Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 212159 CCA

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
559 PM AST Sun Apr 21 2019

Strong surface high pressure in the north central Atlantic will continue
to lift farther northwards, as a low pressure system develops in the
subtropical Atlantic. This will induce a light east northeast
wind flow across the region Monday through Tuesday. The moisture
remnants from a cold front will continue to sink southwards across
the region overnight through Monday bringing an increase in
shower activity mainly across the local Atlantic waters and
windward portions of the islands. The mid to upper level ridge
will gradually erode through Monday as a short wave trough moves
across the west Atlantic.


.SHORT TERM...Rest of today through Tuesday...
Locally and diurnally induced afternoon shower activity will diminish
during the early evening hours leaving partly cloudy to mostly clear
skies over land areas. A surface high pressure lifting farther northwards
into the north central Atlantic and the developing area of low pressure
across the subtropical Atlantic will loosen the local pressure gradient
resulting in diminishing easterly winds overnight through Tuesday. However,
a plume of moisture, remnants from a cold front will sink southwards
across the region later tonight and during the early morning hours,
This will bring bring an increase in cloud cover and shower activity
over the local waters and parts of the north and east coastal
sections of the islands.

The mid-upper level ridge will continue to erode as the short wave
trough moves eastward across the western Atlantic through Tuesday.
In the meantime, an induced surface trough will develop over the
central Atlantic and linger northeast of the region through mid
week. This will promote a more northeast wind flow across the region.
The eroding ridge aloft and diminishing northeast winds will result
in the weakening of the trade wind cap inversion and consequently
enhance low to mid level moisture convergence while favoring
deeper convective instability at least through Monday. Areas of
enhanced afternoon convection can be therefore expected on Monday
with periods of locally heavy rainfall. An improvement is expected
by Tuesday due to diminishing trade winds and decreasing moisture
transport. However, local sea breeze convergence and lingering
moisture will give way to periods of moderate to locally heavy
showers mainly during the afternoon hours. By then activity should
be focused more over the central interior and southwest sections
of Puerto Rico.

.LONG TERM...Wednesday through Sunday...
Trade wind moisture transport is to gradually return by Wednesday
and through the end of the work week as a surface high will move
across the west Atlantic and reestablish north of the region.
Meanwhile the aforementioned surface low northeast of the region
is to weaken and lift northwards. This additional advective moisture
transport will increase the chance for passing early morning showers
and afternoon convection, mainly over the interior and west sections
of Puerto Rico.

For the following weekend, model guidance continued to suggest high
pressure will build across the central Atlantic and sink southward
into the tropical Atlantic, as another area of low pressure moves
across the southwest Atlantic. This will produce a fairly moist
southeasterly flow and also create increasing instability aloft
with the approach of an amplifying upper trough just west of the
region. That said, a somewhat wetter and unstable pattern is far
forecast for the weekend.


.AVIATION...Passing SHRA/VCSH will affect the local terminals thru this
evening. The strongest activity will be in the VCTY of Mayaguez thru
at least 22/00z, affecting TJMZ. Activity will diminish overnight
across west and south PR, but occasional SHRA will affect the
E-PR/USVI and the Leeward Islands overnight. Afternoon convection
is expected btwn 22/16-22/23z. Winds will be from the E at 15 to
20 knots with higher gusts and sea breeze variations, dropping
around 10 kts overnight.


.MARINE...Moderate to locally fresh easterly winds will continue
to create hazardous and choppy seas across the regional waters
overnight through early Monday. Small Craft advisory will remain
in effect for the local offshore Atlantic waters. Mariners are
urged to exercise caution across the remainder of the local
waters and passages due to winds up to 20 knots and seas up to 6
feet. A small northeasterly swell will arrive across the local
Atlantic by Tuesday followed by diminishing winds and seas by


SJU  75  85  73  86 /  70  70  40  40
STT  76  86  74  87 /  70  40  20  20


PR...High Rip Current Risk from Monday morning through Monday
     afternoon for Northeast-San Juan and Vicinity-Southeast.

     High Rip Current Risk through Monday afternoon for North Central-

AM...Small Craft Advisory until 8 AM AST Monday for Atlantic Waters
     of Puerto Rico and USVI from 10 NM to 19.5N.



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