980
FXCA62 TJSJ 050921
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
521 AM AST Sun May 5 2024

SYNOPSIS...

A Flood Watch remains in effect for all Puerto Rico and the U.S.
Virgin Islands until this afternoon, with saturated soils, any
brief period of heavy showers or persistentlight rain could lead
to urban andsmall-streamflooding, localized flashflooding, and
debris flow. The precipitable water content is forecast to remain
above normal levels through at least next Thursday, with a drying
trend anticipated by the end of the week.

&&

.SHORT TERM...Today through Tuesday...

Calm weather conditions prevailed overnight with little to no rain
and a few low-level clouds. GOES-E detected a cloud deck between the
mid and upper levels, with a more significant presence near St.
Croix. Shower activity began to increase offshore across the
Atlantic Waters early this morning. Minimum temperatures have been
in the mid and upper 70s across most coastal sites and in the mid
and upper 60s along mountains and valleys.

The wet pattern, fueled by near to above-normal moisture, will
persist throughout the beginning of this week. MIMIC-TPW2 has
indicated a wet air mass with values between 1.80 and 2.00 inches,
lending further support to the GFS guidance. Later today, the GFS
guidance suggests the possibility of additional moisture being drawn
from the Eastern Caribbean south of us over the islands. The
National Blend of Models (NBM) suggests calm weather conditions
during the day, followed by an active afternoon and evening weather
pattern with showers and thunderstorms developing along the
Cordillera Central and north of it and near La Sierra de Luquillo,
as well as downwind from St Croix. Environmental conditions remain
conducive to flash flooding, river flooding, mudslides, and
landslides, a potential risk due to last week`s weather conditions.
Therefore, it`s crucial to stay vigilant and prepared for any
additional. St Thomas and southern Puerto Rico, both, has the
potential to observe a mixture of sunshine and clouds with little to
no rain most of the day.

An upper-level trough will swing by Monday and Tuesday, which
combined with the lingering above-normal moisture content will
promote the continuation of the wet and unstable pattern. Although
we can anticipate periods of no rain, due to the much above normal
river streamflows, and saturated soils, any period of moderate to
locally heavy rain could result in dangerous flooding problems as
well as sudden mudslides/landslides. Currently, the most active
day, based on the latest model guidance could be expected between
late Monday into Tuesday.

&&

.LONG TERM...Tuesday through Saturday...

By Wednesday, the latest models agree that a surface high pressure
will remain dominating over the central Atlantic promoting light
to moderate northeasterly to easterly winds through the end of the
workweek. At upper levels, another trough should move through
Thursday, maintaining unstable conditionsacross the islands with
a moist airmass lingering over the local area. The Precipitable
Water (PWAT) models are suggesting above-normal climatological
levelsthrough at least next Thursday; with values around 1.90-2.20
inches. Consequently, the wet pattern is expected to continue by
midweek with showers and possible isolated thunderstorms
development each afternoon. We encourage residents and visitors
to remain weather-aware because any additional shower activity
over saturated soils will further enhance the potential for flash
flooding and mudslides.

Thursday night into the weekend, a mid to upper-level ridge
extends into the local area from the western Caribbean, bringing a
drier airmass into the upper levels with PWAT values around normal
levels, decreasing the potential for shower development. By Saturday,
the high pressure over the north-central Atlantic will promote
southeasterly winds across our area. As a result, diurnal and
local effects can promote afternoon showers and thunderstorm
activity mainly acrossthe interiorto westernPuerto Rico, but
not expecting significant accumulations since moisture levels
should be lower. In addition, a Saharan Air Layer should be near
the area, but the greater concentrations should stay over the
Caribbean waters.

In summary, expect unstable weather conditions to continue by the
middle of the week, then more stable conditions are anticipated
from Friday onwards.

&&

.AVIATION...
(06Z TAFS)

VFR conditions will prevail this morning, but the unstable
weather pattern will promote the formation of SHRA/TSRA,
especially in the afternoon and evening. VCTS/TSRA may continue to
promote tempo MVFR to brief IFR conditions btwn 05/16-23z near
JSJ/JBQ/ISX. Surface winds will shift from the ENE aft 05/12Z,
ranging between 10-15 kt, but locally higher due to sea breeze
variations and in/near TSRA.

&&

.MARINE...

A surface high pressure extending from the western to central
Atlantic will promote light to moderate easterly winds through the
forecast period. A northeasterly swell is expected to spread
across the local waters by Tuesday and gradually increase seas to
around 5 to 6 feet through the end of the week. Remnant moisture
from the induced surface trough located to our east will continue
to promote shower and isolated thunderstorms development across
the regional waters during the afternoon and evening for the next
several days.

&&

.BEACH FORECAST...

Low risk of rip currents should continue through Monday, then
becoming moderate from Tuesday onwards. However, life-threatening
rip currents often occur in the vicinity of jetties, and piers.

&&

.HYDROLOGY...

A Flood Watch remains in effect for all of PR and the USVI through
this afternoon. Please refer to the latest Flood Watch (FFASJU)
for more information.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...Flood Watch through this afternoon for PRZ001>013.

VI...Flood Watch through this afternoon for VIZ001-002.

AM...None.

&&

$$

SHORT TERM/MARINE...YZR
LONG TERM/AVIATION....CAM