Weather

484 
fxus62 ktae 281902 
afdtae 


Area forecast discussion 
National Weather Service Tallahassee Florida 
300 PM EDT Thursday Aug 28 2008 


Synopsis...weak surface ridging is parked just off to our northwest early this 
afternoon...while at upper levels a shortwave is digging southeast through 
Tennessee and north Georgia...with its southern extent reaching into southeast Alabama and the 
Florida Panhandle. Despite the fairly low guidance probability of precipitation...this morning's 
12 UTC tae sounding is still fairly moist...and after modifying it 
to t=93, td=70, we get a pw=1.82", a cape=2869 j/kg, and an li=-5.8. 
There is some middle level dry air trying to work in to the area...but 
do not expect it to impede any mature convection which may develop. 
Therefore...based on this new sounding and the latest 06 UTC 
workstation WRF run...already bumped up probability of precipitation to 40 percent across 
the southeast Big Bend as well as Gulf and Franklin counties...30 percent 
across the remainder of The Big Bend and Panhandle...and 20 percent 
across our Georgia and Alabama zones. Over the coastal waters...winds are 
generally light out of the northwest...with a sea breeze expected to 
develop near the coast later in the afternoon. 


&& 


Short term...fortunately...it looks like we'll have somewhat of a break 
in the shower and thunderstorm activity in the near term...and after 
all of the rainfall across the County Warning Area from ts Fay...we certainly need 
it. Hopefully...this will allow many of our swollen rivers and 
streams to gradually recede...before additional rainfall potentially 
threatens from Tropical Storm Gustav. Although the official forecast 
from the National Hurricane Center takes the center of Gustav well 
off to our west...there is still considerable uncertainty towards 
the end of the track forecast. Nevertheless...even with a track well to 
the west of the Florida Panhandle...there appears to be good potential 
for a long fetch of deep layer moisture to the east of Gustav which 
could extend from the Florida straights all the way northward up the 
western Florida Peninsula and into The Big Bend and Panhandle. This alone 
may provide another significant heavy rainfall threat across the 
region...from late in the weekend into early next week. 


&& 


Long term (sunday-thursday)...the first half of the extended forecast 
will be dependent on the future evolution and track of Gustav. The 
deep layer anticyclone over the Florida Peninsula and middle/upper level 
trough over the western Gomex should steer the cyclone toward the central 
Gulf Coast this weekend per the latest numerical guidance suite. The 
latest wind speed probs from the NHC bring 15-20 percent chance of 
34 kts into the Panhandle waters beginning late Sunday and 
continuing through Monday. The 27/12z Euro increases winds to around 
35 kts over our western marine legs, while the 28/00z GFS is about 10 
kts less. Due to the uncertainty this far out in the fcst, will 
include 'tropical storm conditions possible' for the Panhandle 
waters portion of the marine forecast for Sunday night and Monday. Of 
course, this forecast will be fine tuned with later NHC track forecasts. All 
interests along the Gulf Coast should monitor the latest forecasts 
regarding Gustav. Will also need to ramp up the seas, and mention 
swell. Now for the sensible weather, will indicate above climatology probability of precipitation 
for Sunday through Tuesday, as deep layer Gulf moisture on the east 
side of Gustav overspreads the County Warning Area. Drier air advecting into the 
region from a ridge centered over the middle-Atlantic region 
Wednesday and Thursday will lower probability of precipitation to below climatology. 


&& 


Aviation...VFR conditions will prevail through much of the forecast 
period but a scattered to broken cumulus field has developed with 
isolated to scattered showers and storms still expected to develop 
later this afternoon and evening. Thereafter...similar to this past 
morning...with plenty of low level moisture from saturated soils and 
a low level inversion expected to develop overnight...MVFR to IFR 
visible and ceilings will threaten the taf sites once again...with the most 
pessimistic conditions likely at tlh...vld...and aby. 


&& 


Marine...with a weak surface ridge hanging in over the marine area... 
winds across the coastal waters will remain light through 
Saturday...before the gradient begins to tighten up significantly 
later in the weekend. Besides the increasing winds...southerly 
swells will become a concern as well...depending on how quickly 
Gustav strengthens and how large its wind field becomes as it moves 
into the Gulf of Mexico. 


&& 


Fire weather...no concerns over the next several days. 


&& 


Hydrology...river flooding concerns remain at Apalachicola River 
near Blountstown...Ochlockonee at Havana, the St Marks at Newport, 
and the Spring Creek at Iron City. 


&& 


Preliminary point temps/pops... 
Tallahassee 69 94 71 93 74 / 10 20 10 20 20 
Panama City 75 91 73 91 75 / 10 10 10 20 20 
Dothan 69 93 70 93 72 / 10 10 10 20 20 
Albany 71 93 71 93 72 / 10 20 10 20 20 
Valdosta 70 94 71 93 71 / 10 20 10 20 20 
Cross City 72 93 72 93 73 / 10 20 10 30 30 


&& 


Tae watches/warnings/advisories... 
Alabama...none. 
Georgia...none. 
Florida...none. 
GM...none. 


&& 


$$ 


Public/marine...Gould 
aviation/fire weather...Gibbs 
long term...jamski