038
FXCA62 TJSJ 180816
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
416 AM AST Sat May 18 2024

.SYNOPSIS...

Hazy skies due to suspended Saharan dust and hot weather conditions
are expected through the rest of the weekend. However, shower
development is also anticipated each afternoon across western
portions of Puerto Rico and downwind of the local islands. A wet
and unstable weather pattern continues to be expected by midweek
of next week as a deep- layered trough approaches from the west
and combines with tropical moisture.

&&

.SHORT TERM...Today through Monday...

Partly cloudy to mostly clear skies prevailed across the region
overnight into the early morning hours with few passing showers
noted moving over the regional waters and passages. Little or no
shower activity was observed or reported over land areas so far.
Minimum low temperatures were upper 70s to low 80s along the
coastal areas and in the mid 60s to low 70s In higher elevations
and valleys. Winds were calm to light and variable.

A sfc high pressure over the north central Atlantic will slowly move
eastward over the next few days while a sfc low pressure system
develops and crosses the west Atlantic while lifting northeastward
across the west and central atlantic during the rest of the weekend.
By late Sunday and Monday, another Sfc low pressure exits the
eastern seaboard and moves into the western Atlantic. This forecast
pattern will help to maintain the local winds mainly from the east
southeast to southeast during the next several days with limited
moisture advection during the period. In addition, a weak mid to
upper level short wave trough is forecast to cross the region today
through Sunday then weaken just northeast of the islands by Monday.
This may help enhance a few passing showers during the overnight and
early morning hours. For the rest of the weekend however, hot and
hazy conditions are forecast to prevail with the chance of diurnally
and locally induced afternoon showers and isolated thunderstorms
possible across central interior and west to northwest Puerto Rico.
Mainly fair weather and sunny skies are expected in and around the
U.S. Virgin Islands but a brief isolated afternoon showers cannot be
ruled out. A moderate concentration of Saharan dust will continue to
cross the region later today and continue through the weekend into
Monday.

Overall...A typical rainfall pattern is expected for the rest of the
weekend into Monday...with only locally and diurnally induced
afternoon convection each day mainly across central interior and
western Puerto Rico. Isolated showers are forecast for the period
elsewhere including around the U.S. Virgin Island where mostly sunny
but hazy skies will prevail.  The highest concentration of Saharan
dust is expected by Sunday into Monday. This should aid in limiting
afternoon convection across the region but will enhance the hot and
hazy Conditions.

Expected Impacts...Some of the locally induced afternoon shower and
thunderstorm activity may lead to ponding of water on roads and in
poor drainage areas and possibly minor urban and small stream
flooding due to locally heavy rains accompanying isolated.
thunderstorm activity. Excessive daytime heating may lead to the
issuance of heat advisories each day, particularly across the
coastal and urban areas. Stay tuned and Stay Hydrated!

&&

.LONG TERM...Tuesday to Saturday...

A seasonal pattern will continue through Tuesday as a high pressure
across the surface of the central Atlantic allows a diurnal trade
wind pattern to prevail. However on Wednesday onward through the
weekend, the development of a mid to upper-level trough moving
across the Caribbean basin eastward towards Puerto Rico will begin
to cause tropical moisture to rise up from the ITCZ and spread
across the region. A surface low will also begin to develop due to
this feature, appearing to gain structure by Friday north of the
region. Current model guidance has the dirtiest part of the
upper- low remaining over Hispanola through this event, however
the influx of moist air with high precipitable water values and
southerly flow will cause unstable, wet conditions for the local
islands. Mostly all sections of the islands have a chance to see
some impressive rainfall during this event. Thunderstorms are
likely as well due to strong winds aloft allowing ventilation to
occur.

The anticipated period of excessive and heavy rainfall will
therefore increase the risk of urban and river flooding especially
from Tuesday onwards with the most favorable impacts being Wednesday
through Thursday but activity could continue throughout the end
of the work week so tuned and be prepared, as we will continue to
monitor how this pattern unfolds and make the necessary
adjustments to the long term forecast.

&&

.AVIATION...
(06Z TAFS)

VFR durg prd VCSH at TJSJ/TISX/TIST til 18/14z. Mstly Sct lyrs nr
FL025...FL040...SKC ABV.Isold shra ovr regional waters en route btw
islands.  L/lvl wnds FM ESE 5-10 kts BLO FL100 then backing and bcmg
fm W while incr w/ht abv FL180. Sfc wnd calm to lgt/vrb bcmg fm SE
12-15 kts with local sea breeze variations and hir gusts aft 18/14z.

&&

.MARINE...

A surface high pressure across the central and northeast Atlantic
will result in light to moderate easterly winds through the weekend.
Tranquil marine conditions will therefore prevail throughout the
forecast period. Afternoon showers and isolated thunderstorms could
move from western Puerto Rico into the coastal waters each day.

&&

.BEACH FORECAST...

There is a low rip current risk for today across all area beaches
of Puerto Rico and the U.S. Virgin Islands. The risk will likely
remain low through the weekend. However, life-threatening rip
currents can often occur in the vicinity of groins, jetties and
piers. In addition, with possible maximum heat indices between
102-107 degrees or higher, along the local beaches, heat
exhaustion will be likely with prolonged exposure. Stay hydrated!

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Heat Advisory from 11 AM this morning to 5 PM AST this afternoon
     for PRZ001-002-005-008-010-012.

VI...Heat Advisory from 11 AM this morning to 5 PM AST this afternoon
     for VIZ001-002.

AM...None.
&&

$$

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