Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 290036
Area Forecast Discussion
National Weather Service San Juan PR
836 PM AST SAT MAY 28 2016
.UPDATE...Afternoon showers and thunderstorms dissipated rapidly
after sunset...leaving partly to variably cloudy skies across the
region this evening. Doppler weather radar indicated isolated to
scattered showers across the surrounding coastal waters...but at
this time...not significant precipitation was detected over land
areas. For the overnight hours...isolated to scattered passing
showers will affect the U.S. Virgin Islands...Vieques...Culebra...
eastern PR and the surrounding coastal waters. For Sunday afternoon
this moisture will combine with local effect to induce the
development of showers and thunderstorms across interior...western
and northwest PR.
An upper level low just north of Bahamas and its associated upper
trough extending across the greater antilles in combination with
Tropical Storm Bonnie to the east of South Carolina...will
continue to maintain abundant mid to upper level cloudiness across
the forecast area for the next several days. As the Upper trough
moves slowly westward early next week...a week upper ridge is then
expected to establish across the region. The expected southeasterly
wind flow will continue to bring abundant tropical moisture across
the northeast Caribbean...but the expected ridge will inhibit the
development of widespread showers and thunderstorms next week.
.AVIATION...Mostly VFR conditions expected overnight at all TAF
sites with SHRA possible in and around the Leeward and USVI
terminals as well as TJSJ through 29/14Z which may result in MVFR
conds. Cloudiness over the area will cause CIGS at around FL080
tonight and tomorrow. After 29/18Z SHRA and ISOLD TSRA are expected
over and north of the Cordillera and could affect TJBQ/TJMZ and
possible TJSJ. Winds from the ESE at around 10KT overnight...
increasing after 29/13Z to 10 to 15 knots.
.MARINE...Small craft are urged to exercise caution across the
offshore Atlantic waters for winds up to 20 knots. Showers and
isolated thunderstorms expected over the waters through the rest
of the weekend.
.PREV DISCUSSION... /issued 153 PM AST SAT MAY 28 2016/
SYNOPSIS...Upper level low located over the Bahamas and digging
into Cuba...will remain over that general area through at least
the middle of the upcoming week. There is also the current
Tropical Depression 2 to the north of the Bahamas...the proximity
of this Tropical Depression will help pull moisture from the south
and over the local area...the combination of these 2 features will
keep a moist and unstable environment across the Central and
Eastern Caribbean for the next few days. Surface high pressure
northeast of the local area will keep a southeasterly flow through
the end of next week.
DISCUSSION...Scattered to locally numerous showers affected the
local islands in the morning and early afternoon hours...mostly
over the island of St. Croix as well as northern and eastern PR.
Some minor and urban flooding was observed over PR as well as
rapid river rises on those river stemming from El Yunque
Rainforest. As of this writing...showers are still affecting
portions of northern and eastern PR but they have diminished in
intensity. Latest guidance and current observations indicate that
some showers are still expected this afternoon across the north
and eastern portions of PR including the islands of Vieques and
Culebra...some light rain expected over St. Croix.
The upper trough is expected to move slightly to the west by
Sunday...which will cause slightly less instability in the upper
levels over the local area. This means that even though there is
still plenty of available moisture...the expected cloud cover and
the slightly less upper level dynamics should cause less shower
and thunderstorm activity on Sunday. Having said that...there is
still a chance of showers and thunderstorms over the local area.
For next week...the upper trough is still expected to be over Cuba
and perhaps a bit northwest of the Bahamas...this will give way to
an upper ridge establishing over the local islands next week. This
means that we expect to have plenty of moisture with a
southeasterly wind flow but a ridge in the mid and upper levels
which should limit thunderstorm development to only isolated
thunderstorms once the moisture combines with the local effects.
AVIATION...VCSH across most of the local terminals. CIGS at
around FL060 through the afternoon. SE wind flow may cause SHRA to
move into TJSJ later in the afternoon and some SHRA may develop
near TJBQ. Winds will decrease to around 5-10kt after 28/23Z then
increase once again to around 10-15kt after 29/12z.
MARINE...Small craft should exercise caution for winds up to 20
knots and seas increasing up to 6 feet across the offshore
Atlantic waters tonight...decreasing up to 5 feet on Sunday.
Showers and isolated thunderstorms expected over the waters
through the weekend.
.PRELIMINARY POINT TEMPS/POPS...
SJU 78 88 77 88 / 40 40 40 40
STT 79 85 79 86 / 50 50 40 40