Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 260951
Area Forecast Discussion
National Weather Service San Juan PR
551 AM AST Wed Oct 26 2016
.SYNOPSIS...Upper trough will continue to exit the region Today
as ridge builds from the central Caribbean and holds through the
end of the week. Another short wave trof is forecast to move aloft
from the western Atlantic by early next week. At lower levels,
frontal boundary to the north of the area and troughiness will
continue to keep a moist environment for the next couple of days.
An easterly wave will move mainly south of the area through
Thursday. Surface high across the western Atlantic will maintain
an east to northeast wind flow through the end of the work week.
East to southeast winds return during the weekend.
.DISCUSSION...Scattered showers on a northeasterly wind were
observed across the coastal Atlantic waters with a few reaching
coastal areas and the northern U.S. Virgin Islands. However,
mostly clear skies with a few clouds prevailed across the rest of
the forecast area. For the rest of the morning hours, showers are
expected to increase across the northern half of the island.
Enough moisture will lead to another round of showers and
thunderstorm development over the mountains and to the
west/southwest of them during the afternoon hours. A similar
weather pattern is expected each day with easterly wave/steering
east winds favoring convection over the western side of the island
during the afternoons. During the weekend as winds turn more from
the southeast, afternoon convection should focus across the
northwest quadrant of the island.
Moisture content with normal to above normal PWAT will continue
for the next several days even as ridge builds aloft. There seems
to be a slight drop of moisture content during the weekend but
showers and isolated thunderstorms are still expected. The
easterly wave is currently producing scattered showers and
thunderstorm activity to the east of Guadeloupe. This wave is
forecast to move east to the south of the area and aid to the
development of showers and thunderstorms across the offshore
Caribbean waters and increase the available low level moisture
through Thursday. For early next week, another short wave trof
will move from the western Atlantic weakening the ridge and
bringing more unstable conditions.
.AVIATION...VFR conds expected at most of the terminals durg the
forecast period. However, NE trade winds will push SCT SHRA near
TJBQ, TJSJ and TIST thru at least 14Z. As a result...Brief MVFR in
passing SHRA are possible at times. SHRA/TSRA fcst to develop ovr
and downwind of the Cordillera Central of PR. MVFR and mountain
obscurations possible in and around TJMZ/TJPS between 26/17Z-21Z.
NE winds of 10-15 kt will prevail below FL100.
.MARINE...Seas will continue 3-5 feet overall across most of the
waters...increasing to 6 feet by Thursday across the offshore
Atlantic waters. East to northeast winds will continue between
5-15 knots. Turning east to southeast during the weekend. There is
a moderate risk of rip currents across the Atlantic exposed
beaches of the islands.
.PRELIMINARY POINT TEMPS/POPS...
SJU 87 78 88 79 / 50 30 30 40
STT 89 79 88 78 / 50 30 30 40