Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Peachtree City Georgia
737 am EDT Friday Aug 1 2014
Previous discussion... /issued 338 am EDT Friday Aug 1 2014/
Short term /today through Saturday/...
large upper trough remains dominant feature over eastern Continental U.S. During
short term period. Trough axis still prognosticated to remain stationary
west of the state through at least Sunday. Low level cool air still in
place this morning enhancing low level isentropic lift...but should
erode some today. Temperatures and surface-based instability yesterday a little
higher than expected south of I-20. Have adjusted guidance temperatures and
weather grids for today for similar reasons. Not anticipating severe
storms but could see isolated storms become strong. Heavy rain also a
threat though observed and forecast soundings not indicating extreme precipitable water
compared to normal values...around 75th percentile on 00z ffc
sounding. Model and wpc guidance quantitative precipitation forecast also keeping higher amounts
outside of County Warning Area.
Rain showers/thunderstorms and rain coverage about the same or a little higher Saturday.
Difficult to pin down any one area. May see a little more thunderstorms and rain than
previous days on Sat but location/coverage/timing again will depend
heavily on morning rain showers and clouds. Modified bias-corrected blend
for temperatures based on expected cloud/precipitation areas.
Tropical activity in the western Atlantic expected to remain
offshore well east of the state based on TPC and model guidance.
Long term /Saturday night through Thursday/...
a moist upper trough will continue to affect the area in the long
term with the trough expected to weaken Tuesday. GFS and European
begin to differ Thursday with the GFS developing another upper
trough to the west and the European wanting more of a weak ridge.
Highest probability of precipitation favoring central Georgia where the deepest moisture is
expected to be into Tuesday. Probability of precipitation then favoring more toward climatology
for Wednesday and Thursday. Precipitation will still have a diurnal trend
but may not necessarily end at night.
Forecast high temperatures favoring about 5-8 degrees below normal
and getting back closer to normal Tuesday through Thursday. Forecast
low temperatures favoring near to 5 degrees below normal.
IFR ceilings expected to lift to MVFR after 14-15z. Any precipitation this
morning after 15z should be light...used vcsh to cover this.
Better chance of scattered rain showers after 18-19z. Some concern about whether
thunderstorms and rain will occur this afternoon. Based on expected cloud cover and
instability do not think coverage of thunderstorms and rain will be enough to
warrant mention in tempo at atl metropolitan airports and kahn. Could
see a little more coverage of thunderstorms and rain over middle Georgia but still
not enough to warrant tempo or prevailing thunderstorms and rain. Another IFR ceiling
event likely late tonight after 08z Sat.
//Atl confidence...12z update...
low confidence on thunderstorms and rain likelihood.
High confidence on all other elements.
Preliminary point temps/pops...
Athens 84 68 84 69 / 50 40 50 50
Atlanta 84 69 84 70 / 40 40 50 40
Blairsville 78 61 78 63 / 60 40 50 40
Cartersville 85 66 85 67 / 40 40 60 40
Columbus 89 72 87 72 / 40 30 50 50
Gainesville 79 68 81 69 / 50 40 50 40
Macon 87 69 85 71 / 40 40 50 50
Rome 85 68 85 67 / 40 40 60 40
Peachtree City 86 68 86 68 / 40 40 50 50
Vidalia 92 73 90 73 / 50 40 60 50