Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Peachtree City Georgia
136 am EDT Sat Mar 15 2014
Previous discussion... /issued 1006 PM EDT Friday Mar 14 2014/
weak shortwave and mainly middle-upper level moisture has resulted in
pretty decent reflectivity across north Georgia. Cannot rule out
some light precipitation making it down to the ground and winning against
the lower dry levels though has largely been virga. Have therefore
included just a slight chance of showers mainly before midnight.
Midlevel deck advected its way in just in time to trap in the
daytime radiative heat and temperature trends so far starting much
warmer. Have bumped up overnight mins considerably keeping much of
the area in the middle to upper 40s...though might even stay warmer
than this. Rest of forecast looks to be on track and previous
Previous discussion... /issued 732 PM EDT Friday Mar 14 2014/
Previous discussion... /issued 318 PM EDT Friday Mar 14 2014/
Short term /tonight through Saturday night/...
high pressure that has brought sunny skies to the area the last few
days has finally shifted to the east. Shortwave expected tonight has
a few models spitting light rainfall over the area tonight and early
Saturday...but with dry middle levels...expect a large portion of this
to not reach the ground or be just sprinkles. Have continued with
the increase in clouds across the area as well. Upper level moisture
persists through the day Saturday as the next system approaches.
Short term models continue to suggest that onset of precipitation
with this next system will be late Saturday night. Have continued
with quickly increasing pop chances with slight chance moving into
west and northwest Georgia Saturday evening...and likely to
categorical probability of precipitation by the wee Sunday morning hours. Models continue
to show limited instability Saturday and have left out mention of
thunder through Sunday morning. Quantitative precipitation forecast continues to be in the 1-2 inch
range through the weekend with this system. For now...ffg values
suggest we should be able to handle this amount of rainfall with
minimal to no flooding concerns.
Long term /Sunday through Friday/...
only minor changes to the extended forecast. With the rain holding
on into the beginning of next week...have gone ahead and increased
probability of precipitation Sunday night into Monday. Still on track with thunder potential
for Sunday and Sunday night given MUCAPE values up to 500 j/kg.
Have continued the slight chance to chance of thunderstorms in the
grids with near 100 probability of precipitation. Seems the main threat with this system at
this time appears to be rainfall amounts...see the Hydro section
for more details. Still differences with the middle week system
between the GFS and European model (ecmwf). GFS remains the dry solution while the
European model (ecmwf) brings rain though Wednesday night into Thursday with the
front. Have leaned towards the GFS for now which is consistent
with the previous dry forecast.
Models are coming into good agreement with the weekend solution
which is giving a medium to high confidence in the long term. The
short wave developing over the Southern Plains will continue to dig
over the Southern Plains ejecting a surface low into the lower
Mississippi Valley. This will spread ample amounts of moisture into
the County Warning Area Saturday night into Sunday. As the surface low moves closer
and the southwest flow increases...instability will increase
bringing isolated to scattered thunderstorms along with the
widespread on Sunday and into Sunday evening. The models differ
slightly on the strength of the upper system. GFS develops a closed
low while the European model (ecmwf) keeps an open wave. Regardless both models keep
precipitation over the County Warning Area Monday and into early Tuesday. Much drier air
will spread across the County Warning Area Tuesday afternoon and for the rest of the
total rainfall amounts Saturday night through Tuesday with this
next system are forecast to be in the one and a half to two inch
range. The highest amounts are expected to be on Sunday with much
of north Georgia forecast to receive a half inch to an inch of
rainfall in a six hour period. Given these amounts in a shorter
time period...will have to continue to monitor flooding closely.
At this point...main concern would be the potential for minor
flooding along Big Creek between Cumming and Alpharetta.
VFR today but with increasing low VFR cloudiness. Conditions
rapidly deteriorate after 06z Sunday with MVFR ceilings moving in
with -shra. South-southwest winds will veer to nearly west later this
morning...back to SW and south-southeast just after 00z...remaining southeast
through the end of the period.
//Atl confidence...06z update...
medium on timing of wind shifts and MVFR ceilings.
High on occurrence of wind shifts and MVFR ceilings.
Preliminary point temps/pops...
Athens 71 51 60 48 / 10 60 100 80
Atlanta 68 52 63 47 / 10 80 100 80
Blairsville 64 48 57 45 / 10 90 100 70
Cartersville 68 52 63 47 / 10 100 100 70
Columbus 70 54 68 50 / 20 80 90 80
Gainesville 66 51 58 49 / 10 80 100 80
Macon 71 53 64 54 / 10 50 90 80
Rome 69 52 62 47 / 20 100 100 60
Peachtree City 68 51 63 45 / 10 80 100 80
Vidalia 74 54 71 57 / 10 50 90 80