Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 052158
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
558 PM AST Mon Dec 5 2022


.SYNOPSIS...

Northerly wind flow will continue to bring passing showers across
the Atlantic waters and northern sections of Puerto Rico tonight
throught at least Wednesday. Hazardous marine and coastal
conditions will prevail all the week across the Atlantic waters
and local passages.

&&


.SHORT TERM...Rest of Today through Wednesday...

A seasonal pattern will prevail for most of the short term. At
the surface, a building high pressure over the western Atlantic
and an induced low pressure monitored by the National Hurricane
Center will maintain a northerly wind flow across the forecast
area. Embedded in the wind flow, patches of shallow moisture will
reach the local islands, increasing the frequency of the passing
showers. This shower activity is not forecast to be significant;
however, ponding of water in roadways will be possible. On
Tuesday, as the surface low develops and moves more to the Central
Atlantic, bands of moisture and cloudiness will support the
passing shower pattern. Regardless of the moisture reaching the
area, stable conditions in the mid to upper levels will not allow
heavy showers to develop across the region. Therefore, residents
could expect only ponding of water in roadways and poor drainage
areas. Breezy conditions will persist for the entire period,
inhibiting the sea breezes across the islands. A similar pattern
will stay on Wednesday with generally fair weather conditions.

In response to the northerly wind flow, temperatures will drop
below climatological normals for December. Consequently, residents
can expect colder temperatures in the coastal areas, between the
upper 70s to the low 80s, and across the mountain near the mid 50s
to the low 60s.

&&

.LONG TERM...Thursday through Monday...from previous
discussion...

A low pressure system located to the northeast will cause a
breezy north to northeasterly wind flow to prevail across the
local area. Drier, northern sourced air is expected to move in by
this time, reducing the amount of showers over the long term
period. However, the proximity of an upper level jet on Thursday
and Friday will allow these days to be the best time for showers
before a drier weekend lies ahead. Northern to the interior
sections of Puerto Rico and the USVI should receive the best
rainfall due to these conditions. No flooding threat is expected
as the majority of showers will be fast moving and isolated.

By Friday into the weekend, wind flow starts to become more
northeasterly. However, as another trough moves into the Western
Atlantic, northerly flow returns by Sunday afternoon, with a bit
of a westerly component overnight. Precipitable water values
around this time are below climatological average, which is an
indicator that any showers that form will be light and it is
expected that the northern sections of PR and the USVI will
experience the most rain, if any. This pattern of northerly winds
with light passing showers will continue throughout the end of
the long term period as low pressure across the Northern Atlantic
continues to influence a backing windflow pattern.

&&

.AVIATION...
Mainly VFR conditions will prevail across most local terminals
throughout the cycle. Brief showers may result in MVFR conds
anywhere north of the Cordillera Central and in the nrn USVI, incrg
aft 06/02Z. Clds topping mtns drg the period. Sfc winds 10-15 kt
with gusts to 25 ocnly 30 kts in SHRA thru 06/16Z. Max winds NW 70-
80 kts btwn FL340-390 and W 70-75 kts btwn FL440-470. Winds blo
FL130 NNW less than 25 kt xcp at FL070.

&&

.MARINE...

Hazardous marine conditions will prevail due to a northeasterly
swell spreading across the Atlantic Waters. Expect seas up to 10
feet, and occasionally greater, across the Atlantic waters and
Caribbean Passages tonight into Wednesday. As a result, Small
Craft Advisories remain in effect for most of the local waters.
Another northeasterly long dominant period swell will arrive the
local islands, increasing the seas even more on Thursday into the
upcoming weekend. Please stay tuned for additionally information.


Hazardous coastal conditions will prevail due to large breaking
waves. Therefore, a High Surf Advisory and a high risk of rip
currents also remain in effect due to expected breaking waves
around 6 to 12 feet, mainly across north-facing beaches of Puerto
Rico, Culebra, and the northern USVI.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Thursday afternoon for PRZ001-002-
     005-008-010-012-013.

     High Surf Advisory until 6 AM AST Thursday for PRZ001-002-005-
     008-012.

     High Surf Advisory until 6 PM AST Wednesday for PRZ010.

VI...High Rip Current Risk through Thursday afternoon for VIZ001-002.

     High Surf Advisory until 6 PM AST Tuesday for VIZ001.

&&

$$

SHORT TERM...MRR
LONG TERM....LIS
PUBLIC...CAM


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