Area Forecast Discussion
Issued by NWS Atlanta, GA

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948
FXUS62 KFFC 250549
AFDFFC

Area Forecast Discussion
National Weather Service Peachtree City GA
1249 AM EST Sat Feb 25 2017



.PREV DISCUSSION... /Issued 1027 PM EST Fri Feb 24 2017/

.UPDATE...

Although surface CAPE values across the area remain modest at best
barely reaching 500 J/KG in most cases...approaching upper level
jet streak appears to be helping overcome this limitation. Two
distinct segments of showers and thunderstorms have developed
over North Alabama and then into Mississippi. Following
progression of jet streak...see no reason why line wont keep its
intensity and areal coverage as it progresses eastward. This will
require an increase in our gridded pops especially over west
central zones. Remainder of the forecast is on track and no other
changes planned.

Deese

&&

PREV DISCUSSION... /issued 721 PM EST Fri Feb 24 2017/

PREV DISCUSSION... /issued 237 PM EST Fri Feb 24 2017/

.SHORT TERM /Tonight through Saturday Night/...
Still looking at a small chance for a few strong to severe
thunderstorms in the far north tonight. Instability is marginal and
shear, although moderate or better, never quite lines up well with
the better instability in our area. Add to that a lack of strong
forcing and confidence that any severe weather will be realized
remains fairly low. Low-level forcing, albeit somewhat stout,
remains confined to a fairly narrow zone along and just ahead of the
front, and upper-level support is weak as best dynamics sweep by
well north and west of the state. All-in-all this supports SPC`s
marginal risk area in the far northwest, although I am keeping the
mention of thunder with this system as it moves through the entire
area through the overnight and into tomorrow vs. dropping the
thunder across our central and eastern counties.

Precipitation chances move east of the forecast area by mid to late
afternoon Saturday leaving the remainder of the short-term forecast
period from Saturday night through Sunday, dry and about as close to
seasonal, as far as temperatures are concerned, as we have seen
since early January.

Much drier airmass filling in behind the front tomorrow will be
somewhat offset by the cooler temperatures with relative humidities
dropping but probably not for enough of a duration for a Fire Danger
Statement. Also, wind speeds approach Wind Advisory levels in the
mountains Saturday but right now it appears to be confined to the
highest peaks and ridges.

20

&&

.LONG TERM /Sunday through Friday/...
Latter portion of the weekend/start of the long-term looks fabulous
as a 1025mb sfc high sets up shop right over the CWA amidst mid-
level heights rises. Some lingering cold air advection at H85 in the
wake of Saturday`s fropa will keep temps a touch cooler than what
we`ve seen recently with upper 50s expected north to middle 60s
central under sunny skies and light winds.

Sfc high pressure will quickly slide offshore overnight
Sunday...with associated ridging still influencing the CWA. This
will allow lower-level winds to swing to the south and promote
Atlantic/Gulf moisture transport. Expect clouds to gradually
increase Sunday night with moderating low temps upper 30s to lower
40s.

Next southern stream shortwave trough will be enroute toward the
area Monday. As it pushes across the southern Plains...it should
spin up a weak sfc low that will track northeast from TX into the
Midwest. This will create a rather noticeable WAA regime as S/SW
flow rides atop lingering sfc ridge. At this time looks like
scattered to widespread showers will move in late Monday
afternoon/evening and continue through most of Tuesday as influx of
Pacific moisture via subtropical jet influence increases.
Instability is nil on Monday given cooler ridge influenced air
lingering below warmer 850mb flow...however mid level lapse rates
should steepen enough atop increasingly higher theta-e airmass by
Monday night-Tuesday for thunderstorms.

Precip chances remain elevated through Wednesday as next cold
frontal system is progged to push through. Obviously the forecast is
far out at this point...but this fropa could be interesting. Despite
rather warm mid level temps...models are showing noticeable MUCAPE
along/ahead of the sfc boundary...with CWA under the influence of
the right entrance region of a 300mb jet streak with  50-70kt 0-6km
shear accompanying it. Regardless of severe potential...rain and
thunder is expected in the vicinity of this boundary. Boundary
should clear all counties by early Thursday where rest of extended
remains dry under sfc high pressure and dry NW flow aloft.

Overall above-normal temps will continue thru the extended. After a
brief "respite" Sun-Mon...temps will rise back into the 70s Tuesday-
Wednesday before dipping back into upper 50s to middle 60s Thursday-
Friday

Kovacik

&&

.AVIATION...
06Z Update...
Initial cigs ahead of cold front and associated showers/storms
mainly in 4-6 kft range early this morning with gradual lowering
to MVFR after about 09z near KATL. Tempo group for -SHRA (may need
to include TS if line can hold together) and MVFR VSBY/possible
high end IFR cigs across most sites in 10-14z period then
diminishing coverage as front pushes southeast. Clearing skies
expected by 16-18z. Winds will be initially SW to W at 7-10 kts
ahead of front then enhanced NW 12-14 kts gusting 22-26 kts behind
for the afternoon. Gradual lessening for overnight into Sunday.

//ATL Confidence...06Z Update...
Medium on cigs and precip coverage this morning.
High on all else.

Baker

&&

.PRELIMINARY POINT TEMPS/POPS...
Athens          67  35  62  39 /  30   0   0   5
Atlanta         61  34  60  42 /  40   0   0   5
Blairsville     57  29  56  35 /  40   5   0  10
Cartersville    59  32  59  40 /  40   0   0   5
Columbus        64  36  65  43 /  20   0   0   5
Gainesville     60  34  58  39 /  40   0   0   5
Macon           73  34  64  40 /  20   0   0   5
Rome            57  31  59  39 /  20   0   0   5
Peachtree City  61  33  61  39 /  20   0   0   5
Vidalia         76  39  67  44 /  20   5   0   0

&&

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

$$

SHORT TERM...Deese
LONG TERM....Kovacik
AVIATION...Baker



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