Area Forecast Discussion
Issued by NWS San Juan, PR

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642
FXCA62 TJSJ 200103
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
903 PM AST Sun Feb 19 2017

.UPDATE...The ridge overhead is to gradually erode through Monday,
as the base of a mid to upper level trough moving across the southwest
Atlantic will sink south and move across the region Monday through
Tuesday. Low level moisture convergence and pooling of shallow moisture
along old frontal boundary will persist across the region on Monday
and Tuesday as an induced low level trough crosses the region.

This available moisture and increasing mid to upper level instability
will allow for periods of showers across the local waters and the north
and east coastal areas during the overnight and early morning hours.
This will be followed by afternoon convection and increasing cloudiness
across the interior and northern half of Puerto Rico, as well as in
isolated areas over the U.S Virgin Islands. Some afternoon showers
may produce periods of locally heavy rainfall. Thereafter, the ridge
will build aloft and conditions are expected to improve during the
latter part of the work week. No change to the inherited forecast
package at this time as all appear to be in agreement with the present
and expected weather conditions.

&&

.AVIATION UPDATE...SCT-OVC ceiling btwn FL025-FL100 as a frontal boundary
will linger across the local Flying area. -SHRA at times mainly at
TJBQ/TJMZ til 20/06z. SHRA/-SHRA are expected to increase in coverage
and duration across/along the Cordillera Central btwn 20/17-23z. Therefore,
MVFR conds are possible at TJSJ/TJMZ/TJBQ around that time. Calm to
Light and VRB winds overnight, bcmg from the SE-SW at 10kt with sea
breeze variations aft 20/13z.

&&

.MARINE UPDATE...A northerly swell will continue to affect the local
atlantic waters and passages overnight while slowly decaying. Seas
between 2 to 5 feet can therefore across the coastal waters...with
light east to southeast trade winds. Seas will continue to subside
Monday through Wednesday.

&&

.PREV DISCUSSION... /issued 104 PM AST Sun Feb 19 2017/

SYNOPSIS...A dissipating frontal boundary across the local Atlantic
Waters will continue to induce cloudiness and occasional light to
moderate showers across the local islands through Monday.
An upper level trough over the southwestern Atlantic is expected to
move across the Northeast Caribbean tonight and Monday slightly
increasing the chances of showers across the local area. Drier and
stable air mass is expected to encompass the region again Tuesday
and Wednesday.

DISCUSSION...Doppler weather radar indicated an area of
cloudiness and showers moving from the Atlantic coastal waters
across the northern and central sections of Puerto Rico this
afternoon. This activity was associated with a dissipating frontal
boundary across the northeast Caribbean. The associated moisture
will continue to move across the northern sections of Puerto Rico as
well as across Vieques, Culebra and the U.S. Virgin Islands tonight
through Monday. However, only light to moderate shower activity is
expected.

An upper level trough over the southwestern Atlantic this afternoon
is expected to amplify across the northeast Caribbean tonight and
Monday. This feature in combination with the moisture provided by
the aforementioned frontal boundary will result in an increase in
cloudiness and showers activity tonight through early Monday. A
general dry and stable weather pattern will encompass the region
Late Tuesday and Wednesday.

AVIATION...Mainly VFR conditions will continue across the local
flying area through much of the forecast period. However, SHRA and
BKN/OVC cigs will affect some of the local terminals as a frontal
boundary dissipates over the region tonight and early Monday. Light
low level winds from the East to ESE will prevail tonight.

MARINE...A moderate swell will continue to reach the Local
Atlantic waters through late tonight. Seas of 4-6 feet in north
swell have increased the risk of rip current along the north coast
of Puerto Rico. Seas will gradually subside Tuesday and Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  73  86  76  82 /  20  30  50  20
STT  74  80  73  80 /  20  20  50  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 AM AST Monday for North Central-
     Northeast-Northwest-San Juan and Vicinity-Southeast-Western
     Interior.

VI...None.
AM...None.
&&

$$

27/09



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