National Weather Service Today's Weather Impact Levels

071
FXCA62 TJSJ 152108
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
508 PM AST Tue Oct 15 2024

.SYNOPSIS...

Very limited activity is expected through the next few days as a
drier airmass persist over the local area. A gradual increase in
moisture is anticipated on Thursday increasing the potential for
showers and thunderstorms, particularly over the interior and
western Puerto Rico. The National Hurricane Center continues to
monitor an area of low pressure (Invest 94L) located in the
Central Tropical Atlantic. The system has a medium (50%) formation
chance through 7 days and could approach the area by Friday into
Saturday. Residents and visitors should continue to monitor future
updates regarding this system.

&&

.SHORT TERM...Tonight through Thursday...

Sunny skies prevailed across the islands during most of the day. Few
showers were observed today, but the activity remained mainly over
the Mona Passage towards the Hispaniola. It was very hot too across
the region. Highs were seen in the low to mid 90s along the coastal
and urban areas, and from the mid to upper 80s across the mountains.
The Luis Munoz Marin International Airport in San Juan reported a
high of 93 degrees Fahrenheit, breaking a new record of 37
consecutive days with temperatures over 90 degrees.

A drying trend will continue for the next few days as the dry
airmass continues to move into the area. The latest precipitable
water guidance suggest values of 1.0 to 1.4 inches through at least
Wednesday. Therefore, expect limited shower activity until the
latter part of the week. A gradual increase in moisture is
anticipated by Thursday as a surge of moisture move into the
region ahead of a low pressure and tropical wave (Invest 94L) that
is currently being monitored by the National Hurricane Center. On
Thursday, afternoon convective activity is likely across the
interior and northwestern Puerto Rico due to the combination of
daytime heating, local effects and southeasterly winds. Ponding of
water in roads and poorly drainage areas areas is possible with
the heaviest rains.

The National Hurricane Center continues to monitor the
aforementioned area of low pressure , Invest 94L, located over the
Central Tropical Atlantic. There is a very high uncertainty on the
future of this system as it approaches or moves near the Leeward
Islands late this week. Residents and visitors should stay tuned for
further updates.

.LONG TERM...Friday through Tuesday...

PREV DISCUSSION... /issued 458 AM AST Tue Oct 15 2024/

Model guidance indicates gradually increasing moisture on Friday to
start the long term period. The National Hurricane Center (NHC)
continues to monitors a well defined area of low pressure (Invest
94L) over the central tropical Atlantic. Environmental conditions
are expected to become more favorable for gradual development by the
middle to latter part of this week. This system currently has a 60
percent formation chance through 7 days. Model guidance has the
system nearing the local islands Friday into Saturday. It is still
to early to know any direct impacts, that this system could bring.
An increase in overall moisture is still forecast even if the system
doesn`t form, as the system would still pass as a tropical wave and
a broad moisture field would engulf the region, with PWAT values
increasing to above 2 inches possibly through the end of the
forecast period. With the forecast to start the period closely
linked to the future of Invest 94L, uncertainty remains. However,
with increased moisture and overall more unstable conditions, the
chance for overnight and afternoon convection Friday through
Saturday will increase along with the potential for localized
flooding impacts in urban areas, on roads, and along some rivers and
small streams across Puerto Rico and the U.S. Virgin Islands. More
typical weather conditions, albeit with more moisture are forecast
by next week under light to moderate east to southeast winds,
including passing overnight and early morning showers steered by
easterly winds along parts of the east coastal sections of the
islands with afternoon convection expected but mainly focused across
the central interior and northern sections of Puerto Rico. High heat
indices will continue. For more information regarding Invest 94L,
please refer to the latest Tropical Weather Outlook (TWOAT & TWOSAT)
issued by the NHC.

&&

.AVIATION...

(18Z TAFS)

VFR conds to prevail except in isold SHRA in wrn PR with brief MVFR
conds til 15/22Z. LLVL winds 10-15 kt from the ESE with seabreeze
influences. Max winds SE 21-26 kts btwn FL435-475. Winds ovr land to
diminish to less than 10 kts with land breeze influences btwn 15/22Z-
16/12Z then winds will bcm E 10-15kt with hir gusts. Minor SHRA ern
PR aft 16/10Z.

&&

.MARINE...

Gentle to moderate east southeast winds will prevail into mid-week
as a weak surface high pressure pattern continues northeast of the
region. Showers and isolated thunderstorms will move across the
waters with this windflow. Seas up to 4 to 5 feet are forecast for
tonight. The NHC is monitoring Invest 94L over the central tropical
Atlantic, which could increase winds and seas by the end of the
workweek.

&&

.BEACH FORECAST...

There is a moderate risk of rip currents for northwestern to
northeastern beaches of Puerto Rico, as well as for Culebra,
northwestern St. Thomas, easternmost Vieques and easternmost St.
Croix. Low risk elsewhere. Low risk spreading tonight to beaches
western Puerto Rico, St. Thomas and St. John.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

ICP/GRS/LIS

NWS SJU Office Area Forecast Discussion