588
FXCA62 TJSJ 030905
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
505 AM AST Mon Jun 3 2024

.SYNOPSIS...

A wetter and unstable pattern is anticipated through at least
mid- week as a tropical wave continues to affect the region
maintaining high moisture content across the area. Therefore,
the risk of flooding rains will remain elevated across most of
the forecast area. Improving conditions are foreseen by the second
part of the workweek into the weekend.

&&

.SHORT TERM...TOday through Wednesday...

The weather conditions prevailed variably cloudy, and the winds were
from the east-southeast. The minimum temperatures ranged from the
upper 70s along the coast to the upper 60s across mountains and
valleys. The Doppler Radar detected some showers moving from the
Caribbean Sea across St Croix and the south and southeast coast of
Puerto Rico, making their way into the eastern interior, northeast,
and the San Juan Metro Area. Ponding of water in roads and poorly
drained areas was likely with the periods of heavy rain.

An unstable weather pattern will prevail today due to abundant
tropical moisture from a tropical wave and the proximity of an upper-
level trough. The available moisture with the expected maximum air
temperature will produce muggy heat index values in the upper 90s
and surpass 100 degrees Fahrenheit today, especially when rain
activity is absent or after brief showers. We are also anticipating
unsettled weather conditions today, especially by the afternoon,
which means that flooding of urban areas, roads, and small streams
is likely, and flash floods are possible.

On Tuesday, as the surface high pressure (north of the region across
the Western Atlantic) migrates further east into the Central
Atlantic, a surface-low pressure will follow it, inducing a
southerly wind flow and pooling plenty of tropical moisture over the
Northeast Caribbean. GFS total precipitable water suggested values
near or above 2.25 inches, above the normal values for the San Juan
area`s local climatology for June.

Although this wet and unstable weather pattern will persist through
Wednesday as the surface-low pressure promoted additional tropical
moisture to pool over PR and the USVI, the NASA Dust Extinction
(Aerosol Optical Thickness) guidance suggested the presence of
traces of African Desert Particles filtering across the region,
especially Wednesday into the second part of the work week.

&&

.LONG TERM...Thursday through Monday...

Currently, Thursday looks like the transition day as we will
gradually/slowly move from a wet and unstable weather pattern to
dry and mostly fair weather conditions. The Dust Aerosol models
indicate the arrival of Saharan Dust particles reaching the
forecast area, with concentrations potentially reaching 0.20 on
Thursday. These concentrations across Puerto Rico and the U.S.
Virgin Islands will lead to a slight to moderate dust event.
Therefore, we added it to the forecast for Thursday. Nevertheless,
climatological Precipitable Water(PW) models still suggest values
ranging above the 75th percentile or around 2.00 inches as
lingering moisture from the past tropical wave and the mid-upper
level trough across the northwestern Caribbean remains.

From Friday onwards, the latest model guidance shows a deep layered
ridge building and holding just east of the Leeward Islands. We
foresee, mostly fair typical weather conditions with warm
temperatures across the islands as mostly southeasterly winds
will dominate through at least Monday.

&&

.AVIATION...

(06z TAFs)

Expect an unstable weather pattern today with the arrival of
SHRA/TSRA across the local flying area. Therefore, occasional
periods of MVFR or brief IFR conditions at local terminals
(especially 03/10-14z and 03/16-20z) are expected. Winds will
prevail from the ESE at 5 to 10 kt, then between 10-15 kt after
03/13z, with higher gusts and sea breeze variations.

&&

.MARINE...

A surface front stalled in front of a sub tropical high pressure
across the Western Atlantic north of the islands will promote a
south to southeasterly wind flow across the islands. A wetter pattern
is anticipated through at least mid-week as a tropical wave
continues to affect the region maintaining high moisture content
across the area with increasing seas and winds, as a result small
craft should exercise caution across most of the regional waters and
local passages.

&&

.BEACH FORECAST...

A High Rip Current Risk is in effect from this morning to this
afternoon for beaches of St Croix. A moderate risk is expected
across most southern and eastern facing beaches of Puerto Rico,
Vieques, Culebra, St Thomas, and St John, while a low risk is
anticipated for the northern and western beaches of Puerto Rico.
The risk of rip currents is expected to remain between low and
moderate through at least midweek, then return to low by the end
of next week.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...High Rip Current Risk through this afternoon for VIZ002.

AM...None.
&&

$$

SHORT TERM/AVIATION/MARINE...CAM
LONG TERM/BEACH FORECAST...MMC