Area Forecast Discussion
Issued by NWS San Juan, PR

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXCA62 TJSJ 190807

Area Forecast Discussion
National Weather Service San Juan PR
407 AM AST Thu Jul 19 2018

.SYNOPSIS...Tropical wave to move through the local area today,
bringing an increase in moisture, showers and isolated
thunderstorms. Strong surface high pressure across the north
central Atlantic will keep easterly winds for the next several
days. Drier air mass and Saharan dust expected to return on Friday
and Saturday. Upper low northeast of the Leeward islands may
strengthen and move west and north of the local islands for the
next few days, possibly causing some instability on Sunday.


.SHORT TERM...Today through Saturday...

Increasing cloudiness with shower and thunderstorm activity was
observed across Puerto Rico and the U.S. Virgin Islands overnight.
Scattered to numerous showers with isolated thunderstorms began to
move across the region as a tropical wave approaches from the east.
Most of the activity occured across the local waters. Some showers
were moving quickly across the San Juan metropolitan area.

For today, a tropical wave will move across the local islands. As a
result, scattered to numerous showers with thunderstorms will spread
across the U.S. Virgin Islands and eastern half of Puerto Rico
during the morning hours, and across the rest of Puerto Rico this
afternoon and tonight. Moisture associated with the tropical wave
will linger across the region through late tonight into Friday
morning. By Friday morning, a very dry air mass with Saharan dust is
expected to encompass the region. This dry weather pattern will
continue into Saturday.

.LONG TERM...Sunday through Friday...

Some Saharan dust may still be lingering on Sunday morning, but a
break from the Saharan dust is expected early next week. An upper
low may combine with the available moisture to cause some showers
and isolated thunderstorms on Sunday. Then drier air expected on
Monday and Tuesday may limit shower activity before another
tropical wave approaches for Wednesday, which will cause an
increase in shower activity once again. Thereafter, drier air
returns and mainly locally induced showers across Puerto Rico are
expected, isolated and brief showers expected elsewhere.


.AVIATION...Periods of MVFR conditions can be expected from time to
time across TJSJ, TIST and TISX throughout the day. Periods of MVFR
and even IFR conditions will be possible across TJMZ and TJBQ this
afternoon due to +SHRA/+TSRA. Low level winds will be mainly east to
east southeast at 10 to 15 kts with higher gusts.


.MARINE...Choppy seas up to 6 feet expected today and for the next
few days with easterly winds up to 20 knots. For that reason,
small craft operators are urged to exercise caution cross many of
the local waters. The tropical wave will cause showers and
isolated thunderstorms across the local waters today.


SJU  87  79  89  78 /  70  20  20  20
STT  83  81  83  79 /  40  20  20  20




LONG TERM....JA is the U.S. government's official web portal to all federal, state and local government web resources and services.