Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 281921

Area Forecast Discussion
National Weather Service San Juan PR
321 PM AST Wed Jun 28 2017

.SYNOPSIS...Upper trough/low over the central Atlantic extending
southwest to just north of PR/USVI drifting slowly east. Tropical
Wave over the extreme eastern Caribbean moving west at 15 to 20


.SHORT TERM...Tonight through Friday Night...Upper low mentioned
above will remain in place to the northeast of the Caribbean
through at least Friday. Tropical wave over extreme eastern
Caribbean will move west and begin to impact the U.S. Virgin
Islands Late tonight or early Thursday with showers and
thunderstorms spreading westward through Puerto Rico Thursday and
Thursday night. Weak trough aloft will provide good upper level
dynamics that will likely enhance shower/thunderstorms activity
associated with the tropical wave. To that effect decided to
increase probability of precipitation for both Thursday and
Thursday night. Models indicate that moisture associated with this
wave will linger across the local area through Friday night.

.LONG TERM...Saturday through Thursday...A drier airmass is
expected to move in as the wave departs the local area. This will
dominates the weather conditions across USVI and PR through at
least Sunday. Another tropical wave, currently across the central
tropical Atlantic, is expected to affect the local area Monday.
Another dry airmass is expected to move in behind this wave, with
yet another tropical wave affecting the region Wednesday through


.AVIATION...VFR conds expected for the next 24 hours across the
local terminals. VCSH is expected early in the morning for TIST,
TISX, and TJSJ. Afternoon convection is expected mainly across the
western sections of PR, which could affect TJMZ and cause TEMPO MVFR
conds after 28/18Z. Saharan dust is still present, causing haze but
visibility will still be P6SM. Winds from the east at 5-10KT
expected early this morning, increasing to about 15KT with
occasional gusts after 28/13Z.


.MARINE...Seas up to 6 feet and winds up to 20 knots are expected
across the coastal waters. Small craft should exercise caution
across the Atlantic and Caribbean nearshore waters due to winds.
Mariners should always keep in mind that winds and seas are likely
to be higher in the vicinity of thunderstorms.


SJU  80  89  77  89 /  10  50  60  60
STT  80  88  79  88 /  30  60  60  60




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