655
FXCA62 TJSJ 150859
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
459 AM AST Sat Mar 15 2025

.SYNOPSIS...

Today`s instability will decrease as the trough moves away from
the Northeast Caribbean. However, afternoon convection will result
in localized flooding this afternoon. Maximum temperatures in
urban and coastal areas will range between the low and mid 80s,
with localized areas reaching the upper 80s, and in the mountain
areas in the mid to upper 70s. Another mid-to upper- level trough
will amplify from Tuesday onward, with moisture ramping up from
Wednesday onward.

&&

.SHORT TERM...Today through Monday...

Mainly fair conditions prevailed last night, with few clouds moving
over the local area. At this time, stations reported minimum
temperatures slightly colder than yesterday, with lower elevations
of low to mid 70s while higher terrains observed low to mid 60s.

Today will be the wettest day of the short-term period, with a more
stable pattern for the start of the week. The stationary front
remains east of the region, along with a low surface pressure north
of the CWA that will keep winds variable with a northeasterly
component. The latest model guidance suggests that Precipitable
Water values will remain near above normal values (1.4 - 1.5
inches), with enough moisture content for the development of showers
today. Eastern portions of Puerto Rico and the U.S. Virgin Islands
have the highest chance of precipitation in morning. The combination
of local effect, diurnal heating, and sea breeze convergence will
enhance convection activity in the afternoon, mainly over the
interior and southern portions of Puerto Rico. There`s a high chance
of observing ponding of water in roadways, urban, and poorly drained
areas, with isolated urban and small streams flooding. A drier air
mass will filter into the region early Sunday, bringing stability
and fair conditions into the CWA through Monday. Even though PWAT
values will decrease to below normal values, there`s a medium chance
of shower development over interior PR in the afternoon. As the
upper-level trough continues moving away from the local area, warmer
500 mb temperatures and drier air in the mid levels will inhibit
deep convection activity and lower the chance of thunderstorm
activity for the rest of the forecast period.

Temperatures will remain seasonal today, with maximum temperatures
in urban and coastal areas in the low to mid 80s, with localized
areas reaching the upper 80s, and higher elevations in the mid to
upper 70s.

.LONG TERM...Tuesday through Saturday...

On Tuesday, the interaction between an induced surface low in the
Central Atlantic and a cold front moving eastward across the
Western Atlantic will create light and calm winds across the
islands. The Total Precipitable Water (TPW) is expected to be
around one inch, which is below normal and drier than usual for
this time of year. Additionally, a mid to upper-level trough will
approach from the west, potentially enhancing afternoon convection
driven by the sea breeze.

Moisture levels will begin to rise on Wednesday as the frontal
boundary draws nearer to the islands. From Thursday onward,
moisture will pool from the east to east-southeast due to the pre-
frontal trough on Thursday and Friday. This will be followed by
additional moisture being lifted by the low over the Central
Atlantic around Saturday. Instability will be enhanced as the mid-
to upper-level trough also amplifies over the Northeast Caribbean.

&&

.AVIATION...
(06z TAFs)

Mainly VFR conds will prevail at all terminals. Showers associated
with the frontal boundary will enhance -RA/+RA for IST and ISX
around 15/13z and SHRA for JPS after 15/19z, which may reduce CIGs
and lower VIS with temp MVFR conds. Mainly N-NE winds from 5 - 10 kt
btw 15/13-15/23z, then calm to light winds after 15/23z.

&&

.MARINE...

A surface low and associated front moving over the western Atlantic
will maintain light to moderate northeast winds for the next few
days. A long-period northwesterly swell will continue to subside
throughout the day. Another northeast swell will bring hazardous
seas once again late tonight into early next week across the
Atlantic waters and passages.

&&

.BEACH FORECAST...

A subsiding northerly swell will result in moderate to high rip
current risk along the northern coast of Puerto Rico, from Rincon
to Fajardo, as well as northern exposed beaches of Culebra, St
Thomas and St. John. Another pulse of a long-period northerly
swell will spread across the Atlantic waters and local passages
later tonight, increasing breaking waves and promoting life-
threatening rip currents once again. Therefore, the High Rip
Current Risk was extended through late Sunday night.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late Sunday night for PRZ001-002-
     005-008-010-012.

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

AM...None.
&&

$$

SHORT TERM/AVIATION...MNG
SYNOPSIS/LONG TERM/MARINE/BEACH FORECAST...CAM