Area Forecast Discussion
Issued by NWS
FXUS62 KTAE 221335
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
935 AM EDT Tue Jul 22 2014
.Near Term [Through Today]...
Mid-morning radar indicates less marine and coastal clouds and rain
than in previous days. The main features aloft continues to be a
broad cutoff low centered over Wrn FL Panhandle with a well-
defined dry slot wrapping around the west and southwest flank of
the low, over the FL Panhandle and adjacent coastal waters.
Looking Ewd, a ridge is noted over extreme Wrn Atlc. At surface, a
decaying quasi-stationary front was noted from SC, through
central GA, extending Swwd to a broad, 1015mb low centered over
SRN MS. There was an east-west trough along I-10 in the FL
Panhandle. With local area between low to west and ridge to east
aloft and south of front below, this translates to deep near uni-
directional onshore flow bringing low/mid/high clouds across NE
During the rest of today, upper low will translate slowly WSW to
reach SE LA late tonight. Convection will be due to forcing east
of upper low center and by any boundary/Gulf sea breeze clashes.
HI RES guidance shows convection moving NE thru day so expect a
20-50% SW-NE POP gradient. Given a very light steering flow,
locally heavy rain is possible. With a very weak wind field aloft
and lackluster forecast SBCAPE values (1500 J/kg or less), only a
small chance of severe storms. With less morning cloud cover than
in recent days, expect high temperatures to be a little warmer
with highs around 90.
.Prev Discussion [640 AM EDT]...
.Short Term [Wednesday Through Thursday Night]...
A mid-upper level low will continue to retrograde westward along
the Gulf coast and eventually get sheared out near coastal
Louisiana or Texas by Thursday. For Wednesday, this will allow for
a ridge to build into the area with negative vorticity advection
in those same layers. Computer models are in good agreement in
showing suppressed convective activity on Wednesday despite PWATs
very close to seasonal normals (around 1.9"). While this may be
the case, we think that the approx 20% PoPs the models are
advertising for the afternoon hours are too low without any
substantial drying - either at the surface or aloft. By Thursday,
another trough begins to dig into the region from the northwest
and could provide some additional large scale forcing for storms.
Therefore, we indicated scattered thunderstorms both afternoons
with PoPs around 30-40% in most areas. Temperatures should be
warmer than in recent days, with highs in the mid 90s likely.
.Long Term [Friday Through Tuesday]...
The large scale pattern commences rather amplified with ridging
over west, troughing over east and ridge over extreme Wrn Atlc.
At surface, ridge from Wrn Atlc to over local region with cold
front draped over mid-south. During the rest of the period, Wrn
ridge shifts Ewd with downstream trough pivoting and deepening Ewd
over local region on Fri before lifting Newd and flattening Sat
into Sun. Front inches swd shunting Gulf ridge further Swd
allowing for a return to a more WLY flow and normal summer time
sea breeze dominated regime. Will go with generally 30-40% aftn/eve
POPs thru the period. Expect highs generally in the low to mid
90s, lows low to mid 70s.
[Through 12Z Wednesday] Areas of MVFR cigs remain possible this
morning. Otherwise, scattered TSRA will develop today, with the
highest chances (40-50%) around KTLH and KVLD later this morning and
early afternoon, then around KABY later this afternoon. Gusty winds
and brief periods of poor VIS/CIGS are expected with the stronger
storms, but we were not confident enough to explicitly forecast
these conditions at any terminals on this 12 UTC TAF package.
Winds and seas should be relatively calm during the period - winds
generally 10 knots or less and seas generally 2 feet or less.
Red flag conditions are not expected this week.
The Shoal River at Mossy Head briefly approached flood stage early
yesterday morning, but the river levels are now falling. There
will likely be some heavy rain rates today, and the storm motion
will be unusually slow (around 5 kt). This would suggest at least
some potential for flooding. However, there appears to be one
negative factor that will keep the risk of flooding rather low-
the influx of dry air aloft from the south and west. This should
help dampen deep moist convection somewhat, preventing updrafts
from persisting over any one location for too long. We think the
probability of exceeding local flash flood guidance today is about
5% (within 25mi of a point), which is not high enough for a watch.
.Preliminary Point Temps/PoPs...
Tallahassee 90 72 95 73 95 / 40 30 50 20 50
Panama City 87 75 90 76 90 / 30 20 30 20 30
Dothan 89 72 93 73 93 / 30 20 40 20 40
Albany 90 72 94 73 94 / 40 40 30 20 30
Valdosta 90 70 96 72 96 / 50 40 40 20 40
Cross City 90 71 94 73 92 / 40 30 40 20 40
Apalachicola 87 74 88 76 88 / 30 20 30 20 30