Special Weather Statement, NWS JSJ

Area Forecast Discussion
National Weather Service San Juan PR
1152 AM AST Mon Mar 22 2021

.UPDATE...

A drier air mass filtering from the east and combined with a mid
to upper-level ridge will limit shower activity today. However,
local effect and sea breeze convergence will aid in showers across
the western portions of PR and downwind from El Yunque. Tomorrow
an approaching upper-level trough will increase instability over
PR and the U.S. Virgin Islands region. The limiting factor for
Tuesday is the available moisture.

&&

.AVIATION...

VFR conditions will prevail today. Cloudiness and showers will
produce SCT to BKN ceilings across the interior and western PR and
may affect JBQ between 22/18-23z. Winds will continue from the E
at 10-15 kt with higher gusts and sea breeze fluctuations.

&&

.MARINE...
Choppy marine conditions will continue due to winds  between 15
and 20 knots and seas around 5 feet. Therefore, small craft
operators should exercise caution. A Small Craft Advisory is in
effect for the Atlantic Offshore waters between Monday morning (8
A.M.) to Monday afternoon (2 P.M.).

Beachgoers expect a high risk of rip currents across the north-
facing beaches of Puerto Rico, St Thomas, and Culebra.

&&

.PREV DISCUSSION... /issued 441 AM AST Mon Mar 22 2021/

SYNOPSIS...

Mostly tranquil conditions are expected for today as drier air
moves into the region. However, this dry air coupled with breezy
winds will lead to elevated fire danger for the Southern Coastal
Plains. Tomorrow will have a better chance for showers as an
upper level trough moves in from the west along with increased
moisture. A weak swell is currently impacting the Atlantic waters
today, with a Small Craft Advisory in effect till 2 PM this
afternoon.

SHORT TERM...Today through Wednesday...

A shallow area of moisture from a weak low-level trough will move
from the east today across the islands. However, as the upper level
ridge continues to hold over the eastern Caribbean; this should only
cause typical light morning showers over portions of the U.S. Virgin
Islands and eastern sections of Puerto Rico. Due to the presence of
drier air and stable conditions at upper levels, only locally
induced afternoon showers are expected to develop downwind from el
Yunque into San Juan and vicinity and over portions of central and
western Puerto Rico. Ponding of water in roads and in other poor
drainage areas is expected with this activity.

For Tuesday, an upper level jet and short wave trough at 500 mb
moving from the west will further weaken the upper level ridge and
promote unstable conditions over the region. Precipitable water
content is expected to increase from around 1.00 inch today to near
1.40 inches by Tuesday afternoon. The 500 mb temps will also drop
from around -6.5 degrees Celsius to -9.5C by Tuesday evening, these
two factors should promote isolated thunderstorm development during
the afternoon/evening hours over the interior and western sections
of PR. Therefore, the potential for urban and small stream flooding
will increase. For Wednesday, another ridge is expected to build
from the west as the upper trough moves further east. Weather
conditions should improve, however, lingering low-level moisture
will combine with daytime heating, the sea breeze convergence and
other local effects to cause shower development along portions of
the Cordillera Central and western PR during the afternoon.

LONG TERM...Thursday through Monday...

Generally seasonal weather is expected for the long-term period,
with patches of moisture moving in from the east. Thursday looks
fairly dry and uneventful. A high pressure ridge aloft will exist
to our west, with troughing to our east. The atmosphere will
generally be dry, and under the influence of the ridging, with
below average precipitable water expected. High pressure at the
surface to our north will encourage breezy winds and lead to
fairly quick moving isolated showers, and these showers will
likely be unimpactful. Conditions will be more conducive for
showers on Friday. A weak patch of moisture is expected to arrive
during the day on Friday which will encourage shower development.
Furthermore, these showers may be enhanced by a trough of low
pressure aloft that will dig down over our region. One limiting
factor to the showers that will develop is that winds will remain
breezy at low-levels, leading to fast moving and less impactful
showers. However, any persistent showers over a given area may
lead to ponding of water over roadways and low-lying areas.

The weekend looks mostly dry. The aforementioned trough pushes
further south and east and a ridge will once again influence our
region with drier and more stable conditions. A few patches of
moisture will pass through during this period and into Monday as
well, but their impact is forecast to be minimal. Winds will
increase from Friday and into the weekend, and this will keep
showers moving quickly, and also may negatively impact marine
conditions.

AVIATION...

Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hours. However, SHRA is expected to
develop in and around TJSJ/TJBQ from 16z-22z, and may cause tempo
MVFR conds. East-southeast winds increasing to 10-15 kt with sea
breeze variations and higher gusts after 14z.

MARINE...

A weak northerly swell is producing hazardous seas for the outer
Atlantic waters today. There is a Small Craft Advisory out for
these waters through 2pm today, with choppy seas into Tuesday.
However, seas under 5 feet are expected for the next few days
thereafter. Approaching the weekend, winds are expected to pick up
which may once again result in Small Craft Advisory conditions.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  87  73  86  73 /  20  20  40  30
STT  84  73  84  72 /  40  20  30  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late tonight for Culebra-Mayaguez
     and Vicinity-Northeast-Southeast.

     High Rip Current Risk through Tuesday afternoon for North
     Central-Northwest-San Juan and Vicinity.

VI...High Rip Current Risk through late tonight for St.Thomas...St.
     John...and Adjacent Islands.

AM...Small Craft Advisory until 2 PM AST this afternoon for Atlantic
     Waters of Puerto Rico and USVI from 10 NM to 19.5N.

&&

SHORT TERM...CAM
LONG TERM....GL
PUBLIC DESK...CVB

Perspectivas sobre Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorologia en San Juan PR
519 AM AST domingo 21 de marzo de 2021

AMZ710>745-PRZ001>013-230915-
San Juan y Vecindad-Noreste-Sureste-Este Interior-Norte Central-
Interior Central-Ponce y Vecindad-Noroeste-Oeste Interior-
Mayaguez y Vecindad-Suroeste-Culebra-Vieques-Las aguas costeras
cercanas y lejanas a la costa del Atlantico y Caribe-
501 AM AST lunes 22 de marzo de 2021

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Puerto Rico y las aguas costeras del Atlantico.

.Dia Uno...Hoy y esta noche

.Inundaciones...Aguaceros en la tarde pudieran resultar en acumulacion
de agua sobre carreteras y en areas de pobre drenaje.

.Viento...Se esperan vientos en exceso de 20 mph (17 nudos) a traves
de sectores de las aguas mar afuera y aguas costeras de las islas.

.Olas...Se espera oleaje picado de hasta 7 pies a traves de las aguas
mar afuera del Atlantico.

.Corrientes Marinas...Existe un riesgo alto de corrientes marinas
para las playas del norte de Puerto Rico y Culebra.

.Dias dos hasta el siete...lunes a sabado

El riesgo de corrientes marinas se mantendra alto para el norte de
Puerto Rico hasta el martes. Existe la probabilidad de tronadas el
martes sobre sectores del interior, norte y oeste de Puerto Rico, lo
cual pudiera resultar en inundaciones urbanas y de riachuelos. Se
pronostica que el viento y oleaje aumenten durante el fin de semana.

.Comunicado sobre informacion reportada por observadores...

No se espera activacion amplia de observadores. Favor de reportar
cualquier informacion sobre vientos, oleaje y corrientes marinas al
Servicio Nacional de Meteorologia en San Juan mientras siguen las
indicaciones de las autoridades locales y estatales.

AMZ715-725-VIZ001-002-230915-
San Tomas, San John e Islas Adyacentes-
Santa Cruz-Aguas cercanas del Atlantico y aguas
costeras adyacentes del Caribe-
501 AM AST lunes 22 de marzo de 2021

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Islas Virgenes Estadounidenses y las aguas costeras adyacentes.

.Dia Uno...Hoy y esta noche

.Viento...Se esperan vientos en exceso de 20 mph (17 nudos) a traves
de sectores de las aguas mar afuera y aguas costeras de las islas.

.Olas...Se espera oleaje picado de hasta 7 pies a traves de las aguas
mar afuera del Atlantico.

.Corrientes Marinas...Existe un riesgo alto de corrientes marinas
para las playas del norte de San Tomas.

.Dias dos hasta el siete...lunes a sabado

Un riesgo moderado de corrientes marinas prevalecera a traves de las playas
del norte de San Tomas, y a traves de las playas del norte y este de Santa
Cruz hasta el fin de semana. Se pronostica que el viento y oleaje aumenten
durante el fin de semana.

.Comunicado sobre informacion reportada por observadores...

No se espera activacion amplia de observadores. Sin embargo, favor
de reportar cualquier informacion sobre vientos, oleaje y corrientes
marinas al Servicio Nacional de Meteorologia en San Juan mientras
siguen las indicaciones de las autoridades locales y estatales.