Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 190020
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
820 PM AST Wed Oct 18 2017

.UPDATE...
Most of the rains have diminished across the islands with a few
areas of showers moving across the offshore waters. As an upper
level ridge continues to build, drier air and hazy skies will
encompass the region. Tranquil conditions will continue overnight
with a few trade wind showers possible across the eastern portions
of the islands on Thursday morning. East southeast winds will
increase on Thursday, resulting in choppy and dangerous marine
conditions and high rip currents along the St Croix, Vieques and
southern coasts of Puerto Rico.

&&

.AVIATION...
Mostly VFR cond will cont across most of the TAF sites during the
rest of the forecast period. Mtn obscuration and LL FG across
portions of PR overnight. For Thu, Hz will red vis range across
the area. Showers and pos iso t-storms may dev across western PR
with breif periods of MVFR/IFR CIGS/VSBYS in SHRA/TSRA. ESE SFC
winds 10-25 kts.

&&

.MARINE...
Conditions will continue to improve overnight with only a few
showers lingering across the offshore waters. An increase in winds
will continue to produce choppy and dangerous seas. Seas up to 7
feet and locally higher, as well as winds of 15-25 kts can be
expected. Small Craft Advisories will continue through at least
the weekend. Also, a high rip current risk is in effect for St.
Croix, Vieques and the southern coasts of Puerto Rico.


&&

.PREV DISCUSSION... /issued 329 PM AST Wed Oct 18 2017/

SYNOPSIS...
A tropical wave will continue to move across the region today,
transporting widespread showers and isolated thunderstorms across
the waters and the local islands. As the wave continues to move
westward this evening, weather conditions will improve gradually.
A drier air mass will encompass the region during the next few
days as an upper level ridge will build across the region.

SHORT TERM...Today through Friday

Variably cloudy skies prevailed across Puerto Rico and the U.S.
Virgin Islands this morning and early this afternoon. Areas of
showers with isolated thunderstorms were observed across the
Caribbean coastal waters. Some of this activity moved northwest
affecting the southeast and eastern sections of Puerto Rico. High
level cloudiness with some hazy conditions prevailed elsewhere.
Very dry weather conditions prevailed across the U.S. Virgin
Islands.

Showers with isolated thunderstorms will continue to develop
across the Caribbean coastal waters with some of this activity
moving inland across the southeast and south sections of Puerto
Rico. Periods of heavy rainfall can be expected with this
activity. This activity  was associated with lingering moisture
of a tropical wave which will continue to move away from the
region the rest of this afternoon and tonight.

A very dry air mass will encompass the region from the east later
this afternoon into this evening as an upper level ridge builds
across the region. As a result, clear to hazy skies are expected
to prevail across the local islands tonight into Thursday. Even
drier weather conditions are expected on Friday, where SJU-GFS
computer model forecast precipitable water values as low as 1.0
inches.

LONG TERM...Saturday through Thursday...

For Saturday and Sunday, although upper level ridge will hold
through the weekend, surface will shift more easterly. Trade winds
showers are then expected to affect the local islands from time
to time. The Ridge will weaken next Monday into Tuesday as an
upper level trough move in from the east. As a result, a seasonal
weather pattern is then expected across Puerto Rico and the U.S.
Virgin Islands from Thursday through at least next Thursday.

AVIATION...
SHRA/VCTS with broken to overcast conditions will cont across
most of the TAF sites this aft. Areas of MVFR/IFR CIGS/VSBYS are
likely in SHRA/TSRA. Mtn obscuration will continue with LL FG
expected across interior PR overnight. Mostly VFR cond expected
on Thu as drier air moves into the region. E-SE SFC winds 10-20
kts.

MARINE...
A tropical wave will continue to transport widespread showers and
thunderstorms over the local waters this afternoon and evening.
Weather conditions are expected to improve later tonight.
However, hazardous marine conditions will continue due to seas up
to 7 feet and locally high as well as winds up to 20 kts. Small
Craft Advisories will continue during the next few days across
most the waters and local passages.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  80  87  80  87 /  20  20  20  20
STT  81  83  81  83 /  20  20  20  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Friday afternoon for Central
     Interior-Northeast-Ponce and Vicinity-Southeast-Southwest-
     Vieques.

     Flash Flood Watch until 8 PM AST this evening for Central
     Interior-Culebra-Eastern Interior-Mayaguez and Vicinity-
     North Central-Northeast-Northwest-Ponce and Vicinity-San
     Juan and Vicinity-Southeast-Southwest-Vieques-Western
     Interior.

     Small Craft Advisory until 8 AM AST Friday for Southeast.

VI...High Rip Current Risk through Friday afternoon for St Croix.

     Small Craft Advisory until 8 AM AST Friday for St.Thomas...St.
     John...and Adjacent Islands.

AM...High Rip Current Risk through Friday afternoon for Coastal
     Waters OF Southwestern Puerto Rico out 10 NM-Coastal Waters
     of Southern Puerto Rico out 10 NM.

     Flash Flood Watch until 8 PM AST this evening for Coastal Waters
     OF Southwestern Puerto Rico out 10 NM-Coastal Waters of
     Southern Puerto Rico out 10 NM.

     Small Craft Advisory until 8 AM AST Friday for Coastal Waters of
     Southern Puerto Rico out 10 NM-Coastal Waters of Southern
     USVI Vieques and Eastern Puerto Rico out 10 NM.

     Small Craft Advisory until 8 PM AST Saturday for Caribbean
     Waters of Puerto Rico from 10 NM to 17N-Mona Passage
     Southward to 17N.

     Small Craft Advisory until 2 PM AST Friday for Anegada Passage
     Southward to 17N-Atlantic Waters of Puerto Rico and USVI
     from 10 NM to 19.5N.

&&

$$

SHORT TERM...AC
LONG TERM....99


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