AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
445 AM EDT Wed Jul 18 2012

NEAR TERM [Until 6 PM This evening]…
The large scale longwave pattern is highlighted by TROUGH over WRN
most states with quasi-STNRY LOW over NRN CA/OR border. In Nrn
stream, HIGH over CNTRL Plains/Rockies with nearly flat FLOW EWD
across rest of U.S.. SRN stream marked by 586dm TUTT low inching NWD
over SE GA surrounded by RIDGE over Wrn most Gulf into the MS Valley
and another ridge well off FL/GA coast. This places local area in
weakness between both ridges. At surface, ridge from high over
Wrn Atlc SWWD across S/Cntrl FL and a trough over SE GA placing
local area in warm sector.

Of particular local concern is GA low. The combination of vort lobes
rotating around its WRN base, deep layer MOISTURE with PWs near 2
inches and low level CONVERGENCE enhanced by TUTT supported
increasing and ample showers and ISOLD storms across mainly
Apalachee Bay and adjacent counties into the predawn hours.
Elsewhere, only isold CONVECTION occurred. Elsewhere, AS the
ATMOSPHERE has been increasingly worked over, lingering convection
will continue to wane. Ample MID and high level clouds left over
from earlier convection should prevent significant STRATUS/fog
formation western counties. Conversely fog expected over ERN 2/3rd
of CWA THRU at least SUNRISE and added to grids.

TODAY, the low is forecast to move WNW, weaken and open up across
SRN GA with mid level TEMPS that are cooler than NORMAL (producing
steeper lapse rates) that should enhance convection. With persistent
vort energy on srn side of low combined with DIURNAL heating, and the
influence of the surface trough and the Gulf Seabreeze (type 4/5
quadrant with SW flow) should combine for an above average day for
ACTIVE convection, but less so than we saw Tues afternoon due to
more Wrn TRACK of low. POPS will remain in the 50-60 RANGE during
the afternoon with lowest POPs over GA counties. Expect 1500-2000
j/kg MLCAPE offset by weak flow and SHEAR so any severe storms
should be the PULSE variety with damaging winds the primary threat.
AS upper low weakens, forcing will be less so today`s storms should
be modestly weaker than yesterday. SPC has the entire area under a 5
percent risk for WIND related severe storms. Highs from upper 80s
coast to mid 90s inland.

&&

.SHORT TERM [Tonight Through Friday]…
TONIGHT, the remnants of upper low should stall over FL Panhandle or
adjacent SW GA but threat of strong to severe weather should
decrease after SUNSET as the boundary layer stabilizes aided by
cooling from any THUNDERSTORM outflows. SCT evening convection will
become isold to WDLY sct by midnight overland however linger over
the water before inching onshore over SE Bend towards morning. Will
go with 30-40% mainly evening POPS. Lows from low 70s inland to
upper 70s coast.

On THURSDAY, remnants of upper low is PROGGED to further weaken and
move further north away from the area as it gets absorbed into a
digging SHORTWAVE within amplifying Ern trough moving across
mid-Atlc. There is some model disagreement with speed at which upper
low becomes absorbed into upper trough with NAM, GFS AND ECMWF
faster than UKMET and CANADIAN and this could impact Thursday`s
local RAIN. At SAME time ridge will build across FL Peninsula
favoring deep moist onshore flow and another day of at or above
normal RAINFALL. 40-60% daytime and 20-40% nighttime E-W POP
GRADIENT. Highs from upper 80s coast to low 90s inland. Lows form
around 70 inland to upper 70s coast.

On FRIDAY, surface trough moves s of area with deep layer ridge to
our south building further Nwd with drier AIR advecting into area
from SE-NW. POPs return to near normal rainfall. 30-50% SE-NW POP
gradient. Highs upper 80s coast to mid 90s inland.

&&

LONG TERM (Friday NIGHT through next Wednesday)…
Both the 12z Tue EURO and 00z GFS and show the longwave TROF
lingering in the area through Saturday before getting squeezed out
as the ridge to our west and the Bermuda ridge merge. Likewise, the
surface ridge will extend westward across the Gulf with the axis
remaining south of the local area. This will keep a moist low level
flow through the period. Despite the deep layer ridging, time HEIGHT
cross sections show sufficient moisture along with a FEW embedded
impulses to provide at least SCATTERED diurnal convection. Temps
will be a few degrees above seasonal levels.

&&

.AVIATION…
With the abundant low level moisture left over from yesterday`s
WIDESPREAD rains we expect at least a brief period of MVFR/IFR
vsbys/cigs before sunrise at all TAF sites. Then another round of
scattered to NUMEROUS storms are expected today. Went with afternoon
convective tempo groups at all sites with a slightly earlier start
at ECP.

&&

.MARINE…
Winds and SEAS will remain below headline criteria through the
period as the area remains under the influence of the subtropical
ridge. Local enhancements can be expected near the coastline each
afternoon in the coastal sea breeze zone.

&&

.FIRE WEATHER…
Relative HUMIDITY levels are forecast to be well above critical
values for the next several days. Daytime dispersions are also
expected to be very low for the next few days.