Funnel Cloud in Puerto Rico, November 27, 2020

Area Forecast Discussion
National Weather Service San Juan PR
320 PM AST Fri Nov 27 2020

.SYNOPSIS...

Very dry air will persist and even increase across the region over
the next few days. Though showers are possible, primarily for
southwest Puerto Rico tomorrow afternoon, these showers will
likely be unimpactful and even drier air moves in for Sunday and
Monday. The chances for showers look somewhat better later next
week, but drier than normal conditions will continue.

&&

.SHORT TERM...

A very dry airmass is currently over the region, and even drier air
is expected as we head into the weekend. At mid- to upper-levels,
high pressure exists to the west with lower pressure to the
northeast. Northerly flow over our region continues at these levels,
bringing slightly cooler temperatures and dry air. Over the next
24 to 72 hours, high pressure will build in over our region from
the west, warming our atmosphere and drying us out even more. As a
result, very calm weather conditions are expected for the next
few days. East-northeast surface winds will continue over the
region at around 10 to 15 mph each day for the short-term period.

Despite the very dry air, isolated to scattered showers are still
possible at times. In particular, a patch of moisture will move in
tomorrow during the daytime, and possibly be enhanced by the daytime
heating effects. Thus afternoon showers will be possible for
southwestern Puerto Rico, and high-resolution models do advertise
this. Behind this patch of moisture, extremely dry air moves in
for Sunday. In fact, model guidance suggests precipitable water
values dropping to around .7 inches, which is far below average
for this time of year. Thus, only weak isolated showers are
possible.

.LONG TERM...Monday through Friday...

.PREV DISCUSSION... /issued 410 AM AST Fri Nov 27 2020/

The GFS and EURO continue to show drier air and relatively tranquil
weather at the beginning of next week, followed by a return in
moisture at the end.  A surface and mid-level high pressure will
influence the local climate by strengthening the trade wind cap and
producing east to northeast wind flow across the area. The east to
northeast winds will pull drier air from the Atlantic waters into
the region.  The above conditions will inhibit the development of
deep convection. Still, patches of shallow moisture moving in from
time to time and local and diurnal effects will help develop shallow
convection mainly during the afternoon.

Wednesday and Thursday, the GFS has an Upper-level low and a
negatively titled trough near the Great Lakes. The upper-level low
is forecast to deepen and push a frontal boundary through central
Florida and another into the Atlantic Waters.  As the trough moves
into the western Atlantic, it will weaken the mid-level ridge
that has dominated the local weather and allow moisture from the
Atlantic waters to advect into the area.

Thursday, the GFS develops a weak perturbation north of Puerto Rico
and brings a wind surge with moisture into the region. The weak
perturbation and moisture increase will cause an uptick in shower
activity for Puerto Rico and the U.S. Virgin Islands through Friday.

&&

.AVIATION...

VFR conds expected across the local terminals. VCSH is
possible this afternoon across the local terminals, especially for
TJPS. Winds will remain from the NE at around 10 KT through the
afternoon with sea breeze variations. Winds will decrease during the
night time hours with ISOL/SCT SHRA expected, causing VCSH across
the local terminals.

&&

.MARINE...

Seas are continuing to calm down today due to the weakening
northerly swell. Therefore, the Small Craft Advisory has been
cancelled. Seas will still be choppy for tomorrow, so small craft
operators should exercise caution in the Atlantic waters. By
Sunday during the day, seas will be below 5 feet and these calmer
conditions will continue for the next several days thereafter.
High rip current risks continue for the north coasts today, but by
tomorrow only the northwest coast of Puerto Rico will see a high
risk.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  85  76  85 /  40  30  10  20
STT  75  84  76  84 /  30  40  20  20

&&

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

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

AM...Small Craft Advisory until 8 PM AST this evening for Anegada
     Passage Southward to 17N-Atlantic Waters of Puerto Rico and
     USVI from 10 NM to 19.5N-Coastal Waters of Northern Puerto
     Rico out 10 NM-Coastal Waters of Northern USVI and Culebra
     out 10 NM-Coastal Waters of Northwestern Puerto Rico out 10
     NM-Mona Passage Southward to 17N.

&&

SHORT TERM...RAM
LONG TERM....MB
PUBLIC DESK...GL

Perspectivas sobre Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorologia San Juan PR
428 AM AST viernes 27 de noviembre de 2020

AMZ710>745-PRZ001>013-280830-
San Juan y Vecindad-Noreste-Sureste-
Este Interior-Norte Central- Interior Central-Ponce y Vecindad-
Noroeste-Oeste Interior-Mayaguez Vecindad-Suroeste-Culebra-Vieques-
Aguas cercanas y mar afuera y del Atlantico y Caribe-
428 AM AST viernes 27 de noviembre de 2020

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...Lluvias de moderadas a localmente pueden resultar en
inundaciones urbanas y de riachuelos sobre el suroeste de Puerto
Rico.

.Oleaje...Se espera oleaje picado de hasta 7 pies a traves de las
aguas del Atlantico y los pasajes.

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

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

Un riesgo alto de corrientes marinas pudiera continuar para las
playas del noroeste de Puerto Rico hasta el sabado. Luego, se espera
que continue un riesgo moderado para las playas del norte y este de
las islas hasta la proxima semana.

.Comunicado sobre informacion reportada por observadores...

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

AMZ715-725-VIZ001-002-280830-
San Tomas, San John e Islas Adyacentes-
Santa Cruz- Aguas cercanas del Atlantico y aguas costeras adyacentes
del Caribe-
428 AM AST viernes 27 de noviembre de 2020

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

.Dia Uno...Hoy y Esta Noche

.Oleaje...Se espera oleaje picado de hasta 7 pies a traves de las
aguas del Atlantico y los pasajes.

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

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

El riesgo moderado de corrientes marinas continuara durante el fin
de semana para las playas del norte de San Tomas y este de Santa
Cruz. Un riesgo moderado continuara para Santa Cruz durante la
proxima semana.

.Comunicado sobre informacion reportada por observadores...

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