Area Forecast Discussion
Issued by NWS Atlanta, GA
FXUS62 KFFC 271122
Area Forecast Discussion
National Weather Service Peachtree City GA
Issued by National Weather Service Birmingham AL
722 AM EDT Mon Mar 27 2017
.PREV DISCUSSION... /Issued 337 AM EDT Mon Mar 27 2017/
SHORT TERM /Today through Tuesday/...
The short term period begins with high pressure well off the
Carolinas coast..providing a light southerly flow to the local
area. This low level flow off the gulf is allowing for a layer of
stratus to make steady progress inland this morning to affect
mainly portions of SW GA initially. Otherwise...the main
initialized features consist of a shortwave over the Central
Plains and associated surface reflection of a weak low over
Oklahoma that will eventually become the key wx makers for the
local area over the next 24 to 36 hours.
Will be a tough call today wrt shower and thunderstorm timing as
there is no real definitive focus until late this afternoon and
evening but just enough overall dynamics and lift until then to
allow for low end pops. Have basically thrown out the Hi-Res
solutions for today as they just do not seem to capture the
overall potential for storms today in my opinion.
For me...an approaching shortwave...diffluence aloft...increasing
moisture and instability building to around 2000 to 2500 J/KG
should be sufficient for the development of numerous showers and
storms across the northern tier. Have also gone with an earlier
start time than the hi-res would suggest with sct showers pretty
much anytime after 15Z and thunder anytime after mid afternoon and
into the evening hours. Have kept most of the metro at sct
coverage for now but this will need to be watched closely as
moisture and dynamics almost as high in these areas than further
There is a period late this evening as low makes its closest
approach to the area that we see a spike in low level helicity for
northern sections. Residual CAPE combined and we get sig tor
approaching 1 for a 3 to 6 hour period. While winds and hail will by
far be a more prevalent threat for the north...will have to at least
keep an eye out for rotation in any storms that develop this evening.
No real frontal passage but moisture axis sags into the area
through Tue afternoon keeping low end pops in for the metro and
portions of Central GA.
LONG TERM /Tuesday Night through Sunday/...
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.
IFR has now worked into ATL while other sites are at MVFR around
1200 to 1500 feet. Have continued with TEMPO IFR for northern
most sites. Difficult call on timing for potential SHRA/TSRA. Have
gone with a more extended VCSH than normally would but just too
difficult at this point to pin down exact timing. Slowed down the TSRA
as well a couple of hours for the northern sites aas it now
appears to be after 00Z before reaching ATL. For TAF purposes
will hold at Prob30 for now.
//ATL CONFIDENCE...12Z UPDATE...
Medium on IFR potential and TSRA timing. High on remaining elements.
.PRELIMINARY POINT TEMPS/POPS...
Athens 79 59 78 56 / 40 50 30 5
Atlanta 77 61 76 59 / 30 30 30 5
Blairsville 70 55 72 50 / 60 60 50 10
Cartersville 76 60 76 55 / 50 40 30 10
Columbus 81 61 80 60 / 20 20 30 5
Gainesville 75 58 75 56 / 50 50 30 5
Macon 83 60 80 59 / 20 20 30 5
Rome 76 59 77 54 / 60 50 40 10
Peachtree City 78 59 77 56 / 30 30 30 10
Vidalia 83 61 84 63 / 30 30 20 5