Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 210945

Area Forecast Discussion
National Weather Service San Juan PR
545 AM AST Fri Oct 21 2016

.SYNOPSIS...A mid to upper level ridge will continue to build
across the forecast area as trough aloft across the southwest
Atlantic continues to weaken. A surface high pressure across
the north central Atlantic will continue to promote a gentle
to moderate southeasterly wind flow today...becoming easterly
the upcoming weekend. The prevailing southeasterly wind flow
will continue to result in warm to hot temperatures across
the northern slopes of Puerto Rico today.


.DISCUSSION...Variably cloudy skies prevailed across the forecast
area with passing showers observed across the local waters as well
as the southern coastal areas of PR. Minimum temperatures were
between the upper 70s and low 80s under a light southeasterly
wind flow.

Under a building ridge pattern and precipitable water near the
normal range, continue to expect a few passing showers across
the windward areas, followed by locally induced afternoon showers
and thunderstorms. These afternoon showers and thunderstorms will
be focused north and northwest of the Cordillera Central today
and Saturday under a southeasterly wind flow. In fact, this
southeasterly wind flow will continue to result in warm to hot
temperatures along the northern slopes of Puerto Rico during the
next two days or so.

Trade winds will return to the forecast area Sunday and early
next week, focusing the afternoon showers and thunderstorms over
west PR Sunday and Monday and also providing relief to the
expected warm to hot temperatures. Moisture is expected to pool
across the forecast area Monday afternoon and continue throughout
the end of next workweek as the ridge pattern aloft weakens in
response to a broad trough moving across the west and central
Atlantic. Its associated surface boundary will induce a surface
trough across the eastern Caribbean which is expected to increase
the chance of shower and thunder activity across the local


.AVIATION...Passing -SHRA possible at TJPS/TIST/TISX, as well as
in the VCTY of TJSJ early this morning, but most of the SHRA are
expected over the surrounding waters. After 21/16z, SHRA/TSRA
expected along and to the west of the Cordillera Central, to
result in brief MVFR at TJMZ/TJBQ, afternoon SHRA are possible too
at TJSJ/TIST/TISX. This activity is expected til 21/22z. Winds
expected from the SE at less than 15kt, however locally higher
in/around SHRA/TSRA, and sea breeze variations aft 21/13z.


.MARINE...Tranquil marine conditions are expected to prevail
during the next few days with seas below 5 feet and winds up to
15 knots. An increase in shower and thunder activity expected
early next workweek as a surface trough dominates the eastern


.CLIMATE...A record warmest low set at the primary climate data
sites yesterday. A record warmest low of 82 degrees was set at
San Juan Area. This broke the old record of 79 set back in 2014.
A record warmest low of 84 degrees was set at Cyril E. King
Airport in St Thomas. This broke the old record of 81 set back in
1998. This warmest low also tied the warmest low observed for any
given day. A record warmest low of 82 degrees was set at Henry E.
Rohlsen airport in St Croix. This broke the old record of 81
degrees set back in 1987.


SJU  91  79  91  79 /  30  20  20  20
STT  89  80  89  80 /  30  30  30  30




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