Area Forecast Discussion
Issued by NWS San Juan, PR

Home | 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
000
FXCA62 TJSJ 140230
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1030 PM AST Tue Nov 13 2018

.UPDATE...Showers and thunderstorms affected St. Croix during the
evening hours, leaving between 1-2 inches of rain. The flood
advisory was let to expire at 1015 pm as mostly light rain was
observed over the western portions of the islands. However, a
flash flood watch remains in effect for all the islands through at
least Thursday. Winds have shifted from the east to east-southeast
and new showers with isolated thunderstorms were developing across
southeastern Puerto Rico. This pattern is expected to continue
overnight into Wednesday morning, with the best moisture content
moving across the USVI and eastern PR through early Wednesday
afternoon. Although there will be a lull in activity in some
areas, showers and thunderstorms could develop at any time over
the regional waters and over the islands as the upper level
trough continues to interact with the tropical wave.



&&


.AVIATION Update...Mainly VFR conditions expected early in the
forecast period. However, SHRA/-TSRA over the eastern and
southern waters of the islands could move at times over the local
terminals. SHRA/TSRA is expected to increase from 14/12z-18z
across the USVI/Eastern PR terminals, this could cause tempo
MVFR/IFR. Latest 14/00z TJSJ upper air sounding indicated E-ESE
winds at 9-26 kt blo FL050.


&&

.MARINE...No change from previous discussion. Seas should continue
between 6-8 feet for much of the week across the Atlantic and
Caribbean waters and portions of the passages. Winds turn more
east-southeast tonight through Wednesday. Gusty winds and locally
higher waves expected with thunderstorm activity.


&&

.PREV DISCUSSION... /issued 548 PM AST Tue Nov 13 2018/

SYNOPSIS...An active tropical wave interacting with an upper
level trough will result in scattered to numerous showers and
thunderstorms across the region during the next few days. Unstable
weather conditions are expected to continue through at least
Friday. A mid to upper level ridge will build from the northeast
during the weekend, promoting fair weather conditions through
early next week.

SHORT TERM...Today through Thursday...

A flash flood watch is in effect through at least thursday
afternoon for Puerto Rico and the U.S. Virgin Islands. Scattered
convection across the USVI and eastern PR left between 1-2 inches
of rain today. Minor urban flooding was reported today over
portions of eastern PR. An area of strong thunderstorms persisted
over the offshore Caribbean waters just to the south and east of
St. Croix, some of this activity is expected to affect St. Croix
through the evening hours. Breezy conditions will continue with
winds ranging between 15-25 mph, with the higher winds remaining
across the offshore waters.

As the wave axis continues to approach the region from the east
and cross the islands on Wednesday...additional showers and
thunderstorms are expected to increase overnight into Wednesday
morning across the USVI and the eastern portions of PR. Based on
the latest guidance, the heaviest shower activity is expected
between early Wednesday morning through Wednesday evening across
the islands. Rainfall accumulations in general should range
between 1-4 inches with isolated higher amounts through the short
term period.

LONG TERM...Friday through Tuesday...(issued at 538 AM AST Tue
Nov 13 2018)

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 local
terminal sites through 14/03Z. MVRF conds are occurring as a
result of +SHRA/TSRA these are expected to persist through the
next TAF issuances. LLVL winds are out of the east to northeast
ranging from 15 to 25 kts below FL150, with higher gusts when
SHRA/TSRA pass by.

MARINE...Hazardous seas are expected through the weekend across
most of the regional waters. Seas will range overall between 6-8
feet across the Atlantic and Caribbean waters as well across the
Anegada Passage. Winds up to 25 knots are possible with the
passage of an active tropical wave through at least Wednesday.
Thunderstorms are expected to increase overnight through late
Wednesday night across the regional waters, this will result in
periods of frequent lightning as well as gusty winds and locally
higher seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  89  77  88 /  80  60  40  50
STT  78  86  78  86 /  80  60  50  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Thursday afternoon 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.

     Small Craft Advisory from 8 PM Wednesday to 8 AM AST Friday for
     Southeast.

     High Rip Current Risk from 6 AM AST Wednesday through Thursday
     afternoon for Central Interior.

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

     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 from 8 PM Wednesday to 8 AM AST Friday for
     Coastal Waters of Southern Puerto Rico out 10 NM.

     High Rip Current Risk from 6 AM AST Wednesday through Thursday
     afternoon for Coastal Waters of Southern 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-Caribbean Waters of Puerto Rico from 10
     NM to 17N.

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

     Small Craft Advisory until 8 PM AST Friday for Coastal Waters of
     Southern USVI Vieques and Eastern Puerto Rico out 10 NM-
     Mona Passage Southward to 17N.

     Small Craft Advisory until 6 AM AST Wednesday for Coastal Waters
     OF Northwestern Puerto Rico out 10 NM.

&&

$$

DS


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