Area Forecast Discussion
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921
FXUS62 KTAE 140737
AFDTAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
337 AM EDT Mon Apr 14 2014

...Strong to Severe Storms Possible From Late Tonight Through
Midday Tuesday...

.Near Term [Through Today]...
Today we will transition out of an upper level ridging pattern as a
rather amplified trough pushes into the eastern half of the country.
A 06z surface analysis depicted a rather benign pattern locally,
under the influence of high pressure which is centered off the
Mid-Atlantic coastline. As the upper ridge moves east, so will the
surface ridge, veering low-layer flow from the east to the south. As
it does so, weak isentropic ascent will generate scattered showers
up the spine of the Florida Peninsula, through the Suwannee Valley,
and north into south-central Georgia. An isolated thunderstorm may
be possible across Georgia late in the afternoon when the showers
encounter a fairly unstable environment as steep lapse rates advect
east through the Southeast. Otherwise a scattered CU field out ahead
of the sea breeze fronts can be expected today, with a rather solid
high cloud deck persisting all day long. High temperatures will be
similar to yesterday, possibly a degree or so cooler with the
plentiful upper level cloud cover. Convection associated with an
approaching frontal system will likely hold off until later this
evening across southeast Alabama and the eastern Florida Panhandle.


.Short Term [Tonight Through Wednesday]...
The long wave trough over the center of North America will shift
eastward during this period with a potent short wave rotating
through its base as it crosses the forecast area on Tuesday. The
associated cold front will sweep across the area from northwest to
southeast from 09-21z Tuesday. Showers and thunderstorms will
precede the front. At this time, it appears a squall line will enter
the area around 02-04z and bring a threat for damaging wind gusts.
The hail threat will be primarily north of the region, but our
northwestern zones could get some hail. There is also a non-zero
tornado threat of tornadoes, particularly in any discrete cells out
ahead of the main line and closer to the greater instability near
the Gulf Coast. By sunrise, the main band of convection is expected
to be over the FL Big Bend and South Central GA. There still appears
to be sufficient shear and instability in place at that time for a
marginal severe threat in these areas before 18z. Most convection
will exit east of the area by sunset.

An unseasonably cold airmass will arrive behind the cold front with
highs on Tuesday struggling to reach 60 degrees over Coffee County
AL Tuesday afternoon. South Central GA and the FL Big Bend will peak
in the lower 70s. Strong cold advection Tuesday night will drive
temperatures down into the 30s for all but our southeastern FL Big
Bend counties and coastal areas. This is about 15 degrees below
normal. It does not appear that any records are in jeopardy, but
wind chill reading will drop to around 30 degrees give or take a
few. That winter coat may have to come out of the closet one more
time. Highs on Wednesday will rebound to the upper 60s north to
mid 70s southeast.


.Long Term [Wednesday Night Through Monday]...
A gradual warming trend is expected for the end of the week and
into next weekend. As for rain chances by the latter part of the
period, the models have begun to diverge significantly once again,
with the GFS still indicating the potential for a possible two-
pronged rainfall event, while the ECMWF shows a split in the jet
stream flow, which would allow one shortwave to pass to our north
and another to pass to our south. This would leave most of the CWA
protected with fair and seasonable conditions, but it is clearly
too far in advance to buy solely into one of these solutions.
Therefore, will plan on a compromised resultant for the end of the
period, using our statistically verified blend of GFS/ECMWF/HPC
guidance which has shown to be quite difficult to beat over the
long haul.

&&

.Aviation...
[Through 06Z Tuesday] A patchy MVFR to IFR fog/ceiling mixture
will be possible at ECP later this morning, though confidence is
low due to the substantial coverage of high cloudiness. The only
other restrictions through this afternoon could affect VLD late in
the afternoon as showers and possibly isolated thunderstorms
accompanied by low ceilings pass from south to north across the
Suwannee Valley. Overnight a line of storms will move from west to
east across the Tri-State region, likely bringing IFR (or lower)
restrictions to terminals along and west of a line from ABY to
TLH.

&&

.Marine...
Onshore winds will pick up to cautionary levels tonight ahead of a
cold front. After frontal passage, offshore winds will quickly
increase to small craft advisory levels for Tuesday and Tuesday
night before veering to the east and dropping to cautionary levels
from Wednesday into Friday morning.

&&

.Fire Weather...
Relative humidity levels will remain well above critical thresholds
for the next couple of days as flow veers southerly ahead of an
approaching frontal system that is expected to bring a decent amount
of rainfall across the Tri-State region tonight through Tuesday. In
it`s wake, the lowest relative humidities will be on Wednesday, but
it is unclear whether durations or fuel moisture criteria will be
met to warrant Red Flag conditions.

&&

.Hydrology...
The Choctawhatchee, Apalachicola, Ochlockonee, and Withlacoochee
rivers all remain in at least minor flood stage as of this morning.
With the exception of the Withlacoochee, all river flooding remains
confined to north Florida. A frontal system will bring a widespread
swath of 1 to 2 inch totals across primarily basins west of a line
from Albany to Tallahassee. These amounts are represented well in
several of the ensemble forecasts which results in a halt to
lowering river levels. There is however the possibility of isolated
higher rainfall amounts on the order of 3 to 5 inches. Should these
amounts be realized over a basin, sharp increases should be
expected. For real-time detailed river stage monitoring refer to the
following page:

http:/water.weather.gov/ahps2/index.php?wfo=tae

&&

.Preliminary Point Temps/PoPs...

Tallahassee   82  64  72  37  72 /  10  70  80  10   0
Panama City   74  61  66  42  70 /  30  80  70  10   0
Dothan        80  57  63  36  69 /  30  90  60  10   0
Albany        81  62  68  36  70 /  10  80  80  10   0
Valdosta      85  63  74  38  73 /  20  60  80  20   0
Cross City    83  65  75  42  75 /  10  40  70  20  10
Apalachicola  76  64  69  42  69 /  10  70  80  10   0

&&

.TAE Watches/Warnings/Advisories...

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

&&

$$

NEAR TERM...HARRIGAN
SHORT TERM...WOOL
LONG TERM...GOULD
AVIATION...HARRIGAN
MARINE...WOOL
FIRE WEATHER...HARRIGAN
HYDROLOGY...HARRIGAN






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