505
FXCA62 TJSJ 142128
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
528 PM AST Tue May 14 2024

.SYNOPSIS...

Stable weather pattern will prevail during the morning hours,
followed by afternoon convection across the western interior of
Puerto Rico each day. Clear to partly cloudy skies in the morning
will allow warmer temperatures, especially during the early
afternoon hours. Due to warm temperatures and moisture content,
heat indices will fluctuate between 102 and 107 degrees Fahrenheit
or even higher mainly across urban and coastal areas. Therefore,
residents should stay hydrated and tune in for further updates. A
similar pattern is forecasted until Thursday when surface winds
will increase from the southeast. Instability will be a defining
factor for the upcoming workweek, increasing the potential for
shower development.

&&

.SHORT TERM...Tonight through Thursday...

During the morning hours, calm weather conditions prevailed across
the islands with easterly winds around 5 to 10 mph. During the
early afternoon hours, some showers developed across western
central municipalities. Based on radar estimates, around one to
one inch and a half fell across those areas. Warm temperatures
were observed across the coastal and urban areas, with heat
indices generally ranging between 100 to 108 degrees Fahrenheit.
For tonight`s period, expect quiet weather conditions, while some
showers are possible across the Atlantic and western PR coastal
waters.

The short-term period forecast remains on track. A mid-to upper
level high-pressure system will continue spread eastwards across
the region from the west and southwest Atlantic, while a surface
high pressure will build across the west Atlantic. As a result,
a more stable and seasonal trend should continue for the next
several days. Latest model guidance as well as satellite derived
analyses suggest seasonal PWAT values, ranging between 1.4 and 1.7
inches the rest of today, then slightly increase to between
1.5-1.8 inches for the rest of the period. In summary, expect calm
weather conditions with some isolated showers possible across
eastern sections of Puerto Rico during the morning hours, followed
by afternoon convection across the western interior of Puerto
Rico each day due to local effects and diurnal heating.

Warm temperatures will continue to be one of the main topics of
this period, with daytime temperatures peaking in the upper 80s
to low 90s along the coastal and urban areas and heat indices
above 100 degrees Fahrenheit. Residents and visitors to the
islands are urged to stay hydrated and limit direct sun exposure
when possible.


&&

.LONG TERM...Friday through Tuesday...
.PREV DISCUSSION... /issued 457 AM AST Tue May 14 2024/

The long-term forecast remains on track. A broad surface high-
pressure extending from the north-central Atlantic into the
Caribbean will maintain the east-southeasterly wind flow across
the region. During the first section of the period, tropical
moisture dragged by the surface winds and some instability (lower
250 MB height) will trigger afternoon convection each day. An
induced surface trough will weaken the pressure gradient at the
north, resulting in southeasterly light to moderate winds. Surface
winds from the southeast will drive most of the showers across
Puerto Rico`s interior and northwestern quadrant. The most
vigorous shower activity and the light steering flow would result
in enough rainfall accumulation to cause a minor flooding threat.
By Monday into Tuesday, mid to upper-level conditions change, as a
trough results in instability aloft and colder temperatures at the
500 MB level. According to the Galvez-Davison Index (GFS output),
there is a high probability of experiment-isolated thunderstorms,
especially in the afternoon hours each day. Given the expected
conditions, the flood threat is forecast for the last part of the
long-term.

&&

.AVIATION..
(18Z TAFS)

Mainly VFR conditions expected to prevail through the fcst
period. SHRA and possible isolated TSRA expected over the western
Cordillera Central, with mountain obscuration through 14/23Z. VCSH
expected at the TJSJ/TJBQ/TJPS through 14/22-23Z. Winds are from
the ESE btw 10- 13 kts through 14/23Z, then becoming more from the
E at 10 kts or less trough 15/14Z.

&&

.MARINE...

A surface high pressure over the western Atlantic will continue
to promote light to moderate easterly winds across the region.
These conditions will lead to tranquil marine conditions across the
local waters, with seas up to 2 to 4 feet. Winds should veer more
from the east-southeast from Thursday onwards due to a surface
high pressure in the central Atlantic.

&&

.BEACH FORECAST...

There is a low rip current risk tonight across all area beaches of
Puerto Rico and the U.S. Virgin Islands. The risk will likely
remain low for the next several days.

&&

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

&&

$$

SHORT TERM/MARINE/BEACH FORECAST/PUBLIC...YZR
AVIATION...GRS/CAM
PREV LONG TERM....LIS