518 
FXUS62 KFFC 051730
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
1230 PM EST Fri Jan 5 2024



...New 18Z Aviation Discussion...

.SHORT TERM...
(Today through Saturday)
Issued at 438 AM EST Fri Jan 5 2024

The short term period (and into next week) will be characterized by 
a progressive flow pattern at the upper levels. As the morning 
begins, much of the eastern CONUS is positioned underneath an upper 
ridge extending from the northeast Gulf Coast to the Great Lakes 
region. Surface high pressure associated with the ridge is moving 
across the Appalachians and eastward towards the mid-Atlantic coast. 
As this occurs, surface winds have shifted to easterly as a CAD 
wedge develops along the lee side of the Appalachians and into 
northeast Georgia. A cutoff upper low over the southern Great Plains 
will meanwhile lift northeastward over the course of the day today, 
at which time a shortwave on the southwestern side of the low will 
develop a surface low just off the southeast Texas coast. This low 
will move eastward across the northern Gulf of Mexico this afternoon 
and into tonight.

With a dry airmass and clear skies to start the morning, lows will 
start the morning the mid to upper 20s across the majority of the 
forecast area. With the wedge building in across north Georgia, 
temperatures to the north of I-20 will struggle to get above 50 this 
afternoon (and even struggle to get to 40 in the higher elevations 
of far northeast Georgia). High temperatures will range from the mid 
50s to low 60s to the south of the wedge. Upper level cloud cover 
will begin to increase in coverage starting mid-morning and continue 
through much of the day. Tonight, the surface low will move onshore 
near the LA/MS coast and continue northeastward inland. 
Precipitation chances will quickly increase from west to east across 
the area, becoming widespread after midnight. 

Continued cool easterly flow within the wedge will have temperatures 
in the low to mid 30s across portions of northeast Georgia during 
the overnight hours. As a result, a wintry mix will be likely in the 
higher elevations of far northeast Georgia as precipitation 
overspreads the wedge. Model soundings still indicate a fairly deep 
warm nose around the 850 mb level at about 5 degrees. With 
temperatures expected to hover around freezing for much of the 
overnight hours and ample moisture in place, the most likely mode of 
wintry precipitation appears to be freezing rain. At the onset of 
precipitation just after midnight, it is possible that some of the 
light freezing rain could mix with sleet and/or rain. Temperatures 
will gradually warm through the overnight, rising into the mid 30s 
by sunrise, with freezing rain coming to an end shortly after. A 
Winter Weather Advisory has been issued for portions of far 
northeast Georgia from 11 PM tonight until 8 AM on Saturday morning. 
Total ice accumulations of around one-tenth to two-tenths of an inch 
are possible in the highest elevations, with light icing possible 
elsewhere in the Advisory. Will need to continue to monitor the 
observations as the wedge sets up, as cooler temperatures spreading 
further south than forecast could warrant an expansion of the Winter 
Weather Advisory. Winds at the highest elevations could moreover 
gust to as high as 30 mph.

Aside from far northeast Georgia, widespread rain is likely 
overnight and Saturday morning. Isolated thunderstorms will be 
possible in central Georgia (mainly south of Columbus and Macon) 
where marginal instability will be present. The axis of the 
aforementioned shortwave will move quickly northeastward towards the 
Carolinas by Saturday afternoon, at which point the low pressure 
system will move out of the forecast area. Some trailing light rain 
will continue into the early afternoon on the back side of the low, 
with chances diminishing going into the evening. Overall, rainfall 
amounts are forecast to range from 1/2 to 1 inch, with some locally 
higher amounts possible. Similar to this afternoon, the presence of 
the wedge in north Georgia will be reflected by the high 
temperatures on Saturday afternoon, with highs in the upper 40s to 
low 50s within and reaching into the 60s to the south.

King

&&

.LONG TERM...
(Saturday night through Thursday)
Issued at 438 AM EST Fri Jan 5 2024

Key Messages:

 - Potent storm system will approach the area on Monday, bringing 
   the potential for locally heavy rainfall and severe 
   thunderstorms late Monday night into Tuesday.

An upper low pressure trough is forecast to rapidly dig over the 
Rocky Mountains on Sunday, with a low in the base of the trough. 
This low will start out with a 500 mb height of around 536 dam over 
the Four Corners region Sunday evening before moving ESE across the 
S Plains by Monday evening. The low will then lift ENE and deepen as 
it sweeps across the OH Valley by Tuesday evening. Global models 
remain in very good agreement with respect to the progression of 
this feature, with most models similar regarding timing of the 
trough and within about 6 dam height-wise by day 5. 

At the surface, low pressure and an attendant frontal system will 
rapidly develop and move E from near Las Vegas on 12Z Sunday to near 
Little Rock by 12Z Tuesday. Warm, moist air is expected to surge 
northward on increasing southerly winds late Monday night into 
Tuesday morning, with dew points reaching 55+ degrees near and S of 
the Atlanta metro area. MUCAPE values will increase in kind, with 
values approaching 500 J/kg in the aforementioned areas. Effective 
wind shear during this time frame will be around 40 knots. Due to 
the very progressive nature of this storm system, the best chance of 
severe weather will be on Tuesday from early morning in the SW CWA 
through about mid-afternoon in the SE. 

SPC is currently outlooking a 15% chance of severe thunderstorms 
across our southernmost counties during this period. There is still 
the potential for the severe threat, however brief, to extend even 
farther to the N. Residents should continue to monitor the latest 
forecast updates in the coming days.

Another feature of this storm system will be the rapid transport of 
deep moisture into the area. Precipitable water values are forecast 
to surge from around half an inch Monday afternoon to over 1.5 
inches by early Tuesday morning, then drop back to a half inch by 
Tuesday evening. Although the period of heavy rainfall won't be 
particularly long-lived, there is the potential for locally heavy 
amounts in a fairly short period of time. The latest storm total QPF 
amounts with this system range from just over 2" over portions of NW 
GA to over 3" across the SE portion of the area wrapping back into 
the Atlanta metro area. Local amounts over 4" are also possible on 
the SE slopes of the mountains of NE GA due to orographic effects. 
Area rainfall amounts will bring the potential for at least 
localized flooding.

As this storm system rapidly departs, wrap-around moisture and 
colder air will lead to some light snow showers or a rain/snow mix 
Tuesday night across portions of N GA, but accumulating snow is not 
expected at this time. /SEC

&&

.AVIATION...
(18Z TAFS)
Issued at 1224 PM EST Fri Jan 5 2024

The remainder of the afternoon should be VFR with MVFR cigs moving
in after 00Z with some very light precip. Cigs and vsbys will
deteriorate as widespread rainfall moves into the area around
05-06Z. Winds will also be out of the east with sustained speeds
between 10-15kt. Some gusts in the low 20kt are possible. Cigs
look to remain IFR/LIFR through the late morning/early afternoon.


//ATL Confidence...18Z Update...
Med confidence all elements.

NListemaa

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          35  49  40  54 /  90  90  10   0 
Atlanta         38  51  42  52 /  90  70  10   0 
Blairsville     31  47  35  45 /  90  80  20   0 
Cartersville    36  50  38  51 /  90  80  10   0 
Columbus        48  61  43  57 /  90  40   0   0 
Gainesville     34  47  40  50 /  90  80  10   0 
Macon           45  62  42  58 / 100  50  10   0 
Rome            36  50  37  53 /  90  70  20   0 
Peachtree City  39  54  40  53 /  90  60  10   0 
Vidalia         49  70  45  60 / 100  60  10   0 

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 PM this evening to 8 AM EST 
Saturday for GAZ006>009-014>016.

&&

$$

SHORT TERM...NListemaa
LONG TERM....SEC
AVIATION...NListemaa