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Area forecast discussion for the Florida Keys 
National Weather Service Key West Florida 
330 am EDT Sat Jul 5 2008 


Discussion... 
early morning infrared satellite images indicate scattered cumulus pockets out 
over The Straits associated with showers and a few embedded 
thunderstorms. A thin upper cloud shield has cleared our eastern 
Atlantic marine zones quite a while ago. Winds are gentle to 
occasionally moderate out of the east or slightly southeast 
direction. Temperatures are in the lower 80s and dewpoints are in 
the middle 70s along the island chain. 


Analysis shows that a weak upper level low has developed over the 
Florida Peninsula...and this should meander along the state's East 
Coast before filling and lifting out by late Sunday. However...the 
trough that reaches into the Gulf of Mexico gets reinforced by late 
Sunday. And the GFS continues to cut off an upper low in the 
northeastern Gulf of Mexico by early Monday and then retrogrades it. 
The NAM is not as aggressive with this upper pattern evolution...but 
is more significant in lifting a lower level perturbation northward 
in conjunction with a higher slug of moisture late Sunday through 
Sunday night. Both models do ramp up 12 hour probability of precipitation through those time 
periods...with the NAM going likely for both eyw and mth by early 
Sunday night. The GFS stays in the high chance range. Since this has 
been consistently depicted by the GFS...will lean toward those lower 
numbers. At this time will keep our 40 probability of precipitation for Sunday night...but 
the next run or so may dictate nudging that upward. Otherwise...the 
only change in the forecast may be to nudge our first period probability of precipitation up 
another 10 percent...based mostly on how the convection entering our 
outer Atlantic waters behaves. Will make a last minute decision on 
that. Feel that a 40 pop would suffice for an upper limit. No 
changes will be made to the late periods of the forecast. The latest 
GFS delays the onset of slightly drier air sliding into the vicinity 
of the Keys until the latter half of the week. But with a relatively 
deep and persistent easterly flow...will hang on to the 30 pop we 
have going for those later times. Expect highs near 90 during the 
day and lows in the lower 80s overnight through the entire forecast. 


&& 


Marine... 
gentle to occasionally moderate east to southeast winds will prevail 
on Keys waters through tonight...and a more moderate through the day 
on Sunday. The NAM veers the profile much more than the GFS for late 
Sunday through at least Monday with a much more defined wave 
undercutting the surface ridge axis across Florida. Favor the more 
subtle turning depicted by the GFS on this forecast. At this 
time...no exercise or advisories headlines are anticipated for any 
forecast period. 


&& 


Aviation... 
VFR conditions will prevail at the island terminals. There is a 
chance for cloud line development this afternoon to remain near the 
island Chain. Island terminals...especially Key West...may receive a 
brief spell or two of MVFR/IFR conditions due to this activity. No 
explicit mention in the taf's due to uncertainty. Surface winds will 
be mainly from the east at 10 knots or less. 


&& 


Preliminary point temps/pops... 
Key West 89 81 89 81 / 30 30 30 30 
Marathon 93 81 93 81 / 30 30 30 30 


&& 


Key watches/warnings/advisories... 
Florida...none. 
GM...none. 


&& 


$$ 


04/11 


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