Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 251451

Area Forecast Discussion
National Weather Service San Juan PR
1051 AM AST Fri May 25 2018

.UPDATE...Persistent moderate to heavy showers affected
southeastern PR during the morning hours, causing urban and small
stream flooding across the area. By the mid-morning hours, these
showers had mostly dissipated and only brief and isolated showers
remain across some areas of northeastern PR. The rest of the local
area is observing fair weather. Cloudiness is increasing across
eastern PR and propagating west, there is also cloudiness
streaming off the USVI. The weather pattern expected today is
similar to what we have observed the past few days. Moderate to
locally heavy showers expected across portions of the San Juan
Metro with numerous showers and some thunderstorms across the
northwestern quadrant of PR. These showers could cause urban and
small stream flooding. Elsewhere in the local area, isolated to
scattered brief showers are expected.


.AVIATION...Mainly VFR conds across the local terminals with
SHRA/TSRA developing across W-NW PR after 25/17Z which could cause
MVFR conds mainly at TJBQ, VCTS at TJMZ. VCSH expected for TJSJ.
Winds will continue from the east to ESE at 10-15KT with
occasional gusts and sea breeze variations through 25/23Z.


.MARINE...Small craft operators are urged to exercise caution
across the local waters due to seas up to 6 feet and winds up to
20 knots.


.PREV DISCUSSION... /issued 502 AM AST Fri May 25 2018/

SYNOPSIS...The surface high pressure across the central Atlantic
will continue to produce a moderate easterly wind flow across the
local waters. These winds will continue to transport areas of
showers across the region. A tropical wave will affect the local
region from Saturday nigh into early Monday morning.

SHORT TERM...Today through Sunday...

The same weather pattern that has been in place across the forecast
area during the last couple of days will continue for today, with
the difference being that the moisture content will be higher. Some
brief passing trade wind showers may affect portions of eastern PR,
the USVI and surrounding waters during the morning hours, however,
rainfall accumulations are expected to be light. During the
afternoon, under a southeasterly low-level wind flow, showers and
thunderstorms are expected once again across the northwest quadrant
of PR. Additional shower development is also expected across the San
Juan metro downwind of El Yunque as well as some streamers
developing downwind of the USVI. Due to the recent heavy rainfall
activity observed during the last couple of days, the terrain is
saturated. Therefore, additional heavy rainfall will likely result
in rapid rises along rivers and small streams as well as urban
flooding. Mudslides along steep terrain are also likely. The same
pattern is expected to repeat itself on Saturday with the same areas
being affected.

On Sunday, a tropical wave is forecast to reach the forecast area
and it will combine with a digging mid to upper-level trough.
Therefore, an increase in the coverage as well as in the duration of
the shower and thunderstorm activity is anticipated across the
forecast area. Sunday has the best chance to produce more widespread
urban and small stream flooding.

LONG TERM...Monday through Saturday...

Lingering moisture associated with the aformentioned tropical
wave will continue to affect the local region on Monday, however
a drying trend is forecast to occur as a surface high pressure
build across the region. For the rest of next week, a dry air mass
is expected to encompass the region. As a result, only limited
shower activity is expected.

AVIATION...Mainly VFR conds expected across all terminals through
25/16Z. A few brief passing SHRA could affect the USVI and TJSJ
terminals during the morning hours. Once again, +SHRA and isolated
TS development expected across western and northwestern sections of
PR after 25/16Z and lasting through 25/22Z. Therefore, MVFR
conditions can be expected at times across TJBQ and TJMZ terminals.
VCSH possible across TJSJ between 25/18-22Z. Winds will be from the
E-SE at around 15 knots with sea breeze variations and occasional
gusts. Winds expected to diminish below 10kts after 25/23Z.

MARINE...Expect winds of 15-20 knots and seas of up to 5 feet
across the regional waters through tonight. Small Craft should
exercise caution across the Caribbean waters and local passages.


SJU  86  76  87  78 /  40  50  40  50
STT  87  78  87  77 /  40  40  40  50




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