Area Forecast Discussion...CORRECTED
National Weather Service San Juan PR
447 AM AST Mon Feb 8 2021
Generally fair weather will prevail across the region over the next
several days, as a relatively dry air mass sits over the area, along
with stable air aloft. Occasional patches of moisture will pass
through the region, supporting isolated to scattered showers in a
typical pattern. Showers will be relatively quick-moving, carried
along by brisk winds, due to a tight pressure gradient associated
with surface high pressure to the north. Marine conditions have
improved somewhat, and seas of up to 6 feet are expected, with a
moderate risk of rip currents for the majority of local beaches.
.SHORT TERM...Today through Wednesday...
A mid-level ridge is expected to prevail through the period,
resulting in dry and stable weather conditions aloft. This will
inhibit any potential of organized convective activity across the
local area. Meanwhile, at lower-levels, a surface high pressure
located across the central Atlantic will maintain a brisk easterly
wind flow. Currently, a pocket of dry air is over the area, which
has resulted in dry weather conditions over the local islands during
the overnight period. However, an area of shallow moisture is
expected to move across the USVI during the early to mid-morning
hours and across Puerto Rico during the late morning into the
afternoon hours. As this area of moisture moves across, isolated to
scattered shower activity is possible. Given the strong low-level
flow, any showers will be brief with only minor rainfall
accumulations expected. Another area of drier air is expected to
move across by late this afternoon and last through most of the
overnight hours, resulting in mainly dry weather conditions across
the local islands once again.
Similar weather conditions are expected to prevail for Tuesday and
Wednesday. Another surface high pressure moving into the western
Atlantic will continue to maintain a brisk easterly wind flow and
with it pockets of low-level cloudiness and moisture will be
advected into the area from time to time. This will result in
isolated to scattered shower activity across portions of the local
waters during the overnight and morning hours, with some of the
activity possibly affecting portions of the USVI and eastern Puerto
Rico. Then, some activity may develop mainly over mainland Puerto
Rico during the afternoon hours. Once again, any activity should be
brief with only minor rainfall accumulations expected.
.LONG TERM...Thursday through Tuesday...
Generally dry air persists across the region; as such, generally
fair weather is expected to dominate for much of the long-range
period. Patches of moisture will push across the area from time
to time, helping to develop showers in a typical pattern. Further
contributing to the fair weather is ridging aloft. A deep layer
ridge in the mid-levels will provide stability, suppressing
convective activity and therefore inhibiting development. Some
weakening in this mid-level ridge is forecast for the weekend,
likely late Saturday into Sunday. Meanwhile, a more substantial
patch of moisture is also expected to push into the region
Saturday night into Sunday. An increase in shower activity is
therefore expected for Saturday afternoon into Sunday evening.
Scattered showers are expected in northwestern and interior Puerto
Rico during the afternoon, with a secondary peak possible in
eastern Puerto Rico, downwind of orographic features. Scattered
passing showers are also expected for windward portions of the
local islands during the overnight and morning hours. A return to
generally fair weather is forecast for the start of the work week
next week, likely lasting into at least midweek.
Mainly VFR conditions expected through the period. Some passing
SHRA are possible across the USVI and eastern PR terminals between
08/12Z and 08/18Z, resulting in VCSH. However, no impacts to
operations are expected at this time. Winds will be from the E at
less than 10 kts through 08/12z, increasing to around 15 kts with
higher gusts and sea breeze variations after 08/14z.
Conditions have improved across the local waters, and hazardous seas
are not expected for today. Buoy data supports this assessment, with
the offshore buoy, 40143, showing seas of less than 7 feet since
2Z/10 PM AST last night, and the San Juan buoy showing seas of
around 3.5 to 4 feet. However, a tight pressure gradient, associated
with a surface ridge to the north, is bringing stronger than normal
winds to the region, which will maintain choppy seas of up to around
6 feet, especially for the offshore waters in both the Atlantic and
Caribbean, as well as the local passages.
For the beachgoers, there is a moderate risk of rip currents for the
majority of the local beaches; the main exceptions being western
Puerto Rico and south central Puerto Rico.
Despite the patch of moisture approaching the region, dry air will
persist into midday, at least, for the southern coastal plains of
Puerto Rico. Additionally, the KBDI for Camp Santiago is 629, with
the 10 hour fuel moisture being 7.18%. Though relative humidity
values may not fall below critical thresholds today, it is likely
that the 10 hour fuel moisture will remain below the critical
fire weather threshold of 8%. Furthermore, winds will remain
brisk across the region, around 15 to 20 mph, with stronger gusts
likely. As such, a Red Flag Warning has been issued for the
southern coastal plains of Puerto Rico for today.
.PRELIMINARY POINT TEMPS/POPS...
SJU 74 83 74 84 / 20 30 30 40
STT 74 84 73 84 / 20 30 20 30