National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXCA62 TJSJ 140905
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Sun Apr 14 2024

.SYNOPSIS...
A surface ridge over the north-central Atlantic and a broad induced
trough extending northwards from across the eastern Caribbean, will
promote moderate east- northeasterly winds during the rest of the
morning, then become more easterly in the afternoon and on Monday,
as the surface trough spreads farther westwards into the east central
Caribbean. A slot of drier air crossed the region overnight with only
a few passing showers noted across the local waters and brushing the
coastal areas of islands from time to time. A wetter weather pattern
is expected by late afternoon and into the early part of the upcoming
week due to the interaction of an amplifying upper- level trough and
increasing tropical moisture associated with the broad surface trough
across eastern Caribbean. This will support increasingly moist and
unstable conditions across the region, with high potential for
shower and thunderstorm development and the chance for heavy
rainfall across the region. Consequently there will be a heighten
risk of flooding and possible landslides across the forecast area.

&&

.SHORT TERM...Today through Tuesday...

Clear to partly cloudy skies were observed throughout the overnight
hours. An area of low to mid-level moisture reached the eastern
Caribbean, and passing showers were noted across the Anegada Passage.
Light showers were noted over land areas at times. Minimum temperatures
ranged from the low and mid-60s at higher elevations to the mid and
upper 70s at coastal areas. Wind gusts were around 20 mph in coastal
regions.

A more unstable and wet weather pattern will evolve earlier than anticipated
during the short-term period. A surge in moisture from the Leeward Islands
will reach the local area throughout the day today. This will increase
the frequency of passing showers across portions of the USVI and eastern
PR, followed by diurnally induced afternoon showers over the interior
and western sections of PR. Be prepared for ponding of water on roads
and low-lying areas, with increasing chances for minor flooding by
tonight across the eastern half of the CWA.

On Monday and Tuesday, a further increase in showers and thunderstorm
development is expected across the islands as a mid-to- upper-level
trough moves from the northwest and a low-level trough develops over
the eastern Caribbean. These features will promote colder 500 mb
temperatures of -7 to -8 degrees Celsius and cause the precipitable
water content to remain above normal levels (around 2.00 inches) through
the first half of the workweek. The threat of urban and river flooding
will remain elevated during the first part of the workweek. There is
also a possibility of isolated flash flooding and landslides/rockfall
in steep terrain.

.LONG TERM....Wednesday through Sunday...
Wednesday through at least early Thursday morning, inclement
weather and a moist and unstable environment will persist due to
the lingering mid to upper trough crossing into the northeastern
Caribbean. This will provide good ventilation aloft along with the
advective low level moisture pooling for a continued showery pattern
and isolated thunderstorm development. The low level moisture convergence
caused by the east southeast winds and local and diurnal effects will
favor good potential for thunderstorm development and flooding rains
at least until late Wednesday or early Thursday. Thereafter, recent
model guidance continued to initialize well and still suggest moisture
erosion with increasing stable conditions aloft by Thursday afternoon.
A gradual drying trend is expected from then onwards, as a mid to upper-
level ridge will build northwards from the western Caribbean, and a
surface high pressure ridge builds across the west Atlantic. This in
will bring a return of east-northeast winds once again through Friday,
followed by winds becoming more easterly and increasing over the
following weekend. This expected pattern will also lead to an overall
drier airmass at least Thursday through Friday, followed by the return
of occasional passing trade wind showers and more typical isolated
to scattered afternoon showers in and around the islands over the
weekend.

&&

.AVIATION...
(06z)

Mainly VFR conditions expected early in the cycle. SCT/BKN cigs at
FL030-FL060 and periods of SHRA could increase around 14/14z across
the USVI terminals, and after 14/18z across the PR terminals. Winds
will continue from the ENE at 13-17kts, with higher gusts and sea
breeze variations aft 14/13z. MVFR to brief IFR conditions are
possible aft 15/00z and through Monday morning, mainly at
TIST/TISX/TJSJ.

&&

.MARINE...
A surface ridge over the north-central Atlantic and broad trough
over the eastern Caribbean will generate moderate to locally fresh
east- northeasterly winds. A fading northerly swell and choppy wind-
driven seas will continue to promote confused seas. The interaction
of an approaching upper level trough and a broad induced surface trough
spread across the eastern Caribbean will promote increasing
shower and thunderstorm activity across the local waters beginning
by later this evening and into early next week.

&&

.BEACH FORECAST...
Pulses of a weak north-northeasterly swell will continue across
the northern regional waters the rest of today. Additionally wind-
driven seas will contribute to hazardous breaking waves to around
6 feet. As a result, the Rip Current Statement was extended through
at least until Monday afternoon for all beaches across the northern
coastline of Puerto Rico and Culebra. For more information and details
please refer to the latest Surf Zone Forecast (SRFSJU), and the Coastal
Hazard Message product (CFWSJU).

&&

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

VI...None.
AM...Small Craft Advisory from noon today to 6 PM AST Tuesday for
     AMZ711.

     Small Craft Advisory from noon today to 6 PM AST Monday for
     AMZ723.

&&

$$

SHORT TERM...DS
LONG TERM....RAM
AVIATION...DS