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404
FXCA62 TJSJ 290842
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
442 AM AST Sun Mar 29 2026

...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST...

.KEY MESSAGES...
Issued at 433 AM AST Sun Mar 29 2026

* A drier and generally fair weather pattern will prevail today,
  with limited shower activity and mostly fair weather conditions
  across Puerto Rico.

* Moisture will gradually increase starting Monday as a frontal
  boundary approaches from the northwest, leading to a return of
  more frequent showers and afternoon convection, especially
  across interior and southwestern Puerto Rico.

* Across the U.S. Virgin Islands, mainly passing showers are
  expected through Monday, followed by a noticeable increase in
  shower activity by Tuesday as deeper moisture spreads into the
  area.

* Marine and coastal conditions are expected to deteriorate early
  next week as a northerly swell arrives and winds increase. This
  will likely result in Small Craft Advisories and Rip Current
  Statements, with hazardous breaking waves and dangerous surf
  conditions possible.

&&

.Short Term(Today through Tuesday)...
Issued at 433 AM AST Sun Mar 29 2026

A drier and generally fair weather pattern is expected to prevail
across the region today as a relatively dry air mass filters in
under an east-northeasterly wind flow. Model guidance indicates
precipitable water values near to slightly below climatological
normals, supporting limited shower development. Any activity that
forms will be brief and primarily affect windward areas during the
morning, followed by isolated convection across interior and
southwestern Puerto Rico during the afternoon. Overall, rainfall
coverage and intensity will remain minimal. Temperatures will stay
seasonable to slightly cool, especially across higher elevations.

By Monday, conditions begin to transition as moisture gradually
increases across the region ahead of an approaching frontal
boundary. This change is accompanied by a tightening pressure
gradient between a building surface high over the western Atlantic,
in the wake of the boundary, and the frontal boundary to the
northwest. As a result, 925 mb winds increase notably, promoting a
stronger east-northeasterly flow across the local area. This
enhanced low-level flow will advect patches of moisture into the
region, with precipitable water values rising to near or above
normal levels, and 700-500 mb relative humidity increasing to nearly
two standard deviations above normal for this time of year. Expect
more frequent passing showers across windward areas during the
morning, followed by increased afternoon convection across interior
and southwestern Puerto Rico. While instability remains modest, the
combination of moisture and stronger low-level winds will support
periods of moderate to heavy rainfall.

On Tuesday, the frontal boundary draws closer to the region, further
tightening the pressure gradient and maintaining elevated low-level
winds. Moisture content continues to increase, with precipitable
water values exceeding climatological thresholds and deep-layer
humidity becoming more favorable for widespread cloud development.
This will lead to a more active weather pattern, with scattered to
numerous showers and isolated thunderstorms developing across the
Atlantic waters and spreading into the U.S. Virgin Islands and
Puerto Rico. Afternoon convection across interior and
western/southwestern Puerto Rico will become slightly more
widespread, supported by local effects and a lingering troughiness
aloft. The combination of stronger winds and higher moisture content
may result in periods of moderate to locally heavy rainfall. Given
antecedent conditions, there will be an elevated risk of localized
flooding, particularly in urban areas, poorly drained locations, and
along rivers and streams. Nevertheless, faster steering winds will
help limit rainfall accumulations as showers move more quickly
across the region.

In summary, a relatively dry and generally fair weather pattern
today will give way to a progressively more unsettled regime by
early next week, driven by increasing moisture, strengthening low-
level winds associated with a tightening pressure gradient, and the
approach of a frontal boundary.

&&

.Long Term(Wednesday through Sunday)...
Issued at 433 AM AST Sun Mar 29 2026

High pressure centered well north in the Atlantic and an induced
surface trough northeast of the islands will maintain a strong
northeasterly wind flow through the end of the week. As the surface
trough moves north of the island on Friday and the weekend, the
winds will shift from the southeast. It will be breezy through at
least Thursday, with speeds of 15 to 20 knots. On Wednesday and
Thursday, under the northeasterly wind flow, the surface trough will
push a drier air mass above the 700 mb-layer into the northeastern
Caribbean. As a result, precipitable water values will drop to near
normal values for this time of the year. On these days, the focus of
rain should be in the northeast and the Virgin Islands early in the
day, followed by stronger showers in the afternoon for the interior
and southwest. The atmosphere does not look particularly favorable
for heavy rainfall accumulations, although the mid-levels will be
cool enough for at least for isolated lightning each afternoon.

Moving into the end of the week and the weekend, a new upper level
low will dig from the southeastern United States. For Friday and
Saturday, the latest guidance show a vorticity maximum at the upper
levels, with some low level convergence too. However, some dry
intrusion persist in the mid-levels. Since the winds will shift
from the southeast, diurnal heating is expected to be stronger.
Therefore, there is a medium chance that showers may grow enough to
break through the drier air, and reaching the favorable conditions
aloft. For now, the forecast call for stronger thunderstorms in the
afternoon hours, but moderate rainfall accumulations, focused along
the interior and western municipalities of Puerto Rico.

&&

.AVIATION...
(06Z TAFS)
Issued at 433 AM AST Sun Mar 29 2026

Mainly VFR conds expected across all TAF sites thru the pd. Sfc
winds generally light/VRB ovrnght, bcmg E-ENE 8-12 kt aft 29/13Z,
with ocnl higher gusts. Limited SHRA activity expected due to
drier airmass, though brief -SHRA psbl ovr windward areas btwn
29/12-16Z. Aftn convection may support iso SHRA ovr interior/west
PR, but impacts to TAF sites expected to remain minimal.

&&

.MARINE...
Issued at 433 AM AST Sun Mar 29 2026

A surface inverted trough located northeast of the  local islands
will sustain light to moderate east-northeast winds early today, but
winds will be increasing to moderate to fresh by the afternoon,
resulting in choppy seas. Additionally, winds will pick up after a
cold front moves toward the region from the Western Atlantic by
Monday. Furthermore, another long-period northerly swell will create
hazardous marine conditions, expected to last through the entire
week. These conditions will be dangerous for small craft
operators.

&&

.BEACH FORECAST...
Issued at 433 AM AST Sun Mar 29 2026

Today, the moderate risk of rip currents continues along the
northwest, north, and eastern beaches of Puerto Rico and Culebra.
Also, across the U.S. Islands tonight. This means that life-
threatening rip currents are possible in the surf zones, as a result
beachgoers should exercise caution. From Monday night into the rest
of the week, beach conditions are anticipated to become hazardous
due to the arrival of a long-period northerly swell combined with
increasing winds. Life-threatening rip currents will be likely in
the surf zones and dangerous surf conditions along the north-facing
exposed coastlines cannot be ruled out. Residents and visitors are
urged to monitor the forecast and alerts over the coming days.

&&

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

$$

SHORT TERM & AVIATION...CVB
LONG TERM...ERG
MARINE & BEACH FORECAST...YZR

NWS SJU Office Area Forecast Discussion