Area Forecast Discussion
Issued by NWS Atlanta, GA

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637
FXUS62 KFFC 031953
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
253 PM EST Sat Dec 3 2016



.SHORT TERM /Tonight through Sunday Night/...

Short range models show good agreement with overall wet pattern
settling in over the forecast area by this evening and persisting
through early next week. In the short term... areas of mainly light
rain currently seen on regional radars to the west will spread into
north and west central GA areas by this evening as a warm/moist mid
level southerly flow overruns a cool easterly flow near the surface.
The stable lower levels will greatly hinder any thunderstorm
threat... so will word for just rain/rain showers for now. Will also
add some wording for patchy fog and drizzle tonight as the lower
levels become saturated and clouds lower. As for rainfall... strong
isentropic lift will produce widespread light to moderate rains
across the area through the period. A series of disturbances
embedded in the westerly flow aloft will enhance rainfall
intensities at times... mainly Sunday and Sunday night... and latest
model runs are suggesting the heaviest rainfall axis may set up
somewhere near the I-85 Corridor where around 2-3 inches of rainfall
could be observed through Sunday night. If this axis sets up across
Atlanta Metro Area... these rainfall amounts could push several of
the typical flood prone creeks to at least bankfull by Sunday
evening. Will have to closely monitor the potential for minor...
short lived flood problems across maybe parts of north GA over the
next several days where heavier rains fell earlier in the week. Will
issue a Hydrologic Outlook /ATLESFFFC/ to address the potential
heavy rain and flood threat in more detail.

The clouds and cool rains will probably hold temps in the 40s for
most areas both day and night... so don`t expect much diurnal change
with temps at this time... except for those areas along the far
southern reaches where the wedge front may be able to creep northward
far enough to allow those areas to see temps climb into the 50s by
Sunday afternoon... but just briefly. Did not stray far from overall
mos guidances for pops and temps through the period.

39


.LONG TERM /Monday through Saturday/...

Forecast is on track with only minor changes made to this update.
Two rounds of rain are expected early Sunday through Sunday night
and then again Monday night into Tuesday as the main low to the
west moves northward. Storm total rainfall through Tuesday is
still expected to be around 2 to 4 inches. Given the rainfall
expected, we may see localized flooding across urban areas if
training sets up across metro Atlanta. To this end, minor
flooding of the typical flood prone creeks is possible, especially
if we observe high rainfall rates over a short period of time.
Thunderstorms will be limited given the warm front may actually
stay to our south or just across central Georgia Monday night into
Tuesday.

Models are coming into better agreement in terms of timing of the
next front Thursday into Friday with below normal temperatures
expected by the end of the work-week.

26

PREV DISCUSSION... /Issued 325 AM EST Sat Dec 3 2016/

Medium range models remain consistent with recent runs and in
fairly good agreement through the majority of the period. Wet
start to the period as the region remains under strong
southwesterly upper-level flow. Models still flip-flopping a bit
concerning the amount and distribution of any instability
available with the main short wave as it sweeps through overnight
Monday into Tuesday. I still think there will be sufficient
elevated instability across the west and south for at least a
slight chance of thunder Monday night and Tuesday, mainly across
the west/south Monday night and across the south Tuesday. Still
seeing decent shear in the mid-levels but the lower-level shear is
not as impressive. Overall severe threat looks marginal at best at
this time. Large-scale upper flow remains more west to southwest
behind the initial system keeping the better cold air north and
west of the state until Thursday and into next weekend as the
large, deep upper trough settles into the eastern seaboard.

20

&&

.HYDROLOGY...

A moist and unsettled pattern is expected across the forecast area
through Tuesday. Periods of moderate to heavy rainfall are
expected as a series of impulses cross the area Sunday and a more
robust surface low to the west lifts north Monday afternoon
through Tuesday. The greatest chance of rainfall will be Sunday
into Sunday night and then another round Monday night into
Tuesday. Storm total rainfall of 2 to 4 inches is expected.

Isolated flash flooding will be possible if the heavy rain
repeatedly moves over the same area or if heavy downpours result
in high rainfall amounts over a short period of time. Given loss
of leaves over the last couple of weeks, storm drains and ditches
may quickly clog with debris and cause street flooding and road
ponding.

Minor flooding of some of the typical flood prone creeks is
possible, especially if training sets up anywhere along and north
of the I-85 corridor.


&&

AVIATION...
18Z Update...
VFR conditions expected to prevail through late tonight... with
mainly mid and high level clouds. Models agree on MVFR cigs settling
in over most taf sites by 12z Sun along with prevailing -radz.
Increasing rain intensity should help lower cigs to IFR levels by 18-
20z Sun and these low cigs will persist through Sun night... with
gradual improvement expected on Mon. NE to East winds will prevail
through the taf period. Wind speeds will increase toward 12Z Sun
with occasional gusts to around 18-20kts expected on Sun.

//ATL Confidence...18Z Update...
Medium on timing of RADZ tonight.
Medium on MVFR and IFR cigs late tonight and Sunday.
High on remaining elements.

39

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          43  47  43  53 /  60  90  80  70
Atlanta         44  49  45  54 /  80  90  80  80
Blairsville     38  45  41  54 /  90  90  80  70
Cartersville    43  48  44  54 /  90  90  80  80
Columbus        46  56  50  61 /  60  80  70  70
Gainesville     43  45  42  53 /  70  90  90  70
Macon           42  55  49  59 /  40  70  70  70
Rome            42  48  45  55 / 100 100  80  70
Peachtree City  42  49  44  55 /  70  90  80  80
Vidalia         46  65  57  66 /  20  40  60  70

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...39
LONG TERM....26
AVIATION...39



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