National Weather Service San Juan PR
313 AM AST Tue Apr 21 2020
.SYNOPSIS...
A mid to upper level ridge will continue to hold across the
region, promoting a mainly fair weather pattern across the
islands. However, patches of moisture embedded in the trade winds
will cause brief showers interruptions from time to time. This
pattern is expected to continue through early next week, although
with stronger winds for the end of the workweek into the weekend.
&&
.SHORT TERM...Today through Thursday...
Mid to upper level ridge will hold across the region through the
most of the period to maintain fairly dry and stable conditions
aloft. Surface high pressure ridge across the north central Atlantic
will maintain an east to southeast tradewind flow across the
forecast area. Expect a moderate trade wind cap inversion to persist
across the forecast area and consequently promote mostly fair
weather conditions. Light to moderate east southeast tradewinds will
persist through the short term period. This will continue to bring
shallow patches of low level moisture with a few embedded showers
across the region from time to time. The overall weather pattern
will therefore limit moisture pooling and only favor brief periods
of passing showers, mostly of light to moderate intensity each
morning along some of the coastal areas. This will be followed by
locally and diurnally induced afternoon showers. The shower activity
should be focused mainly across portions of the interior and west to
northwest sections of Puerto Rico, as well as around parts of the
San Juan metro where a brief showers cannot be ruled out. Some of
the heavier rain-showers may lead to ponding of water on roadways
and in poor drainage area in isolated areas. Mostly sunny to partly
cloudy skies and fair weather conditions should prevail elsewhere
and across the U.S. Virgin Islands.
Significant and persistent rainfall is not anticipated over the
islands during the period, except for the passing morning showers,
followed by the diurnally induced afternoon showers in isolated
areas. However, the best potential for afternoon convection will be
on Wednesday and Thursday when a weak easterly perturbation and
a surge of shallow moisture will cross the region.
.LONG TERM...Friday through Wednesday...
High pressure at all levels will continue to hold over the
Atlantic ocean through much of the long-term forecast period. The
surface feature will tighten the pressure gradient over the
eastern Caribbean resulting in increasing winds through the
weekend. Otherwise, a mainly tranquil weather pattern is expected
to prevail, with precipitable water values forecast to remain at
0.9 to 1.2 inches through Monday. However, patches of moisture
embedded in the trade winds will continue to arrive to the area,
causing passing showers across eastern Puerto Rico and the U.S.
Virgin Islands. In the afternoon hours, as is usual with this
pattern, additional activity is expected to develop over western
Puerto Rico. Since moisture is expected to be trapped at the lower
levels due to the mid-level high, significant rainfall activity
is not anticipated. By Tuesday and Wednesday, the latest guidance
are showing an increase in moisture as an easterly disturbance
reaches the area, that should increase the chance of showers over
the islands.
&&
.AVIATION... VFR durg prd. SCT ocnl BKN lyrs nr FL028...FL050
en route btw islands and ovr regional waters with Isold SHRA til
21/14Z. VCSH at TJBQ/TJMZ/TJSJ btw 21/17Z-21/22Z. SFC wnds lgt/vrb
AT 5 kts or less, bcmg 10-15 kts with sea breeze variations aft
21/14Z.
&&
.MARINE...
Seas up to 5 feet with winds mostly at around 15 knots are
expected across the local waters. A northerly swell will arrive
later today, but seas should remain below small craft advisory
criteria. A moderate rip current risk continues for the northern
coast of Puerto Rico and Culebra, and for a few beaches at Vieques
and the U.S. Virgin Islands.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 89 76 90 77 / 30 30 40 30
STT 81 77 82 78 / 30 40 40 40