Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
316 PM EDT Friday may 29 2015
Short term /tonight through Saturday night/...
Although the County Warning Area remains in the southwest flow through the short
term...the upper level trough does slowly push towards the
east...moving the trough axis closer to Georgia. This will
eventually bring something more Concrete to key in off of for
precipitation...but that will not occur until the very end of the
short term into the long term. Until then...isolated to scattered
convection will continue each afternoon for much of the County Warning Area.
Do expect convection to continue to be focused across north Georgia
today with storms dissipating tonight. For tomorrow...hi-res models
are picking up on sea breeze convection making it into the SW
portion of the County Warning Area. This does not preclude the rest of the County Warning Area from
convection but appears there could be a lull in activity between the
sea breeze and convection to the north and west...however hard to
Pin Point where this lull will set up.
Low temperatures tonight will only be a few degrees warmer than this
Long term /Sunday through Friday/...
12z model run showing no significant departures from recent trends.
Current extended forecast grids cover this well and minimum changes
were made at this time. Please see the previous long term forecast
Previous long term forecast discussion...
Saturday night through Thursday...
Synopsis...00z GFS and European model (ecmwf) in general pattern agreement at the
beginning of the extended through midday Monday before differences in
the evolution of a cut off low over the southern Mississippi Valley
Saturday and Sunday...mean trough that has been anchored over the
western US for the last month it seems begins shifting east into the
central US with ridging building across the West. Georgia will remain
under the influence of upper ridging centered off the East Coast
particularly Saturday and waning by late Sunday as the trough shifts
eastward along with a weak surface front. Best chances for rain on
the weekend will remain generally confined to far northwest Georgia Sat and north
and west of i85 on Sunday afternoon and evening. Look for typical
afternoon thunderstorms to develop across the aforementioned regions
Monday through Thursday...differences begin to appear on Monday between
the GFS and European model (ecmwf) over the evolution of a cutoff low as energy rides
over the developing western ridge into the base of the fairly shallow
trough centered over the MS river at that time. Operational GFS wants
to cut the low off over la which puts our region on the moist flow
side with a tap into a moisture plume from the Caribbean by Wednesday and
making for a much wetter week. The European model (ecmwf) on the other hand delays the
onset of cutting the low off until the mean trough gets to around the
85th parallel and thus centering the low over Florida. This
difference puts our area on the drier north side of the low middle to
late week. GFS ensemble resembles the operational GFS quite a bit
more thus making the European model (ecmwf) an outlier for now. Carrying above climatology
probability of precipitation each day for now that will likely need to be fine tuned each day
for nuances as confidence increases. Localized flood threat will
certainly be on The Table each day as precipitable water values...per the GFS...each
day through Thursday range from 1.50 to 1.75 inches across the region
which statistically is in the 90th percentile. Stay tuned to the
forecast for next week.
some showers/convection have developed across north Georgia and
these will persist through the afternoon. Theres a small chance
these showers could develop around the atl area taf sites but the
better chances are activity will remain north...at least of
atl. Main uncertainty with the taf is potential for low stratus
tomorrow morning at sites. Have included few-sct005 to hint at
//Atl confidence...18z update...
high confidence on wind and visibility. High confidence on ceilings through
08z and then low confidence.
Preliminary point temps/pops...
Athens 65 85 67 86 / 10 20 20 30
Atlanta 67 84 69 84 / 10 20 20 40
Blairsville 60 79 62 79 / 20 20 20 50
Cartersville 64 85 66 84 / 10 20 20 40
Columbus 67 88 69 88 / 5 10 10 30
Gainesville 65 82 67 83 / 10 20 20 40
Macon 65 88 67 87 / 5 20 20 30
Rome 64 85 66 84 / 20 20 20 50
Peachtree City 64 85 66 85 / 5 10 20 30
Vidalia 68 86 69 88 / 5 40 20 30