Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 261633

Area Forecast Discussion
National Weather Service San Juan PR
1233 PM AST Fri May 26 2017

Saharan Dust Particles diminished and trade wind showers were
observed moving over the U.S. Virgin Islands and the east half
portion of Puerto Rico. The available moisture will result in
showers and thunderstorms across the interior and west portions of
Puerto Rico. The U.S. Virgin Islands their surrounding waters and
east Puerto Rico can expect passing showers from time to time
through the evening hours.


Vis are improving across the region, however, mount obsc is
increasing along the Cordillera central. SHRA/TSRA are expected to
produce SCT-BKN ceilings at FL025-080. SHRA/TSRA expected to
affect TJMZ and the VCTY of JBQ til 26/23z. Elsewhere passing
showers are possible. Easterly winds at 10 to 17 knots with
higher gusts, then calm to light and variable overnight.


Mariners can expect seas between 3 and 5 feet with easterly winds
below 18 knots.


.PREV DISCUSSION... /issued 500 AM AST Fri May 26 2017/

SYNOPSIS...An upper level trough is forecast to move over the
area by early next week. A tropical wave is forecast to enter and
move across the eastern Caribbean by Tuesday.

Short Term... Friday through Sunday...

The Saharan dust that has been affecting the local area is expected
to clear off today but then increase slightly on Saturday into
Sunday. However, the concentrations do not seem to be as high as it
has been this past week. The available moisture is expected to also
increase today with precipitable water values at around 1.5 inches
and hanging on close to that value thorough the weekend. The local
winds will remain from the east at about 10-15 mph due to the strong
surface high pressure across the central Atlantic. There is an upper
low to the northeast of the local islands that is expected to move
west a little bit then north and east as it weakens and dissipates
by Sunday. This means that the upper level dynamics do not seem to
be particularly conducive to sustained thunderstorm development even
with less Saharan Dust concentrations. For that reason, the forecast
is for isolated to scattered showers with afternoon convection
occurring across western PR every afternoon this weekend.

Long Term...Monday through Saturday...

Latest model guidance indicated an upper level trough is forecast
to move over the area by early next week. Also, a tropical wave
is forecast to enter and move across the eastern Caribbean by
Tuesday. These two features promise to bring an increase in low
level moisture across the region beginning on Monday night and
continuing through most of next week. As a result, showers and
thunderstorms are expected to affect the region.

AVIATION...VFR conds expected through the forecast period. Winds
from the east with sea breeze variations at about 10-15kt and
occasional gusts. VCSH likely for TJMZ and TJBQ after 26/16Z due to
afternoon convection across western PR. SHRA activity to dissipate
mostly over PR by 26/23Z.

MARINE...Seas up to 6 feet and winds up to 20 knots can be
expected across the local waters. Small Craft should exercise
caution across the Atlantic water north of Puerto Rico. Moderate
risk of rip currents expected today across much of the beaches of
the islands.


SJU  89  78  90  77 /  20  40  40  20
STT  88  78  88  77 /  20  40  40  30




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