National Weather Service Today's Weather Impact Levels

000
FXCA62 TJSJ 222027
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
427 PM AST Mon Apr 22 2024

.SYNOPSIS...

Scattered showers will continue to move overnight across portions
of eastern Puerto Rico and the USVI. A wet and unstable weather
pattern is expected to continue through at least the end of the
workweek. Weather conditions will gradually improve by Saturday
with the entrance of a drier airmass. Saharan dust is forecast to
arrive on Tuesday promoting hazy skies across the region.

&&

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

Persistent shower activity was observed today across the local area.
Heavy showers and isolated thunderstorms affected portions of
eastern and northern Puerto Rico, including the San Juan metro area.
Doppler radar estimated rainfall accumulations between 2 to 4
inches from Dorado to Canovanas, and around 1 inch elsewhere
during the afternoon hours. Flood Advisories (FLS) were issued for
the mentioned areas. Line of showers and gusty winds were also
observed across the local Caribbean and Atlantic waters, where
Marine Weather Statements (MWS) were issued. Daytime temperatures
stayed in the mid 80s along the coastal and urban areas, and in
the upper 70s to low 80s across the mountains. Winds prevailed
from the northeast at 10 to 15 mph, with higher gusts embedded in
the heavy showers.

Scattered to numerous showers will continue across the region during
the overnight hours. The main focus area will be the eastern half of
Puerto Rico and the waters of the Anegada Passage. This unstable
weather pattern will persist until the end of the workweek,
promoting showers and isolated thunderstorms each day. Tuesday
seems to be the day with less activity due to Saharan dust.
However, instability will return on Wednesday, maintaining
elevated the potential for flooding, excessive runoff, and
landslides. Please be aware that flood advisories/warnings are
possible with the expected rainfall activity.

.LONG TERM...Thursday through Monday...

.PREV DISCUSSION.../Issued 414 AM AST Apr 22 2024/

The wet pattern will not give way by the end of the workweek.
Moisture associated with an old frontal boundary will reach the
islands, triggering another round of showers and isolated
thunderstorms. At the same time, a deep layered trough moving east
of the United States will cause the winds to shift from the south
at the mid and upper levels, while winds will remain from the east
steered by a surface high pressure over the central Atlantic. The
southerly flow will bring a moist column into the region, while a
short wave trough (the type that increase instability aloft) will
approach the region. These factors should combine to generate more
rainfall activity. Since it has been raining for a couple of days
now, rivers will remain high and soils saturated, hence the risk
for urban and small stream flooding will be elevated.

A change in the pattern will begin on Saturday. A broad surface
high pressure exiting the eastern seaboard will push a drier air
mass into the region...finally. Winds will become more northerly,
so temperatures will cool down a little too. The probability of
precipitation decreases Saturday onward, although with some
showers due to local effects still possible. This drier pattern
should stretch into early next week.


&&

.AVIATION...(18Z TAFs)

SHRA/TSRA could lead to MVFR conditions at TJBQ/TJSJ/TJPS thru
22/23z. MVFR conds should prevail thru the rest of the period. HZ
due to Saharan dust has reached the USVI terminals, but VSBY should
remain P6SM. Winds blo 2500 ft from the SE up to 20 kts, bcmg light
and variable overnight.

&&

.MARINE...

A surface high pressure north of the area will continue to yield a
moderate northeasterly wind flow through at least today. Winds are
expected to become from the east southeast on Tuesday as a surface
trough prevails across the northeast Caribbean. Showers and isolated
thunderstorms will continue to affect the local waters through at
least Tuesday.

&&

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

$$

SHORT TERM...CAM
LONG TERM....GRS
PUBLIC DESK...LIS

NWS SJU Office Area Forecast Discussion