Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 040254

Area Forecast Discussion
National Weather Service Peachtree City GA
954 PM EST Thu Dec 3 2020


Only small changes to the forecast this evening. A cold front will
sweep through the CWA tomorrow bringing rain beginning around 15Z.
While there is still some disagreement on when the front pushes
into the area, the general consensus is that it should push out
by 00Z. There is very little instability out ahead of the front
so kept thunder out of the grids but there is the possibility of
an isolated rumble or two.



.PREV DISCUSSION... /Issued 649 PM EST Thu Dec 3 2020/

PREV DISCUSSION... /Issued 237 PM EST Thu Dec 3 2020/

.Thursday Afternoon Forecast Discussion...

SHORT TERM /Tonight through Friday Night/...

Increasing cloud cover and humidity expected across the area
through today and into tonight as a mid/upper level cutoff low
traverses across the Mississippi River Valley. This low is expected
to bring a shot of showers starting Friday morning and lasting
through the day as the associated cold front pushes through the CWA.
Not expecting a widespread soak from this system with QPF totals
ranging between 0.5 to 1.0", with the highest totals in the N GA
mountains. Made tweaks to thunder in the grids as model guidance
keeps slowly pushing the "best" dynamics further south of the CWA
with each run. As the system moves out and NW flow takes over, a
brief dip in temps with lows in mid 30s are forecast in the metro
overnight Friday into Saturday.


LONG TERM /Saturday through Thursday/...

The long term begins on Saturday, after the passage of the surface
low pressure that spawned off the Gulf coast baroclinic zone as it
zips up the northeastern coastline. For the Southeast, it`s the
start of a longer dry period as several more shortwaves will follow
in quicker succession with some question if ample return flow from
the Gulf is able to establish itself back into the region making for
an uncertain rain forecast.

Following the frontal system from the short term, the forecast area
will be embedded in quasi-northwest flow and transitioning to quasi-
zonal flow through the weekend. All of this in preparation for a
weak upper-level cutoff low pressure that had resided over
northwestern Mexico and the Southern Plains to meander in through
the Southeast as it is swept up by the broader synoptic wave. To
complicate things, the timing of this low being swept coincides with
at least one, if not two, if the GFS has its way, shortwave troughs
rounding the base of the synoptic-scale trough over the eastern
CONUS. The timing and interaction of all these waves is pretty
uncertain and while most deterministic models are putting these wave
together in such a way to squeeze at least some light scattered
areas of precip around from Sunday night to Monday night, confidence
is not yet high enough in regards to timing or areal extent to
include in the forecast area just yet, but may likely add in some
lower Pops as the forecast becomes more settled.

Following the mass of shortwaves will be strong anticyclonic
vorticity advection, leading to strong subsidence and resulting in a
strong surface high pressure system that will stream from the
Northern Plains down to the Southern Plains and the Southeast by
Tuesday and Wednesday. All in all, despite multiple shortwaves
kicking through the area, pops will be relatively minimal and temps
will not vary by much with highs generally in the 50s from Saturday
through Wednesday and lows generally from the upper 20s to upper
30s. These values typically run from 0-5 degrees below average for
this time of year.


00Z Update...
MVFR cigs are possible Friday 12Z with lowering clouds. High res
models are in good agreement on SHRA approaching the ATL area Friday
around 14Z bringing OVC004 LIFR ceilings by 20Z with winds out of
the SE at 5-8kts. Vis drops to 2SM around 20Z during the heaviest
precip. After the the front passes, conditions should begin to
rapidly improve with 12-15Kt winds gusting to 20kts out of the SW
around 00Z on Saturday.

//ATL Confidence...00Z Update...
Medium confidence on timing of precip and cigs.
Medium to High confidence on all other elements



Athens          41  59  39  56 /  20  90  70   0
Atlanta         43  58  37  52 /  20  90  50   0
Blairsville     38  50  34  46 /  30  90  70   0
Cartersville    42  56  36  53 /  30  90  50   0
Columbus        45  64  39  57 /  10  80  40   0
Gainesville     41  52  38  52 /  30  90  70   0
Macon           43  67  39  59 /  10  80  50   0
Rome            42  55  36  54 /  40  90  50   0
Peachtree City  41  61  36  54 /  10  80  50   0
Vidalia         47  71  44  59 /   5  50  60   5




LONG TERM....Thiem
AVIATION...Vaughn is the U.S. government's official web portal to all federal, state and local government web resources and services.