National Weather Service San Juan PR
543 AM AST Sat Mar 30 2019
.SYNOPSIS...A surface low north of the region and associated
front to the west and north of the forecast area, will continue
to promote instability, low level moisture convergence and light
southeasterly winds through the rest of the weekend. A mid level
ridge will promote drier air and more stable conditions during the
workweek.
&&
.SHORT TERM...Saturday through Monday...
The combination between a surface high pressure over the Central
Atlantic and a low with it associated frontal boundary off to the
north of the islands will maintain a southeasterly wind flow across
the region through at least Sunday. The frontal system will continue
to slowly drift across the Atlantic until it dissipates. This
weather pattern will promote the arrival of patches of moisture
across the islands. In addition, a sub-tropical jet associated with
a mid-to-upper-level trough will aid in afternoon convection along
and to the north of the Cordillera Central and downwind from El
Yunque each afternoon. The U.S. Virgin Islands and the southern
sections of Puerto Rico can expect mostly sunny skies with a few
passing showers during the overnight and morning hours. A similar
weather pattern will prevail on Sunday.
For Monday, the easterly winds are forecast to return as a migratory
high pressure moves from the eastern US into the western Atlantic.
At upper levels, a mid to upper-level ridge will build aloft
reinforcing the trade wind inversion. Moisture will slowly erodes and
temperatures are likely to reach the mid to upper 80s along the
northern sections. Under this pattern, patches of low-level moisture
embedded in the trade winds will move in from time-to-time.
.LONG TERM...Tuesday through Saturday...
Mid level ridge is forecast to build from the western Caribbean
and move over the forecast area during the end of the week. This
will promote dry air and stable conditions aloft. An upper level
westerly jet is expected to remain north of the islands across the
Atlantic. Low level moisture will be capped at 700 MB or less and
peaks on Wednesday and Saturday due to weak surface troughs
moving from the east. In general, diurnally induced afternoon
showers are expected each day over the interior and western
sections of PR and rainfall amounts should be light to moderate.
Passing trade wind showers are expected through the long term
period across the regional waters and they could move at times
across the U.S. Virgin Islands.
&&
.AVIATION...VFR conditions expected to prevail across all terminals
thru 30/16Z. Then, -SHRA/SHRA are expected to develop across the
mountain range of Puerto Rico and downwind from El Yunque. This
activity could affect TJBQ/TJMZ and possibly over TJSJ. Calm to
light and variable winds will continue thru at least 30/13z,
becoming from the southeast around 10 knots with sea breeze
variations after 30/13z.
&&
.MARINE...Fading northerly swell will continue to result in a
high rip current risk across the beaches of Rincon and northern
Puerto Rico. Small crafts should exercise caution due to seas up
to 6 feet across the Atlantic waters. Elsewhere, seas should range
between 3-5 feet. Light southeasterly winds will prevail through
the rest of the weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 86 75 87 75 / 30 30 30 20
STT 85 74 85 74 / 20 20 20 30