Home > Products > Valid Products > AFD

000
FXCA62 TJSJ 250117
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
917 PM AST TUE MAY 24 2016

.UPDATE...Minor changes were introduced to forecast package
in order to match current weather conditions.

A mid to upper level ridge will hold across the northeastern
Caribbean, as a trough continues to meander in the vicinity
of Bahamas. Ridge aloft is then expected to erode the upcoming
weekend and into next week. At lower levels, a high pressure
across the central Atlantic, and an induced trough northwest of
the local islands will continue to promote east southeast winds
through friday, becoming southerly the upcoming weekend and early
next week.

Under the aforementioned weather pattern, continue to expect
limited shower activity across the local islands through at
least the end of the workweek with the potential for shower
and thunderstorm development increasing during the weekend
as ridge aloft erodes and moisture increases.

&&

.AVIATION...VFR conds expected thru the rest of the forecast period.
High clouds will continue to move across the flying area overnight.
Light passing SHRA possible E of the region and local waters.
Light and variable winds overnight...becoming ESE at 5-15 kt aft
25/12z.

&&

.MARINE...No change to previous discussion, seas expected to
subside during the next few days. Meanwhile continue to expect
seas up to 6 feet and winds around 20 knots during the overnight
hours.

&&

.PREV DISCUSSION... /issued 144 PM AST TUE MAY 24 2016/

SYNOPSIS...Strong surface high pressure across the central
Atlantic is expected to remain in place for the next few
days...causing easterly winds over the area...with a few
variations from ENE on Wednesday to ESE by Friday. Upper trough is
expected to remain across the western Atlantic and keep the local
islands under a ridge for the next few days. Available moisture
will remain near normal for the next few days...increasing
slightly for the latter part of the week.

DISCUSSION...Temperatures in the low 90s were observed today
across many of the coastal municipalities and other areas of lower
elevations. The higher elevations remained in the 80s. This was
due to the combination of the southeasterly wind and the Saharan
dust that is still over the local area. Very little to no shower
activity was observed over land areas in the morning hours and
only a few showers over the waters. High clouds moved in later in
the morning and into the afternoon hours. So far...no afternoon
showers have developed across land areas and satellite imagery
shows very little cloudiness developing due to convection. As the
Saharan dust diminishes overnight and the winds shift to a more
easterly direction overnight...isolated to locally scattered
showers are expected through tonight into Wednesday morning. Winds
are expected to shift to a more ENE direction on Wednesday while
moisture increases slightly. This means that we could observe some
showers develop across the interior into the SW quadrant of PR on
Wednesday afternoon while the rest of the local area remains with
only a slight chance of showers...mostly fair weather. This also
means that with the ENE winds we could observe slightly lower max
temperatures across the San Juan metro area.

Similar pattern is expected for Thursday but winds shifting to a
more easterly direction by Thursday afternoon. A few showers could
develop across western PR on Thursday afternoon while isolated to
scattered brief showers are expected elsewhere due to a slight
increase in moisture. This slight increase in moisture is expected
to linger through the weekend...which could increase the chances
of rain across the local area...especially on Saturday and Sunday
according to both the GFS and ECMWF models.

AVIATION...VFR conds expected thru the forecast period. However...
Saharan dust particles across the flying area will reduce somewhat
the visibilities at times...but VIS should remain above 6SM. SE
winds of 10-20 kt will prevail below FL050.

MARINE...Small craft should exercise caution as seas will be up
to 6 feet and winds up to 20 knots the rest of today and tonight.
Seas will diminish slightly on Wednesday and for the following few
days.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  79  89  77  87 /  30  30  20  30
STT  80  89  76  87 /  20  20  20  20

&&

.SJU Watches/Warnings/Advisories...
PR...None.
VI...None.
AM...None.
&&

$$

05/23





000
FXCA62 TJSJ 241744
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
144 PM AST TUE MAY 24 2016

.SYNOPSIS...Strong surface high pressure across the central
Atlantic is expected to remain in place for the next few
days...causing easterly winds over the area...with a few
variations from ENE on Wednesday to ESE by Friday. Upper trough is
expected to remain across the western Atlantic and keep the local
islands under a ridge for the next few days. Available moisture
will remain near normal for the next few days...increasing
slightly for the latter part of the week.


&&

.DISCUSSION...Temperatures in the low 90s were observed today
across many of the coastal municipalities and other areas of lower
elevations. The higher elevations remained in the 80s. This was
due to the combination of the southeasterly wind and the Saharan
dust that is still over the local area. Very little to no shower
activity was observed over land areas in the morning hours and
only a few showers over the waters. High clouds moved in later in
the morning and into the afternoon hours. So far...no afternoon
showers have developed across land areas and satellite imagery
shows very little cloudiness developing due to convection. As the
Saharan dust diminishes overnight and the winds shift to a more
easterly direction overnight...isolated to locally scattered
showers are expected through tonight into Wednesday morning. Winds
are expected to shift to a more ENE direction on Wednesday while
moisture increases slightly. This means that we could observe some
showers develop across the interior into the SW quadrant of PR on
Wednesday afternoon while the rest of the local area remains with
only a slight chance of showers...mostly fair weather. This also
means that with the ENE winds we could observe slightly lower max
temperatures across the San Juan metro area.

Similar pattern is expected for Thursday but winds shifting to a
more easterly direction by Thursday afternoon. A few showers could
develop across western PR on Thursday afternoon while isolated to
scattered brief showers are expected elsewhere due to a slight
increase in moisture. This slight increase in moisture is expected
to linger through the weekend...which could increase the chances
of rain across the local area...especially on Saturday and Sunday
according to both the GFS and ECMWF models.

&&

.AVIATION...VFR conds expected thru the forecast period. However...
Saharan dust particles across the flying area will reduce somewhat
the visibilities at times...but VIS should remain above 6SM. SE
winds of 10-20 kt will prevail below FL050.


&&

.MARINE...Small craft should exercise caution as seas will be up
to 6 feet and winds up to 20 knots the rest of today and tonight.
Seas will diminish slightly on Wednesday and for the following few
days.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  88  77  87 /  30  10  20  30
STT  80  88  76  87 /  20  10  20  20

&&

.SJU Watches/Warnings/Advisories...
PR...None.
VI...None.
AM...None.
&&

$$

11/25





000
FXCA62 TJSJ 241451
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1051 AM AST TUE MAY 24 2016

.UPDATE...Hazy skies has prevailed across the islands this morning.
Some light showers moved inland across portions of south PR early
this morning but no shower activity was observed by mid-morning.
The rest of today...expect a generally fair weather pattern
dominating the local region as a relatively dry and stable air
mass remains over PR/USVI. Any shower that develops over the NW PR
this afternoon will be brief. Minor changes were made to the forecast
grids this morning...mainly to decrease slightly the POPs across
the local islands.

&&

.AVIATION...VFR conds expected thru the forecast period. However...
Saharan dust particles across the flying area will reduce somewhat
the visibilities at times...but VIS should remain above 6SM. SE winds
of 10-20 kt will prevail below FL050.

&&

.MARINE...Wind waves of around 3-5 feet will continue across the
local waters. The dominant period of these wind waves is 5-7 sec...
resulting in slightly choppy conditions especially across the
Caribbean Waters. Winds will continue moderate to locally fresh
between 10-20 kt.

&&

.PREV DISCUSSION... /issued 536 AM AST TUE MAY 24 2016/

SYNOPSIS...High pressure at mid and upper levels will generate
only modest showers and possibly a few thunderstorms today and
tomorrow. Moisture increases over the weekend and low level flow
becomes more southerly.

At upper levels...A ridge extends north out of South
America and across the Anegada Passage...while a low forms north
of Cuba and a trough moves northeast toward Hispaniola today
through Thursday. The trough will continue to hover around the
windward passage through the weekend and areas of divergence will
move through as fragments of a jet around the trough pass over the
local area.

At mid levels...High pressure over the windward islands will
continue to build north and spread over and beyond the local area.
On thursday a low pressure will form over the Bahama Islands
affecting the local area weakly, but it will move northwest.

At lower levels...High pressure over the Central Atlantic will
slowly weaken during the week and over the weekend...and moderate
east southeast trade winds will weaken and shift to the southeast
late in the week at the surface. Above the surface flow turns
more southerly on Sunday and better moisture is seen to start the
coming week.

DISCUSSION...Spotty light showers developed over the Caribbean
overnight and a few moved onshore across southern Puerto Rico. In
the pre-dawn hours heavier showers developed between Vieques and
Culebra and passed over the eastern tip of Puerto Rico and the
inner waters to the north. Little activity was seen yesterday
during the day and conditions are not expected to change much
today. It is expected that southeasterly flow will persist just
long enough today to allow the temperatures on the north coast of
Puerto Rico to touch the lower 90s. Dew points overnight in San
Juan were in the mid 70s despite the light land breeze and
although they will be lower during the day today, they will still
contribute to spotty areas of heat indices between 100 and 102
degrees in some places along the north coast and possibly along
the immediate south coastal areas as well.

According to the GFS, moisture gradually increases during the
week, over the weekend and again early next week, reaching over
2.2 inches of precipitable water mid week next week. The best
conditions for convection, that is showers and thunderstorms do
not occur until moisture from South America reach the area on
Saturday night and Sunday. This is when mid levels finally become
much wetter, but stability also increases somewhat. Therefore
expect increasing rain amounts and a higher risk of urban and
small stream flooding in Puerto Rico and possibly even in the U.S.
Virgin Islands.

AVIATION...Mostly VFR conds expected during the rest of the
forecast period. VCSH psbl across TJSJ/TIST/TISX this morning.
Isolated SHRA can be expected over NW PR...psbly affecting TJMZ
and TJBQ btwn 25/17- 23z. Sfc winds mainly from the east southeast
at 5 to 10 kts increasing at 10 to 20 with higher gusts.

MARINE...Winds and seas will fluctuate in the normal daily
pattern generally between 10 and 18 knots and between 4 to 6 feet
today and tomorrow, but conditions are expected to improve after
Wednesday. Small craft advisory conditions are not expected.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  91  78  88  77 /  10  30  10  20
STT  89  80  88  76 /  20  20  10  20

&&

.SJU Watches/Warnings/Advisories...
PR...None.
VI...None.
AM...None.
&&

$$

11/25





000
FXCA62 TJSJ 240116
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
916 PM AST MON MAY 23 2016

.UPDATE...A mid to upper level ridge of high pressure continues to
dominate the eastern Caribbean region. As a result moderate to
strong subsidence continues to inhibit precipitation across Puerto
Rico and the U.S. virgin islands this evening. Will expect these
conditions to persist overnight and so will only indicate
isolated showers over eastern areas of PR and over the U.S. Virgin
Islands. Southeast flow across the region combined with local
effect and topography may result in afternoon showers and
thunderstorms developing over northwestern portions of Puerto Rico
Tuesday afternoon, but only isolated to scattered showers will be
expected over the rest of the area.


&&

.aviation...Mostly VFR cond expected during the rest of the forecast
period. VCSH pos across TJSJ/TIST/TISX. Isolated SHRA can be
expected over NW PR...pos affecting TJMZ and TJBQ after 25/17z. Sfc
winds overnight will be mainly southeast at 5 to 10 kts.

&&

.PREV DISCUSSION... /issued 208 PM AST MON MAY 23 2016/

SYNOPSIS...Subequatorial ridge will dominate the local weather
conditions through most of the week as high amplified trough
remains over the Western Caribbean. Then...a polar low will induce
a mid to upper level trough over cuba and bahamas...favoring the
moisture transport across the central and east caribbean later in
the week. As a result...weather pattern may become more unstable
across the local area by the end of the week.

DISCUSSION...Hazy skies and southerly winds have resulted in
above normal temperatures across the islands today. Max temps
were in the lower 90s so far this afternoon. A few showers are
still possible across portions of Northwest Puerto Rico later
this afternoon. Any shower that develops later this afternoon
will shower activity will be short- lived.

Ridge aloft combined with drier air at mid level will likely
result in a generally fair weather pattern across the islands
most of the work week. Some Saharan Dust particles will continue
to affect the local islands through at at least Tuesday...diminishing
the concentrations Wednesday and Thursday. Typical showers over
northwest PR can not ruled out each afternoon...but the coverage
will be isolated to scattered through midweek. Mid to upper clouds
will stream across the islands starting on Tuesday.

GFS suggests a wetter pattern by the end of next week as a mid-
upper level trough develops over Cuba/Bahamas. However...the rest
of the operational models disagree with the GFS solution. At this
time...the location of the aforementioned of the upper trough is
still unknown at this time. Considering the persistence of the
mid-upper ridge pattern over the Eastern Caribbean...we are
leaning towards the dryer solution for the weekend and probably
next week.

AVIATION...Mostly VFR cond expected today. Brief -RA are possible
across TJPS/TIST/TISX/TJSJ this morning. Although...VFR conditions
are expected...we cannot ruled out afternoon convection and mount
obsc across the Interior/Western sections of PR this afternoon. In
addition...showers may developed downwind from El Yunque to affect
the vicinity of TJSJ late in the morning into early this afternoon.
Sfc winds will be from the east to southeast at 5 to 15 kts
increasing at 10 to 20 kt with higher gusts after 23/13z.

MARINE...Fresh winds of 15-20 kt will keep the seas around 4-6
feet through Tuesday. Winds and seas will subside sightly by
midweek as surface high pressure over the Central Atlantic
weakens. Therefore...expect moderate winds and seas of 3-5 ft
from mid to the end of the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  90  78  87 /  10  20  30  10
STT  78  89  80  88 /  20  30  20  10

&&

.SJU Watches/Warnings/Advisories...
PR...None.
VI...None.
AM...None.
&&

$$

05/08





000
FXCA62 TJSJ 231808
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
208 PM AST MON MAY 23 2016

.SYNOPSIS...Subequatorial ridge will dominate the local weather
conditions through most of the week as high amplified trough
remains over the Western Caribbean. Then...a polar low will induce
a mid to upper level trough over cuba and bahamas...favoring the
moisture transport across the central and east caribbean later in
the week. As a result...weather pattern may become more unstable
across the local area by the end of the week.

&&

.DISCUSSION...Hazy skies and southerly winds have resulted in
above normal temperatures across the islands today. Max temps
were in the lower 90s so far this afternoon. A few showers are
still possible across portions of Northwest Puerto Rico later
this afternoon. Any shower that develops later this afternoon
will shower activity will be short- lived.

Ridge aloft combined with drier air at mid level will likely
result in a generally fair weather pattern across the islands
most of the work week. Some Saharan Dust particles will continue
to affect the local islands through at at least Tuesday...diminishing
the concentrations Wednesday and Thursday. Typical showers over
northwest PR can not ruled out each afternoon...but the coverage
will be isolated to scattered through midweek. Mid to upper clouds
will stream across the islands starting on Tuesday.

GFS suggests a wetter pattern by the end of next week as a mid-
upper level trough develops over Cuba/Bahamas. However...the rest
of the operational models disagree with the GFS solution. At this
time...the location of the aforementioned of the upper trough is
still unknown at this time. Considering the persistence of the
mid-upper ridge pattern over the Eastern Caribbean...we are
leaning towards the dryer solution for the weekend and probably
next week.

&&

.AVIATION...Mostly VFR cond expected today. Brief -RA are possible
across TJPS/TIST/TISX/TJSJ this morning. Although...VFR conditions
are expected...we cannot ruled out afternoon convection and mount
obsc across the Interior/Western sections of PR this afternoon. In
addition...showers may developed downwind from El Yunque to affect
the vicinity of TJSJ late in the morning into early this afternoon.
Sfc winds will be from the east to southeast at 5 to 15 kts
increasing at 10 to 20 kt with higher gusts after 23/13z.

&&

.MARINE...Fresh winds of 15-20 kt will keep the seas around 4-6
feet through Tuesday. Winds and seas will subside sightly by
midweek as surface high pressure over the Central Atlantic
weakens. Therefore...expect moderate winds and seas of 3-5 ft
from mid to the end of the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  90  78  87 /  20  20  30  10
STT  78  89  80  88 /  10  10  20  10

&&

.SJU Watches/Warnings/Advisories...
PR...None.
VI...None.
AM...None.
&&

$$

72/11





000
FXCA62 TJSJ 231453
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
1053 AM AST MON MAY 23 2016

.UPDATE...Only isolated showers were observed mostly across the
Caribbean waters this morning with few of them affecting the
southeastern Puerto Rico. Elsewhere across the region not
significant precipitation was observed so far this morning. An
upper level ridge will remain as the main weather feature across
the forecast area for the next several days. this Feature will
continue to suppress the thunderstorms development across the
local islands. however...the limited moisture across the region is
enough to produce isolated to scattered showers across eastern
Puerto Rico...Vieques...Culebra and the USVI overnight and early
in the morning...followed by some afternoon convection over
western and interior Puerto Rico. An upper level trough is
expected to amplify across Greater Antilles and central Caribbean
late in the work week. This feature will increase the instability
and moisture transport over the region during the upcoming weekend
and early next week.

&&

.AVIATION...Mostly VFR conditions are expected across the local
flying area until at least 23/17Z. Although...mostly VFR
conditions are expected...we cannot rule out afternoon convection,
isolated TSRA and mountain obscurations across the Interior/Western
sections of PR. Surface winds will be from the east to southeast
at 10 to 20 kt with higher gusts.

&&

.MARINE...Seas up to 6 feet and winds up to 20 knots will
continue across the regional waters for the next few days. Small
craft will have to exercise caution in the local outer waters and
the Mona Passage.

&&

.PREV DISCUSSION... /issued 549 AM AST MON MAY 23 2016/

SYNOPSIS...At upper levels...A ridge of high pressure over the
anegada passage will shift east and build farther north during
the next 24 hours. A trough will dig over Cuba through mid week.
This pattern, with minor variations, will continue through mid
week next week.

At mid levels...Low pressure over the eastern United States will
cut-off over the Bahama Islands on Wednesday and continue spinning
in the area through the end of the week. High pressure over the
Central Atlantic will build west to the east coast of the United
States later this week and hold over the weekend.

At lower levels...Low pressure continues over the western
Atlantic while high pressure prevails over the central atlantic
and the northeastern Caribbean sea. High pressure will fill in
just east of Georgia overnight on Tuesday. High pressure over the
Atlantic will fade later this week. Moderate to fresh trade wind
flow from the east southeast will shift to mainly east by mid
week. Although the marine layer will be rich in moisture it will
reach to little over 5 kft this week so as to limit shower
activity.

DISCUSSION...Although 500 mb temperatures will decrease during
the week for greater instability, mid level moisture is lacking
and affects even the upper portion of the lower levels. This
explains both the limited activity yesterday and the similar
forecast today. East south east flow will continue today and will
keep high temperatures on the north coast in the upper 80s and
lower 90s with a heat index approaching 100 degrees, and even
exceeding 100 in a few places--some near the greater San Juan
metropolitan area. Convection will be limited in the area but
local rains could be heavy for one or two hours in western and
interior Puerto Rico. Models also continue to bring in higher
clouds Tuesday through Thursday that will form a fairly deep
layer. This will reduce the amount of direct sunshine and surface
heating for thunderstorms, keeping them isolated during the
afternoons later this week. The GFS continues to forecast very wet
weather at the end of the period as it has for several weeks.
Although it is possible, confidence that this very wet weather
will materialize is low. Nevertheless, precipitable water values
could exceed 2 inches by Thursday and 2.2 inches by Sunday.

AVIATION...Mostly VFR conds are expected today. Brief -RA is possible
across TJPS/TIST/TISX/TJSJ this morning. Although...VFR conditions
are expected...we cannot rule out afternoon convection, isold TSRA and
mtn obscurations across the Interior/Western sections of PR this
afternoon. In addition...showers may develop downwind from El
Yunque to affect the vicinity of TJSJ late in the morning into
early this afternoon. Sfc winds will be from the east to southeast
at 5 to 15 kts increasing at 10 to 20 kt with higher gusts after
23/13z.

MARINE...Winds and seas continue somewhat above normal in both
the Atlantic and Caribbean waters and small craft will have to
exercise caution in the local outer waters and the Mona Passage.
The wavewatch even suggests that winds could be locally strong
enough in the outer Caribbean waters for 7 foot seas on Thursday
morning. Conditions subsequently subside.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  92  78  90  78 /  10  20  20  30
STT  89  78  89  80 /  10  10  10  20

&&

.SJU Watches/Warnings/Advisories...
PR...None.
VI...None.
AM...None.
&&

$$

72/11





    US Dept of Commerce
    National Oceanic and Atmospheric Administration
    National Weather Service
    1325 East West Highway
    Silver Spring, MD 20910
    Page Author: NWS Internet Services Team
Disclaimer
Information Quality
Credits
Glossary
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities