River Flood Warning 164, NWS Atlanta, GA

Area Forecast Discussion
National Weather Service Peachtree City GA
1235 PM EST Thu Mar 7 2024

...New 18Z Aviation Discussion...

.SHORT TERM...
(Today through Friday)
Issued at 334 AM EST Thu Mar 7 2024

Key Messages:

 - Dry weather will prevail in the region through tonight.

 - A couple light rain showers could develop by Friday afternoon,
   but in generally the next precipitation event should hold off
   until Friday night.

Today through Friday Afternoon:

Weak upper level ridging and surface high pressure will settle into
the region today, resulting in dry weather and fair skies. Winds
will be light out of the northwest this morning, but should
transition to a easterly direction this afternoon as the surface
high nudges eastward. Modest boundary layer mixing should result in
a few fair weather cumulus this afternoon. High temperatures
reach the mid 70s this afternoon (6 to 12 degrees above average).

The harbinger of our next storm system will move into to the region
tonight in the form of increasing high cloud cover. The high cloud
cover and a slightly drier airmass should work against any fog
formation tonight, while light and variable winds could favor fog.
Our general thinking is that a few patches of fog could form in
eastern Georgia, but most of the region should be fog free through
Friday morning.

Southerly flow (above 850 mb) ahead of the next trough should bring
additional increases in moisture and cloud cover to the region on
Friday. The 00Z HREF guidance suggests a slight chance (15-25%) of
light rain in the north Georgia mountains from mid morning onward.
This precipitation signal looks to be associated with a very weak
shortwave and upslope flow. As we inch towards sunset a few showers
(10-20% chance) could develop over central and southern Georgia in
the warm advection ahead of an advancing warm front. In general
though, dry weather is favored for most of the region through sunset
Friday. Temperatures should be cooler in the mountains on Friday due
to cloud cover and a weak wedge (lower 60s for highs). Elsewhere
highs in should be in the upper 60s or 70s.

Albright

&&

.LONG TERM...
(Friday night through Wednesday)
Issued at 334 AM EST Thu Mar 7 2024

Key Messages:

 - A significant heavy rainfall and flash flooding threat will
   exist from Friday night into Saturday. A Flood Watch is in
   effect for much of the area for this time frame.

 - There will also be some potential for severe weather for at
   least portions of the area from early Saturday morning to
   Saturday afternoon.

 - Cooler and quieter conditions will return by Sunday into early
   next week.

A significant threat for heavy rainfall and flash flooding will be
quickly ramping up to start the forecast period. A southern stream
shortwave will be lifting northeastward across the Deep South toward
the area by Friday night while the attendant surface low tracks
northeastward from the Arklamiss region. Deep moisture will rapidly
surge into the area from Friday evening into Friday night, bringing
PWATs at or above climatological maximums for early March into the
1.5 to 1.8" range. Widespread rainfall, some heavy, will thus be
increasing from west to east Friday night into Saturday morning.

Confidence continues to increase in the likelihood that a swath of
enhanced high rainfall totals will occur within the forecast area
centered along/near the near stationary midlevel front. Latest
guidance, while still maintaining a degree of variability between
model solutions, continues to favor a region bisecting the CWA that
includes much of the Atlanta metro and surrounding areas for this
QPF maximum. This would be a particularly concerning region for the
highest QPF to fall, especially considering that a bullseye of 2-3+"
rainfall fell on Tuesday night/Wednesday morning in this area and
already caused flooding issues. For this reason, collaboration with
WPC resulted in the upgrade of the Day 2 Excessive Rainfall Outlook
to a Moderate Risk within a region centered across the Atlanta metro
and points westward into central Alabama. A Slight Risk remains for
much of the remainder of the CWA surrounding this area. Rainfall
totals of 2-4" Friday night into Saturday morning with locally
higher totals over 5" would lead to substantial flash flooding
concerns as well as rapid rises on already elevated waterways. For
this reason, a Flood Watch has already been hoisted for much of the
area with the exception of the far NW and SE counties from Friday
night through the day Saturday. All interests should monitor this
heightened flood potential Friday night into Saturday.

Beyond the primary flooding concern, there does remain a window for
severe potential, primarily after midnight Saturday through early
Saturday afternoon. Confidence is highest for this risk existing for
Middle Georgia. While this severe potential could extend farther
northward to the I-85 corridor vicinity, this will be dependent on
the warm front nudging farther northward and bringing resultant
SBCAPE farther north which is a less-certain scenario. Given the
strong LLJ in place, damaging wind gusts and perhaps a brief tornado
threat will be the primary concerns within the warm sector. The
severe threat may then gradually wane and lift east/northeast of the
area as better dynamics become displaced by Saturday afternoon.

Finally, quiet weather will return by Sunday and likely persist into
at least midweek next week as northwest flow aloft gradually
transitions into zonal flow and surface high pressure traverses west
to east across the region. Temperatures will briefly return a bit
below normal from Sunday into Monday before gradually warming
through midweek.

RW

&&

.AVIATION...
(18Z TAFS)
Issued at 1229 PM EST Thu Mar 7 2024

VFR with the possibility of a some SCT050 this afternoon. SAT is
already showing a CU field forming over NW GA. Winds have gradually
begun to pick up out of the NE at 5-8kts and will stay on the E side
through the TAF period.

//ATL Confidence...18Z Update...

High on all elements.

Vaughn

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          53  67  55  69 /  10  20 100  90
Atlanta         56  68  58  71 /   0  30 100  70
Blairsville     51  60  51  64 /  10  50 100  80
Cartersville    53  68  56  71 /   0  40 100  60
Columbus        57  76  63  75 /   0  30 100  70
Gainesville     53  65  55  67 /   0  30 100  80
Macon           56  74  61  73 /   0  10  90  90
Rome            53  68  57  71 /  10  60 100  60
Peachtree City  55  70  58  72 /   0  30 100  70
Vidalia         55  74  61  78 /   0   0  60  90

&&

.FFC WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Friday evening through late Saturday night for
GAZ005>009-011>016-019>025-027-030>039-041>061-066>073-078>084-
089>095-102.

&&

SHORT TERM...Albright
LONG TERM....RW
AVIATION...Vaughn

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