037 
fxus62 kkey 202011 
afdkey 


Area forecast discussion for the Florida Keys 
National Weather Service Key West Florida 
411 PM EDT Sat Mar 20 2010 


Discussion... 
cumulus clouds have remained shallow and scattered mostly off to the 
southeast side of the Florida Keys thus far today. The kbyx radar 
been void of precipitation echoes in the suppressed environment even 
as winds have turned to the east/southeast and have picked up to 
between 10 and 15 knots at all of our available cman sensors. 


A middle to upper level cyclone will continue to strengthen over the Red 
River valley through the overnight period...head eastward on Sunday 
and then northeastward on Monday on its way towards the middle Atlantic 
coast. Surface pressures will continue to fall in the lower 
Mississippi Valley and in the northern Gulf of Mexico tonight and 
then become consolidated across the southeast states on Sunday. A 
trailing cold front will be pulled through the Gulf of Mexico tonight 
and Sunday...and all short range guidance has the front crossing the 
Florida Keys and surrounding waters by early Monday morning. 


The reasoning for the afternoon forecast package has not changed to 
any significant degree. Surface breezes will continue to veer ahead 
of the approaching front through Sunday and Sunday evening. Graphical 
guidance does however point to a slightly lower wind speed through 
both tonight and again through Sunday night ahead of and along the 
front when compared to previous runs for the local area. Have made 
just a minor downward adjustment in the grids for those periods...but 
by no means to a large degree. Have maintained a slight mention of 
showers for the second half of Sunday...and the likely probability of 
showers through Sunday night. Included a mention of thunder through 
that overnight period even though the best middle level vorticity and 
upper level speed maximum favors points to our north. But believe a 
slight mention should cover any storm that comes through. 
Also...there will continue to be cyclonic flow through Monday with 
another trailing axis of higher moisture pulling through the Keys and 
South Florida. So will maintain the high chance...50 
percent...probability through then. A northwesterly flow continuing 
through Monday night may drag a few light showers across the 
Keys...but the chance of measurable rain is low so only a 10 pop will 
be kept for the early overnight period. 


A relatively flat middle to upper level flow with limited available 
moisture calls for a dry forecast all the way through Thursday night. 
Another cold front is expected to pull into the Gulf of Mexico on 
Friday as high surface pressure again exits the East Coast of 
Florida. This front is expected to cross the local area by early 
Saturday. The middle to upper level flow is much more attenuated than 
the first front...but a slight mention of light showers will be 
inserted from Friday through Saturday thanks to a return flow. 


Marine... 
thanks to fair agreement among the models in regards to the expected 
wind speeds overnight tonight and again Sunday night...have backed 
the gridded wind speeds back only slightly. At this point am not 
inclined to insert an exercise caution in the Atlantic waters for 
later tonight. But it would not be overly surprised if later shifts 
may need to insert that headline should the observations trend higher 
than current expectations. 


&& 


Aviation... 
expect VFR conditions through the overnight period at both the eyw 
and mth island terminals. If there are any brief ceilings later this 
evening...the will have bases close to fl040. Surface breezes will be 
from the east southeast between 10 and 15 knots. 


&& 


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


&& 


$$ 


Public/marine.........04 
aviation/nowcasts.....Dfm 
data collection.......fuentes 


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