Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 280137
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
937 PM AST Mon Feb 27 2017

.UPDATE...Sea breeze convergence and day time heating led to afternoon
shower development over southwestern Puerto Rico. Just over half
an inch of rain was reported with this activity in Cabo Rojo.
Also, showers from streamers were observed between the USVI and
eastern PR. During the early evening hours trade wind showers
were increasing across the regional waters. Breezy conditions are
expected to bring periods of passing showers across the USVI and
the north and east sections of Puerto Rico through early Tuesday
morning. Latest 28/00z TJSJ sounding indicated the ENE trade wind
cap at 15-23 kts.

&&

.AVIATION...VFR conditions will prevail across the flying area
through the forecast period. VCSH are expected across TJSJ, TIST and
TISX, TNCM and TKPK overnight. Low level winds will be mainly from
the ENE at 15-25 kts below FL150.

&&

.MARINE Update...As of 8 PM, buoy data across the coastal waters
of the islands were indicating seas between 3-5 feet and east to
northeast winds between 15-17 knots with gusts up to 21 knots.
Winds and seas are forecast to gradually increase overnight
through the rest of the week across much of the local waters. Wind
driven seas are expected to reach 8 feet on Tuesday and small
craft advisories will be in effect through the rest of the work
week. A high risk of rip currents is expected by Tuesday
afternoon across most of the east and north facing beaches of
Puerto Rico and St. Croix.

&&

.PREV DISCUSSION... /issued 157 PM AST Mon Feb 27 2017/

SYNOPSIS...
A ridge pattern aloft will continue through at least mid week. A
weak shortwave trough is forecast to move near the islands by
Wednesday afternoon. A strong surface high pressure to the north
of the area will produce breezy conditions through the workweek.
Patches of surface moisture will move across the islands each day.
Therefore, a trade wind pattern will dominate the local weather
through the week.

DISCUSSION...
Shower activity diminished across the islands as a dry air mass
spread from the east over the region. However, the available
moisture combined with the local effects and diurnal heating will
be enough to produce scattered showers across the interior and
southwest portions of Puerto Rico. In addition, shower activity is
expected to form downwind from the U.S. Virgin Islands. Elsewhere,
expect mostly sunny to partly cloudy skies with little or no
shower activity. Satellite imagery showed another surge of
moisture near the Lesser Islands, which is expected to reach the
U.S. Virgin Islands by tonight. Therefore, once again another
round of passing showers is expected across the Windward sections
overnight and early Tuesday morning.

A strong surface high pressure over the Western Atlantic will
maintain breezy conditions most of the week. This trade wind
pattern will bring patches of moisture with showers and clouds
from time to time each day.

An upper level shortwave trough will swing by the region around
Wednesday afternoon. Although local instability will increase as a
result of this feature, the limiting factor will be the lack of
surface moisture. After midweek, once again another ridge pattern
is forecast to return.

AVIATION...
VFR conds will prevail across the flying area. VCSH will affect
the TJMZ later afternoon. Another band of moisture will bring
scattered showers to the forecast area on Tuesday. As a result...
Brief MVFR cigs are possible after 28/10Z at TNCM/TKPK, TIST/TISX
and TJSJ at times. Low level winds of 15-25 kts will continue
below FL150.

MARINE...
Winds and seas are forecast to increase. This will produce wind
driven seas between 6 and 8 feet and easterly winds between 15 and
25 knots. Therefore, Small Craft Advisories remains in effect
from this evening through most of the week. Refer to the local
marine products for additional information.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  76  85  76  85 /  30  40  20  20
STT  75  85  75  85 /  30  40  20  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...

AM...Small Craft Advisory until 8 PM AST Friday for Anegada Passage
     Southward to 17N-Atlantic Waters of Puerto Rico and USVI
     from 10 NM to 19.5N-Caribbean Waters of Puerto Rico from 10
     NM to 17N-Mona Passage Southward to 17N.

     Small Craft Advisory from 2 AM Wednesday to 8 PM AST Thursday
     for Coastal Waters of Southern Puerto Rico out 10 NM.

     Small Craft Advisory from 2 AM Tuesday to 8 PM AST Friday for
     Coastal Waters of Northern USVI and Culebra out 10 NM-
     Coastal Waters of Southern USVI Vieques and Eastern Puerto
     Rico out 10 NM.

     Small Craft Advisory from 2 PM Tuesday to 8 PM AST Friday for
     Coastal Waters of Northern Puerto Rico out 10 NM.

&&

$$

71/13


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