Dunwoody, Georgia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

054
FXUS62 KFFC 180853
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
353 AM EST Sat Jan 18 2025


...Morning Area Forecast Discussion...

.SHORT TERM...
(Today through Sunday)
Issued at 324 AM EST Sat Jan 18 2025

A mid-level shortwave trough is advancing across the Mississippi
River Valley and, along with an associated surface low, will
continue eastward towards Georgia over the course of the day today.
Southwesterly mid-level flow ahead of the shortwave and southerly
low level flow are serving to pull Gulf moisture northward into the
forecast area as the morning begins. Numerous to widespread showers
have begun to overspread north and portions of central Georgia as a
result. An overcast cloud deck over north and central Georgia will
serve to inhibit radiational cooling through the early morning
hours. As such, lows this morning are forecast to be mainly in the
low to mid 40s, with some upper 30s in the higher elevations of far
north Georgia. With morning lows trending warmer than previous
forecasts, the potential for a rain/snow mix in the highest
elevations of far northeast Georgia has diminished. The
aforementioned rain showers are expected to advance eastward through
the morning and early afternoon.

This afternoon into tonight, the southwesterly mid-level flow
associated with the subtropical jet will remain and amplify over the
region as a longwave trough associated with the polar jet swings
through the Great Plains and towards the eastern CONUS. With
continuing warm air advection, high temperatures this afternoon will
rise into the mid 50s to low 60s across the majority of the forecast
area, though areas in far northeast Georgia could struggle to get
out of the 40s. Dewpoints will also increase into the mid 40s to low
50s in north Georgia and mid to upper 50s in central Georgia. Some
isolated to scattered showers are expected to persist through the
afternoon. Then this evening, as the axis of the longwave swings to
the east, it will allow for the development of a new surface low to
the immediate east of Georgia, which will promote additional
precipitation tonight into early Sunday morning, most likely in east-
central Georgia. Marginal MUCAPE values will be present in portions
of central Georgia this afternoon and tonight, which will lend to
the possibility of a few rumbles of thunder. However, severe weather
is not expected at this time. Rainfall totals today through Sunday
morning are forecast to range from 0.5 to 0.75 inch across the
majority of the area. Flooding concerns are not anticipated as a
result.

On Sunday morning, the low will begin to move quickly away to the
northeast, with rain chances diminishing through the early morning
hours. At this time, a noticeably cooler airmass will begin to
spread into the area behind the axis of the longwave trough and with
a strong, Arctic surface high approaching the Southeast. As
temperatures drop below freezing in portions of far north Georgia,
lingering wraparound moisture on the back side of the retreating low
could be sufficient to produce a light mix of rain/snow in the far
northern tier through late morning, and possibly some isolated snow
flurries in the afternoon. At this time, any accumulations of snow
are expected to be confined to the highest elevations of far north
Georgia, and significant impacts are not forecast at this time.
Colder air will continue to advance south and east through the
forecast area through the daytime on Sunday. By the end of the day,
temperatures are forecast to be in the upper 20s to low 30s along
and north of the I-85 corridor and in the upper 30s and 40s to the
south. This cooling will only continue Sunday night, setting us up
for a very cold start to the long term period.

King

&&

.LONG TERM...
(Sunday night through Friday)
Issued at 324 AM EST Sat Jan 18 2025

At a glance:

    - Hazardous cold to start the week -- portions of north Georgia
      are likely to see dozens of hours below freezing Monday through
      Wednesday

    - Monitoring increasing chances for winter weather Tuesday into
      Wednesday

We enter the extended range on Monday with north and central Georgia
freshly post-front, and the center of a strong (1035+ mb) Arctic
surface high nudging toward the Eastern Seaboard. With a reinforcing
shot of cool, dry air rounding the base of the broad mid-level
trough situated across southern CONUS, the stage is set for a
hazardous cold snap. The airmass that is progged to settle in across
the South originated from over Siberia, and it will certainly feel
like it. Highs on Monday and Tuesday will be in just the 20s to near
40 areawide (20-28 degrees below average) -- with highs in the teens
possible on Monday for portions of northeast Georgia at elevation.
Lows will be positively frigid, in the single digits to lower 20s
each morning through Wednesday. Lingering breezy to gusty winds in
the wake of the front Monday will support morning windchills as much
as 5-10 degrees below zero for portions of northeast Georgia, and in
the single digits to teens elsewhere. We`re looking at a slam dunk
for Cold Weather Advisory conditions pretty much everywhere, but
cannot rule out the necessity for Extreme Cold products for the far
northern part of the forecast area. Some areas along and north of
the I-20/I-85 interchange may not see real chances for temperatures
to rise above 32F until Wednesday. Proper precautions will need to
be taken to prepare for an extended period of frigid temperatures --
remember the 4 P`s of winter preparedness (people, pets, pipes,
plants) and be sure to leave your faucets dripping and under sink
cabinets open before heading to bed.

Beyond Monday, the elephant in the room is increasing confidence in
some type of wintry precipitation impacting portions of north and
central Georgia from Tuesday afternoon through Wednesday morning.

What We Know:

1) Unlike the previous storm system, greatest impacts are likely to
be felt further south. WPC`s Key Messages yesterday evening painted
a 40% chance of moderate winter impacts primarily along and just
slightly north of the Columbus to Macon corridor. Highest GFS and
Euro ensemble probabilities of >=1" of snow also highlight areas
south of the Metro. Some especially interesting probabilities to
note from the 01Z (most current as of the time of writing of this
AFD) NBM run:

    - Probability of at least 1.5" of snow in the 24 hour period
    ending 7AM Wednesday for Columbus/Macon corridor: ~40-43%

    - Probability of at least 2" of snow in the 24 hour period
    ending 7AM Wednesday for Columbus/Macon corridor: ~30-35%

    - Probability of at least 2.5" of snow in the 24 hour period
    ending 7AM for Columbus/Macon corridor: ~30%

2) 24-36 hours of unseasonably cold conditions before precipitation
onset will support very cold ground/road temperatures, allowing for
impacts to ramp up quickly. It will not take much accumulation to
create hazardous travel conditions, and what accumulation does fall
is likely to linger courtesy of the cycle of diurnal melting (highs
in the 30s Wednesday, near 40 Thursday) and re-freezing (lows in the
teens Wednesday night, 20s Thursday night).

3) Our initial airmass looks to be much drier than January 10th`s.
We are currently forecasting dewpoints in the single digits to teens
areawide mid-morning/early afternoon Tuesday. This increases the
potential for wet-bulbing (evaporation of precipitation falling into
a drier airmass removes heat and introduces moisture, tugging
temperatures down and dewpoints up), which could result in
temperatures cooler than forecast.

4) The dominant p-type at this time appears to be snow for a
combination of the above reasons, with chances for freezing
rain/sleet/a wintry mix relegated to our far southern/southeastern
tier. At this time, any ice accumulations are unlikely to be as
impactful as forecast snowfall, but things can and will change over
the next several days as features become better resolved.

5) The 00Z runs of the GFS and Euro ensembles have trended wetter
than their 18Z counterparts (with the GFS serving as the theoretical
floor for this event). The Euro ensemble has also trended toward a
broader and higher snow accumulation footprint, and progs the onset
of winter precipitation to be earlier than the GFS (late
morning/early afternoon vs. mid-to-late afternoon, respectively).
The Canadian ensemble continues to be the coldest and snowiest
solution, and remains our far upper bound/ceiling for this event.
Our chances of a non-event precipitation-wise thus appear to be
lower.

What We Don`t:

1) How much wet-bulbing will occur -- could have a large impact
on who receives snow and just how much (we saw the upper bound of
wet- bulbing with the band of heavy snow that set up across the
Metro last week, and dewpoints this time around are forecast to be
even lower.

2) Exact accumulation amounts. This will depend heavily on
temperature profiles, the number of p-types, and the placement of
any surface features. Once we introduce HiRes guidance into the
mix (the next day or so) details will be able to be expounded
upon.

Given remaining uncertainty (coupled with the knowledge that
ensemble guidance overall has trended toward at least SOME snowfall
for much of the area, with higher totals the further south you go),
feel that the NBM continues to have a decent handle on the forecast.
Interests in the Atlanta Metro and points further south -- and
especially areas along and south of a line extending from Columbus
to Macon -- should keep a close eye on the forecast. If trends hold
(BIG if), this could pan out to be one of the more impactful
southern/coastal winter storms in recent memory. Stay tuned.

96

&&

.AVIATION...
(06Z TAFS)
Issued at 1243 AM EST Sat Jan 18 2025

Showers have begun to spread into northwest Georgia and are
expected to become widespread over the ATL metro area between
08-12Z this morning. The highest intensity of rain is expected to
be over this time window as well, with showers becoming lighter
once again after sunrise. Ceilings are currently VFR, but are
expected to lower to MVFR around 08Z, and further to IFR by 13-14Z
this morning. Lingering showers will be scattered in coverage this
afternoon, coming to an end this evening. Brief improvement to
MVFR may be possible after 20Z, but will be short- lived. IFR
ceilings are anticipated to redevelop shortly after sunset. Winds
will be primarily S to SE at 4-8 kts throughout the day, becoming
light and variable after sunset.

//ATL Confidence...06Z Update...
Medium confidence on the timing of ceilings and precipitation.
High confidence on all other elements.

King

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          55  43  51  18 /  90  50  10   0
Atlanta         59  38  47  16 /  70  40   0   0
Blairsville     52  31  42   7 /  80  40  20   0
Cartersville    59  35  44  13 /  70  40   0   0
Columbus        64  42  52  20 /  90  30   0   0
Gainesville     51  40  48  16 /  80  40   0   0
Macon           59  46  56  21 /  90  50  10   0
Rome            58  35  42  14 /  70  40   0   0
Peachtree City  61  38  49  16 /  80  40   0   0
Vidalia         60  55  62  25 /  90  70  30   0

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...King
LONG TERM....96
AVIATION...King