National Weather Service San Juan PR
441 AM AST Sat Apr 22 2023
.SYNOPSIS...
Today, expect the surface induced low and mid-level trough
northwest of Puerto Rico to continue approaching the area through
the weekend. This weather pattern will increase the potential for
stronger showers during the weekend, with an enhanced risk for
flooding. The weather will improve by early next week as drier air
moves in across the region.
&&
.SHORT TERM...Today through Monday...
A surface low is located about 600 miles north-northwest of the
islands. This is resulting in weak surface winds over the region. It
is also associated with a frontal boundary that is now just
north/northwest of the islands, promoting increased moisture over
the area. Aloft is also a deep-layer trough, as well as an upper-
level jet around 250 hPa with speeds of around 70 kts. As such,
there is good instability over the area today. Passing showers will
continue over the waters this morning, pushing onshore from time to
time. This afternoon, showers will develop over the interior of
Puerto Rico, primarily along the mountains, with the initial focus
along the Cordillera Central. Showers and thunderstorms will drift
generally eastward/northeastward, with the stronger storms meeting
with the stronger winds aloft, and therefore those are the ones most
likely to reach eastern and northeastern Puerto Rico and beyond.
Rainfall totals of around 1 to 3 inches are expected in the affected
areas, but locally higher amounts are possible. Flooding is a
concern, mostly in the form of minor and urban and small stream
flooding, but some flash flooding is possible.
Moisture persists tomorrow, as well, with the bulk of the moisture
from the frontal boundary remaining over or near the islands, moreso
in the south and east. Furthermore, a shortwave trough aloft will
bring a resurgence in instability following a decrease overnight.
Overall, a decrease in shower and thunderstorm activity is expected
for Sunday compared to today, but still it will be an active day.
During the overnights and mornings, the passing showers are more
likely to affect western and northwestern Puerto Rico. Through
Sunday night, activity will decrease as drier air moves into the
region. Much less active weather is expected for Monday.
&&
.LONG TERM...Tuesday through Sunday...
No significant changes have been introduced into the current
forecast. On Tuesday, as the low-pressure surface system opens,
expect a more typical weather pattern of occasional morning
showers across the east and afternoon convection across the
interior and western quadrant of Puerto Rico and the U.S. Virgin
Islands. This weather feature will be followed by a high surface
pressure system east of the Leeward Islands. The high pressure is
forecast to bring an area of enhanced moisture into the
northeastern Caribbean. The moisture content will remain below
normal to around normal climatological levels. Precipitable water
model at all levels shows most PWAT values below the 700mb through
at least Saturday. By the end of the weekend, models are showing
some discrepancies in the forecast. Therefore, the long-term
period remains under revision.
&&
.AVIATION...Overall VFR conds expected for terminals today. SHRA/TSRA
developing over interior PR, esp Cordillera Central, and into NE
and N central PR. Could see MVFR or worse at TJSJ, with lower risk
for MVFR at TJPS/TIST. Terrain obscurations likely. Low risk for
impacts in afternoon for TJBQ/TISX. Passing SHRA/TSRA tonight over
the waters, moving onshore in W and NW PR. Cannot rule out MVFR
for TJBQ, mostly betw 23/02Z & 23/10Z. Winds light to around
FL050, except in/near SHRA/TSRA.
&&
.MARINE...Small craft operators can expect winds out form the
south around 5 and 10 knots with ocasional seas up to 5 feet. The
small northerly swell continues to propagate across the Atlantic
Ocean and Caribbean Passages. The risk of rip currents is moderate
along the north- facing beaches in Puerto Rico, St Croix and
Culebra.
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&
$$
SHORT TERM...CS
LONG TERM....MMC