Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
229 PM AST Thu Oct 20 2016
Synopsis...mid to upper ridge will continue to build from the
east through the weekend. Upper trough across the Bahamas will
continue to weaken. A polar upper trough will exit the U.S. Late
in the weekend with a short wave moving close to the area by early
next week. Southeasterly wind flow will continue through at least
Friday becoming more east to southeast and then east-northeast by
Monday. Warmer than normal temperatures expected during the next
few days due to southerly winds.
Discussion...fair weather conditions with mostly sunny skies prevailed
during the day across the forecast area. A few isolated morning
showers were noted over coastal areas of southern PR and over the
surrounding waters of the U.S. Virgin Islands but rainfall was not
significant. It was warm along the northern coast of PR with
temperatures reaching the low to mid 90s around noon. For the rest
of the afternoon hours a couple of showers could still develop
over the mountain ranges and northwest quadrant of PR. Southerly winds
can bring brief periods of light showers across the USVI and the
southeastern sections of PR through early Friday morning.
As ridge pattern builds aloft expect trade wind cap to limit
shower activity through the weekend, with mostly diurnally induced
afternoon showers favored by sea breeze convergence over the
interior and northwest sections of PR. Across the USVI, mostly
fair weather conditions will prevail with streamers developing
each day. As polar trough and associated short wave moves near the
forecast area by early next week the ridge will weaken and
moisture is expected to increase once again across the forecast
Aviation...VFR conds will continue through 21/16z at all taf sites,
except for very brief MVFR ceilings in rain showers vcnty tncm/tkpk til 20/21z.
Winds southeast up to 12 kt. Rain showers/thunderstorms and rain just west-northwest of local area.
Marine...small craft should exercise caution as seas of 4-6 feet
will continue through at least tonight across the Atlantic waters
and Mona Passage. Seas should continue to subside during the next
few days. High rip current risk continues for the much of the
northern beaches of the islands.
Preliminary point temps/pops...
sju 78 91 78 93 / 10 40 20 20
stt 80 89 81 86 / 30 30 30 30
PR...high rip current risk until 6 PM AST this evening for Culebra-
Mayaguez and vicinity-north Central-Northeast-northwest-San
Juan and vicinity-southeast-western interior.
Vi...high rip current risk until 6 PM AST this evening for St Croix-
St... John.. and adjacent islands.
Am...high rip current risk until 6 PM AST this evening for coastal
waters of northern USVI and Culebra out 10 nm-coastal
waters of southern USVI Vieques and eastern Puerto Rico out
Small Craft Advisory until 2 PM AST this afternoon for Atlantic
waters of Puerto Rico and USVI from 10 nm to 19.5n-Mona
Passage southward to 17n.