646
FXCA62 TJSJ 070824
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
404 AM AST Sat Jun 7 2025

.KEY MESSAGES...


* Increasing surface winds will likely generate moderate to
  locally fresh winds, resulting in wind-driven seas. Therefore,
  small craft operators should exercise caution. Small Craft
  Advisories may be needed across the offshore waters.

* Warmer-than-normal temperatures are likely to continue through
  the weekend across most coastal and lower elevations of the
  islands.A heat advisory could needed on Monday.

* Above-normal moisture associated with a tropical wave, along
  with increasing instability, might result in a rise in showers
  and thunderstorms by midweek next week.

&&

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

Isolated morning showers will drift across the local waters,
primarily affecting the eastern portions of Puerto Rico and the
surrounding island, but are not expected to produce significant
rainfall accumulations through at least mid morning.

Showers amd cloud cover are expected to increase later this morning
as available moisture combines with daytime heating and local sea
breeze convergence, generating sufficient instability for convective
development by early afternoon. The main area of activity will be
over the western interior and northwestern Puerto Rico.
Additionally, CU lines may develop over La Sierra de Luquillo and
drift westward, potentially impacting the San Juan Metro area later
this afternoon.

A surface high pressure system over the central Atlantic will
maintain an easterly wind flow, gradually shifting to an east-
southeasterly direction later today. As the high pressure
strengthens over the region, wind speeds are expected to
increase, resulting in breezy to locally windy conditions across
the forecast area.

On Monday, a southerly component of the winds will increase the
potential for high temperatures...a Heat Advisory could be issued.

.LONG TERM...Tuesday through Friday...

Current model guidance has precipitable water (PWAT) values at up to
above normal to start the long term period as moisture, in part from
a tropical wave over the Caribbean Sea, is steered into the local
islands under east-southeast flow. However, a Saharan Air Layer
(SAL) will also reach the islands, promoting hazy skies. While PWAT
values will gradually decrease, a more notable mass of drier air is
forecast to arrive by Friday. A surface high pressure over the
Atlantic will continue building during the period, promoting breezy
to locally windy easterly to east-southeasterly steering flow. A mid-
level ridge will be present to start the period, but it will
gradually weaken as a mid-level low moves into the central Atlantic.
The typical diurnal pattern will continue with patches of moisture
and showers reaching windward sectors of the islands, especially
during the mornings and overnight hours, and with afternoon showers
and thunderstorms mainly over interior to western Puerto Rico due to
sea breeze convergence, diurnal heating and local effects. Lines of
showers can also develop downwind of the local islands and El
Yunque. An elevated flood potential will persist over interior to
western Puerto Rico. Highs will be in the upper 80s to low 90s at
lower elevations and coastal areas , with heat indices over 100
degrees. A limited heat risk will persist for most coastal and lower
elevation areas. Lows will be in the 60s for higher elevations of
Puerto Rico and in the 70s to around 80 over lower elevations of the
islands. Although moisture will gradually decrease, the frequency of
showers could be higher due to an upper level trough from the
northeast, and another tropical wave moving into the Caribbean Sea
by the end of the forecast period.


&&

.AVIATION...
(06Z Taf)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. Any SHRA that develops will be brief, ESE
winds and local effects can produce VCSH near TJBQ/TJSJ through
07/22Z, no impacts to operations expected. Winds from the ESE at
15- 20kts, with higher gusts, through 07/23Z when they are
expected to decrease. Winds will increase to similar values again
after 08/13Z.


&&

.MARINE...A surface high pressure system over the central Atlantic
will continue to support moderate to locally fresh trade winds,
shifting from the east to southeast over the weekend. This will
generate choppy conditions across the local waters mainly during
the peak of sea breeze wind speed enhancement. Isolated
thunderstorms are expected to develop each afternoon over the
western waters of Puerto Rico. Additionally, a tropical wave is
forecast to move across the eastern Caribbean around Tuesday.


&&

.BEACH FORECAST...Increasing winds across the region will continue
to elevate the threat of rip currents along most beaches in Puerto
Rico and USVI through the reminder of the weekend. As wind driven
seas build, hazardous swimming conditions will become more
widespread. Even when the rip currents threat is categorized as
low , dangerous rip currents can still form unexpectedly,
especially near structures such a piers, reefs, and jetties.
Beachgoers are reminded to remain vigilant and exercise caution
when entering the waters, regardless of the daily risk level.


&&

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

$$

SHORT TERM...EM
LONG TERM....MRR
AVIATION...EM