Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 271515
Area Forecast Discussion
National Weather Service San Juan PR
1115 AM AST FRI MAY 27 2016
.UPDATE...Mostly cloudy skies have prevailed across the local
islands during the morning hours as a large area with high clouds
moves over. Scattered brief showers have also affected the USVI
and eastern PR as well as the local waters as moisture moves in
with the prevailing southeasterly flow. Because of the
cloudiness...the temperature at the San Juan International Airport
has only reached 87 degrees...which is a few degrees lower than it
has the past few days. The USVI has also remained at 87 degrees or
Some adjustments were made to the inherited forecast. The latest
guidance suggests that additional moisture will be moving in for
this afternoon and into the evening...with it bringing scattered
showers which may continue to affect eastern PR and the USVI. Also
the northern half of PR...especially the northwestern quadrant of
PR...may observe developing showers with a slight chance of
thunderstorms. Despite the cloudiness...the clouds are thinner
across N-NW PR...which may allow for some more showers to develop
once the available moisture combines with the sea breeze
convergence. So the pops were taken down slightly but there is
still a chance of rain and isolated thunderstorms in the
afternoon. Scattered brief showers across the rest of the local
Latest guidance also suggests that the weekend could bring some
more significant rain to the local area. Moisture may increase
quite a bit but there is some uncertainty because some of this
moisture advection may be heavily influenced by the development of
the disturbance to the north of the Bahamas. We will have to
monitor the development of this disturbance.
.AVIATION...VFR conds expected through the forecast period with
VCSH for most of the terminals. Cloudiness over the area will
cause CIGs at around FL080 today. SHRA and ISOLD TSRA possible
across NNW PR...which could affect areas near TJBQ after 27/18Z.
Winds from the ESE at around 10KT...decreasing winds after 27/23Z.
.MARINE...No changes from the previous discussion. Seas generally
3 to 5 feet and up to around 15 knots. Winds to increase late
tonight into Saturday to 15 to 20 knots.
.PREV DISCUSSION... /issued 617 AM AST FRI MAY 27 2016/
At upper level, a ridge aloft will continue to slowly erode
during the next few days, as a deep mid-upper level trough, with a
close low over Bahamas-Cuba, sinks southeast into the forecast
area during the weekend. At the surface...a low pressure system
located over the Bahamas is favoring moisture transport across the
Central and Eastern Caribbean. A broad area of high pressure
across the Central Atlantic continues to weaken. A tropical wave
located near the Lesser Antilles will approach the local area
during the next few days.
Mostly cloudy skies prevailed across the local area overnight.
The Doppler radar detected shower activity across the local
waters...some of them moved inland but less than 0.10 inches of
rain were estimated. Coastal winds were light and variable with
temperatures ranging between the upper 70s and low 80s. For the
morning hours, expect partly to mostly cloudy skies with
occasional passing showers across the local waters, the U.S.
Virgin Islands and the southern and eastern sections of Puerto
Rico. At this time, we cannot ruled out afternoon convection over
the interior and western sections of Puerto Rico.
Over the weekend and into early next week, the operational models
suggest a wetter pattern, as a mid-upper level ridge erodes and
the trough aloft amplified into the region. As a surface low
pressure system, near the Bahamas moves toward Eastern U.S., deep
tropical moisture will move into the local area. As a result, high
moisture content combined with favorable upper dynamics will
increase the potential for organized convection across the
forecast area, especially Sunday and Monday. This expected moist
weather pattern is all dependent on how the expected weather
pattern unfolds over the western Atlantic during the next few
days. Regardless, all models suggest a much wetter pattern during
the latter part of the Memorial day weekend.
AVIATION...Mostly VFR conditions thru the rest of the night and
early in the morning with only VCSH across the Leeward
Islands...USVI and TJSJ taf sites until 27/14Z. SHRA and pos VCTS
after 27/17Z across TJMZ and TJBQ. Sfc winds will remain from the E
at around 10-15 knots.
Fairly tranquil seas will continue today with seas up to 5 feet
and winds generally around 10 to 15 knots...by Saturday winds are
expected to increase at 15 to 20 knots. Shower and thunderstorm
activity is expected to increase across the local waters during
the weekend and into the upcoming week.
.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 87 77 / 50 30 50 40
STT 86 79 86 78 / 40 40 40 40