Area Forecast Discussion
Issued by NWS San Juan, PR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

000
FXCA62 TJSJ 260116
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
916 PM AST Wed May 25 2022

.UPDATE...The 26/00z TJSJ sounding indicated a 500 mb temperature
of -10.2 degrees C, and good low to mid-level columnar moisture
with a PWAT of 1.85 inches. Water vapor imagery shows the TUTT-low
just north of the region, and isolated thunderstorms with periods
of heavy showers developed along the base of the mid-level trough
over portions of southern and eastern PR, as well as across the
Caribbean waters during the evening hours. Near 2 inches of rain
were observed with this activity between Naguabo and Fajardo. For
the rest of the overnight hours, moisture content is expected to
continue to increase across the region, and showers with possible
isolated thunderstorms could develop over the coastal waters and
affect portions of the islands due to the proximity of the upper
low.

&&

.AVIATION...Mainly VFR conditions expected overnight, however,
SHRA/TSRA could develop over the local waters and briefly affect
the local terminals. Tempo MVFR to brief IFR conditions are
possible btw 26/16z-22z across the PR terminals due to TSRA. The
26/00z TJSJ sounding indicated E-ESE winds at 8-18 kt blo FL050.


&&

.MARINE... A small northerly swell will continue to move across
the Atlantic waters and passages tonight, and a High Rip Current
Risk was issued for the northern beaches of PR and Culebra through
Thursday night. Seas will remain between 3 and 5 feet in general
through the weekend. Moderate trades will prevail through late
Friday, increasing during the weekend.


&&

.PREV DISCUSSION... /issued 520 PM AST Wed May 25 2022/

SYNOPSIS...Favorable weather conditions for heavy showers and
thunderstorms activity will continue as the upper-level trough
moves over the area. The threat of urban and stream flooding will
remain elevated through the end of the workweek with possible
flash floods and mudslides in localized areas. A small northerly
swell moving across the local waters will increase the risk of
rip currents for the north-facing beaches of Puerto Rico by this
evening.

SHORT TERM...Tonight through Friday...

Western, western interior and central interior portions of Puerto
Rico started very active with heavy showers and strong thunderstorms
by early afternoon. Several flood advisories and two Special Weather
Statements were issued for some of those municipalities. The
long-lasting regenerating thunderstorms over Orocovis developed
very high vertically integrated liquid (VIL) close to 70 g/m2 with
elevated reflectivity values above 60 dBZ indicative of possible
hail formation within the storm. Later pea-size hail at the
surface was confirmed by several social media posts and news over
that same area. Currently, shower activity is more stratified over
central interior, north central and San Juan metro area with
thunderstorms developing across the southwest moving over the
local waters. Expect a gradual decrease in activity over land
areas through early evening hours with a few thunderstorms
developing over the local waters through the night hours,
especially over the Caribbean waters where the bulk of moisture in
the atmospheric column is present as observed by satellite
imagery. Some trade wind showers can be expected over the eastern
third of Puerto Rico, Vieques, Culebra and the U.S. Virgin Islands
late tonight into the morning hours.

As the the mid- to upper-level trough continues to strengthen,
another active afternoon is forecast for Thursday. In fact, Thursday
looks to be the most active day of this event with below normal mid-
level cold temperatures and strengthening of the upper-level jet
rounding the trough with winds between 50 to 60 knots. The jet
will be positioned over the U.S. Virgin islands and eastern Puerto
Rico which could enhance activity in that region. A surge of
moisture with precipitable water values above 2.0 inches over the
Caribbean waters and U.S. Virgin Islands will combine with
instability aloft promoting heavy showers and isolated to
scattered thunderstorms across Puerto Rico and the local islands.
Therefore, elevated threat for urban and stream flooding will
continue, with localized flash flooding and mudslides in steep
terrain possible, especially in those areas with saturated soils
and increased vulnerability from previous rains. Friday will be
transitioning day as the trough weakens and moves away from the
area. However, unstable weather conditions aloft and sufficient
moisture will persist and, although less widespread than Thursday,
another active afternoon can be expected with the diurnal
convective activity.

LONG TERM...Saturday through Thursday...

PREV DISCUSSION... /issued 411 AM AST Wed May 25 2022/

As an upper level trough moves away from the local area, a
building high pressure in the western Atlantic will be in charge
of promoting fair weather conditions to the local islands. This
system will allow trades winds form the east-southeast. As a
result, expect morning showers across the U.S. Virgin Islands, and
eastern sectors of Puerto Rico from time to time. Much drier air
will filter into the region, leading to warmer temperatures along
Puerto Rico and the U.S. Virgin Islands. Nonetheless, because of
the daytime heating and local effects the atmosphere will be
conductive for mid-afternoon convection and will feed the
development of shower activity and isolated thunderstorms across
the interior, western and northwestern Puerto Rico. Streamers also
cannot be ruled out to form over El Yunque are and moving over
the metropolitan area of San Juan. Overall, fair weather
conditions likely to prevail.

AVIATION...VFR durg prd. SCT- BKN lyrs nr FL025...FL050..FL080 en
route btw PR and the U.S. Virgin Islands with SHRA/Isold TSRA psbl
ovr the regional waters. Aftn SHRA/Isold TSRA fcst in and around the
islands and some of the local terminals til at least 25/23Z. MVFR
due to low CIG/SHRA and Isold TSRA along with brief MTN Top Obscr
ovr central mountain range of PR. SFC wnds mainly fm E btw 12-18 kts
with ocnl hir gusts and sea breeze variations...bcmg Lgt/Vrb aft
25/23Z.low level wnd fm E-SE 5-15 kts and veering w/ht...bcmg FM
W and incr w/ht ABV FL180.

MARINE...A small northerly swell is building seas up to 5 feet
across the Atlantic waters and local passages. Light to moderate
trade winds are expected to prevail until Friday, then are
expected to increase due to a building high pressure in the
central Atlantic. For beachgoers, there is a moderate risk of rip
currents across most of the local beaches. This evening, a high
risk of rip currents will be in effect for the north facing
beaches of Puerto Rico and Culebra.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  76  88  78  87 /  60  60  60  50
STT  76  87  77  87 /  50  60  50  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late Thursday night for Culebra-
     North Central-Northeast-Northwest-San Juan and Vicinity-
     Southeast.

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

$$

SHORT TERM...DSR
LONG TERM....CVB
PUBLIC DESK...MRR


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.