Scientific Forecaster Discussion
fxus62 kffc 230548
Area forecast discussion
National Weather Service Peachtree City Georgia
148 am EDT Tue may 23 2017
Previous discussion... /issued 1000 PM EDT Mon may 22 2017/
no changes to the forecast. Showers increasing tonight with
some storms. Flash Flood Watch continues.
Previous discussion... /issued 710 PM EDT Mon may 22 2017/
Short term /tonight through Tuesday night/...
surface boundary has become nearly stationary with convection
developing in the vicinity of the front and also areas southward.
These showers and tstorms appear to be pretty efficient rain
producers with precipitable waters of 1/5 to 2 inches across most of the County Warning Area
through tonight. With the front lingering and the second short wave
moving across the County Warning Area tonight, thinking that the quantitative precipitation forecast amounts may be
a bit too low but confidence in raising them is not quite there yet.
Having said that, still think there is a risk of isolated flash
flooding tonight and will therefore maintain the Flash Flood Watch.
The short wave will exit the County Warning Area Tuesday bringing a brief respite to
the County Warning Area. The h5 trough and will continue to dig southward and eject
a strong cold front that will move into the County Warning Area late Tuesday
night/early Wednesday morning. Quantitative precipitation forecast amounts are not as great with
this, however instabilities increase with convective available potential energy increasing ahead of
the cold front as well as lapse rates and 6km bulk shear. This
should bring a risk of isolated severe storms late Tuesday night
across mainly the western parts of the County Warning Area.
Long term /Wednesday through Monday/...
no changes made to the extended forecast. The extended period
starts off with the GFS and NAM both increase deep layer shear
going into the Wed morning hours which is juxtaposed with the
left exit region of the 250mb jet. Models are more sporadic and
broad with quantitative precipitation forecast in this period so confidence is medium on how
things will evolve...especially given the unknown impact of the
first wave moving through Tuesday am. For now have kept pops in
the likely category and included thunder as well. May see a fairly
Stout line of convection develop in the eastern half of the state
late Wed am into the afternoon as models forecast additional
destabilization during the day.
Of greater note is the 00z ECMWF solution with an upper low
cutting off much further south than previous solutions over
central Alabama and shifting eastward across Georgia on Thu. GFS is much
further north with the cut off portion...but does extend the base
of the trof into the same general area. GFS and European model (ecmwf) 500 mb temps
with the low/trof drop to -21 to -22 across the region on Thu.
Sounding climatology suggests that those temps would be one of and
very close to the coldest on record for may at atl should it
occur...and most certainly a record for the date. In
response..afternoon highs both Wed and Thu are forecast to remain
in the low 70s which is right around record low Max temps.
Overnight lows drop into the low 50s Thu am and Fri am as well and
while much below normal and cool...records are generally in the
Nice weather on tap through Sunday before another trof digs into the
central US and rain chances again increase in response. Models vary
on the evolution of the trof...but agree that one is forecast to
Yet another very challenging cig forecast for the next 24 to 36
hours with a series of weak areas of low pressure moving across
the terminals. Cigs thus far slow to fall but expect an overall
trend to IFR by daybreak with continued increase in rain showers and
embedded thunderstorms and rain. Models holding onto IFR a little longer and will
follow suit in keeping til 17z. Winds will be tricky as well with
the vicinity of low and have gone with a brief period of NE before
low shifts to the east of the terminals and winds go back to light
//Atl confidence...06z update...
medium on wind direction and IFR start time.
High on remaining elements.
Preliminary point temps/pops...
Athens 77 64 76 56 / 90 70 70 30
Atlanta 77 65 75 57 / 80 70 70 30
Blairsville 72 59 69 51 / 70 70 80 30
Cartersville 78 64 74 54 / 70 70 70 30
Columbus 79 67 78 58 / 80 70 70 20
Gainesville 75 64 73 56 / 90 70 80 30
Macon 77 67 79 58 / 90 70 70 30
Rome 77 62 75 54 / 70 70 70 30
Peachtree City 77 65 76 55 / 80 70 70 30
Vidalia 79 68 79 62 / 80 70 70 50
Flash Flood Watch through Wednesday afternoon for the following