Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
900 PM AST Sat Dec 20 2014
Update...partly to variably cloudy skies prevailed across Puerto
Rico and the U.S. Virgin Islands this evening. Light passing showers
affected briefly the east coastal sections of PR as well as portions
of the USVI. Additional light showers embedded in the trades could
move inland over the windward areas during the overnight hours.
However...minimal rainfall accumulation is expected across the
local islands through Sunday morning. The fair weather pattern is
forecast to continue across the islands the rest of the weekend.
However...a moisture band will reach the USVI and eastern PR
Tuesday morning...allowing scattered showers to form over the
local islands on Tuesday. No changes were introduced to the
forecast package this evening.
Aviation...VFR conds expected for the next 24 hours across the local
terminals with only isolated passing -shra across the local flying area.
Light surface winds overnight...increasing to around 15kts after 21/13z
from the east with sea breeze variations.
Marine...seas 3-5 feet with occasional waves up to 6 feet in the
offshore Atlantic waters are forecast over the next few days.
Winds of 15-20 knots can be expected through rest of the weekend.
Previous discussion... /issued 243 PM AST Sat Dec 20 2014/
Synopsis...a fair and stable weather pattern will continue to
prevail across the local islands during the next several days
as a middle to upper level ridge holds across the Caribbean into
the western tropical Atlantic. Surface high north of the area
will promote fresh northeasterly winds through early next week.
Discussion...mostly sunny to partly cloudy skies prevailed
across the local islands through the day...with brief passing
showers observed over the Caribbean waters south of Saint Croix
and Puerto Rico. Some showers have been developing across portions
of southwest Puerto Rico early this afternoon...however minimal
rainfall accumulations observed so far. Winds were from the
northeast at 10 to 15 miles per hour...with coastal temperatures in the
A fair and stable weather pattern will continue to prevail across
the local islands during the next several days under subsidence
aloft and below to normal precipitable water. Although...shallow
low level moisture embedded in the trades will result in isolated
to locally scattered passing showers across windward areas from
time to time. In fact...best chance expected early Monday morning
and Tuesday. As subsidence cap holds across the area...afternoon
convection each day should remain limited...if any.
Fresh northeasterly trades will continue through Sunday becoming
more easterly early next work week. This will promote near normal
maximum temperatures across local islands.
Aviation...VFR conditions expected during the next 24 hours. Shallow/
isolated rain showers cannot be ruled out...but no significant weather event
are expected at the taf sites. Sounding data showed east-northeast at 3-17 knots
up to 2kft.
Marine...a moderate to fresh northeasterly wind flow will prevail
through Sunday...becoming more easterly Monday and Tuesday as
surface high north of the area moves further north. Seas building
slightly tonight and Sunday across the offshore Atlantic waters.
Seas up to 6 feet.
Preliminary point temps/pops...
sju 74 84 74 84 / 20 30 30 30
stt 76 85 76 85 / 20 30 30 30