Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 220026
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
826 PM AST Tue Nov 21 2017

.UPDATE...Partly cloudy skies prevailed across Puerto Rico this
evening. Doppler weather radar and satellites images depicted
only few passing showers across the local waters. However, not
significant precipitation was observed over land areas. Although
a mid to upper level ridge will continue to build across the
forecast area tonight and hold through much of the week, east
southeasterly winds will continue to bring patches of low level
moisture at times. Therefore, expect a fair and generally stable
weather pattern tonight through at least Wednesday with light
passing showers across eastern PR in the morning followed by
limited shower activity across western Puerto Rico in the
afternoon. The chance for shower activity will increase Wednesday
night into Thursday as low level moisture increases across the
eastern Caribbean.

&&

.AVIATION...Mostly VFR conditions expected across the local flying
area during the period. Few -SHRA en route btw islands with FEW-
SCT cld lyrs nr FL030...FL050 overnight til 22/14z. L/lvl wnds from
SE 10-15 kts, blo FL100...bcmg SW-W then incr w/ht abv. SFC Wnd
lgt/vrb...bcmg E-SE 10-15 kts with sea breeze variations along
the coastal areas aft 22/14z. No sig wx impact across the region
attm.

&&

.MARINE...Seas will continue between 3-5 feet across the offshore
waters and between 2-4 feet across the coastal waters overnight.
Seas increase up to 7 feet across the offshore Atlantic waters
between Wednesday night and Thursday. A small craft advisory will
be in effect through this period. A moderate risk of rip currents
will continue for the next several days across the Atlantic
beaches of the islands.

&&

.PREV DISCUSSION... /issued 505 PM AST Tue Nov 21 2017/

SYNOPSIS...A mid to upper level ridge will continue to dominate
the local weather pattern during the next several days. Drier air
will continue through Wednesday. Moisture increases once again on
Thursday and Friday as an induced surface trof moves from the
east. Drier conditions return during the weekend.

SHORT TERM...Today through Thursday...

Little to none rain was observed today over land areas. Mostly
sunny skies prevailed across all islands. Fair weather conditions
will continue through Wednesday. A few isolated showers cant be
ruled out across western PR during the afternoon hours. On
Thursday, as a weak perturbation/induced trof moves from the
east...moisture will increase and a better chance for shower with
possible isolated thunderstorm development is expected along the
the Cordillera Central during Thursday afternoon. Temperatures
will continue between the high 80s to low 90s across the lower
elevations each day.

LONG TERM....FROM PREVIOUS DISCUSSION....Friday through
Wednesday...

High pressure that forms just north of the Mona channel Wednesday
night will bring in moisture on Thursday from the northeast that
will linger until early Saturday morning. This and the easterly
wave that will move through on Friday will continue the good
chances for both night and early morning showers in eastern Puerto
Rico and the U.S. Virgin Islands and showers and isolated
thunderstorms in western Puerto Rico in the afternoon. A break in
the moisture will occur over the weekend. As a cold front sweeps
down through the last of the Bahama islands on Monday a new surge
of tropical moisture invades the area from the Caribbean Sea to
the south. Lower levels will then see wet and dry periods during
the first part of next week and the front will lift to the north
mid week next week before reaching the area.

The ridge of high pressure at upper levels will continue just
east of the area and keep convection limited. The deep long wave
trough invading the western Atlantic on Sunday will weaken in the
process of flattening that ridge in its passage through the area
on Wednesday of next week. Although good moisture will be
available during the week next week it will not be as strong as
has occurred in the last few days.

AVIATION...VFR conds across the flying area and at all terminals
durg the prd. Few SHRA en route btw islands with FEW-SCT cld lyrs nr
FL030...FL050 overnight til 22/14z. L/lvl wnds fm SE 10-15 kts,blo
FL100...bcmg SW-W then incr w/ht abv. SFC Wnd lgt/vrb...bcmg E-SE 10-
15 kts with sea breeze variations along the coastal areas aft
22/14z. No sig wx impact across the region attm.

MARINE...Seas will continue between 3-5 feet across the offshore
waters and between 2-4 feet across the coastal waters through
Wednesday. Seas increase up to 7 feet across the offshore Atlantic
waters between Wednesday night and Thursday. A small craft
advisory will be in effect through this period. A moderate risk of
rip currents will continue for the next several days across the
Atlantic beaches of the islands.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  88  76  88 /  20  20  30  50
STT  76  87  77  85 /  20  30  50  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flash Flood Watch through Wednesday afternoon for Northwest-
     Western Interior.

VI...None.
AM...Small Craft Advisory from 8 PM Wednesday to 2 PM AST Thursday
     for Atlantic Waters of Puerto Rico and USVI from 10 NM to
     19.5N.

&&

$$

SHORT TERM...JF
LONG TERM....DS



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