Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 220635
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
235 AM EDT Tue Apr 22 2014
.Near Term [Today]...
The surface high slides east and the mid/upper level ridge flattens
as a low amplitude trough and associated cold front move into our
region by this evening. The deepest moisture and best lift with this
system will stay to our north. PoPs by afternoon will be tapered mid
range chance north to silent 10% for most of our coastal areas and
southeast Big Bend. Kept mention of isolated TSTMS. QPF amounts will
generally be under one-quarter of an inch. Max Temps will be in
lower 80s inland areas and mid to upper 70s along the coast.
.Short Term [Tonight Through Thursday]...
The 500 mb positive tilted trough (currently beginning to cross the
Southeast) will pass southeastward over our forecast area tonight,
but the accompanying weak cold front will stall across extreme North
FL and become oriented east to west. The forecast Q-vector and
omega fields are not that impressive, which may help explain why
neither the GFS or NAM MOS "likes" this system, and have PoPs of
only around 20%. However, our local Ensemble of Convection Allowing
Models (ECAM) forecasts good coverage of rain this evening across
South GA & AL, and its PoP is in the 50-80% range (but only 20%
around Tallahassee and Panama City). We blended the two sets of
differing guidance to come up with a PoP of around 50%. All of the
MOS and dynamical guidance forecast a strong weakening/drying trend
after midnight. Despite lack-luster synoptic scale forcing and
SBCAPE values of only around 1000 J/kg, a few thunderstorms are
possible- perhaps aided by fairly steep mid tropospheric lapse rates
of 6.5 deg/km. The lack of strong winds aloft, marginal CAPE, and
the rapid onset of nocturnal cooling all make severe thunderstorms
unlikely. Forecast updraft speeds are in the 10-15 m/s range, which
are usually not enough to support severe hail.
Despite the presence of a quasi-stationary front in extreme North FL
on Wednesday, the PoP will be 10% or less as the mid troposphere
warms and dries considerably. There may be a slight increase in deep
layer moisture on Thursday afternoon, and with the frontal system
still in the region, could lead to a shower or two. However, we`re
only carrying a 10% PoP for now. Temperatures will be near
climatology through the period, with lows in the 50s and highs in
the lower to mid 80s.
.Long Term [Thursday Night Through Monday]...
The large scale Srn stream pattern commences fairly progressive with
near zonal flow over Wrn states...weak trough over Cntrl states and
weak ridging over Ern states. On Friday...ridging moves offshore
leaving near zonal flow over SE region reflected in uni-directional
flow on model soundings. Flow shifts to weak WNW flow into Sat. On
Sun into Mon...upstream amplified ridging builds Ewd into Gulf
region. At surface...ridge becomes established over Nrn Gulf
thru Fri night. Then...a low well to the north of CWFA
brings a trailing weak front to our area on Sat where it likely
stalls by Sat eve providing a small chance of convection. Sheared
out front then lifts back Nwd on Sun. This will place local area in
warm sector allowing for a weak seabreeze to develop Sat-Mon.
Next cold front moves into SE on Mon yielding a modest increase on
precipitation across mainly NW half of CWA on Mon. With local area
in warm sector...temperatures are expected to be slightly above
climo with inland highs in the low to mid 80s and under the sea
breeze influence...somewhat cooler at the coast.
[Through 06Z Wednesday] VFR conditions will prevail but we do expect
brief periods of MVFR cigs/vsbys in the pre-dawn hours and shortly
thereafter as fog develops. A front approaching from the west will
cause ceilings to lower after 18Z but remain at VFR levels.
Afternoon thunderstorms around DHN and ABY may act to briefly lower
visibilities. Winds will be light from the west to southwest.
Despite the front approaching from the north later today, then
stalling across extreme North FL through Thursday, winds and seas on
the whole will remain quite low. The exception will be a moderate
increase in onshore winds and chop near the coast each afternoon
because of the daily sea breeze.
Red Flag conditions are not expected through the remainder of the
Most of our area rivers are above normal stage with many in flood
stage. The Choctawhatchee at Bruce is forecast to reach major flood
stage this morning, with several others in moderate flood stage.
Most area rivers will crest soon or have already crested. The
exception is the Suwannee River which will rise slowly for the
remainder of the week. QPF amounts through tonight are expected to
be a third of an inch or less (mainly in Southeast AL and Southwest
GA), and should not have a major impact on river levels.
The most up-to-date river forecast information can always be found
on our AHPS page (below).
.Preliminary Point Temps/PoPs...
Tallahassee 82 60 83 58 84 / 20 20 0 0 10
Panama City 78 63 79 63 78 / 20 20 0 0 10
Dothan 81 59 83 58 84 / 40 50 0 0 10
Albany 83 58 83 56 84 / 40 50 0 0 10
Valdosta 82 59 84 59 85 / 20 20 10 10 10
Cross City 80 59 83 59 84 / 10 10 10 10 10
Apalachicola 75 61 76 63 77 / 10 10 0 0 10