Area Forecast Discussion
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FXUS62 KTAE 220253
AFDTAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
953 PM EST Sun Dec 21 2014

.Near Term [Through Tonight]...

A stalled frontal boundary is lingering just south of the CWA along
with a decaying Gulf Low. Moisture is abundant with easterly wind
flow from the Atlantic. Rain will continue overnight with heavier
rain and possibly thunder for the Big Bend region. Patchy fog is
expecetd particularly in the early morning hours. With abundant
cloud cover tonight temps will be steady with lows in the 50s.

&&

.Aviation...
[Through 00Z Tuesday]...

Poor conditions will continue through the next
24 hours with ceilings generally in the IFR to LIFR range with rain
or drizzle. A stalled frontal boundary south of the area will begin
to lift northward on Monday with low ceilings and areas of rain
continuing.


&&

.Prev Discussion [354 PM EST]...

.Short Term [Monday Through Tuesday Night]...
A prolonged period of isentropic ascent will continue through this
period over the frontal boundary as it slowly works its way
northward across the region on Monday and Tuesday. By late Monday
afternoon, parts of the FL Big Bend could already be in the warm
sector with dew points in the mid 60s. With an increasingly sheared
environment already in place, a few isolated strong to severe
supercells cannot be ruled out. This threat will continue Monday
night. Greater destabilization could occur on Tuesday as the warm
front moves further inland and dew points reach the upper 60s.
Again, we would expect development of discrete convective cells.
With low level helicity enhanced near the warm front, isolated
supercell tornadoes would be the primary threat through Tuesday.
As a 130-150 kt upper level jet streak enters the base of the
Great Plains trough, deep layer QC forcing will increase
downstream over the eastern Gulf Coast region as a low level jet
strengthens. The primary storm mode will evolve toward a pre-
frontal squall line Tuesday night into Wednesday with QLCS
tornadoes and damaging straight line winds possible with this
line.

Another concern we have been monitoring is the potential for
heavy rain. Confidence is increasing that we will see periods of
heavy rain, particularly from Tuesday afternoon into Wednesday as
PW approaches 2 inches, near the December record for TLH. See the
hydrologic discussion below for details on any flood threats.


.Long Term [Wednesday Through Sunday]...
As alluded to above, the threat for severe weather and flooding will
continue into Wednesday. The timing trend for the cold frontal
passage has been slowing down for the most part in the various
models and the boundary may not be cleared east of the forecast area
until closer to 00Z Thursday.

Noticeably cooler and drier air will arrive behind the front.
Overnight temps will remain above freezing, but the daytime high
on Christmas day will be chilly, generally in the upper 50s. Near
normal temperatures are then expected through Saturday night.
There a big difference in the models with the timing of the next
frontal system. The GFS brings a dry front quickly through the
area on Saturday, while the latest Euro develops a wave on the
front, pulls much more moisture into the system, and doesn`t clear
the boundary east of the area until midday Sunday.


.Marine...
Light to moderate northeast winds will become onshore by Monday,
increase to cautionary levels on Tuesday and then reach advisory
levels Tuesday night. A shift to westerly winds will occur after a
cold frontal passage on Wednesday. Strong to severe storms could
precede the front. Winds will then veer to the northwest and drop
below headline criteria Thursday morning. Light onshore winds are
forecast for later in the week.


.Fire Weather...
Low level moisture will be abundant over the next few days with
drier air moving in on Wednesday. Red flag conditions are not
expected over the next week.


.Hydrology...
While there is still some uncertainty with respect to the exact
placement of heaviest rainfall with the storm system on Tuesday and
Wednesday, confidence is increasing that there will be a period of
significant rainfall occurring across the region. At this point,
highest storm total accumulations of 4 to 6 inches are forecast for
the FL Big Bend and South Central GA with 2 to 3 inches across the
northwestern zones. The bulk of this rainfall will occur from
Tuesday through Wednesday morning. Locally higher totals will be
possible.

Rainfall totals of this magnitude will increase the potential for
localized flooding across the region, particularly during times of
heaviest rainfall on Tuesday Night into Wednesday Morning.

With area rivers and associated tributaries at or below normal flows
for December, the currently predicted rainfall amounts are generally
expected to produce only rises to action stage on most of the river
forecast points. The notable exceptions to this may be within the
Ochlockonee and Withlacoochee River Basins where there`s increased
potential to reach minor flood stage later this week.

&&

.Preliminary Point Temps/PoPs...

Tallahassee   55  71  61  72  63 /  70  60  50 100 100
Panama City   56  71  64  72  64 /  70  50  50 100 100
Dothan        50  66  59  71  61 /  50  50  50 100 100
Albany        48  64  56  72  62 /  60  60  50 100 100
Valdosta      53  68  60  73  63 / 100  70  50  90 100
Cross City    60  74  62  76  65 / 100  70  40  70 100
Apalachicola  58  70  64  71  65 /  70  60  50  90 100

&&

.TAE Watches/Warnings/Advisories...

FL...None.
GA...None.
AL...None.
GM...None.

&&

$$

NEAR TERM...MCDERMOTT
SHORT TERM...WOOL
LONG TERM...WOOL
AVIATION...MCDERMOTT
MARINE...WOOL
FIRE WEATHER...MCDERMOTT
HYDROLOGY...WOOL/GODSEY






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