732
FXCA62 TJSJ 271952
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
352 PM AST Mon May 27 2024

.SYNOPSIS...

As the tropical wave continues to depart tonight, the east-
southeasterly flow will continue to bring plenty of moisture into
the islands enhancing unstable conditions until at least mid-
week. A drier airmass is expected to filter into the region,
promoting stable weather conditions and warm temperatures by the
end of the workweek.

&&

.SHORT TERM...Tonight through Wednesday...

In the morning, showers filtered across the southeastern and
southwestern municipalities of Puerto Rico, leaving less than
an inch of rain, while the remaining parts of the islands
experienced mostly calm weather conditions. By the early
afternoon, showers and thunderstorms started to develop over the
northwestern and interior sections of Puerto Rico as well as along
the San Juan Metropolitan area. Overall, due to the tropical
wave`s proximity, mostly cloudy skies prevailed over Puerto Rico
and the U.S. Virgin Islands throughout the day. Temperature-wise,
they remained in the upper 80s to low 90s along the coastal and
urban areas, while over the higher elevations, they stayed in the
80s. Despite the passage of the tropical wave some heat indices
along the north central and western Puerto Rico ranged from 105 -
111 degrees Fahrenheit occasionally. The prevailing wind flow was
out of the east- southeast.

Tonight, expect the development of shower activity, particularly
along the eastern half of Puerto Rico and the U.S. Virgin Islands,
as patches of moisture associated with the tropical wave that is
now to the southwest of Puerto Rico filter inland. With this
rainfall, we also foresee some thunderstorm activity. Overnight,
the temperatures should remain in the upper 70s to low 80s along
the coast and in the 70s across the mountains. We anticipate that
the tropical wave will continue to move away overnight.

Despite the anticipated departure of the tropical wave, the deep
east-southeasterly flow will continue to bring plenty of moisture into
the islands through at least mid-week. The latest model guidance
continues to suggest above-normal precipitable water values as
well. The 500mb temperatures will range around -7 degrees Celsius,
meaning that there is a potential for strong thunderstorms to
develop mainly in the afternoons across the interior and western
Puerto Rico through at least the end of the short-term period.
Additional activity is also expected elsewhere at times. The risk
of flooding will stay elevated these days. Also, breaks of
sunshine will be more frequent tomorrow and Wednesday, allowing
for temperatures and heat indices to climb up so that it will feel
muggy, too.

&&

.LONG TERM...Thursday through Monday...
//from previous discussion//

No significant changes have been introduced to the long term
forecast. A mid-to-upper level ridge over the eastern Caribbean is
forecast to persist for much of the period. A drier airmass is
expected to filter into the region, promoting stable weather
conditions and warm temperatures. The general wind flow will
prevail from the southeast and will shift from the south by early
Sunday in response to a building surface high pressure in the
central Atlantic. Despite of the drier air, there is sufficient
low- level moisture from the Caribbean Sea moving into the local
area. This moisture in combination with daytime heating, and
local effects will result in afternoon convective activity across
the interior, north- central and northwestern portions of Puerto
Rico every afternoon. With the expected activity, there is a
limited to elevated risk of urban and small stream flooding in
roads and poor drainage areas. Latest precipitable water model
guidance suggest values between 1.80 to 2.00 inches between Friday
and Sunday. By Friday through Monday a relatively wet pattern is
expected to prevail across Puerto Rico and the U.S. Virgin Islands
as a weak surface trough develop between the Dominican Republic
and the local region. In response, an enhancement in shower and
thunderstorm activity is anticipated as moisture increases. By
Sunday, winds are expected to shift from the south and prevailing
from this direction until at least mid- week. With this
meteorological scenario, warmer temperatures are going to be
present with values between the upper 80s to low 90s along the
coastal and urban areas of the islands. Heat indices are
anticipated to surpass the mid 100s, and could result in
excessive heat conditions for the islands.

&&

.AVIATION...
(18z TAFs)

SHRA/VCTS will result in gusty winds btwn 15-20kt, and will possibly
affect TJBQ (thru 26/23z) and IST/ISX (thru 27/02z). Winds will
prevail mainly from the E-ESE at 13 kt or less, pushing passing SHRA
across JSJ overnight. Afternoon convection will develop tomorrow
(28/16-22z) across PR`s mountain areas and downwind from the USVI.
Expect E winds at 10-15 kt with sea breeze variations and higher
gusts near TSRA after 28/13z, tomorrow.

&&

.MARINE...

A moderate east to southeast wind flow will prevail across the region
over the next few days. The next tropical wave will likely be
approaching the area by mid-week. Currently, it is located in the
central Atlantic along 39W and south of 11N.

&&

.BEACH FORECAST...

There is a low risk of rip currents across all beaches of Puerto
Rico and the U.S. Virgin Islands tonight. Moderate to heavy
showers and isolated thunderstorms are possible with the influence
of a tropical wave just southwest of the region.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...MMC/RAM
LONG TERM....GRS
AVIATION...CAM
PUBLIC DESK...ICP