Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Peachtree City Georgia
1000 PM EDT sun Sep 14 2014
have lowered probability of precipitation across the area for the remainder of the night. A
few showers may develop during the night...thunder mainly central.
short term /tonight through Monday night/...
for the remainder of today and into tonight...interesting fine
line feature or boundary moving through the low overcast and
passing through atl and toward Macon. Such a defined feature
moving toward the clearing zone to the south defined by increasing
convective available potential energy to 2000 to 3000 j/kg is almost certain to act as a focus for
enhanced thunderstorm development. Already advertising likely probability of precipitation
in this area but will need to monitor closely for possible bump up
for probability of precipitation into the categorical range given these new developments.
Where this boundary eventually stalls out could mark a location
for enhanced flood risk this afternoon and will be monitoring for
that as well.
To the north...instability as would be expected is
much much less with values of zero over the northeast withing
wedge. Have kept just the mention of showers in this region as
model forecasts of cape show little to no improvement for the
balance of today and tonight.
Once convection dies out...looks like another round of low clouds
and patchy dense fog tonight. Models indicate a southerly flow
developing at 925mb around 10 to 15 kts which will likely allow
for more in the way of low clouds vs fog and will indicate such in
afternoon grid set.
For Monday...deep layer moisture returns to the north but
instability axis remains largely in place favoring the southern
sections. Because of this...feel best chances of precipitation
will reside across the central portions of the County Warning Area...namely the
Atlanta metropolitan but the best chances of thunder will remain to the
Frontal boundary moves through the area Monday night and Tuesday with
much drier air working its way into the north marked by
precipitable water values of 1.3. Still approaching 2 to the south
so will have to keep probability of precipitation high there but from the metropolitan
northward...will be difficult to even get low end scattered coverage.
Long term /Tuesday through Sunday/...
mainly only tweaks to the long term based on the lastest guidance.
the extended forecast starts out with the front mentioned in the
short term positioned over central Georgia. A second front
approaches north Georgia from the Tennessee Valley Tuesday morning to help
reinforce the weakening first front. These two front move into
south Georgia/North Florida by Wednesday morning as a strong high pressure ridge
builds in behind them from the eastern Great Lake states. A bit
drier airmass moves in over north Georgia Wednesday/Thursday but both the GFS and
European model (ecmwf) how moisture lingering over eastern and southern sections of
the state through day 7. Model precipitable waters stay really slack off by Wednesday
with 1.5 to 2 inch values Monday and Tuesday to less than an inch by 00z
Wednesday. These values are right in line with the drier air moving in
for the middle of the week. Have decided to lower probability of precipitation to slight
to chance on Wednesday...with slight to nothing Thursday through Sat. Models
also continue to indicate cooler temperatures are in store for the
state...especially with the cooler drier air mass moving in. By
the latter half of the week we could be below seasonal normals.
IFR clouds will persist overnight with most sites going to LIFR
before sunrise. Some gradual improving toward noon. Developing low
level wind jet should keep it more low clouds as opposed to fog.
Increase in moisture for Monday will result in increased thunderstorms and rain
chances once again mainly during the afternoon. Winds light east
overnight and into the morning...becoming southwest after 18z.
//Atl confidence...00z update...
medium on timing of wind shift to southwest on Monday.
High on remaining elements.
Preliminary point temps/pops...
Athens 67 80 68 86 / 30 60 60 30
Atlanta 68 82 70 84 / 30 60 60 30
Blairsville 60 77 63 80 / 20 50 50 20
Cartersville 66 82 66 85 / 20 60 60 20
Columbus 72 87 72 86 / 60 60 60 50
Gainesville 66 79 68 83 / 20 60 60 30
Macon 71 86 71 87 / 60 70 60 50
Rome 66 83 66 86 / 20 60 50 20
Peachtree City 68 83 68 86 / 40 60 60 30
Vidalia 72 87 72 88 / 60 70 50 60