Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 260146
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
946 PM AST Fri May 25 2018

.UPDATE...
Cloudiness and shower activity continued to diminish over the
islands during the late evening hours leaving partly cloudy skies.
Few passing showers will continue across the regional waters and
between the islands, with some reaching the east coastal sections
of the islands from time to time during the rest of the overnight
hours. No significant changes to the forecast reasoning and short
term forecast package at this, as the overall forecast both short
term and long term seems to be on track based on the most recent
model guidance and present weather pattern.

&&

.AVIATION UPDATE...No change to previous AVN discussion. VFR conds
to prevail en route and at all terminals except for SHRA/-SHRA
en route btw islands overnight...with SCT ocnl BKN cld lyrs nr
FL030...FL050. Few Tops nr FL100. SFC wnds FM E less than 10 knots
bcmg E-SE around 15 kts and ocnl higher gusts aft 26/14z.

&&

.MARINE UPDATE...No change to previous marine discussion.


&&

.PREV DISCUSSION... /issued 400 PM AST Fri May 25 2018/

SYNOPSIS...
Once again, low level convergence, the available moisture and
local effects enhanced shower activity downwind from La Sierra de
Luquillo to affect the San Juan Metro area. Afternoon convection
developed across the northwest quadrant and will continue through
this evening. Expect urban flooding, rapid river rises and
mudslide with the strongest activity. Shower activity should
slowly diminish across the west quadrant with just passing showers
across the eastern sections of Puerto Rico and the U.S. Virgin
Islands overnight.

SHORT TERM...
The weather pattern expected for the rest of this afternoon is
similar to the weather that has been in place during the last
couple of days. The San Juan Metro area will continue to be under
the influence of periods of moderate to locally heavy showers, as
well as the interior and northwest quadrant of Puerto Rico where
isolated thunderstorms are possible. The rest of the islands can
expect partly to sunny conditions with little or no rainfall
activity.

For Saturday, a similar weather pattern will continue with passing
showers across the U.S. Virgin Islands and eastern Puerto Rico.
Afternoon showers are expected to affect the municipalities
downwind from El Yunque, where urban and small stream flooding
will remain possible. Isolated thunderstorms as well as periods of
moderate to locally heavy showers are expected to affect the
northwest quadrant of Puerto Rico. Recent heavy rains saturated
NW-PR soils and any additional activity could trigger mudslides
along steep terrains as well as rapid river rises and urban
flooding. On the other hand, the rest of Puerto Rico and the U.S.
Virgin Islands will have sunny to partly skies with high
temperatures from the mid 80s to low 90s with little or no shower
activity.

A tropical wave is expected to reach the local Archipelago on
Sunday. It will combined with a amplifying TUTT enhancing the
intensity and coverage of showers and thunderstorms across the
islands. At this time, unsettle weather conditions are possible on
Sunday.

LONG TERM...Monday through Saturday...
Based on the latest model guidance, lingering moisture associated
with the aformentioned tropical wave will continue to affect the
local region on Monday. A seasonal weather pattern, similar to
weather conditions that has been in place across the forecast area
this week, is expected through at least the upcoming mid-week.
After mid-week, a dry air mass with possible suspended Saharan
Dust particulates could encompass the islands. Another tropical
wave is trailing this dry air mass, which could cross the Lesser
Antilles around Thursday and move near the local islands by
Friday.

AVIATION...
TSRA/SHRA across western PR should end before 23z. Mainly
VFR conditions are expected to prevail across all the terminals
during the next 24 hours. However, SHRA/TSRA expected to develop
between 26/16-22z across the NW quadrant of PR. Low level winds will
continue E-ESE between 10-15 kt.

MARINE...
Small craft operators are urged to exercise caution across the
coastal and offshore Atlantic waters due to seas between 4 and 6
feet with occasional seas up to 8 feet and winds up to 20 knots
with higher gusts. Elsewhere mariners can expect seas between 3
and 5 feet and below 3 feet across protected waters. Marine
conditions are expected to slowly improve through the forecast
period, however as a tropical wave move into the Caribbean Basin
on Saturday, hazardous weather conditions with locally higher seas
would be possible across the regional waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  76  87  78  89 /  50  40  50  50
STT  78  87  77  86 /  30  30  50  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...RAM
LONG TERM....RAM



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