Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 200851
Area Forecast Discussion
National Weather Service San Juan PR
451 AM AST Mon Feb 20 2017
.SYNOPSIS...Trough pattern aloft and induced surface trough across
the western Atlantic will move across the forecast area today.
This will enhance showers and possible thunderstorm development
over the northern interior of PR and across the Atlantic waters
this afternoon. Winds will shift to the south to southwest today
and become northerly late tonight into Tuesday as the trough moves
over the islands and surface high build over the western Atlantic
by mid week. Upper Ridge will build quickly from the west on
Tuesday and hold for the rest of the work week.
.DISCUSSION...Cloudy skies were observed across mainland PR
through the overnight hours. Light showers persisted over portions
of the western coastal areas of the islands through the overnight
hours. However, no significant rainfall accumulations were
observed. Clear to partly cloudy skies prevailed across the U.S.
Virgin Islands through the overnight period. Light winds with an
easterly component continued across the forecast area. Moderate to
brief heavy isolated showers were noted over both Atlantic and
Caribbean coastal waters.
For the rest of the morning hours, a few breaks in clouds and
fair weather conditions are expected to prevail. However, a mid to
upper trough and associated surface trough will move during the
afternoon through evening hours across the forecast area. This
will result in periods of showers with possible thunderstorm
development over the Atlantic waters and north of the Cordillera
Central. Drier conditions and fair weather conditions are expected
to return on Tuesday and persist for much of the work week. Trade
wind shower activity and limited afternoon shower development is
expected each day after today.
.AVIATION...Weak front over the flying area will keep SCT-BKN clouds
at FL025-FL070 and -SHRA at times. SHRA/ISOLD TSRA will develop near
TJSJ between 17Z-22Z. Brief MVFR conds possible the afternoon SHRA
at TJSJ. Elsewhere, mostly VFR expected. ESE Winds of 10 kts will
veer to the SSW by 18Z.
.MARINE...Latest buoy data at San Juan and Rincon are indicating
seas less than 5 feet and therefore canceled the high risk of rip
currents. However, a moderate risk of rip currents will continue
across the Atlantic coastline of PR, Culebra and St. Thomas. Winds
will be mainly light with a southwesterly component later in the
day as the low level trough moves from the northwest across the
local waters. This can result in scattered to numerous showers
with possible thunderstorm development over the Atlantic waters.
Seas should range between 3-5 feet over the northern waters and
below 4 feet across the Caribbean waters.
.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 82 73 / 50 40 40 30
STT 82 73 82 72 / 20 60 50 30