Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 010101
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
901 PM AST Sun Apr 30 2017

.UPDATE...Numerous showers and isolated thunderstorms developed
during the afternoon and this evening across most sections of
Puerto Rico and across the surrounding coastal waters. The
heaviest activity occurs across the eastern half as well as
across western sections of Puerto Rico. Radar estimated between 2
to 3 inches of rain in several spots across east, southeast and
western Puerto Rico. Several urban and small stream flood
advisories were issued for numerous municipalities along these
sections of the island. A marine weather statement were also issue
for most of the coastal waters due to thunderstorms and gusty
winds. Showers and thunderstorms persisted during the evening
hours. Some rivers across southeastern and western Puerto Rico are
running high. The showers activity is expected to slowly diminish
overnight. The upper level trough and associated area of low
pressure is expected to linger just north of the region and will
continue to enhance showers and thunderstorm development across
the local area through Tuesday. Therefore, for Monday and Tuesday,
a similar weather pattern is expected with showers and a couple
of thunderstorms during the mornings across the windward areas
followed by numerous afternoon showers and isolated thunderstorms
across western and interior sections of Puerto Rico. Weather
conditions are expected to improve slowly by Wednesday.

&&

.AVIATION...VCSH are expected across most TAF sites through at
least 01/16Z. Tempo MVFR and even IFR conditions with mountain
obscurations can be expected after 01/16Z in and around TJSJ,
TJMZ and TJBQ in SHRA/TSRA. Low level winds will be mainly east at
10 knots through 01/14Z, increasing to 10-15 knots with higher
gusts near showers and thunderstorms after 01/14Z.

&&

.MARINE...Mariners should exercise caution across most of the
regional waters due to seas between 4 and 6 feet and winds
between 15 and 20 knots with higher gusts. Isold thunderstorms
will remain possible across the coastal waters and local passages
creating hazardous marine conditions. Stay tuned for any
additional special marine statement or warnings.

&&

.PREV DISCUSSION... /issued 408 PM AST Sun Apr 30 2017/

SYNOPSIS...TUTT and associated area of low pressure and good
moisture pooling across the region will result in periods of
enhanced convection at least until Wednesday. The chance of urban
and small stream flooding each day with localized river flooding
will remain high. A gradual improvement in the overall weather
conditions is forecast during the latter part of the work week, as
the Tutt weakens and high pressure builds aloft limiting low
level moisture transport.

SHORT TERM...For the rest of the afternoon and evening, the very moist
and unstable environment will aid in the development of additional showers
and possible thunderstorms across the region. Shower activity over
land areas should however diminish by late evening, but is expected
to return along portions of the north and east coastal areas by early
morning. Soils are saturated and rivers and small creeks are swollen,
therefore any additional moderate to heavy rain will result in minor
flooding, sudden rises in river levels along with the possibility
of mudslides.

The upper level trough and associated area of low pressure is expected
to linger just north of the region and will continue to enhance showers
and thunderstorm development across the local area through Wednesday.
Low level moisture transport will remain high and as a result continued
cloudiness, with periods of showers with thunderstorms can be expected.
The best chance for thunderstorms and heavy rainfall should be
focused mainly across the eastern and northern half of Puerto
Rico including part of the San Juan metro area. Soils across
Puerto Rico remain saturated from present and recent rainfall. The
potential for flooding of rivers and streams as well as poor
drainage areas will remain high. Mudslides and debris flow will
also remain likely in areas of steep terrain. Local residents and
visitors in Puerto Rico are urged to stay tuned during the next
few days.

LONG TERM...As the TUTT weakens, a mid to upper level ridge will gradually
build across the forecast area. The ridge is then expected to hold through
at least the upcoming weekend. At lower levels, as the broad high pressure
across the central Atlantic lifts north and east of the region,the local
pressure gradient will weaken. Local winds are then expected to diminish
and become more east southeast by the end of the week. Although convection
will not be as widespread and frequent due to the building high pressure
ridge aloft and decreasing moisture transport, periods of showers and
isolated thunderstorms will remain possible across parts of the islands
and coastal waters through most of the upcoming week.

As the upper level ridge builds and low level moisture transport erodes,
a gradual improvement in the weather conditions is so far expected for
the latter part of the upcoming week, with slightly warmer temperatures
expected by Friday and into the following weekend.

AVIATION...SHRA/Isold TSRA across PR/USVI expected thru fcst
prd. Prds of SHRA/+SHRA may briefly reduce visibilities btwn 3SM-
5SM mainly at TJBQ/TJMZ/TJNR/TJSJ til 30/23z. BKN-OVC cld lyrs btw
FL020-FL100 durg prd. Isold TSRA psbl ovr ctrl mtn range of PR and
ovr coastal waters btw islands...N and S of PR. MVFR/psbl IFR conds
w/mtn top obscr psbl ovr west and ctrl and east PR til 30/23z. Low
level winds mainly E at 15-20 kts. Sfc wnds E-SE 10-15 kts w/ocnl
higher gusts mainly with SHRA...bcmg 10 kts or less aft 30/23z.

MARINE...Mariners should exercise caution due to seas between 4
and 6 feet and winds between 15 and 20 knots with higher gusts.
Isold thunderstorms will remain possible across the coastal waters
and local passages creating hazardous marine conditions. Stay tuned
for any additional special marine statement or product.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  84  75  85 /  50  60  20  50
STT  74  84  74  86 /  60  60  30  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...JF
LONG TERM....99



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