National Weather Service San Juan PR
435 AM AST Fri Dec 21 2018
.SYNOPSIS...Patches of low-level moisture embedded in moderate
easterly trade winds will continue to move across the forecast
area from time-to-time. However, the presence of a mid level high
pressure will limit the intensity and coverage of any associated shower
activity, resulting in mostly fair weather conditions through the
forecast period. A slight increase in moisture content and shower
activity is expected during the weekend, but no significant
rainfall accumulations are expected. A seasonal and relatively
dry weather pattern will return next week.
&&
.SHORT TERM...Today through Sunday...
Seasonal weather pattern had prevailed this week and will continue
through much of the forecast period. Mid/upper level ridge pattern
will hold aloft inducing a strong trade wind cap through the short
term period. At the surface, a high pressure drifting into the north
central Atlantic Ocean will promote a breezy trade wind flow across
the region. In addition, a frontal boundary which is forecast to
move across the western Caribbean and Atlantic ocean today, will
linger off to the west and northwest of the local islands.
Model guidance continue to suggest a drier than normal airmass
through the short term period. However, trade wind perturbations
will bring pockets of moisture/clouds at times, which will lead to
fast moving passing showers across the windward sections of Puerto
Rico and the U.S. Virgin Islands each day. However, moisture content
and shower activity should increase somewhat by the upcoming
weekend. Meanwhile, the high pressure aloft will make difficult
vertical development and afternoon convection over the western and
interior sections of Puerto Rico, but should not be ruled out.
Rainfall amounts should be light to moderate.
.LONG TERM...Monday through Friday...
Patches of low-level moisture embedded in the trade winds will
continue to move across the forecast area through the long term
period. As a high pressure system exists the eastern coast of the
United States and moves over the western Atlantic late Wednesday
night into Thursday, there will be a slight increase in the
moisture transported with these patches. However, a mid level
high pressure that is forecast to hold over the region will limit
the intensity and coverage of any shower activity that develops
over the forecast area. As a result, mostly fair weather
conditions will prevail across Puerto Rico and the U.S. Virgin
Islands. No significant rainfall accumulations are expected.
&&
.AVIATION...Mainly VFR conditions are expected to prevail across all
terminals through the forecast period. However, -SHRA/SHRA possible
this afternoon in and around TJSJ/TJMZ/TJBQ/TIST/TISX. Light to calm
and variable winds, increasing at 10 to 15 knots out from the east
with higher gusts and sea breeze variations after 21/13z.
&&
.MARINE...Choppy/Rough marine continue will continue through at
least this evening across the offshore Atlantic waters and the
Anegada Passage with seas up to 7 feet. Thus, Small Craft
Advisories remain in effect. Small craft operators should exercise
caution across nearshore Atlantic waters and Mona Passage due to
seas up to 6 feet. Elsewhere, seas up to 5 feet are expected.
Moderate easterly winds will prevail today and on Saturday, but
are forecast to increase on Sunday into early next week. A high
rip current risk is in effect for beaches along the north coast of
Puerto Rico, Culebra, and Saint Thomas. Marine conditions will
improve during the weekend.
&&
.FIRE WEATHER...Relative humidity values are expected to drop
into the mid 40s to low 50s today. Although winds are forecast to
range between 10-15 mph, recent KBDI and 10-hour fuel moisture
observations show that a drying pattern continues to dominate the
local islands and given that no significant wetting rains are
expected, elevated fire weather conditions can be expected. As a
result, a Fire Danger Statement has been issue for today,
particularly for the southern coastal plains of Puerto Rico where
KBDI values are near or above 600.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 85 73 85 75 / 10 40 40 30
STT 85 75 84 74 / 10 50 50 30