Area Forecast Discussion
Issued by NWS Atlanta, GA

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FXUS62 KFFC 041953

Area Forecast Discussion
National Weather Service Peachtree City GA
253 PM EST Fri Dec 4 2020

...Afternoon Area Forecast Discussion for Dec 04...

.SHORT TERM /Tonight through Saturday Night/...

The upper low and associated frontal system is continuing its
trek across the southeast and is providing a few showers across
the CWA this afternoon. Slightly lower updated QPF totals with
.25" to 1" across the area, with the highest totals remaining up
in the N GA mountains. The majority of the CWA is generally
stable, but seeing areas of MUCAPE values around 300-400 J/kg near
the warm front so left thunder in this grids for SE Central GA.
This low pressure system should move NE and get absorbed into the
digging trough over the New England area, leaving the CWA in NW
flow by late tonight. The NW flow is short lived though as the
area returns to near zonal before going SW ahead of the next
developing system.

Temps expected to get down to the low to mid 30s across much of
north and central Georgia tonight before warming back up to around
the mid to upper 50s for a high tomorrow.


.LONG TERM /Sunday through Friday/...

Complex evolution of the upper level flow leads to multiple waves
phasing together over Georgia early next week, though models
continue to have small differences with the timing and placement
of these features that have meaningful impacts on the forecast.
Cut off low currently over northern Mexico will eject towards the
SE CONUS and begin to merge with a broader trough over the region
during the day on Sunday. Simultaneously, two separate quickly
moving shortwaves will be rounding the base of the larger east
coast trough. Two primary camps seem to exist (and this can be
seen in the WPC 500 mb ensemble cluster analysis), with one camp
merging the first shortwave with cut off low to the west of the
area allowing for more broad ascent to overspread the CWA with the
development of a better defined surface low, while the other camp
keeps these two features a little more separate and brings a
surface wave across the CWA that primarily impacts central GA.
Given these scenarios, opted to introduce low end slight chance
PoPs across the area Sunday night with increased to chance PoPs
across central GA.

Sunday night into Monday morning, the second shortwave rounding
the base of the trough quickly dives into the CWA and deepens.
There will be a several hour window in the early morning hours of
Monday where some broad ascent will exist in conjunction with
NWerly flow at the surface. Cross sections taken across TN into
the GA mountains show that the lower 100 mb will likely be close
to saturated through the layer to very near the surface. This
should allow for some light precipitation to occur during the
morning, especially where aided by orographic lift. Temperatures
will likely be hovering near or just below freezing in some of the
higher elevations, so looking increasingly likely that some
snowflakes could fly in these locations. Even with the more coarse
resolution, GEFS does highlight this, showing some decent
probabilities of snowfall in far north GA along the ridgeline.
Currently not expecting much in the way of accumulations with the
system, as the window will be brief.

After Monday, surface high pressure moves into the area with
seasonable temps in the 50s Tuesday and Wednesday. Another 500 mb
shortwave moves past the area, but doesn`t have any baroclinic
zone to work with given the cool, stable airmass will have pushed
well into the gulf, preventing any real chances of precipitation.
Next shot at rain looks to be by the end of next week on Saturday.



18Z Update...
Prevailing MVFR with -SHRA across the metro sites this afternoon,
expected to go widespread IFR cigs by 21z with pockets of LIFR
and visibilities of 2-5sm through 23z. SE winds expect to turn SW
around 21z. Conditions should improve to VFR after 00z as the
front passes bringing NW winds of 10-15kt and gusts up to 25kt.
Winds should ease back to 5-10kts by 12z tomorrow.

//ATL Confidence...
18Z Update...
Medium confidence on cigs.
High confidence on all other elements.



Athens          37  57  33  56 /  70   0   0   5
Atlanta         36  54  35  55 /  50   0   0  10
Blairsville     32  49  28  53 /  60   5   0  10
Cartersville    34  54  31  55 /  30   5   0  10
Columbus        37  59  37  59 /  10   0   0  20
Gainesville     37  54  34  54 /  60   0   0  10
Macon           37  60  34  60 /  60   0   0  10
Rome            33  56  31  55 /  30   0   0  10
Peachtree City  34  56  32  56 /  40   0   0  10
Vidalia         42  60  39  60 /  60   0   0  10




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