FXCA62 TJSJ 060935

Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
804 AM AST Thu Feb 6 2020

.SYNOPSIS...Moderate to strong easterly trade winds will continue
as surface high pressure holds over the region for the next few 
days. This will result in breezy and hazardous marine conditions, 
at least through the weekend. A more active weather pattern is 
expected for the first part of the next workweek due to an increase
in moisture and instability aloft.

&&

.SHORT TERM...Thursday through Saturday...

Variably cloudy skies prevailed across the islands overnight with
frequent passing showers observed across the eastern coastal 
areas of Puerto Rico, as well as around the adjacent islands. 
Rainfall accumulations associated with these showers, however, 
were minimal. Winds were from the east at 10 MPH or less with 
coastal temperatures in the mid 70s.

A mid to upper level ridge will hold across the forecast area 
through at least the end of the workweek. This feature is expected 
to weaken Saturday onwards as a TUTT establishes east of the local 
area. At lower levels, a high pressure across the central Atlantic 
will continue to yield moderate to fresh east southeast winds. The 
aforementioned east southeast wind flow will continue to bring 
patches of low level moisture across the local islands which are 
associated with remnants of old frontal boundaries. The latest 
guidance suggested that available moisture will remain confined 
below 850 MB. 

As a result, due to the lack of upper level dynamics and low level 
moisture near or slightly below the normal range, the chance for 
passing showers across the east coastal sections of Puerto Rico, 
as well as around U.S. Virgin Islands, will continue today 
through Saturday. Locally induced afternoon showers can't be ruled
out. The chance for shower development is forecast to increase 
from late Saturday onwards as the ridge aloft gradually weakens.

.LONG TERM...Sunday through Thursday

GFS model suggests a gradual increase in moisture on Sunday into 
the beginning of the workweek. This will enhance shower activity 
over the region. However, no significant rainfall accumulation is
expected with this activity. This is due to the fact that a 
moderate to strong easterly wind will prevail over the area 
resulting in the generation of showers of a fast-paced nature. The
strong surface high pressure will enhance the advective weather 
pattern resulting in periods of fast- moving showers across 
eastern sectors of PR and USVI during the morning hours. Then, 
afternoon showers should be focused over the interior and western 
sectors of the islands due to diurnal and local effects. 

By mid-week, model guidance suggest better dynamics at the mid to
upper levels. The 500 mb temperature is expected to drop to -7 
degrees C, indicating increased instability aloft. Furthermore,
moisture is expected to increase across the region, thus promoting
a favorable environment and better potential for the development 
of thunderstorms across the forecast area. 

&&

.AVIATION...VFR conds will continue to prevail with VCSH possible in 
and around the Leeward and USVI TAF sites as well as JSJ in the 
morning hours. Aft 06/16z brief period of MVFR conds will remain 
possible at JBQ in SHRA. ESE winds at around 15 knots with sea 
breeze variations and higher gusts are expected today.

&&

.MARINE...A moderate to fresh easterly wind flow will hold across
the local waters. A strong surface high pressure will maintain
increasing winds and consequently hazardous seas, which will 
continue through the weekend. As result, small craft advisories 
will be in effect this morning through Saturday for the offshore 
Atlantic waters and the Mona Passage. Moderate to high risk of 
rip currents is forecast to continue, at least until Saturday, 
for most of the local beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  87  75  86  74 /  40  40  40  70 
STT  86  76  85  74 /  50  40  50  70 

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...Small Craft Advisory from 8 AM this morning to 2 PM AST Saturday 
     for Atlantic Waters of Puerto Rico and USVI from 10 NM to 
     19.5N-Mona Passage Southward to 17N.

&&

$$

SHORT TERM...OM
LONG TERM....FRG
PUBLIC DESK...99