207
FXCA62 TJSJ 270916
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
516 AM AST Fri Sep 27 2024

.SYNOPSIS...

A tropical wave is expected to cross the local islands today.
Periods of locally heavy showers and thunderstorms are expected
across the area at times. Therefore, there is an elevated
rainfall risk across the eastern and western portions of Puerto
Rico. For the weekend, a drying trend is anticipated. However,
there is the potential to observe afternoon induced convective
activity across the western portions of Puerto Rico each day.

&&

.SHORT TERM...Today through Sunday...

Scattered showers and isolated thunderstorms were observed overnight
across the local waters and over portions of the islands as a
tropical wave is crossing the local area. Additional shower and
thunderstorm development is expected through at least the evening
hours under a moist E-ESE wind flow. The 27/00z TJSJ sounding
indicated 2.17 inches of precipitable water (PWAT) and it is
expected to peak near 2.40 inches by noon today. Therefore, any
period of locally heavy rainfall can cause quick urban and small
stream flooding, as well as isolated flash flooding and mudslides in
areas of steep terrain. The thunderstorm activity over the waters
may produce strong gusty winds across the coastal areas of the USVI
and PR.

For the weekend, a drying trend is expected as a broad ridge
develops from the western Atlantic and an upper-level low develops
over the Leeward Islands. This will cause PWAT values to drop below
2 inches. However, afternoon showers and isolated thunderstorms will
develop over the western sections of PR due to the combination of
daytime heating, the available moisture, and the sea breeze
convergence. For Sunday, instability increases due to the proximity
of the upper-level low and the afternoon thunderstorms could produce
strong gusty winds.

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

A dominant high pressure located in the western Atlantic north of
The Bahamas will promote east to northeast winds through much of the
period. Therefore, mainly calm and fair weather conditions are
expected. On Monday and Tuesday patches of moisture will enter the
region producing few showers during the morning hours across the
windward portions of the islands. Then, in the afternoon hours
shower development with few thunderstorms are likely over the
interior and southwestern portions of Puerto Rico. However, shower
accumulations are not significant at this time across these areas.
From Wednesday through the rest of the workweek, winds will turn
from the northeast in response of the high pressure and a possible
tropical system developing in the tropical Atlantic away from the
region (based on the latest guidance). Despite of the wind
direction, hot temperatures are very likely during most of the
period with highs reaching the upper 80s to low 90s along the
coastal and urban areas of the islands. The precipitable water
content will remain below 2.0 inches across the region for most of
the workweek.

&&

.AVIATION...

(06Z TAFS)

A tropical wave is producing sct SHRA/TSRA across the local area.
This may cause tempo MVFR conds across all terminals through at
least 27/22z. Max tops were nr 45 kft btw TJSJ and TJBQ early this
afternoon. Mtn obscd expected over the eastern range of PR. East
winds will increase btw 12-16 kt with higher gusts and sea breeze
variations aft 27/14z.

&&

.MARINE...

A high pressure ridging over the region will maintain gentle to
moderate easterly winds over the next few days. A northerly swell
will maintain seas to around 4 to 5 feet through the weekend. Shower
and thunderstorm activity will continue and increase today as a
tropical wave move across our region.

&&

.BEACH FORECAST...

Breaking waves up to 8 feet and locally higher at times are
expected along the north facing beaches of Puerto Rico, from
Fajardo to Rincon, and Culebra. This is due to a long period north
to northeasterly swell. A high risk of life-threatening rip
currents is in effect along the northern coast of Puerto Rico and
Culebra today.


&&

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

VI...None.
AM...None.
&&

$$

DSR/GRS