National Weather Service San Juan PR
551 AM AST Fri Feb 23 2018
.SYNOPSIS...High pressure will fade in the western Atlantic just
north of the local area over the weekend and into early next
week allowing winds to diminish and hazardous marine conditions
to subside. Moisture will peak on Sunday with increasing showers
until then. A gradual drying trend will then continue through next
Thursday.
&&
.SHORT TERM...Today through Sunday...
Satellite imagery detected patches of clouds approaching the islands
from the northeast. As these clouds approached, the Terminal Doppler
radar indicated showers with periods of moderate to locally heavy
rain. Through the morning hours, most of the activity is expected to
affect the local Atlantic Waters, the U.S. Virgin Islands, Vieques,
Culebra as well the northern and eastern sections of Puerto Rico.
Although rainfall amount are expected to be minimal, brief periods
of heavy showers could produce hazardous driving conditions. Showers
are forecast to develop across the interior and western sections
around noon, but some brief trade wind showers will remain possible
across the St Thomas, Culebra, the north and east Puerto Rico.
A strong but fading surface high pressure over the western
Atlantic will continue to dominate the local weather conditions
through at least the upcoming week. An upper level trough will
extend southwest over Hispanola through the weekend. Although the
surface moisture is not significant, the surface high pressure
will continue to push patches of moisture across the local
islands, which will result in scattered to numerous showers mostly
during the overnight and early morning hours. Then during the
afternoon hours, this moisture will combine with the upper level
dynamic to result in showers over the western portions of Puerto
Rico as well as downwind from the U.S. Virgin Islands each
afternoon.
.LONG TERM...Monday through Saturday...
Surface high pressure will fade in the western Atlantic just
north of the local area early next week, but will be replaced by a
second high moving out of the eastern United States Wednesday
through Friday. The rumpled remains of a cold front will pass
through the area Monday through Tuesday next week with continued
shower activity, even while precipitable water values trend
downward from Sunday`s peak. This will be due to drying at the top
of the lower levels of the atmosphere. A drier and much more
stable air mass will be ushered in behind the remnants of the cold
front passage on Tuesday. This will limit shower activity area-
wide. Moist air behind a second front on Friday of next week will
prepare the area for possibly more shower activity and a more
vigorous pre-frontal trough early in the week after next.
&&
.AVIATION...SHRA will continue to move across TJSJ/TIST/TNCM/TKPK
through the morning hours. Some of these SHRA will produce brief BKN
ceilings btwn FL020-FL050 at these sites. VFR conds are expected
elsewhere. SHRA will develop near TJMZ and in the VCTY of TJPS
during the afternoon (btwn 23/16-23z). ENE winds 10-15 kt
increasing at 15-20 knots with higher gusts aft 23/12z.
&&
.MARINE...Seas are expected to subside slowly this evening through
Sunday, such that by Sunday night all small craft advisories
should be down. Swell from a strong low in the northern Atlantic
mid week next week will send another surge of swell into the area
Wednesday night and Thursday when small craft advisories will
again be needed for the Atlantic waters and passages.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 81 73 82 73 / 60 60 60 60
STT 83 72 83 72 / 60 60 60 60