Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 240854

Area Forecast Discussion
National Weather Service San Juan PR
454 AM AST Mon Jul 24 2017

.SYNOPSIS...Drier and more stable air mass is forecast today as
Saharan Dust particles spread over the Northeast Caribbean. As a shower activity is anticipated today. Moisture
content will increase Tuesday and Wednesday as a tropical wave
approaches from the east and an upper level trough retrogress
across the Western Atlantic.


.SHORT TERM...Monday through Wednesday...

Ridge pattern aloft will continue to erode through the forecast
period as TUTT low which is now located across the central Atlantic
shifts westward and relocates north of the local islands. This
feature will then promote moisture advection from the east northeast
on Tuesday. The next tropical wave passage is expected on Wednesday
with bulk of moisture remaining south of the area. Therefore, under
weakening ridge and moisture near or slightly above the normal range
which is 1.75 inches, expect trade wind showers across USVI and E PR
at times as well as afternoon showers and thunderstorms across the
interior and west sections of Puerto Rico Tue-Wed.

Meanwhile for today, expect a fair weather pattern with hazy skies
and warm to hot temperatures. Showers if any will be focused across
Mayaguez and vicinity.

.LONG TERM...Thursday through Sunday

Upper level trough/TUTT northeast of the region will be the dominant
weather feature Thursday and Friday...dissipating as it moves
northward during the weekend. The proximity of the TUTT combined
with slightly above normal moisture will enhance somewhat the
afternoon showers and thunderstorms each afternoon. In addition...
bands of low level moisture embedded in the trade winds will
bring light showers over the U.S. Virgin Islands and Eastern
Puerto Rico especially at night and early in the morning. After
the wave passage on Wednesday, southeasterly flow will establish
across the Northeast Caribbean Region leading to above normal
temperature once again across the northern half of Puerto Rico the
second part of the week. Operational models suggest breezy and
more stable conditions for early next week.


.AVIATION...VFR conds are expected to prevail at all TAF sites
through the forecast period. However,  Aft 24/16z SHRA expected to
develop near JMZ with MVFR conds possible through 24/22z. Easterly
winds 10-15 knots aft 24/13z with some sea breeze variations.
Although hazy skies are expected to prevail across the forecast
area, visibilities expected to remain P6SM.


.MARINE...Fresh winds of 15-20 kts will create wind waves of 4-6 feet
across the regional waters today. Therefore...Small craft should
exercise caution across the coastal waters of Puerto Rico through
tonight. Winds will subside to 10-15 kts the rest of the week giving
way to typical seas of 3-5 feet over the next several days.


SJU  91  81  88  79 /  30  60  30  30
STT  91  80  90  79 /  30  60  50  40




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