125 
fxca62 tjsj 180043 aaa 
afdsju 


Area forecast discussion...updated 
National Weather Service San Juan PR 
843 PM AST Wednesday Mar 17 2010 


Synopsis...front just north of the area will lift north and away 
from the area overnight and early Thursday. Strong ridge of high pressure 
from the surface through the troposphere will build across the eastern 
Caribbean this weekend. 


&& 


Discussion...dewpoint discontinuity looks to be just to the north 
of PR as indicated by a 63f dewpoint at buoy 41043 while 
convergence line/shearline looks to be to the south as shown by an 
1425z ascat pass and as suggested by model guidance. Shallow 
convective instability as seen on 00z acars sounding enough to 
generate low topped rain showers this evening. Model guidance indicates 
rain showers moving offshore by 06z tonight if not sooner as winds 
continue to veer more to the southeast and land areas continue to 
stabilize with loss of heating. Have expanded/increased probability of precipitation and 
raise sky cover grids across Atlantic waters north of PR where satellite 
imagery already shows quite a bit of cloud cover and k indices forecast to 
climb overnight. Isolated rain showers could linger until about middle morning 
tomorrow. 


Rapid drying expected tomorrow afternoon with both k index and 
precipitable water values dropping sharply after 12z. Removed probability of precipitation for the 
afternoon hours. 


&& 


Aviation...prevailing VFR conditions are expected across all the 
local taf sites for the next 24 hours. Winds will be mainly light 
and variably overnight...and eventually become east-southeast by 18/14z. 


&& 


Marine...buoy 41043 shows 2.1 meter seas while a ship report 
north of tist indicated 1.5 meter seas. So marginal Small Craft Advisory conditions 
probably still occurring across NE portions of amz710. Will 
continue Small Craft Advisory until curr expiration time of midnight. Seas expected 
to remain 5 feet or less rest of the forecast period across all waters. 


&& 


Previous discussion... /issued 250 PM AST Wednesday Mar 17 2010/ 


Discussion... for the rest of the afternoon and evening hours... 
limited rainfall is forecast across the region with...with only a 
few diurnal and local terrain induced showers expected to develop 
along parts of the Cordillera Central. These showers should slowly 
drift northwards while dissipating early in the evening. 
Thereafter... and into Thursday expect mostly clear skies followed 
by fair weather and mainly sunny conditions across the region for 
the next several days and through the upcoming weekend. The 
prevailing winds will become southeasterly on Thursday...then 
continue into the weekend. This will result in limited shower 
activity if any for the next several days and unseasonably warm 
temperatures especially across northern Puerto Rico and the rest 
of the local islands. In addition... latest GFS guidance continued 
to suggest mostly dry and stable conditions across the region with 
no significant weather feature expected to affect the area...at 
least until the middle on next week...therefore look for an 
enjoyable and pleasant weather weekend. 


&& 


Preliminary point temps/pops... 
sju 78 88 75 89 / 20 10 10 10 
stt 78 86 76 84 / 20 10 0 0 


&& 


Sju watches/warnings/advisories... 
PR...none. 
Vi...none. 
&& 


$$ 


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