Wednesday night/...
upper low over the western Carolinas persists during the short term
although it becomes somewhat broader and weaker. Accompanying
surface low gradually moves up the coast of the Carolinas. This will
keep an east to northeast low level flow across the region with a
varying amount of clouds. For tonight...think some scattering late
this afternoon...but with some clouds lingering overnight. More
cumulus developing again for Wednesday. Models show drying
aloft...but with some amount of lower level moisture through the
period. This makes for an uncertain sky cover forecast. Have left
slight chance showers in for much of the period for the east central
zones mainly due to the upper low in the vicinity. However the bulk
of any showers that develop should be to our east. Easterly flow is
stable so no thunder has been included.
Mav/met temperatures look reasonable with highs and lows running a
bit below normal most places.
Long term /Thursday through Tuesday/...
no major changes made to the extended forecast. The long term
period begins with persistent closed upper low finally opening up
into a broad trough but remaining over the area. Although not much
effects on local weather...upper trough will continue to allow for
surface reflection of an inverted trough off the southeast coast.
Surface convergence with this feature along with ample moisture
will result in a healthy amount of shower activity along the
Florida and Georgia coasts through the end of the week. Big
question will be how much of this activity will translate into the
local area in low level easterly flow regime. Most of the time in
such patterns...the showers remain closer to the coast than models
suggest and for this forecast will follow suit and limit areal
coverage to the far southeast corner of the forecast area and
limit probability of precipitation to 20 percent in general.
Inverted trough weakens into the weekend with pop axis becoming
elongated more west to east but remaining largely south of the
forecast area. This begins to change for the latter half of the
weekend as cutoff low over the Central Plains begins moving
northeast. This acts to bring a deep and very moist southwest
fetch off the Gulf of Mexico...eventually spreading up and over
relatively cooler airmass over the southeast. Excellent adiabatic
Omega profile develops Sunday into Monday with just timing
differences in the models. Despite the decent agreement...forecast
remains quite uncertain given the setup of a closed upper low
within a large upper high. Movement of low could really be just
about anywhere and would not be surprised to see models change
several times on this solution between now and then.
At this point...thinking that various possible solutions would
eventually yield to the same results which will be a good
isentropic profile working in tandem with increasing deep layer
moisture (pwats increasing to 2 inches). Have therefore gone with
likely probability of precipitation for late Sunday into Monday which could wind up being
Monday into Tuesday if you believe the Euro. Clearing conditions by the
middle of next week and used a bcconsall blend for temperatures.
mostly VFR conditions expected across the western half of the
forecast area through this forecast period with a mixture of MVFR
and VFR conditions across the east. Winds will be east to northeast
at 6-10kt through 14z...increasing to 8-12kt after with gusts
//Atl confidence...00z update...
Preliminary point temps/pops...
Athens 56 77 60 81 / 5 0 10 5
Atlanta 58 77 61 80 / 0 0 0 5
Blairsville 52 76 52 79 / 0 0 5 5
Cartersville 56 80 58 82 / 0 0 0 5
Columbus 61 80 63 82 / 0 0 0 5
Gainesville 57 76 61 80 / 5 0 5 5
Macon 58 78 61 82 / 5 5 5 10
Rome 54 80 57 83 / 0 0 0 5
Peachtree City 55 79 58 81 / 0 0 0 5
Vidalia 62 80 64 83 / 20 20 20 10