Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 302007

Area Forecast Discussion
National Weather Service San Juan PR
407 PM AST Mon Jan 30 2023

.SYNOPSIS...Variable and drier weather conditions will persist,
though slightly drier than previous days. Near normal moisture
levels may promote increased cloud cover and showers by the latter
part of the workweek. Below seasonal temperatures are likely due
to persistent northeasterly winds. Breezy conditions and small
northeasterly swells will maintain choppy to hazardous marine
conditions for small craft and life-threatening rip currents for


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

Although local weather conditions remain variable, extended
periods below seasonal moisture values will lead to slightly drier
conditions. Except for flooding hazards, which no longer pose a
threat, the remaining potential hazards remain the same, with rip
currents at moderate to high risk levels and marine and winds at
limited to elevated risk levels. A meandering mid-level high
pressure centered over Cuba will maintain a strong trade wind cap
and drier conditions aloft, hostile to deep convective
development. At the surface, a set of high pressure systems over
the western Atlantic and a trough well to our east-northeast will
remain the dominant synoptic features through the cycle. This
combination will continue to promote moderate to fresh
northeasterly winds, steering irregular patches of moist and drier
air into the region while leading to choppy to hazardous seas for
small craft.

Precipitable water vapor variations from these patches will
fluctuate between 0.9 and 1.2 inches, but extended periods below
1.1 inches will support a generally fair and dry weather pattern.
Still, following the wettest patches` possible arrival times,
cloud cover and shower activity will likely increase by Wednesday
evening, when precipitable water vapor values could peak around
normal seasonal levels. During the rest of the period, expect a
mixture of sunshine or clear skies interrupted by the occasional
passing shower. The resulting daily rainfall accumulations, which
can peak around 0.25-0.50 inches with the most frequent showers,
should not pose a threat. Yet, localized ponding of waters on
roadways and poorly drained areas is possible. Limited afternoon
convective development is also possible across the interior to
southwestern sections of Puerto Rico, but any effect will be

Normal to slightly below-normal seasonal temperatures will
continue, ranging from the mid 80s across lower elevations during
the daytime to the mid 50s across higher elevations at nighttime.
However, increased cloud cover may keep maximum (minimum)
temperatures at lower (higher) values. Surface winds will remain
out of the northeast, varying from 5-10 mph with land breeze
variations at night to 10-20 mph with higher gusts and sea breeze
variations during the daytime.


.LONG TERM...Wednesday through Sunday...

From previous discussion issued at 435 AM AST Mon Jan 30 2023

The current forecast continues on track. A surface high pressure
located in the western to central Atlantic is forecasted to be the
dominant feature across the local area. Local weather is expected
to be variable with patches of moisture dragged by the trade
winds. These patches will support shower activity across the
northern, northeastern and eastern Puerto Rico at times and as
well the US Virgin Islands. The general wind flow will continue
from the east to northeast, supporting afternoon convection across
the western portions of Puerto Rico with showers that could lead
to ponding of water in roads and poor drainage areas. By the
second half of the long term period, a small perturbation coming
from the east will increase the potential for more showers across
the local area. A slight change on the wind flow from the east to
southeast will bring more humidity, increasing the frequency of
showers towards the central interior and northwestern portions of
Puerto Rico. The Precipitable Water content values between 1.35 to
1.62 inches indicates a humid a wetter pattern for the end of the
period. Temperatures across the islands are expected to be lower
than normal due to the northeast winds. Expect cooler
temperatures, especially over the mountains during the overnight


.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals during the next 24 hrs. Generally NE winds up to around 20
kts, will steer passing trade wind showers inland from the offshore
Atlantic. Shower activity could impact TJSJ/TJBQ/TIST/TISX, higher
wind gusts especially near the strongest showers could be


.MARINE...Moderate to locally fresh northeast winds up to 20
knots, gusting up to 30 knots, and small northeasterly swells will
maintain hazardous marine conditions across most local waters. As
a result, Small Craft Advisories remain in effect for the
nearshore and offshore Atlantic waters, offshore Caribbean waters,
Anegada and Mona Passages, and the coastal waters of northwestern
Puerto Rico. Elsewhere, small craft operators should continue to
exercise caution due to wind-driven choppy conditions. Some
improvement is likely late tonight, but Small Craft Advisories
will remain for the most exposed waters.

For beachgoers, a high risk of rip currents remains in effect for
beaches across the northwest to the northeast coast of Puerto
Rico, Culebra, and all the U.S. Virgin Islands, where life-
threatening rip currents are likely. Life-threatening rip currents
are possible across the remaining north- and southeast-facing
beaches of Puerto Rico and Vieques.


PR...High Rip Current Risk through late Wednesday night for PRZ001-

VI...High Rip Current Risk through late Wednesday night for VIZ002.

     High Rip Current Risk through late Tuesday night for VIZ001.

AM...Small Craft Advisory until 2 AM AST Thursday for AMZ710-712.

     Small Craft Advisory until 2 PM AST Wednesday for AMZ715-741.

     Small Craft Advisory until 2 AM AST Wednesday for AMZ722-742.

     Small Craft Advisory until 2 PM AST Tuesday for AMZ732.



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