AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
235 PM EDT SAT Jul 28 2012

.NEAR TERM [Rest of Today and Tonight]…
The large scale longwave pattern remains highlighted by TROUGH over
WRN states, RIDGE over CNTRL states anchored by subtropical HIGH
over OK Panhandle, MEAN trough over ERN states with axis from Ern
Great Lakes SWWD into E/Cntrl gulf, and a ridge over extreme Wrn
Atlc with deeply stacked ridge axis SWWD across SRN FL and into Ern
Gulf of MEX. This places local area in weakness between INSTABILITY
of trough and SUBSIDENCE of ridge. Satellite water vapor shows plume
of deeper MOISTURE moving NEWD across area. This reflected in area
RAOBs and model soundings which show PWs above 2 inches and K
indices in the MID 30s. At the surface cold FRONT was noted from NE
states SWWD THRU TN Valley and WWD into Srn IL and MO. Assocd
pre-frontal trough was note from Ern VA swwd thru Carolinas, S/Cntrl
Ga and Srn AL. Remnant MCV interacting with Gulf coast sea breeze
over our waters pinned assocd CONVECTION near coast and adjacent
waters into the mid-AFTN. Surface ridge remains over SW FL.

During the rest of today, the Ern trough axis will continue to dig
slightly SEWD in response to potent SHORTWAVE that will eject EWD
across the LWR MS Valley thru this EVE eventually diving SEWD into
the Cntrl Gulf by SUNRISE Sun. This will help drag cold front SEWD
reaching NRN GA/AL before eventually stalling over Cntrl AL/GA on
Sun. Pre frontal trough remains quasi-STNRY. With the surface trough
LIKELY to remain near or just north of the NRN part of our area, and
the sea-breeze moving only slowly inland, showers and storms began
to develop away from the coast after 130 PM EDT and will continue
to lift further NWD into the late afternoon or early evening and
mainly SRN half of our forecast area, in the warm sector. South of
the trough, DEW points are high and PWs will remain at or above 2
inches so brief heavy RAIN, frequent CLOUD to ground LIGHTNING and
gusty winds a good bet. Cant discount brief wet MICROBURST with
damaging gusts.

Tonight, 20-30% mainly evening convection with focus over Big Bend.
This supported by all the HI RES guidance and local confidence tool.
A FEW storms may continue to be strong to ISOLD severe. Lows in LOW
to mid 70s.

&&

.SHORT TERM [Sunday through Tuesday]…
Little change in the large scale pattern is expected on Sunday
with upper ridging encompassing a large area from the great BASIN
and Rockies down to the Gulf of Mex. Trough Ewd into extreme WRN
Atlc with axis down Ern seaboard. Trough will nudge ewd rest of
period with axis lying along or just east of coast keeping forecast
area in persistent light NLY FLOW. TAE Model soundings show PWs will
remain at or above 2 inches thru Wed.

At surface, with a trough or decaying front likely to be lingering
somewhere nearby over the Southeast, we expect to remain in warm
sector. The combination of trough to our N and seabreeze development
each aftn will maintain a confluent zones, especially south of I-10
and over Big Bend where CAM shows CAPE will exceed 2000 j/kg. This
will allow POPS to remain at or just above CLIMO with a fairly
WIDESPREAD convective coverage each day with increasing focus on
east half of CWA. POPs will be enhanced by any embedded shortwaves
that rotate down ern side of upper ridge which would favor late
developing strong to isold storms each day.

Will go with 40-60% NW-SE POP GRADIENT on Sunday, 20-40% Sunday
NIGHT, 20-50% nw-se POP gradient on Monday. NIL pops Monday night,
and 30-40% on Tuesday. MAX TEMPS generally in the low 90s in FL and
mid 90S N of the border. Apparent temps should remain below heat
ADVISORY levels.

&&

.LONG TERM [Tuesday Night through next Sunday]…
AS has been predicted for the past several model cycles, the
global models forecast a mean 500 MB trough to remain over the
Eastern CONUS through much of this upcoming work week, with
perhaps a bit of weakening of this feature by next weekend.
Meanwhile, a the western extent of the subtropical surface ridge
will remain to our south, providing our forecast area with south
to west winds for much of the period.

While we expect a fairly strong DIURNAL signal in terms of
THUNDERSTORM activity (i.e. mainly afternoon & evening thunderstorms
primarily due to the sea breeze CIRCULATION combined with peak
heating/destabilization); there remains a possibility that MESOSCALE
Convective Systems (MCS) and/or other 500 mb impulses could
translate south through our forecast area and generate thunderstorms
as well…even during the overnight areas. Our skill at forecasting
such features is generally 24 hours or less (if that), so trying to
forecast such details in the long term forecast is not possible. We
are just letting people know that this type of large scale weather
pattern can be favorable for southward-propagating MCSs. Why do we
keep repeating this in our discussions? Mainly because MCSs can
sometimes be associated with an increased risk of severe weather
(from damaging WIND gusts), and that our rain chances may linger
through the entire overnight periods (as opposed to dropping to less
than 20% after midnight). Our forecast continues to follow the HPC
guidance very closely, except that our TEMPERATURE forecast is
generally a few degrees warmer during the afternoon hours. Overall,
we expect near-climo 24-hour PoP & temperatures, except that our
overnight PoP is slightly above climo.

&&

.AVIATION…
[Through 18 UTC Sunday] SCATTERED TSRA will continue to develop
across the tri-state region this afternoon before diminishing later
this evening. Brief periods of heavy rain with MVFR/IFR vsbys will
be possible at all terminals mainly between 18z-22z. Patchy low cigs
and FOG will develop between 08z-13z with MVFR vsbys/cigs possible.

&&

.MARINE…
Rather benign conditions on tap for the marine forecast outside of
scattered thunderstorms. Winds look to be generally around 10
knots or less through the weekend (on average) with SEAS 1-2 feet.
Moderate risk of rip currents tomorrow along the Panhandle beaches
with onshore flow around 10-12 knots expected and surf building
close to 2 feet.

&&

.FIRE WEATHER…
Relative HUMIDITY levels are expected to remain above critical
thresholds for the next several days, so Red Flag conditions are
unlikely.