943 
fxus62 kjax 240826 cca 
afdjax 


Area forecast discussion...corrected 
National Weather Service Jacksonville Florida 
355 am EDT Thursday Jul 24 2008 


Synopsis...water vapor imagery and RUC 400 mb analysis show a 
well-defined trough extending from Virginia to S central Georgia to the western Florida 
Panhandle. Much drier air is filtering in on the back side of this 
trough and entering our Georgia zones. Deeper moisture resides over the 
southern zones with recent GPS-met data and RUC indicating precipitable waters  of 1.9 
inches near Gainesville. At surface...troughing is north of the area from NC 
to S central Georgia to near eastern Alabama. Synoptic flow from surface to 10 kft is 
becoming northwest as seen in latest vwp and model output guidance. So far 
radar is quiet but anticipate some convective activity to develop 
later this morning over the SW zones. 


Short term... 
today and tonight...models are in good agreement that northwest flow in the 
7h-500 mb layer will become more northerly as the troughing over the region 
moves eastward and heights rise. Surface troughing north of the area will drop 
southward and deeper moisture moves well S and east with skies becoming 
mostly clear to partly cloudy. A north to S pop gradient is in order 
today with only 20% for Georgia and 30-40% over NE Florida. Slightly higher 
pop is anticipated from Marion County to Flagler County in area of 
deepest moisture. Showers and storms should first begin over the 
interior NE Florida zones where low level moisture convergence and higher 
Theta-E air will reside through middle morning. Due to drying aloft 
and temperatures pushing the lower 90s...any storms that get going will be 
capable of producing damaging downburst winds and marginally severe 
hail. Modified cape from GFS and NAM is about 2300-2600 and Li of 
-6. Differential Theta values are estimated around 20-25 but higher 
in southeast Georgia. Maximum temperatures higher today than Wednesday due to less cloud cover. 
Tonight...isolated thunderstorms in the evening with patchy fog 
occurring late. 


Friday...surface troughing over the area and a relatively dry airmass 
will again yield lower probability of precipitation than previous days. Precipitable waters  of 1.4 to 1.7 
inches are anticipated and driest air will be from about 750-450 mb. 
East Coast sea breeze will have an easier time moving inland and best 
low level forcing will be over inland zones. Will continue with the north to 
S probability of precipitation with 20% in southeast Georgia and 30-40% over inland NE Florida. Temperatures 
expected to push into middle 90s over southeast Georgia and inland NE Florida and heat 
indices just over 100 degree at times. Friday night...mainly expect 
isolated thunderstorm activity over inland areas in the evening with 
patchy fog possible again. 


Saturday...surface trough is not as apparent and ridging may work northward 
over Florida. Moisture is still somewhat limited and East Coast sea breeze 
should have no problem moving inland. Will keep probability of precipitation limited to 
about 20-30% for most areas. Maximum temperatures in the lower to middle 90s 
expected. Isolated evening showers and storms anticipated Saturday 
night. 


Long term...Sunday-Wednesday. Model guidance has shown indications 
of eastern Continental U.S. Trough to deepen a bit during this time frame or at 
least keeping a weakness in the middle level ridge over the forecast 
area. GFS ensemble in general agreement with this pattern and keeps 
500 mb temperatures in the -6 to -8 c degree range. At surface...ridge axis will 
remain S of the area and weak troughing will be over the southeast states 
will keep a southwesterly flow over the region. This pattern should favor 
typical afternoon and evening showers and thunderstorms and probability of precipitation in 
the 30-50% range at this time. Temperatures appear to be close to 
normal...lows in the lower 70s and high around 90. 


&& 


Aviation...prevailing VFR with middle/high clouds at most terminals 
early this morning. The exception will be gnv where there will be 
a scattered deck at 400 feet and possibly tempo MVFR visibility until 12z. 
With much drier air aloft filtering in today behind short wave... 
expecting much less coverage of storms and primarily during the 
afternoon. However...with with light synoptic flow...will probably 
have seabreezes and associated outflows develop and move inland 
during the afternoon which may bring in enough moisture to help 
produce a few strong storms with strong wind gust potential. 
Have gone with previous forecast of cumulonimbus at jax...crg...ssi after 
18z and thunderstorms in the vicinity at gnv after 18z. Some of these terminals may need 
some amendments this afternoon. 


&& 


Marine...a surface trough moves across the waters this morning 
and then washes out. A ridge remains across central Florida. 
This produces a weak pressure pattern with winds mainly south or 
southwest 10 knots or less except southeast along the coast 
in the afternoons. Seas 1 to 3 feet. Scattered afternoon and 
evening storms. Strong wind gust potential with some of the 
storms near shore. 


&& 


Preliminary point temps/pops... 
amg 94 70 96 71 / 20 20 20 10 
ssi 90 75 89 76 / 20 20 10 10 
jax 91 71 93 72 / 30 20 20 10 
sgj 89 72 88 73 / 40 20 20 10 
gnv 90 70 93 70 / 40 20 40 20 
ocf 89 70 92 70 / 40 20 40 20 


&& 


Jax watches/warnings/advisories... 
Florida...none. 
Georgia...none. 
Am...none. 


&& 


$$ 


Shashy/Peterson