Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Peachtree City Georgia
745 PM EDT Wed Sep 28 2016
leading cold front now southeast of an Americus to Macon line with
all associated clouds and convection also well southeast of that
line. The few showers and storms currently developing across areas
from Wilcox to south Emanuel counties will continue to diminish and
push southeast of that area early this evening... so will update to
word for only a slight chance of thunder across the far southeast
zones through around 10 PM... then gradually end convective wording
there shortly after midnight. Otherwise... a reinforcing cold front
will sweep across north Georgia late tonight-Thu morning... then across
central Georgia Thu afternoon... with a gusty northwest wind in its wake. The
deck of mid level clouds just northwest of north Georgia will likely spread into
parts of far north Georgia overnight... but not expecting anything but
maybe a sprinkle if anything from that tonight. These clouds should
erode before getting to Atlanta by early Thu morning. Therefore...
current forecasted lows in the 50s north and 60s central still looks
on track... so will only tweak pops down across the far southeast
zones for now. No strong or severe storms are expected their this
evening as well. /39
Previous discussions.../issued at 333 PM EDT Wed Sep 28 2016/
..fall has finally arrived in north and central Georgia...
Short term /tonight through Thursday night/...
cold front - or leading edge of drier air - currently extends from
around Athens Georgia (ahn) to Macon (mcn) to Eufala Alabama (euf). To the
west and north of this line, much drier air has filtered across the
area with dewpoints have fallen into the 40s and 50s - some 10 to as
much as 25f degrees lower than this time yesterday. Ahead of the
front, pronounced cumulus field exists with scattered showers in an area
from Albany to Swainsboro Georgia.
The front will continue to slide south and east tonight allowing the
drier/cooler air to spread across the remainder of the forecast
area. May see a few showers linger along the front into this evening
but expect much of the activity to diminish shortly after sunset
with loss of daytime heating.
Thursday, a large upper level low currently just south of the
central Great Lakes is expected to move nearly due south over the
next 24-36 hours, centering itself somewhere over Kentucky. Low
level moisture and steep lapse rates along the Georgia/Tennessee state line
should generate some sct-bkn cumulus and perhaps a rogue shower
during afternoon peak heating. Otherwise, much of the area will
experience dry/stable conditions resulting in abundant sunshine. It
will feel much cooler with high temps in the 70s for a good portion
of north/central Georgia - north of a La Grange to Covington to Athens
line. Higher elevations in north Georgia could only reach the mid to upr
Long term /Friday through Wednesday/...
the long term period begins with strong closed upper low
continuing its slow trek southward into the Tennessee Valley.
Embedded shortwaves will rotate around the base of this trough but
moisture remains limited. Could certainly envision a few showers
developing on Friday but chances still appear too low for
inclusion in the forecast at this time.
Main story for the initial portion of the extended will be the
beginning of Fall like weather across the area. Both highs and
lows on Friday look to be some 3 to 5 degrees below climo which
will seem cooler given we have been close to 10 degrees above for
quite a while now. Highs will recover very quickly through the
weekend with a return to the 80s and above normal for the Atlanta
Metro. Lows will be slower to moderate and look for continued near
climo conditions with values in the lower to mid 50s.
Much uncertainty exists as we get to the tail end of the extended
period. GFS/European model (ecmwf) and Canadian models continue to differ on
evolution of Tropical Storm Matthew with GFS curving quickly but
the Euro remaining slower and further south. The Canadian is
similar in forward speed to the GFS but further west. Will just
need to wait until models come into better agreement but
regardless... looks like there will be enough return flow from the
Atlantic to warrant low pops for southeast sections early next week.
dry air will be spreading into the County Warning Area today. This will allow
humidities to drop to near 25 percent for an hour or two this
afternoon across northwest Georgia. Fuels at this time are running
around 10 percent. However time requirements will not be met for a
Fire Danger Statement. This will continue to be watched.
a cold front has slipped southeast of a csg to mcn line with
associated clouds and convection also southeast of that line. A
second dry/reinforcing cold front will sweep across the area early
on Thursday. This will allow VFR conditions to prevail through the
period... with maybe a few cu Thu afternoon. Winds will stay on the
west to northwest side of things... and become gusty Thu afternoon behind
the reinforcing cold front. Ocnl gusts from the northwest at around 18-
20kts can be expected between 17-23z Thu.
//Atl confidence...00z update...
high confidence all elements.
Preliminary point temps/pops...
Athens 60 80 53 76 / 5 5 5 5
Atlanta 60 75 54 74 / 5 5 5 5
Blairsville 53 68 46 70 / 10 10 10 5
Cartersville 56 73 50 74 / 5 5 5 5
Columbus 64 82 56 79 / 5 0 5 5
Gainesville 60 74 53 73 / 5 10 5 5
Macon 61 85 54 80 / 20 5 5 5
Rome 56 73 50 74 / 5 5 10 10
Peachtree City 58 77 51 75 / 5 5 5 5
Vidalia 68 87 60 82 / 30 5 5 5