Area Forecast Discussion
Issued by NWS Atlanta, GA
FXUS62 KFFC 280556
Area Forecast Discussion
National Weather Service Peachtree City GA
156 AM EDT Tue Mar 28 2017
.PREV DISCUSSION... /issued 949 PM EDT Mon Mar 27 2017/
Based on current radar trends, have adjusted the pops across north
GA. The current area of tsra will continue moving east. The next
band moving into northwest AL is expected to move into north GA by
05Z based on the hi-res models. No other changes planned.
PREV DISCUSSION... /Issued 343 PM EDT Mon Mar 27 2017/
SHORT TERM /Tonight through Tuesday Night/...
Frontal boundary moving east of the Arklatex. A pre-frontal
trough/convective line has developed just east of the MS river and
is also moving eastward.
Hi-res models keep the line moving across AL and entering the
western portions of the CWFA later this afternoon into the early
evening hours. Models have been pretty consistent with weakening the
line as it moves through. However, there should be enough
instability/mid level energy/steep lapse rates to support some
strong/isolated severe thunderstorms. In addition, the hi-res models
bring in another round of storms overnight, mostly associated with
the cold front. These storms could also be strong with the potential
for isolated severe. The main threats for any severe thunderstorms
would be damaging wind gusts and large hail.
The frontal boundary looks to sag slowly southward during the day
tomorrow. Convection should fire along any old outflow boundaries
from the overnight convection and/or the weak front. With copious
cloud cover, marginal surface instability and weak lapse rates,
storm coverage should be limited to iso/sct and the potential for
strong/severe should be limited.
LONG TERM /Wednesday through Monday/...
Limited changes through the extended period aside from slight
massaging for latest model consensus. Overall, forecast looks on
track. Previous forecast discussion is included below.
/Issued 337 AM EDT Mon Mar 27 2017/
At the beginning of the forecast period, the system that traversed
the area on Tuesday will have exited eastward. As upper ridging
builds in on Wednesday a warm and generally drier day can be
expected. A few showers or an isolated thunderstorm can`t be ruled
in the vicinity of a remnant weak boundary, but most places will
Rain chances will be increasing again by Thursday afternoon,
especially across eastern sections of the area where showers and a
few thunderstorms will develop near the wedge front along the
periphery of the CAD airmass over the Carolinas.
The opportunity for showers and thunderstorms will increase in
earnest Thursday night into Friday morning across the remainder of
the area as the primary storm system approaches the area from the
west. There is generally better model agreement with regard to the
track of this system as the parent low lifts across the Midwest into
the Ohio Valley. This system evolution would favor the chance for
some strong to severe thunderstorms in our region with 0-6 km bulk
shear values as high as 40-60 knots and 0-1 km values around 30
knots during the Friday morning time frame. Forecast instability is
not overly high, but the several hundred J/kg of CAPE forecast by
the GFS would likely still be sufficient given aforementioned shear
values and favorable upper dynamics. One thing to note is that
models have been indicating the development of weak low pressure
along the Gulf coast which could rob some instability. Nevertheless,
the severe potential with this system late Thursday into Friday
morning will continue to be watched over the coming days.
After this system departs Friday, upper ridging once again takes
hold for the weekend. At this point next weekend`s weather appears
benign with warm and dry weather before models diverge on the timing
and details of the next storm system for early next week.
With SHRA/TSRA moving through in waves...environment remains mixed
enough to prevent any developing MVFR or IFR across the area.
Indications are this will be changing toward day break with lower
cigs developing to the west and then moving in with low level SW
flow. Have gone TEMPO IFR for now for the ATL sites and then
improvement to VFR by early afternoon. Continued threat of TSRA
this afternoon with low end chance in the grids requiring a Prob30
for the terminals.
//ATL CONFIDENCE...06Z UPDATE...
Medium on IFR development.
High on remaining elements.
.PRELIMINARY POINT TEMPS/POPS...
Athens 79 56 84 58 / 30 5 5 10
Atlanta 77 58 82 60 / 30 5 20 10
Blairsville 73 50 77 53 / 30 10 5 10
Cartersville 77 54 81 58 / 30 10 10 10
Columbus 80 61 86 60 / 30 5 20 5
Gainesville 76 55 81 58 / 30 5 5 10
Macon 81 58 84 59 / 30 5 20 10
Rome 78 53 81 56 / 30 10 10 10
Peachtree City 77 56 83 57 / 30 10 20 10
Vidalia 84 62 85 63 / 20 5 20 10