National Weather Service San Juan PR
450 AM AST Sat Apr 9 2022
.SYNOPSIS...A seasonal weather pattern will prevail today. Mainly
fair weather conditions are expected with some showers across the
island from time to time. Winds are expected to be from the ESE
today at 10-20 mph.This weather pattern will continue through
midweek, when an upper level trough will promote unstable weather
increasing the potential for thunderstorms, heavy rainfall and
flooding.
&&
.SHORT TERM...Today through Monday...
Relatively benign weather is expected through the weekend and on
Monday. Near to below normal moisture is expected across the local
islands with a few patches of moisture over the Caribbean waters,
stable conditions aloft, and overall a seasonable weather pattern is
expected. The day with the highest moisture in the short term period
would be Sunday, and it will peak at near normal levels, and for a
short time during the day. Therefore, brief isolated to scattered
showers are forecast in the overnight and early morning hours across
the USVI and eastern PR as well as the local waters. In the
afternoon hours, showers are expected to develop across portions of
western Puerto Rico. Given the below normal moisture, the shower
activity in the afternoons is expected to be limited in coverage,
but isolated areas could receive up to a half an inch or so of
rain.
The local winds are expected to be from the ESE today at 10-20 mph,
to E-ENE at 10-15 mph by Monday. This is due to a couple of surface
high pressures in the Atlantic that will be dominating the local
wind flow, one of them is over the central Atlantic, which will
dominate through Sunday, then another SFC High will move into the
western Atlantic by Monday. The temperatures will also be near
normal through the short term, but Sunday may have a few degrees
above normal high temperature across the northern portions of PR.,
to E-ENE at 10-15 mph by Monday. This is due to a couple of
surface high pressures in the Atlantic that will be dominating the
local wind flow, one of them is over the central Atlantic, which
will dominate through Sunday, then another SFC High will move into
the western Atlantic by Monday. The temperatures will also be
near normal through the short term, but Sunday may have a few
degrees above normal high temperature across the northern portions
of PR.
.LONG TERM...Tuesday through Saturday...
The forecast continues on track. A mid to upper-level ridge is
expected to diminish as a trough approaches the islands from the
Western Atlantic. This trough is expected to amplify across the
region, promoting unstable weather for the local islands and it will
linger across the area for several days. This pattern will support
the development of showers with rainfall accumulations over Puerto
Rico and the U.S. Virgin Islands. A shift on the winds from the
north-northeast will noticeable, when the trough merge with a
frontal system located in the east coast of the U.S..
Latest model guidance continues to forecast the development of
organized convection, heavy rainfall and thunderstorms. Bands
associated with the trough and the frontal system will place over
the islands by Wednesday (moving into Thursday), enhancing
unstable conditions aloft and shower formation. This pattern will
linger through the end of the long period. Impacts to take in
consideration are: urban and small stream flooding, thunderstorms,
landslides flash flooding, ponding of water in low drainage
areas, and dangerous driving conditions.
&&
.AVIATION...VFR conditions expected across the local terminals
through the forecast period. However, brief VCSH through 09/14Z
possible for TAF sites TJSJ/TIST/TISX. Then, sct SHRA possible
across NW PR between 09/17Z and 09/22Z. Winds will be from the E-ESE
at 5-10 KT through 09/13Z, increasing gradually to 15 to 20 KT with
sea breeze variations thereafter.
&&
.MARINE...Choppy marine conditions will persist throughout the weekend.
Breezy east-southeast winds up to 20 knots will prevail for the next
couple of days. Small Craft should exercise caution across the local
waters and passages. For beachgoers, high risk of rip currents are
in effect for the eastern beaches of Culebra & Saint Croix, and a
moderate risk of rip currents will continue across most local
beaches.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 87 74 89 76 / 10 20 20 20
STT 83 75 85 74 / 10 20 20 10