Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 261530
Area Forecast Discussion
National Weather Service San Juan PR
1130 AM AST THU MAY 26 2016
.UPDATE...No significant changes from the previous discussion and
forecast package. High clouds are present over the local
area...particularly over Puerto Rico and the northern USVI.
Visible satellite shows some cloudiness developing in the lower
levels as the winds comes onshore and lifts with the local
mountains. There is also some clouds streaming off the
USVI...Vieques and Culebra. The 12Z sounding indicated that the
available moisture is about normal for this time of the year and
enough to help produce a few showers across the western interior
and western portions of Puerto Rico in the afternoon. However
these high clouds currently over Puerto Rico may limit the
shower development to only scattered showers.
Available moisture will decrease slightly tonight into Friday
morning...increasing moisture once again during the day on
Friday...which will increase the chances of rain.
.AVIATION...VFR conditions expected through the forecast period.
VCSH across TJMZ and TJPS after 26/17Z until 26/22Z...with a
slight possibility of the SHRA affecting the terminals and causing
MVFR conds. Winds prevailing from the E-NE with sea breeze
.MARINE...No changes from previous discussion. Seas up to 5 feet
and winds generally around 10-15 knots.
.PREV DISCUSSION... /issued 555 AM AST THU MAY 26 2016/
At upper levels, a mid to upper level ridge will continue over the
Eastern Caribbean. While a trough, and it associated Low near
Bahamas, continues anchored over the Western Caribbean. At low
levels, a surface high pressure over the Central Atlantic will
weakens. An induced surface low, off to the north of Hispanola,
will move toward the Florida Peninsula.
Mostly cloudy skies prevailed over during the overnight hours...as
mid to upper level clouds moved over the region. The Doppler
radar detected showers moving across the local waters and some of
them moved inland but no significant amounts were measured.
Satellite imagery showed plenty of clouds across the region or
moving toward the local islands, as a result partly to mostly
cloudy skies are expected this morning. Although little to no
shower activity is expected...some brief passing showers still
possible across the eastern sections of Puerto Rico and the U.S.
Virgin Islands this morning. Then during the afternoon, locally
and diurnally induced convection is likely mainly across portions
of the west interior sections of Puerto Rico. Elsewhere, expect
little to no shower activity. A similar pattern is expected on
Both the GFS and the ECMWF guidances are suggesting the erosion of
the upper level ridge...as a deep layer trough amplifies over Cuba
and Bahamas during the next few days. This pattern will promote
the transport of tropical moisture across the Caribbean region. If
this pattern hold, the potential for shower and thunderstorm
activity should increase across the local region during the
weekend and the upcoming week.
AVIATION...VFR conds expected to prevail at all TAF sites during
the forecast period, with thin but incrg high/mid clouds moving
across the from the SW. SHRA/TSRA development expected across W PR
aft 26/17z and will cause mtn obscurations and areas of MVFR conds
in and around TJMZ through 26/22z. Winds increasing to 10 to 15
knots from the east after 26/12Z. Winds alf bcmg SW arnd FL170 and
incrg to W 60 kt by FL460.
MARINE...Winds and seas will continue to slowly subside across
the region as the surface High pressure over the Central Atlantic
weakens. Therefore...expect moderate winds and seas of 3-5 ft over
the region. However...if the model guidance are correct...mariners
should expect an increase in shower and thunderstorm activity
across the local waters by the weekend and into the upcoming week.
.PRELIMINARY POINT TEMPS/POPS...
SJU 88 79 90 76 / 20 30 30 30
STT 89 79 87 78 / 20 30 30 40