285
FXCA62 TJSJ 292148
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
548 PM AST Mon Apr 29 2024

.SYNOPSIS...

The surface high pressure over the western Atlantic will continue
to promote breezy northeasterly winds through at least midweek.
Moisture content will oscillate between normal to above-normal
values tonight resulting in additional showers tonight and
Tuesday. By mid-week onwards, instability and moisture levels
increase once again as a mid to upper level trough lingers over
the western Atlantic and lighter east to southeast winds return.
Coastal and marine conditions will remain hazardous through at
least late Wednesday.

&&

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

During the morning hours until noon, the isolated to scattered
showers moved through the northern, eastern, and interior sectors
of PR and the US Virgin Islands. Doppler radar estimates showed
about an inch of rain in Rio Grande and surrounding municipalities.
By early afternoon, rain continued to move into those areas.
Additionally, the development of more intense showers was recorded
over the southwest of PR. At the moment, the Doppler radar
estimated between 2 and 4 inches of rain over the municipalities
of the SW of PR, where a Flood advisory continues in effect.
Maximum temperatures were from the mid-to-upper 80s across coastal
areas to the 70s and lower 80s across higher elevations.

Tonight into Tuesday morning, additional showers are anticipated to
develop across portions of the USVI, northern and eastern sectors
of Puerto Rico, and the Caribbean waters along with some breezy
and gusty periods. By Tuesday afternoon, expect another active day
with diurnally induced afternoon convection over portions of the
interior and south/southwest PR. We encourage residents and
visitors to remain alert and exercise caution on the roads as
soils are saturated and rain activity may result in additional
floodings.

For the rest of the period, the main weather feature continues to
be a broad surface high pressure moving slowly toward the Central
Atlantic during the next few days. The surface high will promote
breezy conditions with moderate to fresh northeasterly winds
through at least tomorrow, then winds will shift from the east to
southeast and become light to moderate on Wednesday as the surface
high weakens. By the end of the period, an upper-level trough
approaches the area from the west and an induced surface trough
develops over the northeastern Caribbean. Precipitable Water (PW)
models suggest values above the normal climatological levels for
this time of the year. This will enhance shower and thunderstorm
development across much of Puerto Rico. For that reason, the risk
of flooding will likely remain elevated across most islands,
especially during the afternoon hours. It is crucial to be
cautious and aware of these potential risks.

High temperatures will remain in the mid-to-upper 80s along the
coastal and urban areas and in the mid-to-upper 70s along the
mountains and valleys. Minimum temperatures will range from the
upper 70s to low 80s across coastal areas to the mid-60s in the
higher elevations.

&&

.LONG TERM...Thursday through Monday...
.PREV DISCUSSION... /issued 434 AM AST Mon Apr 29 2024/

The inherited forecast remains unchanged. Recent model guidance
suggests a mid-to-upper-level trough developing and staying
nearly stationary over the west to southwestern Atlantic, at least
through the long-term period. From Thursday onwards, expect the
winds to become lighter as the surface high pressure north of the
area continues to weaken. By Thursday, remnants of an old frontal
boundary will reach the island from the northeast and merge with a
trough or perturbation over the northeastern Caribbean. This will
lead to unstable and wetter weather conditions across Puerto Rico
and the U.S. Virgin Islands, with possible flooding impacts and
mudslides in areas of steep terrain across Puerto Rico. At this
time, Precipitable Water (PW) models suggest values above two
standard deviations and, therefore, above the normal
climatological levels for this time of the year. We anticipate
active afternoons during the long-term period, with possible
flooding impacts and mudslides in areas of steep terrain across
Puerto Rico. For the USVI, an increase in the frequency of showers
and isolated thunderstorms is possible from Thursday onwards.
Heat indices across the lower elevations of the islands could
likely range between 102 and 106 degrees on Friday and Saturday
before the onset of afternoon convection. Overall, an unstable and
wetter patternis expectedto evolve over thelong-term.

&&

.AVIATION...
(18z) TAFS

VCSH and period of SHRA are possible tonight into tomorrow morning
across TJSJ and USVI TAF sites. Tomorrow around 14Z, possible
TSRA in TJPS and prevailing VCSH across the rest of the sites. NE
winds at 12 or less during the overnight period, increasing
tomorrow morning with stronger gusts near 25-30 kt during the day.

&&

.MARINE...

A sub tropical high pressure across the western Atlantic will
continue to promote moderate to fresh trade winds through at least
Wednesday night. As a result, expect hazardous seas for small
craft operators due to confused seas associated with the
increasing winds and a northeasterly swell spreading across the
local waters. Small Craft Advisories are in effect for the
Atlantic waters and most local passages.

&&

.BEACH FORECAST...

A northerly swell and stronger winds are resulting in High Risk
of Rip Currents across beaches from Mayaguez to Fajardo, Culebra,
and USVI through at least late Wednesday. For more information
and details about the latest forecast please refer to the Surf
Zone Forecast (SRFSJU) and the Coastal Hazard Message product
(CFWSJU).

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late Wednesday night for PRZ001-
     002-005-008.

     High Rip Current Risk through late Wednesday night for PRZ010-
     012.

VI...High Rip Current Risk from Tuesday morning through late
     Wednesday night for VIZ001.

     High Rip Current Risk from Tuesday morning through Tuesday
     afternoon for VIZ002.

AM...Small Craft Advisory until midnight AST Wednesday night for
     AMZ711-712.

     Small Craft Advisory until 6 PM AST Wednesday for AMZ716.

     Small Craft Advisory until noon AST Wednesday for AMZ723-742.

     Small Craft Advisory until noon AST Wednesday for AMZ741.

&&

$$

SHORT TERM/MARINE/BEACH FORECAST...YZR
AVIATION..YZR/CVB
LONG TERM....MMC
PUBLIC...ERG