648 
fxus62 kjax 181850 
afdjax 


Area forecast discussion 
National Weather Service Jacksonville Florida 
250 PM EDT Thursday Mar 18 2010 


Short term...upper low continues to spin along the NC/SC coast 
while another disturbance over the southeastern Gulf of Mexico is moving 
toward S Florida. A surface low is located over open waters east of 
the upper low and a weak trough extends across the southern portion of 
our forecast area. Echoes on radar S of ocf to Palatka and Bunnell 
are mostly virga but a few weak showers or patches of drizzle are 
possible for the rest of the afternoon. 


Low pressure system will pull farther out to sea tonight through 
Saturday followed by a surface high and upper ridge building into the 
local area. This will bring decreasing cloudiness beginning 
tonight and temperatures warming steadily through the weekend to near 
normal by Sunday. Next cold front will approach Sunday as another 
shortwave dives into the lower MS valley. GFS/NAM are in agreement 
that a line of showers will move through the area during the middle 
to late part of the day. Will keep isolated thunderstorms in forecast and at this time do 
not anticipate storms to be too strong. 


Long term...following the passage of the front...temperatures 
will once again drop to near 10 degree below climatology Sun night through Monday 
night. Upper shortwave trough will lift NE by Tuesday with high pressure 
building over the region and temperatures returning to normal by middle 
week. Models forecast another cold front to approach Thursday the 
25th. The European model (ecmwf) is slower than the GFS and will keep probability of precipitation low 
at this time. 


&& 


Aviation...VFR condtions look to prevail with broken clouds around 4 
kft rest of afternoon. Clouds expected to gradually dissipate tonight 
with skies clearing from north to S. VFR expected on Friday. 


&& 


Marine...pressure gradient is fairly weak but winds are still near 
15-20 knots offshore and seas estimated near 6 feet at buoy 41012. Observation 
from the buoy have been sporadic and not consistent today. Bulk of 
the wave spectrum is the NE swell component with periods near 13-15 
seconds. Due to marginal nature of winds and most of the sea state 
in the form of swell will adjust the Small Craft Advisory to include just offshore NE 
Florida marine zones. Will replace Small Craft Advisory in Georgia offshore waters with scec 
headline. Seas expected to diminish slowly into Friday with seas still 
elevated due to northeasterly swells. Winds expected to increase from the S 
ahead of next cold front on Sunday with strong offshore winds 
possible Monday in the wake of cold frontal passage. 


&& 


Fire weather...we are coming up with 4-5 hours of low relative humidity values on Friday 
afternoon and min relative humidity values just under 30% in some areas. Thus...will 
hoist a Fire Weather Watch for most of the NE Florida...except for St Johns 
and Flagler counties where slight onshore component and slightly 
shorter durations does not warrant a watch at this time. Another red flag 
event is certainly possible on Sat with low relative humidity durations again. 


&& 


Preliminary point temps/pops... 
amg 43 74 45 77 / 10 0 0 10 
ssi 47 69 50 71 / 10 0 0 0 
jax 45 73 47 75 / 10 0 0 0 
sgj 47 68 49 71 / 10 0 0 0 
gnv 43 74 43 77 / 10 0 0 0 
ocf 43 74 44 77 / 10 0 0 0 


&& 


Jax watches/warnings/advisories... 
Florida...Fire Weather Watch from Friday afternoon through Friday evening 
for Alachua-Baker-Bradford-Clay-Columbia-Duval-Gilchrist- 
Hamilton-Marion-Nassau-Putnam-Suwannee-Union. 


Georgia...none. 
Am...Small Craft Advisory until 4 am EDT Friday for Fernandina Beach 
to St Augustine Florida 20 nm to 60 nm offshore-St Augustine to 
Flagler Beach Florida 20 nm to 60 nm offshore. 


&& 


$$ 


Trabert/shashy/presnall