Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 240826

Area Forecast Discussion
National Weather Service San Juan PR
426 AM AST Tue Apr 24 2018

.SYNOPSIS...Enhanced amounts of moisture will linger into today
but drier air is expected to move in by late this afternoon. The
upper trough is expected to continue to move east through the
local islands and the axis should be to our east by this evening,
leaving the local islands in the subsident side of the upper
trough. Ridge aloft to prevail for the rest of the week along with
normal or slightly below normal moisture. Any afternoon shower
and thunderstorm activity for the rest of the week is expected to
be mainly due to local effects. Moderate easterly winds to
continue through the rest of the week.


.SHORT TERM...Today through Thursday...

Cloudy skies prevailed across Puerto Rico and the U.S. Virgin
Islands overnight. A line of showers moved across the eastern half
of Puerto Rico, with only light passing showers affecting the
southeast municipalities of Puerto Rico. Little shower activity was
observed over the U.S. Virgin Islands. Low level moisture embedded
in the trade winds will continue to produce isolated light showers
across the region this morning. For this afternoon, the combination
of low level moisture, with daytime heating and orographic effects
will induce the development of showers with thunderstorms mainly
across the western interior and northwest sections of Puerto Rico.
In the U.S. Virgin Islands, partly cloudy skies are expected with
some passing showers affecting the territory from time to time.

For late this afternoon into tonight, a slot of dry air will
encompass the region. As a result, limited shower activity is
expected tonight and Wednesday. For Thursday, another patch of low
level moisture will affect the region. In addition, a moist east
southeast wind flow will result in good chances for shower and
thunderstorm development mainly during the afternoon hours on

.LONG TERM...Friday through Wednesday...

Near normal moisture and upper ridge will cause a weather pattern
of some isolated to scattered brief showers across the local
waters, USVI and eastern PR during the overnight and early morning
hours. Afternoon shower and possible thunderstorm development will
be mainly due to local effects over PR. Therefore, the available
moisture will combine with the diurnal heating and sea breeze
convergence to cause some showers and possible thunderstorms. This
weather pattern can be expected through the weekend and into
early next week.

The very long range models started hinting at a significant
increase in moisture and in shower activity by next Wednesday as
a frontal boundary settles north of the local islands. This is way
too far into the forecast period and the confidence is very low.
We will continue to monitor but it would not be surprising if the
model guidance varies widely from today until that date arrives.


.AVIATION...VFR conditions will prevail across all TAF sites through
23/17Z. Increasing cloudiness with SHRA/TSRA are expected across
TJSJ, TJMZ and TJBQ from 24/18-24/22z. As a result, brief periods of
MVFR conditions can be expected. Low level winds will be mainly east
southeast at 10 to 15 kts.


.MARINE...Seas are now at 6 feet or less and the winds are
expected to be up to 15 knots across most of the local waters with
some areas that could reach 20 knots. The local seas are expected
to remain up to 6 feet or less for the next several days. There is
a moderate risk of rip currents across many of the local beaches,
please refer to the local surf zone forecast for more information.


SJU  84  75  89  76 /  40  20  20  40
STT  85  75  86  77 /  20  20  40  40


VI...High Rip Current Risk until 6 AM AST early this morning for St



LONG TERM....JA is the U.S. government's official web portal to all federal, state and local government web resources and services.