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000
FXCA62 TJSJ 110923
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
523 AM AST Thu Apr 11 2024

.SYNOPSIS...Breezy conditions expected through Saturday. The
remnants of an old front will move across the region from later
today through early Saturday. A drier air mass should prevail
through Monday morning. An upper-level trough and higher moisture
content is expected to increase shower and thunderstorm activity
across the islands during by midweek next week. Hazardous seas and
life threatening rip currents will continue for the next few
days.


&&

.SHORT TERM...Today through Saturday...

An overnight radar and satellite imagery analysis indicated
persistent passing shower activity affecting northern and eastern
Puerto Rico, with less frequent showers across Vieques, Culebra, and
the US Virgin Islands. In the last 6 hours, surface observing
stations have reported up to a quarter of an inch in isolated areas.
Clear to partly cloudy skies prevailed elsewhere, particularly over
southwestern Puerto Rico. As reported by official sites, overnight
minimum temperatures ranged from 62 degrees in higher elevations to
78 degrees across lower elevations. Winds were generally from the
east to east-northeast at 10-15 mph with gusts up to 20-25 mph
across windward areas, but light to calm and variable elsewhere.

A strengthening high-pressure system over the western-central
Atlantic will maintain breezy east-to-east-northeast trade winds
during the forecast period. These conditions will be most noticeable
in windward areas, where daytime wind speeds are expected to peak at
15 to 20 mph, diminishing to 10-15 mph at nighttime. The sea breeze
may cause slightly higher speeds and gusts throughout the day. The
prevailing wind flow will maintain an influx of moisture from the
remnants of an old frontal boundary, maintaining moisture levels
within seasonal levels, with precipitable water values fluctuating
between 1.3 and 1.7 inches through Saturday afternoon. By Saturday
night, a drier-than-normal airmass will cause precipitable water to
fall below seasonal thresholds. Meanwhile, a persistent mid-level
ridge and associated trade wind inversion, centered across the
Greater Antilles and west of the forecast area, will prevent
significant convective development. The gradual weakening of the
trade wind inversion is likely from Friday onward as the ridge
shifts further westward.

Passing showers, driven by the prevailing flow, will continue to
affect northern and eastern Puerto Rico, Vieques, Culebra, and the
US Virgin Islands this morning. As the day progresses, the focus of
the showers will shift further inland, driven by sea breeze
convergence, clustering over central to western-southwestern Puerto
Rico. Despite hostile conditions, shallow afternoon convection, like
the morning activity, is likely to occur, producing rainfall totals
of as much as half an inch. Minor flooding on roads and poorly
drained areas is possible. By tonight, the showers` focus will shift
to the local waters into windward areas, producing similar rainfall
amounts. Temperatures should range from the mid 80s at daytime to
around 60 degrees at nighttime. Breezy conditions, as previously
stated, will persist, with a limited to elevated wind hazard risk
across coastal areas and the local islands, where unsecured or
outdoor items could blow around or be damaged.

Friday is expected to follow a similar weather pattern, with
potentially higher rainfall totals and a broader area under a
limited flooding risk as conditions become more conducive to deep
convective activity. However, as moisture levels decrease on
Saturday, fair weather conditions are likely, with fewer and less
frequent showers. Nonetheless, breezy conditions will persist,
posing a limited wind hazard risk.

.LONG TERM...Sunday through Thursday...

Fair weather conditions are expected to prevail on Sunday as a drier
air mass moves briefly over the region. However, diurnally induced
afternoon showers are expected to develop over portions of the
southwestern quadrant of Puerto Rico. Seasonable temperatures are
expected to prevail through early next week. Weakening of the
surface ridge is expected by Monday, and winds speeds will
decrease in general as a front approaches from the northwest, but
remains well north of the region. At the same time and through
midweek, a strong upper level trough is expected to linger over
the region. In response, an induced surface trough is expected to
develop over the eastern Caribbean and promote moisture pooling
over the islands. Therefore, the potential for thunderstorm
activity will increase, as well as for flooding rains as a wetter
and unstable pattern evolves through at least Wednesday night.
Model guidance suggest a quick drying trend from Thursday onwards.


&&

.AVIATION...

(06Z TAFS)

Mainly VFR conditions are expected across all terminals,
with prevailing E-NE winds at 10-15 knots increasing to 15-20 knots
between 11/13-23Z, accompanied by higher gusts and sea breeze
variations. SCT-SHRA may cause VCSH to SHRA and, thus, brief MVFR
conditions across TJSJ through most of the forecast period, USVI
terminals through 11/13Z, and between 11/16-22Z across TJBQ.


&&

.MARINE...

A surface ridge now extending eastward into the central Atlantic
will continue to generate fresh to locally strong east-northeasterly
winds through the rest of the week. This will aid in bringing
periods of passing showers and brief gusty winds to the regional
waters. Northerly swells will continue to spread across the
Atlantic waters and passages through tonight. The wind and swell
interaction will maintain confused, hazardous seas for small craft
over the next few days. For detailed information, please refer to
the Marine Weather Statement (MWWSJU). Seas are forecast to
improve briefly late in the weekend into early next week, and
mainly across the southern and western waters of the islands.


&&

.BEACH FORECAST...

Increasing winds and a long-period northerly swell will generate
dangerous swimming and life-threatening rip current condition,
due to large breaking waves of up to 12 feet and higher at times.
Given these conditions, a High Surf Advisory and High Rip Current
Risk are in effect for the northwest to northeast beaches of
Puerto Rico, Culebra, and the northern US Virgin Islands, where
localized minor beach erosion is possible. Across Vieques and St.
Croix, there is a High Rip Current Risk in effect. For detailed
information, please refer to the Coastal Hazard Message (CFWSJU)
and Surf Zone Forecast (SRFSJU). The high risk of rip currents
will continue through the weekend across the north-facing beaches
of the islands.


&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Saturday afternoon for PRZ001-002-
     005-008-010-012.

     High Surf Advisory until 6 PM AST this evening for PRZ001-002-
     005-008-010-012.

     High Rip Current Risk through Friday afternoon for PRZ013.

VI...High Rip Current Risk through Saturday afternoon for VIZ002.

     High Surf Advisory until 6 PM AST this evening for VIZ001.

     High Rip Current Risk through Friday afternoon for VIZ001.

AM...Small Craft Advisory until 6 AM AST Saturday for AMZ711-712-716-
     723-726-733-741.

     Small Craft Advisory until 6 AM AST Friday for AMZ742.

&&

$$

AVIATION/SHORT TERM...ICP
BEACH/MARINE/LONG TERM....DSR