342
FXCA62 TJSJ 242017
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
417 PM AST Tue Dec 24 2024

.SYNOPSIS...
Passing moderate to locally strong showers are expected to
continue during the Christmas Eve and Christmas Day, with the
strongest activity anticipated for southwestern Puerto Rico. A
unusually strong pulse of Saharan dust has reached the islands,
with hazy skies expected through mid- week. Marine conditions are
deteriorated due to breezy conditions across the Atlantic waters
and Mona passage.

&&

.SHORT TERM...Tonight through Thursday...

Most sections across western and southern PR, St Croix, and St
Thomas/St John observed calm weather conditions during the morning.
Meanwhile, the eastern third of PR had showery weather through the
morning hours. By the afternoon, showers and a couple of
thunderstorms developed across the western, interior, and south
PR. The maximum temperature for the area of San Juan was 86. A
Flood Advisory was issued for southwest PR because a strong
thunderstorm produced intense downpours.

Satellite data and ground observations indicate an atypical pulse of
suspended African dust particles that will create hazy skies tonight
and tomorrow. Regardless of the suspended dust particles, pockets of
moisture enhanced by low-level convergence will result in showery
weather, especially across the windward sections across the north
and east PR. Ponding of water due to moderate to locally heavy rains
will occasionally affect these locations.

We expect a peak in suspended dust concentrations on Christmas Day.
Each day of the short term, the trade winds will also bring pockets
of moisture with clouds and showers, especially across the north and
northeast PR windward locations. Meanwhile, the rest of the islands
(the USVIs, the leeward locations, and the mountain areas of PR) can
expect a mixture of sunshine or clear skies with clouds. Then,
afternoon showers will develop each day across the interior and
western locations.


.LONG TERM...Friday through Tuesday.../from prev discussion/

Variable weather conditions are anticipated over the long-term
period, with a transition from a relatively wet into a dry and
stable weather pattern. Moisture associated with a frontal boundary
lingering north of the region will continue to promote showery
weather conditions over the weekend. At the same time, a strong
surface high pressure building in the western Atlantic and a surface
low in the central Atlantic will promote a north northeast wind flow
for most of the period. As the surface high pressure migrates
towards the central Atlantic, winds will become more from a
northerly component and pushing the frontal boundary over the local
islands. The latest precipitable water content analysis (PWAT)
guidance has values between 1.64 to 1.85 inches. Under this pattern,
the US Virgin Islands and northeastern Puerto Rico will observe
isolated to scattered showers in the morning hours. Then, followed
by afternoon rainfall over the southwestern quadrant of Puerto Rico.
By Monday into Tuesday, weather conditions are expected to dry out
as a cooler and dry airmass filters into the region. Tropical winter
temperatures will return into the islands, promoting lows in the 50s
and low 60s in the Cordillera Central and from the upper 60s to mid
70s along the coastal municipalities.


&&

.AVIATION...
Expect VFR conds, with passing SHRA, especially at JSJ/IST/ISX
betwn 25/02-12z and near JPS btwn 24/18-22z and 25/18-23z.
Although SHRA will move quickly, it will result in brief MVFR
conditions and gusty winds. Winds will persist from the NE/ENE at
10-15 kt with high gusts during the morning and afternoon,
becoming calm to light and vrb overnight. SHRA/TSRA will develop
north of the islands across the regional waters. Hazy skies with
VIS above 6SM will prevail late tonight into tomorrow.

&&

.MARINE...
A building surface high pressure over the Western Atlantic will
yield moderate to locally fresh east to northeast winds, creating
choppy conditions for small craft. Confused seas will create
hazardous marine conditions across the Atlantic waters. In the
meantime, the remnants of an old frontal will continue to generate
scattered showers and isolated thunderstorm. The Saharan Air Layer
embedded in the trade winds arrived, promoting hazy conditions.

&&

.BEACH FORECAST...
Strong winds are enhancing the risk of life-threatening rip
currents along the north coast of Puerto Rico. Elsewhere, the risk
is moderate. This risk is expected to linger into tomorrow.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Wednesday afternoon for PRZ001-002-
     005-008-010.

VI...None.
AM...Small Craft Advisory until noon AST Wednesday for AMZ711-741.

     Small Craft Advisory until midnight AST tonight for AMZ712.

     Small Craft Advisory until 6 AM AST Wednesday for AMZ742.

&&

$$

SHORT TERM...ERG
LONG TERM....MNG

NWS SJU Office Area Forecast Discussion