Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
409 am AST Friday Dec 19 2014
Synopsis...upper level ridge will gradually build through the end
of next week and maintain fair weather conditions. Weak high pressure
will build over the region during the weekend and into early next
week then weaken on Christmas evening.
Discussion...morning clouds and light showers associated with
surface-700 mb trough currently moving westward through the area are expected
to gradually fizzle out through the day as drier air advects in on
east-northeast winds. Dry and pleasant weather tonight and Sat under building
ridge surface and aloft. A moisture surge is forecast for sun-Sun night
associated with an area of higher tpw air just east of the Lesser
Antilles and possibly a weak trade wind surge. Drier air begins to
filter in again Monday through the end of next week as upper level
ridge and associated subsidence inversion strengthens further.
Aviation...mostly VFR conds expected at all terminals through the
forecast period. Passing -shra should continue through the early
morning hours across the Atlantic and Caribbean waters...with vcsh
affecting northern PR...USVI and leeward terminals. Scattered layers
between fl050-100. After 16z...vcsh possible at tjps. East winds
below fl100 at 10-18 knots.
Marine...winds around 15 knots through Tuesday then diminish Christmas
evening and Christmas day as high pressure weakens and shifts east. Seas
4-6 feet in mixed swells and wind waves.
Preliminary point temps/pops...
sju 83 70 84 72 / 10 0 20 20
stt 85 75 86 74 / 0 10 20 20