Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 121939
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
339 PM EDT Wed Jun 12 2013
.NEAR TERM [Through Tonight]...
Isolated to scattered thunderstorms will develop this afternoon,
mainly between I-10 and the coast. This is where the low level
convergence and MLCAPE will be greatest as the slow-moving sea
breeze fronts interact with orthogonal horizontal convective rolls.
Most of the cumulus clouds will be unable to grow substantially
because of the very dry air above 700 mb, but in a few spots (where
mesoscale forcing is strongest and CAPE/boundary layer moisture is
maximized) there could be a strong enough updraft to support a pulse
strong/severe storm. Isolated storms may develop in south GA this
evening (as indicated by some of the Convection Allowing Models like
the HRRR and our local WRF), as the FL sea breeze fronts
Temperatures were already in the 90s early this afternoon, and
will top out in the mid to upper 90s. Heat index values may reach
105 deg at a few inland locations. Lows tonight will be in the lower
to mid 70s, with plenty of humidity.
.SHORT TERM [Thursday Through Friday Night]...
Despite the upper level ridging over the U.S. which has been keeping
the weather hot and dry (with the exception of afternoon sea-breeze
showers and thunderstorms near the coast), the pattern gets a little
more interesting as a short wave trof digs down the east side of the
ridge. The shortwave trof will enhance surface pressure drops and
upper level winds (and thus shear). A line of showers and
thunderstorms along a weak frontal boundary from the surface low is
expected to dip into our area Thursday night. There is some model
disagreement as to whether or not these storms will dip as far south
as our forecast area, but if they do the model MLCAPE values of
around 3000 J/kg and 0-6 km bulk shear of around 30 kts suggest that
they will be strong to severe storms. SPC has our AL and GA
counties in a slight risk for severe thunderstorms in the day 2
outlook. The bulk shear is a little low for supercell development,
but stronger individual cells may form along the line, especially
with such a high amount of instability. Looking at the Fri 00Z
model soundings, there are conditionally unstable lapse rates
through most of the profile and drier air has made its way in the
mid levels thanks to the high pressure we`ve been under. CAPE
contribution in the -10 to -30 C range is around 1000 J/kg and
DCAPE is 1500-2000 J/kg. These parameters suggest that there is a
threat for both severe winds (58+ MPH) and 1" hail. Lower level
vorticity and wind shear is higher to the north of our area, but a
tornado from a stronger cell can`t be ruled out either.
Highs tomorrow will be in the upper 90s, similar to today, but may
be a little lower Thursday depending on the cloudiness ahead of the
line of storms and the timing of the storms themselves. Lows
Thursday night will be in the low-mid 70s, a little warmer due to
higher cloud cover and rain chances, but return to the lower 70s
.LONG TERM [Saturday through Tuesday]...
After the potential system passes Thursday night, high pressure
aloft and at the surface will build eastward and be the main
synoptic scale influence on the forecast area`s weather through
Tuesday. On Tuesday, another shortwave will propagate through the
upper level ridge and set up a pattern similar to Thursday night
(see short term). Highest PoPs in the forecast period are Tuesday
and Wednesday. Expecting highs in the 90s and lows in the low 70s
through the long term period.
.AVIATION [Through 18Z Thursday]...
Widely scattered TSRA will develop this afternoon from I-10 to the
coast, so there could be a brief period of TSRA at KTLH and KECP.
Isolated TSRA may develop in south GA this evening, but the PoP at
KVLD and KABY is only 20%. Otherwise, VFR conditions are likely
outside of any isolated TSRA.
A low pressure system to our northwest will dip ito the SE US and
increase chances of showers and thunderstorms Thursday night and
Friday. Although most of the storms will be inland, some stronger
storms are expected, so there is the possibility of brief periods
of cautionary to advisory winds as these storms pass through.
Otherwise, winds and seas will remain below headline criteria
through the period.
Red Flag conditions are not expected for the remainder of the work
week. Dispersion values may climb above 75 Thursday afternoon, from
a combination of strong vertical mixing and increasing winds aloft.
The Ochlockonee River at Thomasville is in action stage and may
rise slightly with rain tomorrow night, but it is not expected to
reach minor flood stage. MMEFS shows no sites are forecast to
reach flood stage in the near future. Although there is potential
for some severe thunderstorms Thursday night, WPC QPF for our area
is 0.25" or less and is not expected to cause significant rises on
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 95 73 96 75 95 / 20 10 20 20 30
Panama City 90 76 91 78 92 / 30 10 10 20 20
Dothan 97 75 99 74 95 / 10 10 10 30 10
Albany 97 75 99 74 93 / 10 20 10 40 10
Valdosta 99 73 97 74 93 / 10 20 20 30 30
Cross City 93 72 92 73 92 / 20 10 20 20 30
Apalachicola 89 76 89 77 91 / 20 10 10 20 30