Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 100201
Area Forecast Discussion
National Weather Service San Juan PR
1001 PM AST Fri Dec 9 2016
.UPDATE...A few light to moderate showers affected portions of
the central and southwest sections of PR during the afternoon
hours. The activity was of short duration with no significant
rainfall accumulations reported or observed. During the late
evening, some low to mid level clouds with embedded trade wind
showers moved across the coastal waters and affected portions of
the north and east coastal sections of Puerto Rico and the adjacent
islands. Most of the showers were of light to moderate intensity
and quick passing.
Recent TJSJ 10/00z upper air sounding suggests trade wind inversion
in place with only a slight increase in pwat values mainly due to
some low level moisture pooling. Overall dry and stable airmass
above 800 millibars. Therefore, expect periods of passing showers
to continue during the rest of the overnight hours and into the
early morning. Gradual clearing and improvement in the weather conditions
can be expected by late morning and the rest of the day on Saturday.
Some locally and diurnally induced afternoon showers will be possible.
However, activity should develop and quickly stream across the region.
No major changes made to the inherited forecast package and reasoning
at this time.
.AVIATION...Mainly VFR conditions expected across all terminals
overnight. VCSH will occur near TIST AND TJSJ but significant
impact on operations not expected. Light and variable winds
expected overnight increasing to 10 to 15 knots from the ENE after
.MARINE...Winds and seas of up to 15 knots and 5 feet or less can
be expected across the regional water overnight. Increasing winds
and Seas expected by Saturday evening and into next week as the
local pressure gradient tightens. This is in response to surface
high pressure building north of the region resulting in locally
fresh trade winds and choppy seas. Precautionary statements will
likely be required.
.PREV DISCUSSION... /issued 200 PM AST Fri Dec 9 2016/
SYNOPSIS...Mid to upper level ridge will hold through at least
midweek. Trade wind pattern will return to the islands during
the weekend. Low level winds will increase across the region as a
strong high pressure builds over the Western Atlantic early next
DISCUSSION...Dry weather conditions prevailed across the local area
this morning. No shower activity prevailed this morning across
land areas. Very dry weather conditions will continue to limit the
shower development across the region. A slight increase in low
level moisture is expected for Saturday night into Sunday as a
patch of cloudiness and showers affect the local region.
High pressure ridge will remain as the main weather feature
across the region for the next few days. Only light passing
showers will continue to affect the local region from time to
time. Overall, dry weather conditions are expected without any
significant weather events affecting the local region in the long
AVIATION...Mainly VFR conditions expected across all terminals
through 10/18z. VCSH could occur near TJMZ but significant impact
on operations not expected. Winds ENE at 10-15 kt with sea breeze
variations across W PR through 23z. Light and variable winds
MARINE...Seas up to 6 feet and winds up to 20 knots are expected.
Small Craft should exercise caution.
.PRELIMINARY POINT TEMPS/POPS...
SJU 78 86 75 85 / 20 20 40 40
STT 76 86 76 87 / 30 30 40 40