Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
146 am EDT Thursday Jul 28 2016
Previous discussion... /issued 950 PM EDT Wednesday Jul 27 2016/
Forecast updated to reflect radar trends and obs. Continuing to
see a decrease in shower activity and cloud cover. Temps look good
with lows in the 70s. Tranquil night expected.
Evening WV loop showing two mid/upper level
highs centered across Great Basin and just offshore coast of
Carolinas (respectively) with a weak vort Max sandwiched between
them across AR/MS/la. A stronger belt of cyclonic flow exists
north of these features with numerous embedded impulses. As these
impulses push east...cyclonic flow will strengthen across the
Ohio/Tennessee valleys...ingest the the Arkansas/MS/la low...and push the
Carolina high east. This will be the beginning of a pattern shift.
In the lower levels...winds will take on a marked increase
overnight between 850 mb and 700 mb...while a weak Lee trough persists
east of the mtns thru Thursday.
For Thursday...aforementioned Arkansas/MS/la low will shear as it
becomes absorbed in the cyclonic flow. However...its DCVA coupled
with SW upslope flow across higher terrain will support a storm
threat across far north GA during the afternoon/evening. Mid
level flow approaching 30kts/0-6km shear near 20kts could yield a
few storm clusters...but thinking highest coverage will be across
Tennessee/NC (consistent with current Storm Prediction Center marginal risk depiction). High
precipitable water air and large T and TD spread indicate downburst winds and
heavy rain the main threat with any storm across north GA.
Otherwise...breezy conditions seem likely by mid morning as low
level flow increases and bl mixes. Temps should be a few degrees
cooler (upper 80s low 90s) north GA with more cloud cover/shifting of
ridge. Central GA will top off in upper 90s and stay below heat
Previous discussion... /issued 755 PM EDT Wednesday Jul 27 2016/
Short term /tonight through Thursday night/...
no major changes in the short term with the over all atmospheric
pattern. The main east- west oriented upper ridge continues to
control the weather pattern across the southeastern states. The
wave that was over the northern Gulf yesterday is now a weak low
center rotating near the la/AR/MS border. Showers and
thunderstorms are rotating northward across MS and Alabama and into
west central Georgia this afternoon. Right now we are only seeing
showers as the best instability continues to stay west of our
area. With the increased Gulf moisture moving into the region
coverage may be a bit more Thursday than today. Temps should
continue slightly above normal with heat index values remaining
below 105 so no advisory expected.
Long term /Friday through Wednesday/...
no major changes needed to the long term portion of the forecast.
Ridging aloft begins to break down by Friday into early Saturday as
a weak trough/shear axis develops across Alabama. This shear axis/trough
will settle across northern Georgia for much of the weekend into early
next week. At the surface...weak Lee trough may try to set up across
north eastern Georgia as high pressure remains situated across the
southern County warning forecast area. The ridging aloft should begin to build back over the
area by the middle of next week.
Scattered showers and thunderstorms are expected each day and should
be diurnal in nature. Highest pop values should be in the vicinity
of the shear axis/trough or the surface trough through early next
week. The current grids reflect this...so didn't make any changes.
No strong indicators for widespread severe weather are noted at this
One thing to watch...the 00z run of the European model (ecmwf) and the new GFS bring
a low pressure system into the Caribbean by the early/middle part
of next week.
VFR conditions expected through most of the taf period with mostly
clear skies observed tonight. Do not anticipate widespread low stratus
this morning, but may see broken mid level deck form by sunrise. Cumulus
development by late morning around 5-6kft. Southwest winds will
increase through the morning hours topping out in the afternoon
with momentum transport illustrating gusts up to 18-20kt. Convective
coverage will be highest north of the Metro taf sites, so have
kept vcsh in from 18-01z. Any precip will dwindle after sunset.
//Atl confidence...06z update...
high confidence on all elements.
Preliminary point temps/pops...
Athens 96 73 93 74 / 20 20 30 20
Atlanta 92 72 89 74 / 20 20 30 20
Blairsville 86 69 84 67 / 40 40 50 40
Cartersville 91 72 88 72 / 30 30 40 30
Columbus 95 74 94 75 / 20 20 20 20
Gainesville 91 72 88 73 / 30 30 40 20
Macon 98 74 97 75 / 10 10 20 20
Rome 91 72 89 71 / 50 40 50 40
Peachtree City 93 73 90 73 / 20 20 30 20
Vidalia 99 74 99 76 / 10 10 20 20