Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 270121
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
921 PM AST Sun Mar 26 2017

.UPDATE...Weakening mid to upper level trough across the western
Atlantic and into the central and eastern Caribbean will continue
to enhance shower and thunder activity across the forecast area.
Shower and thunder activity overnight should be focused across
the local waters with a few of them probably brushing the eastern
coastal areas of PR as well as USVI. Tomorrow afternoon with
plenty of sunshine; locally induced showers and thunderstorms are
expected over and north of the Cordillera Central including the
San Juan Metro Area.

&&

.AVIATION...Brief periods of MVFR conds will remain possible at
the Leeward and USVI terminal overnight. SHRA/TSRA expected aft
27/16z in and around JMZ/JBQ and JSJ. Light and variable winds
are expected overnight.

&&

.MARINE UPDATE...Although seas are expected to subside overnight,
a moderate risk of rip currents will continue to prevail across
some areas during the next few days. Seas up to 7 feet across the
offshore Atlantic waters.

&&

.PREV DISCUSSION... /issued 340 PM AST Sun Mar 26 2017/

SYNOPSIS...A surface low over the Atlantic waters northwest of
PR will continue to move north northeast into the western Atlantic for
the next few days. A surface high will build across the Western
Atlantic just northwest of the surface low, spreading into the
local area by midweek as the surface low moves east into the
central Atlantic. Drier air at mid levels is expected to continue
moving in through the end of the week. Light southerly winds will
continue until Monday, becoming very light on Tuesday, then
northerly and increasing on Wednesday and Thursday.

SHORT TERM...Today through Wednesday...
A few showers are forming in northern Puerto Rico due to local sea
breeze convergence with the southerly flow. A band of showers has
been quasi stationary from about 12 miles south of Arroyo to the
western tip of Vieques and through the passage between Puerto Rico
and Culebra to the northeast since about 26/08z. In the last hour or
so showers have also formed between 6 and 15 miles south of the
coast of Puerto Rico as far west as Guanica. This band is being
maintained by the flow out of the south and into a low pressure that
formed on Friday north of the eastern tip of the Dominican Republic.
The low is located moving north at about 360 miles north of Punta
Cana at 9 knots. The models have had no precision in locating the
location of this band and tend to show the showers associated with
it more diffusely across the area. Higher resolution models tend to
agree that some showers will persist between Puerto Rico and Saint
Croix in a northeast-southeast band through Tuesday. As the low
moves more to the east Monday and Tuesday, flow around it will
come from the north in the local area and this band will
begin to dissipate as drier air moves in from the north on
Wednesday. That drier air will initiate a significant drying and
clearing trend.

Interaction between flow around the low to the north northeast and
the trade wind flow through the Caribbean will keep a col lurking
close by so that local low level flow will be light and often
governed by local sea/land breezes. Moisture at lower levels will
persist so that local convergence patterns over Puerto Rico will
generate showers in the afternoons Monday and Tuesday over the
western interior which will drift north in the 850 mb flow into the
Atlantic late in the afternoon and early in the evening. These will
leave some rains but heavy amounts with flooding are not expected
owing to the limited instability of the sounding and general
dryness in the mid levels.

LONG TERM...Northerly winds and drier conditions expected on
Thursday, which if it verifies would be a pleasant day with max
temps in the low 80s across the lower elevations and dew points in
the mid 60s. Thereafter winds will turn easterly for Friday and
Saturday but still somewhat dry. However, a lone of enhanced
moisture could move through on Sunday and Monday, which will cause
an increase in the shower activity over the local area once again.

AVIATION...VFR conditions prevail. Areas of SHRA have initiated
over nrn PR and may spawn isold TSRA bfr 26/22z. Areas of mtn
obscurations some of which have not cleared from this morning will
persist til 26/02z. Local brief MVFR arnd TJBQ, TJMZ and TJSJ is
psbl. Otherwise TAF sites to continue VFR except for brief MVFR CIGS
in SHRA arnd TNCM/TKPK btwn 25/19-26/09Z. Winds alf S-SW 10 to 20 kt
up thru FL150. Max winds WSW 70 kts at FL400 decreasing slightly
thru 27/18Z.

MARINE...Local buoy 41115 in Rincon is still reporting seas of up
to 7 feet, for that reason a small craft advisory was issued for
the Atlantic waters, waters of NW PR and the Mona passage through
this evening and then through 2 AM AST Monday for the Atlantic
offshore waters. The rest of the waters should be up to 6 feet
tonight. High risk of rip currents continue this afternoon and
tonight.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  74  88  77  85 /  30  60  40  40
STT  75  85  75  82 /  40  50  40  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk until 6 AM AST Monday for North Central-
     Northwest-San Juan and Vicinity-Western Interior.

VI...None.
AM...Small Craft Advisory until 2 AM AST Monday for Atlantic Waters
     of Puerto Rico and USVI from 10 NM to 19.5N.

&&

$$

UPDATE.......OM
AVIATION.....OM



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