Flash Flood Warning 58, NWS JSJ

Area Forecast Discussion
National Weather Service San Juan PR
502 PM AST Thu Sep 29 2022

.SYNOPSIS...

A wet pattern is forecast for the rest of the short term period
as tropical moisture from the will reach the islands embedded in
the wind flow. This moisture will combine with an upper low and
will result in long periods of showers and thunderstorms across
the area. Given the expected conditions there is a potential for
urban and small stream flooding each day. For tonight, seas will
remain up to 5 feet with winds up to 15 knots.

&&

.SHORT TERM...&& Rest of Today through Saturday…

A wet and unsettled weather pattern is expected during the short
term period. At the surface, a south-southeast wind flow
generated by the influence of Hurricane Ian located far away over
the northwestern Atlantic will push plenty of tropical moisture
from the ITCZ (Intertropical Convergence Zone) over the region.
Meanwhile, the divergence side of a Tropical Upper Tropospheric
Trough (TUTT) moving westward with the axis over the Hispanola
will induce unstable conditions aloft for all the period.
The deep upper low will also reflect at the mid levels,resulting
in colder temperatures at the 500 MB, between -8 to -9 Celsius,
Given the expected conditions, expected periods of heavy rainfall
activity with scattered thunderstorms, gusty winds and frequent
lightning across the interior, northwestern quadrant, and the San
Juan Metro area each day. With the heaviest activity, expect
urban and small stream flooding, as well ponding of water in
roadways and poor drainage areas. Daytime temperatures are
forecast to round between the upper 80s to the mid 70s, with heat
indices in the upper 90s to the 100 degrees.

.LONG TERM...Sunday through Friday...from previous discussion...

Southerly induced winds due to Hurricane Ian's northward path will
continue to affect the local islands on Sunday. Therefore, deep-
layered moisture advected from the south in combination with lasting
instability aloft will support wet and unstable weather
conditions throughout the day. Increased areal coverage of showers
with isolated thunderstorms can be expected to develop across the
local waters and over portions of the islands on Sunday,
especially during the day with diurnal convection favoring along
interior and northern slopes of Puerto Rico. This activity will
continue on Sunday night and extend to early Monday. Therefore,
the flood threat will remain elevated on Sunday and Sunday night
with a flooding potential across urban, roads and small streams.
Localized flash flooding cannot be ruled out.

According to model guidance, this pattern will gradually diminish
by early next week as winds shift out of the east by late Monday
into Tuesday. Although instability aloft may decrease slightly due
to a building ridge aloft, enough low-level moisture along with
surface heating and local effects will be sufficient for afternoon
convective development. Therefore, expect showers and isolated
thunderstorms across interior and western portions of Puerto Rico
each afternoon along with showers across windward coastal areas
of the local islands during night and morning hours. Flooding
threat for Monday through mid week will be limited with the
potential of ponding of water in roads and poorly drained areas.
Localized urban and small stream flooding can be expected at times.
Both GFS and ECMWF models suggest the arrival of a vigorous
tropical wave by the end of next week. The eventual path and
strength of this tropical wave will determine how significant the
impacts will be and which locations will affect the most.
Therefore, please continue to monitor the latest forecasts as more
details emerge as we get closer to the forecast period.

&&

.AVIATION...
SHRA/TSRA will develop across the local flying area thru at least
30/00z. These SHRA/TSRA will create MVFR and mtn obsc across the
local islands that will last thru arnd 29/23Z. TJSJ/JBQ/IST/ISX have
TEMPO due to TSRA and MVFR conds. SHRA/TSRA will develop tomorrow
btwn 30/16-23z. Sfc winds E-ESE 6-12 kt with gusts to 25 kt psbl
arnd TSRA. Winds will become calm to light and vrb overnight, winds
will return from the E/ESE at 10 kt with higher gusts and sea breeze
variations aft 30/13z.

&&

.MARINE...

Across the local waters, seas will remain up to 5 feet. Winds
will continue from the south-southeast at 15 knots with gusty
winds near the heaviest shower activity. With the heaviest
activity, isolated thunderstorms and gusty winds could not be
ruled out tonight. There is a moderate risk of rip currents
across all the north, and east coast of Puerto Rico, Culebra, and
Saint Croix.

&&

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

JA /LIS/ RC

Perspectivas sobre las Condiciones Peligrosas del Tiempo
Servicio Nacional de Meteorologia en San Juan PR
437 AM AST jueves 29 de septiembre de 2022

AMZ710>745-PRZ001>013-301000-
San Juan y Vecindad-Noreste-Sureste-Este
Interior-Norte Central-Interior Central-Ponce y Vecindad-Noroeste-
Oeste Interior-Mayaguez y Vecindad-Suroeste-Culebra-Vieques-Las
aguas costeras cercanas y lejanas a la costa del Atlantico y del
Caribe-
437 AM AST jueves 29 de septiembre de 2022

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Puerto Rico y las aguas costeras adyacentes.

.DIA UNO...Hoy y Esta Noche

.Rayos...Tronadas numerosas son posibles a traves de Puerto Rico y
las aguas adyacentes. Mantengase pendiente a tronadas en su area y
preparese a buscar refugio.

.Lluvia excesiva...Inundaciones urbanas, carreteras y riachuelos.
Inundaciones repentinas aisladas son posibles.

.Corrientes Marinas...Corrientes marinas amenazantes a la vida
son posibles en la zona de olas rompientes particularmente a traves
de las playas del norte y este de Puerto Rico y Culebra.

.DIAS DOS HASTA EL SIETE...viernes a miercoles

Existe riesgo de calor excesivo limitado a lo largo de las areas
bajas de la costa norte de Puerto Rico. Un riesgo moderado de
corrientes marinas regresara a las playas del norte y suroeste el
martes y miercoles. Existe riesgo elevado de lluvia el viernes hasta
el domingo y riesgo limitado el lunes y martes. Existe riesgo
elevado de tronadas el viernes y sabado y riesgo limitado para el
sabado hasta el martes.

.Comunicado sobre informacion reportada por observadores...

No se necesita la activacion de los observadores.

AMZ715-725-VIZ001-002-301000-
San Tomas, San John e Islas Adyacentes-Santa Cruz-
Aguas cercanas del Atlantico y aguas costeras adyacentes del Caribe-
437 AM AST jueves 29 de septiembre de 2022

Esta perspectiva sobre las condiciones peligrosas del tiempo es para
Islas Virgenes Estadounidenses y las aguas costeras adyacentes.

.DIA UNO...Hoy y Esta Noche

.Rayos...Tronadas numerosas son posibles a traves de las Islas
Virgenes Estadounidenses. Mantengase pendiente a tronadas en su area
y preparese a buscar refugio.

.Lluvia excesiva...Inundaciones urbanas, carreteras y riachuelos.
Inundaciones repentinas aisladas son posibles.

.Corrientes Marinas...Corrientes marinas amenazantes a la vida son
posibles particularmente en Santa Cruz.

.DIAS DOS HASTA EL SIETE...viernes a miercoles

Existe riesgo moderado de corrientes marinas el viernes, martes y
miercoles para Santa Cruz. Inundaciones urbanas son posibles el
viernes y sabado. Se esperan tronadas aisladas desde el viernes
hasta el lunes.

.Comunicado sobre informacion reportada por observadores...

No se necesita la activacion de los observadores.