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FXCA62 TJSJ 202033

Area Forecast Discussion
National Weather Service San Juan PR
433 PM AST Thu Jul 20 2017

.SYNOPSIS...Bands of moisture in minor troughs will cross through
the local area tonight, Friday and Friday evening, and Saturday.
A tropical wave will move across the area Saturday night followed
by generally drier air with patches of low level moisture through
most of next week.


.SHORT TERM...Tonight through Saturday
A band of moisture has moved through the area and spawned a few
showers off of the coast at Cabo Rojo. There are also weak
streamers dissipating off of Vieques and Saint Croix. Another band
of moisture is moving toward Saint Croix out of the Leeward
Islands and will arrive overnight tonight with scattered showers.
Another patch of moisture will move through the area late Friday.
A dry area follows Friday night although low-level moisture will 
bring the usual late night and early morning showers to the 
northeast coast and slopes. Moisture begins to increase on 
Saturday and will continue through Saturday night when the next 
tropical wave moves through.

At upper levels...flow from the southwest will bring in an area of
divergence aloft overnight across western Puerto Rico, but with no
convection present to enhance, it will be of little effect. Upper
level flow then shifts to the southeast and becomes less than 15 
knots. However some divergence aloft over the northwest third of 
Puerto Rico will enhance the afternoon convection ahead of the 
tropical wave and thunderstorms should be expected.

.LONG TERM...Sunday through Wednesday
After the passage of the tropical wave on Saturday night, moisture
will diminish through Tuesday evening. This will keep shower
activity limited during the period. Moisture patches at lower
levels will continue to pass through the area both Monday morning
and Monday evening in the easterly flow as high pressure at the
surface continues to dominate the central Atlantic. Moisture
returns Wednesday and Wednesday night for another increase in


.AVIATION...VFR conditions expected, but -SHRA in the VCTY of 
TJSJ/TIST and TISX/TNCM/TKPK are possible at times. Although hazy, 
conditions with P6SM VIS continue, the Saharan air particles are 
expected to diminish across the flying area through the rest of 
the FCST Period. VCTS are expected after 21/00z at TNCM/TKPK, and 
SHRA/+SHRA will affect E-PR/USVI terminals after 21/06z. Northerly
winds at 15 to 20 kt with higher gusts, decreasing at 10 to 15 kt
aft 20/22z.


.MARINE...Highest seas will pass through the area tonight with
subsiding seas through Thursday of next week. Hence no small craft
advisories are expected for the next 7 to 10 days. 


SJU  78  88  81  89 /  40  30  30  30 
STT  80  88  80  90 /  50  50  20  20 



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