Scientific Forecaster Discussion
fxus62 kffc 210802
Area forecast discussion
National Weather Service Peachtree City Georgia
302 am EST Tue Nov 21 2017
Short term /today through Wednesday/...
surface high pressure over the western Atlantic and eastern
Seaboard is causing low level moisture/clouds to increase
across the forecast area. This low level flow will also aid
the potential for enough upward vertical motion to allow for
mainly small chances for light rain across much of the forecast
area favoring only slightly the far NE mountains and the southern
portion of central Georgia.
A weak cold front is forecast to move across the area tonight and
the first portion of Wednesday. This will continue mainly small
chances for light rain overnight favoring east and central Georgia and
portions of central Georgia on Wednesday.
The increase of low level moisture today will allow for areas
of fog tonight and will need to monitor for dense fog potential.
Forecast high temperatures are running within 1-3 degrees of
normal today and Wednesday. Forecast low temperatures are running
4-8 degrees above normal tonight.
Overall confidence is low to medium.
Long term /Wednesday night through Monday/...
Models in the long term continue to vary from run to run on the
evolution of Thanksgiving day system but fortunately have more
agreement among themselves than at any point in the last several
days. Both indicate a developing area of low pressure by the start
of the extended period over the Gulf of Mexico. The GFS is
slightly stronger and further north with the system than the European model (ecmwf)
but overall deep moisture profiles are very similar with this run.
By Wed night, precipitable water values in excess of 1.4 inches
are moving into portions of central Georgia in increasing favorable
isentropic upglide environment.
Given the good model agreement, will go with likely pops for the
extreme southern tier but give a sharp gradient to pops with less
than 20 for the Atlanta Metro. It should be noted though that it
would take very little in surface low displacement northward to
go from nothing to near washout for areas along i20 on
Model differences continue through Friday with GFS faster with the
progression of low and European model (ecmwf) remaining displaced southward
although both models show a Florida Peninsula track. This should
allow drier air to be drawn in on the north side of the system
Friday into the weekend effectively ending rain chances. Fairly
benign pattern thereafter with just a dry front to contend with
before high pressure builds in for the remainder of the period.
Aviation... 06z update... increasing potential for MVFR and
possibly IFR ceilings this morning along with patchy to areas of
light rain and drizzle during the day. Confidence for ceiling
heights and rain/drizzle chances are low and will need to be
monitored. Some improvement during the day to high MVFR to VFR
ceilings. Surface winds light and variable or light se-NE.
Potential for low clouds and fog tonight.
//Atl confidence...00z update...
high confidence for winds today.
Low to medium confidence for all other elements.
Preliminary point temps/pops...
Athens 57 44 62 39 / 20 10 0 5
Atlanta 59 45 60 40 / 20 10 0 5
Blairsville 56 38 56 32 / 20 10 0 5
Cartersville 58 41 57 35 / 20 10 0 5
Columbus 65 49 65 42 / 20 20 5 10
Gainesville 55 44 60 39 / 20 10 0 5
Macon 65 47 65 43 / 20 20 5 10
Rome 60 40 57 33 / 10 5 0 5
Peachtree City 61 44 61 37 / 20 10 0 5
Vidalia 68 52 67 47 / 30 30 10 20