Scientific Forecaster Discussion
fxus62 kffc 171140
Area forecast discussion
National Weather Service Peachtree City Georgia
640 am EST Tue Jan 17 2017
Previous discussion... /issued 348 am EST Tue Jan 17 2017/
Short term /today through Wednesday/...
water vapor analysis reveals a broad trough across the SW US and
into Mexico with several notable perturbations rotating
within...while downstream of this feature flow becomes more
anticyclonic...with center of ridge across the Yucatan and quasi-
zonal to SW flow across the southeast. At the sfc...low pressure was
centered across the Midwest/associated with a strong 500 mb shortwave/
and its cold front draped S into arklatex...while sfc wedge has held
on a little longer/stronger than previously thought across Georgia.
Will see wedge front retreat while the cold front pushes south and
east during the short term.
Low cloud cover and fog associated with wedge front has been slowly
creeping west from NE GA over towards the atl Metro. This should
persist into mid morning across this general area. All other
locations will experience increased cloudiness today with temps
continued warm /upper 60s north to upper 70s central/. Rain chances
will be confined to mainly north Georgia today and will increase as
the day wears on with aforementioned cold front moving towards
the state. By early to mid-afternoon...instability will increase
enough across north Georgia to warrant mention of general thunder.
Overnight Tuesday the cold front will push through north Georgia.
With the best dynamics displaced well to the north...most of the
precip will diminish...but enough forcing along front itself along
with moist airmass in place... chance for rain and thunder will
continue across north GA.
Wednesday...a few showers will persist along the front as it
continues to push slowly across the state. Not seeing enough
instability to carry thunder on Wednesday. The front will stall near
Metro atl and areas west and east of the city by Wednesday evening.
Temps will continue well above normal. With weak sfc high pushing
into north counties behind the front on Wed...kept highs a touch
cooler in the low-mid 60s. Areas near and south of the front will
see highs in the lower-upper 70s.
Long term /Wednesday night through Monday/...
unsettled weather still on tap for the long term portion of the
forecast. Fast flow will dominate aloft, so expect several systems
to impact the area through the end of the week into early next week.
An old frontal boundary will begin pushing back northward as a warm
front Wednesday night into Thursday as a low pressure system moves
into the lower Mississippi River valley. Pops will be on the
increase during the day Thursday as the boundary pushes north and
the low pressure system/front approaches from the west. Models are
progging some minimal instability with this system, so thunder still
looks appropriate. The front briefly settles across southern
Georgia/northern Florida before beginning to push back north late on Saturday
ahead of the next low pressure/frontal system.
Copious moisture is expected ahead of the late weekend/early next
week system. Pops remain high. The parent low with this system
rapidly moves east from the center of the country to the Tennessee Valley
by early Sunday, dragging a frontal boundary through the County warning forecast area later
Sunday/early Monday. This is a potent system...strong mid level
energy aloft will give support for widespread showers and
thunderstorms. Currently, good shear and very steep lapse rates are
progged, so there is good potential for severe thunderstorms. Now,
this is still day 5/day 6, so the forecast could change, stay tuned!
expansive area of LIFR/IFR/MVFR visibilities still exist across
all taf sites except csg. Expect these conditions to continue for
another hour or two...sticking around ahn the longest...but still
think most sites will hold steady with MVFR ceilings for most of
the day today after fog erodes/visibilities rise. Could see VFR
ceilings this evening before conditions rapidly deteriorate again
Wednesday morning. Shower and thunder activity looks to stay north
of all taf sites...though could see an isolated shower pop up
near northern sites. Winds will shift to the SW this morning with
speeds generally between 5-10kts.
//Atl confidence...12z update...
low on duration of low vsbys.
High on wind speed and direction.
Medium on all other elements.
Preliminary point temps/pops...
Athens 71 57 70 49 / 20 30 30 20
Atlanta 71 58 68 53 / 20 30 30 20
Blairsville 64 52 62 46 / 50 60 40 30
Cartersville 70 55 65 50 / 40 50 40 30
Columbus 75 59 74 55 / 10 20 20 20
Gainesville 68 57 67 51 / 30 50 40 20
Macon 75 57 74 54 / 10 20 20 20
Rome 70 55 65 50 / 50 60 40 30
Peachtree City 72 57 70 52 / 20 30 30 20
Vidalia 77 57 76 56 / 10 20 20 10