Area Forecast Discussion
Issued by NWS San Juan, PR

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892
FXCA62 TJSJ 081453
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1053 AM AST Thu Dec 8 2016

.UPDATE...Doppler radar indicated only few isolated showers
across the Caribbean coastal waters. Not precipitation was
detected over land areas so far this morning. Still however
expect the moderate easterly trade winds to bring some showers
across western and interior sections of Puerto Rico this
afternoon. These showers however will be of short duration and
mainly of light intensity. No change to the inherited forecast
package at this time which had good handle on present and expected
short term weather conditions. High pressure ridge will remain as
the main weather feature across the region for the next few days.
Easterly disturbance is expected to pass through the area late
tonight into Friday. This will cause an increase in shower activity
over the area. A more typical December pattern is expected
thereafter with tradewind showers moving in.

&&

.AVIATION...Mostly VFR conditions expected at all TAF sites through
the forecast period. SHRA to develop over PR after 08/16Z, and
may result in brief MVFR conds at JMZ through 08/22z. Winds will
be ENE at 10-15 kt with sea breeze variations developing after
08/13Z.

&&

.MARINE...Slowly subsiding north swell and increasing easterly
trade winds will continue to create a high risk of rip currents
along the Atlantic coastlines of Puerto Rico...Culebra and ST.
Thomas today. Seas are likely up to 6 feet across the offshore
Atlantic waters and the local passages.

&&

.PREV DISCUSSION... /issued 430 AM AST Thu Dec 8 2016/

SYNOPSIS...Surface high pressure to the north of the local
islands will continue dominating the local wind pattern for the
next few days. Winds will be generally from the ene today but
then turning mainly easterly on Friday and continuing for the
next several days thereafter. Ridge in the mid levels will
suppress convection over Puerto Rico but a few showers are still
expected to develop across the interior and western sections of PR
with isolated and brief showers elsewhere. Easterly disturbance expected
to pass through the area late tonight into Friday. This will
cause an increase in shower and thunderstorm activity over the
area. A more typical December pattern is expected thereafter with
tradewind showers moving in.

DISCUSSION...Little to no shower activity was observed across
the local area during the overnight hours. Only isolated showers
across the Caribbean waters were observed. This mainly fair
weather pattern is expected to continue through the morning hours
but modest afternoon convection is expected mainly across the
southwestern quadrant of Puerto Rico...where a few significant
showers are possible. These showers could cause some ponding of
water on roadways and poor drainage areas since the soils are
still very saturated in that area of PR. Only a slight chance of
showers for the rest of the forecast area.

Local available moisture is expected to rise slightly today to a
value of about 1.3 inches for this afternoon before an easterly
disturbance moves in tonight, causing an increase in moisture and
instability...however the deeper moisture is expected to remain to
our south. With the easterly disturbance there will also be an
increase in shower activity and possibly even some thunderstorms.
After the disturbance passes, easterly wind flow will prevail
with patches of higher moisture over the local area. This means
that tradewind showers are expected for the weekend.

AVIATION...Mostly VFR conditions expected at all TAF sites through
the forecast period with VCSH possible at JSJ/IST/ISX through
08/14Z. SHRA to develop over PR after 08/16Z, and may result in
brief MVFR conds at JMZ through 08/22z. Winds will be ENE at 10-15
kt with sea breeze variations developing after 08/13Z.

MARINE...Slowly subsiding north swell and increasing easterly
trade winds will continue to create a high risk of rip currents
along the Atlantic coastlines of Puerto Rico...Culebra and ST.
Thomas. Local buoys are reporting seas generally between 3 and 5
feet...which is consistent with the forecast. Seas are likely up
to 6 feet across the offshore Atlantic waters and the local
passages. Small craft operators are urged to exercise caution for
seas up to 6 feet across the Atlantic waters and local
passages...with winds up to 20 knots across the Caribbean waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  85  76  86  77 /  30  30  30  20
STT  86  77  86  76 /  30  50  50  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 PM AST this evening for Culebra-
     North Central-Northeast-Northwest-San Juan and Vicinity-
     Southeast-Western Interior.

VI...High Rip Current Risk until 6 PM AST this evening for
     St.Thomas...St. John.. and Adjacent Islands.

AM...High Rip Current Risk until 6 PM AST this evening for Coastal
     Waters of Northern USVI and Culebra out 10 NM-Coastal
     Waters of Southern USVI Vieques and Eastern Puerto Rico out
     10 NM.

&&

$$

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