Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 131542
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1142 AM AST Tue Nov 13 2018

.UPDATE...
Showers and isolated thunderstorms are progged to continue to
increase this afternoon and remain through Thursday. Puerto Rico
and the U.S. Virgin Islands will experience moderate to heavy
rainfall as a result of increasing moisture provided by the
tropical wave. Therefore, on the forecast update this morning
a Flash Flood Watch was issued for Puerto Rico, U.S. Virgin
Islands and adjacent islands through Thursday. In addition,
additional rainfall over the next several days would likely cause
rapid rivers rises, as well as mudslides in mountains areas.


&&

.AVIATION...
MVFR/VRF conds are currently prevailing over most the terminal
sites with MVFR conds occurring due to +SHRA/TSRA. +SHRA/TSRA
are forecast to continue through 13/22Z over terminals TJSJ, TJMZ,
TJBQ. Winds will be out of the east to northeast at 15 to 20 kts
with higher gust up to 30 kts.

&&

.MARINE...
Marine conditions will remain hazardous through the end of the
work week due to strong easterly winds, as well as increasing
showers and thunderstorms. Seas will range from 6 to 8 feet with
seas occasionally reaching 10 feet in the offshore waters. Winds
will be out of the east to northeast at 15 to 20 kts with higher
gusts up to 30 kts.


&&

.PREV DISCUSSION... /issued 538 AM AST Tue Nov 13 2018/

SYNOPSIS...
A surface trough east northeast of the region that the National Hurricane
Center is monitoring for potential development Invest 96L, has become
less organized overnight. The potential for becoming a tropical cyclone
has therefore decreased and it is expected to move west northwest across
the Atlantic Waters north of PR/USVI over the next few days. However,
enhanced showers and thunderstorm activity associated with an active
tropical wave now moving through the Leeward Islands has continued
during the overnight hours as it continued westward while interacting
with a mid to upper level trough and associated Low. The brisk northeasterly
winds will continued to transport periods of showers and isolated thunderstorms
with gusty winds to the north and east coastal sections of the islands
today through at least Wednesday.

SHORT TERM...Today through Thursday...
The combination of an active tropical wave over the eastern
Caribbean and an upper level low over Puerto Rico and the U.S.
Virgin Islands will maintain a very moist and unstable pattern
through Thursday. Both features will move in phase westward over
the next few days enhancing the moisture transport and low level
convergence across the northeast Caribbean region. With good upper
level dynamics and moisture well above normal, showers and
thunderstorms are forecast to affect the U.S. Virgin Islands and
most of Puerto Rico at times...producing rainfall accumulations of
1- 4 inches during the next 72 hours. This additional rainfall
over saturated soils will likely result in landslides and flooding
in portions of the U.S. Virgin Islands and Puerto Rico. Therefore
the people in PR/USVI stay tuned for any statements, watches or
warnings from your National Weather Service forecast office in San
Juan over the next 48-72 hours.

LONG TERM...Friday through Tuesday...
The tropical wave is expected to exit the region by Friday as
high pressure ridge will build north and east of the region while
increasing the east to northeast trade winds. Although a gradual
drying trend is expected by Friday and into the weekend, expect a
surge of moisture in the brisk easterly trade winds to move across
the region and bring periods of cloudiness and periods of quick passing
trade winds showers to the islands and coastal waters. Afternoon
convection each day will be focused mainly over parts of the interior
and downstream of El Yunque rainforest around the San Juan metro,
as well as on the west end and downwind of the U.S.V.I. By then
most of the activity should be in the form of streamers.

Over the weekend and through the early part of the following week,
the mid to upper level ridge is forecast to build across the region
resulting in continued erosion of low level moisture and the suppressing
of widespread afternoon convective development. The Atlantic surface
high pressure ridge is to also build north of the region and tighten
the local pressure gradient. This will lead to increasing easterly
trade winds through early next week resulting in breezy conditions.
Showers and thunderstorm development if any, should be then limited
to the overnight and early morning hours, followed by the more typical
afternoon convection each day.

AVIATION...Quick passing SHRA/ISOLD TSRA will affect the terminals
at times through the forecast period. As a result, brief periods
MVFR conds are possible as the SHRA/TSRA pass by. Mountain
obscurations are likely along the interior portions of Puerto Rico.
LLVL winds will increase to 15-25 kts below FL150, with higher gusts
when SHRA/TSRA pass by.

MARINE...Increasing and deteriorating wind driven seas are
expected to create continuous hazardous marine conditions for the
next several days across the regional waters. Overall seas should
range between 6-8 feet occasional up to 10 feet offshore, with
breezy trade winds of 15-25 kt with higher gusts. These conditions
are expected to persist through Wednesday with the passing of a
tropical wave, currently moving across the Leeward islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  85  78  89  77 /  50  70  60  40
STT  86  78  86  78 /  50  60  60  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 PM AST this evening for Culebra-
     North Central-Northeast-Northwest-San Juan and Vicinity-
     Southeast-Vieques-Western Interior.

     Flash Flood Watch through Thursday afternoon 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.

VI...High Rip Current Risk until 6 PM AST this evening for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

     Flash Flood Watch through Thursday afternoon for St Croix-
     St.Thomas...St. John...and Adjacent Islands.

AM...Flash Flood Watch through Thursday afternoon for Coastal Waters
     OF Southwestern Puerto Rico out 10 NM-Coastal Waters of
     Northern USVI and Culebra out 10 NM-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 6 PM AST this evening for Caribbean
     Waters of Puerto Rico from 10 NM to 17N.

     Small Craft Advisory until 6 PM AST Wednesday for Coastal Waters
     of Northern Puerto Rico out 10 NM.

     Small Craft Advisory until 6 PM AST Saturday for Anegada Passage
     Southward to 17N-Atlantic Waters of Puerto Rico and USVI
     from 10 NM to 19.5N.

     Small Craft Advisory until 6 AM AST Thursday 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 until 6 AM AST Wednesday for Coastal Waters
     OF Northwestern Puerto Rico out 10 NM-Mona Passage
     Southward to 17N.

&&

$$

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


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