Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 170107
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
907 PM AST Mon Oct 16 2017

.UPDATE...
Showers and thunderstorms continued to spread over most of Puerto
Rico, Vieques and Culebra during the late afternoon and evening
hours, resulting in several rivers above flood stage and many near
flood stage. Also, because of the long duration of the rain along
with saturated soils and areas with poor drainage, floods waters
quickly developed even in locations of light to moderate rainfall.
Several Flood Advisories as well as Flash Flood Warnings continue
in effect across these areas. The shower and thunderstorm activity
is expected to decrease in intensity later tonight, but showers will
remain possible overnight.

A Moist southerly flow will continue to aid in the development of
showers and thunderstorms across the local waters and portions of
the islands tomorrow. Since the soils are already saturated and
rivers are currently flowing high from yesterday`s and today`s
heavy rains, any additional rainfall will result in additional
urban and small stream flooding, as well as rapid river rises.

&&

.AVIATION...
Broken to overcast conditions and SHRA will continue as well as
Mtn obscuration for the rest of the forecast period. Light and
VRB winds expected. Aft 17/15Z SHRA/TSRA will dvlp across E PR and
then spread along and north of the Cordillera Central. Areas of
MVFR/IFR CIGS/VSBYS are likely in SHRA/TSRA. Tops may exceed 50
kft. Winds will become SE 15-30 kt SFC-FL100 aft 17/12Z.

&&

.MARINE...
Marine conditions will improve slightly, but southeast flow will
keep the Atlantic and Caribbean waters rough and choppy. Small
craft advisory conditions continue in parts of these waters and
the Anegada passage through late Tuesday night. Hazardous
conditions are expected to return on Thursday or Friday.

&&

.PREV DISCUSSION... /issued 626 PM AST Mon Oct 16 2017/

SYNOPSIS...
The trailing edge associated to a broad low pressure system
located several hundred miles east of Bahamas and southeasterly
flow, resulted in another round of very active weather conditions
for the local islands today. Moist southerly flow will aid in
shower and thunderstorm activity on Tuesday and Wednesday though
not as widespread as today. Conditions will improve Thursday as an
upper level ridge builds across the region.

SHORT TERM...
A very active afternoon prevailed across mainland Puerto Rico.
Showers and thunderstorms were observed across the U.S. Virgin
Islands, Vieques and Culebra. Several flash flood warnings were
issued, mainly across the eastern half of Puerto Rico. Many rivers
across this area were near or above flood stage. Rainfall amount
between three to four inches with isolated amounts up to near
seven inches were observed due to this activity.

All this activity was associated with trailing moisture from
yesterday`s tropical wave and a moist southeast wind flow across
the region. For tonight, pulses of showers and thunderstorms will
continue to affect mainly the south, southeast, east and northeast
sections of Puerto Rico as the moist southeast wind flow
continues across the region.

For Tuesday, another round of showers and thunderstorms are
expected to develop. However, the main focus of the activity will
occur across the western interior and northwest sections of Puerto
Rico. For Wednesday, another pulse of deep tropical moisture will
encompass the region. As a result, active weather conditions are
expected across the eastern half of Puerto Rico mainly during the
morning hours. This will aggravate the flood and mudslide
situation across the Puerto Rico. As a result, Flash flood watch
will continue in effect through Wednesday night. Stay tuned for
the latest information on this wet pattern across the local area.

LONG TERM...Thursday through Monday...
A gradual drying trend is expected to occur across the region
beginning early Thursday and continuing through the weekend as an
upper level ridge builds across the region. The Ridge will weaken
next Monday 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 Monday.

AVIATION...
Broken to overcast conditions will continue as well as Mtn
obscuration for the rest of the forecast period. SHRA/TSRA
activity expected to decrease by 17/00Z. Winds will also become
light and VRB. Aft 17/15Z SHRA/TSRA will dvlp along and north of
the Cordillera Central. Areas of MVFR/IFR CIGS/VSBYS are likely in
SHRA/TSRA. Tops may exceed 50 kft. Flow will continue SE 15-30 kt
SFC-FL100.

MARINE...
Marine conditions will improve slightly, but southeast flow will
keep the Atlantic and Caribbean waters rough and choppy. Small
craft advisory conditions will continue in parts of these waters
and the Anegada passage through late Tuesday night. Hazardous
conditions are expected to return on Thursday or Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  81  89  81  88 /  40  40  40  30
STT  83  84  82  84 /  40  30  50  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flash Flood Watch through Wednesday 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.

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

AM...Flash Flood Watch through Wednesday evening for Coastal Waters
     OF Southwestern Puerto Rico out 10 NM-Coastal Waters of
     Southern Puerto Rico out 10 NM.

     Small Craft Advisory until 6 PM AST Tuesday for Caribbean Waters
     of Puerto Rico from 10 NM to 17N-Mona Passage Southward to
     17N.

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

&&

$$

SHORT TERM...AC



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