470
FXCA62 TJSJ 192110
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
510 PM AST Sat Oct 19 2024

.SYNOPSIS...

A series of trough and a cold front north of the region will
maintain unstable conditions until mid week. Moisture content will
remain around normal to above normal values, supporting daily
shower activity across eastern sectors of Puerto Rico during the
morning and then the strongest activity is forecast to develop
along the Cordillera Central, moving into northwestern Puerto
Rico. A northerly swell will spread across the Atlantic waters and
passages tomorrow afternoon into Monday.

&&

.SHORT TERM...Tonight through Monday...

The day started with passing showers over eastern sectors of
Puerto Rico and surrounding marine passages. The San Juan
streamer started developing, leaving radar rainfall estimates of
around 1.88 inches in San Juan. A flood advisory was issued for
this area. A Heat Advisory was in effect for the coastal areas of
Puerto Rico, including Vieques, Culebra, and the U.S. Virgin
Islands, until 4:00 PM AST due to heat indexes exceeding the
thresholds established. Occasional showers will continue for the
east coast of PR including Vieques, Culebra, and St. Thomas and
St. John in the U.S. Virgin Islands and the local waters.
Overnight temperatures will drop to the mid 70s to low 80s along
the urban and low elevations while upper 60s to low 70s in the
higher terrains.

Tomorrow, Sunday, similar conditions are expected again with
ESE winds and available moisture, producing showers and
thunderstorms over Cordillera Central and the west/northwest
sections of PR. Rainfall accumulations in roads and poorly drained
areas would increase flooding potential. The latest model
guidance shows precipitable values for Monday ranging from normal
to above-normal values due to a mid to upper-level trough
associated with the cold front. Winds from the SE will pull
tropical moisture into the region, resulting in shower activity
over the southeast and northwest sections of PR including Vieques
and Culebra. Flooding of urban and small streams, with possible
isolated flash floods, are expected.

The latest bulletin from the National Hurricane Center shows
Hurricane Oscar, former Invest 94L, located about 5 miles S of the
Grand Turk moving westward at 10 mph, presenting no threat to Puerto
Rico and the U.S. Virgin Islands.

&&

.LONG TERM...Tuesday trough Friday...

PREV DISCUSSION... /issued 403 AM AST Sat Oct 19 2024/

A mid to upper level trough is expected to exit the eastern coast
of the United Sates on Tuesday. This will result in a south-
southeasterly wind flow through at least Thursday. Therefore, an
increase in moisture pulled from the Caribbean waters is
anticipated. As the moisture field reaches the islands, the
potential for showers and thunderstorms will increase. The
expected activity could result in ponding of water in roads and
low drainage areas, urban and small stream flooding and quick
river risers mainly across the Cordillera Central towards western
Puerto Rico. The latest precipitable water guidances suggest from
1.75 to 2.00 inches for the first half of the period. However, the
second part of the period looks wetter with PWAT values of 1.90
to 2.13 inches. Overall, unstable and wet conditions will persist
through the next weekend. Conditions will slightly improve on
Saturday as drier air establishes over the region. Despite of the
rainfall activity, hot conditions are likely to continue with
elevated heat threat.

&&

.AVIATION...

(18Z)

VFR conds are expected to prevail at all TAF sites through the
forecast period. However, brief period of MVFR conds will remain
possible at JSJ and JBQ through about 19/22z in SHRA/TSRA. ESE winds
at 12 knots to continue with sea breeze variations and higher gusts,
becoming at 10 knots or less overnight. No major hazard expected at
this time.

&&

.MARINE...

A light to moderate east southeast wind flow will continue to
prevail across the local waters during the next several days. A
northerly swell will spread across the Atlantic waters and passages
tomorrow afternoon into Monday, gradually deteriorating marine
conditions particularly across offshore Atlantic Waters.

&&

.BEACH FORECAST...

There is a moderate rip current risk along northern Puerto Rico,
Culebra and the U.S. Virgin Islands. However, a Rip Current
Statement is in effect from Sunday afternoon through Monday
afternoon for most of the north-facing beaches of Puerto Rico,
Culebra, St. Thomas, and St. John. For a more detailed forecast,
please refer to the Coastal Hazard Message (CFWSJU) and the Surf
Zone Forecast for Puerto Rico and the U.S. Virgin Islands
(SRFSJU).

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk from Sunday evening through Monday
     afternoon for PRZ001-002-005-008-012.

     High Rip Current Risk from Sunday evening through late Sunday
     night for PRZ010.

VI...High Rip Current Risk from Sunday evening through late Sunday
     night for VIZ001.

AM...None.
&&

$$

SHORT TERM/MARINE...MNG/YZR
LONG TERM....ERG/GRS
AVIATION...OMS