Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 211420
Area Forecast Discussion
National Weather Service San Juan PR
1020 AM AST Tue Feb 21 2017
.UPDATE...Fast moving showers affected the northern and eastern
municipalities of Puerto Rico and the U.S. Virgin Islands.
Rainfall accumulation were less than a quarter of an inch. This
activity was associated with the backside of a trough which moved
rapidly trough the area. Latest satelite images indicated a drier
air mass behind the trough which is expected to encompass the
region later today. As a result, very dry weather conditions are
expected tonight into Wednesday.
.AVIATION...Mainly VFR conditions are expected to prevail across
most TAF sites through at least 21/22z. Brief periods of MVFR
conditions can be expected over TNCM and TKPK in SHRA. Low level
winds will be mainly North at 10 to 15 kts.
.MARINE...Local buoys are showing seas up to 6 feet mainly across
the Atlantic waters and local passages. As a result, a high risk
of rip current has been issued through 6pm AST. Small Craft should
exercise caution across these waters.
.PREV DISCUSSION... /issued 458 AM AST Tue Feb 21 2017/
SYNOPSIS...Upper trof north of the area and associated weak
surface boundary will continue to move to the east and exit the
forecast area today. Ridge pattern will follow from the west and
drier fair weather is expected to prevail for the rest of the
week. Northerly winds will shift to the southeast on Thursday as
surface high moves north of the area.
DISCUSSION...Scattered to numerous showers with isolated
thunderstorms over the Atlantic coastal waters moved across the
forecast area during the overnight. The heaviest showers remained
just north of the northern USVI. For the next few hours
additional showers are expected to move across the islands but
sunny skies are expected to return by the late morning hours.
Overnight temperatures were in the low to mid 60s across the
higher elevations to the low 70s across coastal areas.
Overall fair weather conditions are forecast to prevail for the
rest of the week as ridge pattern builds from the west and cap
inversion keep moisture below 800 MB. However, diurnally induced
afternoon showers cannot be ruled out each day and trade wind
showers should prevail across the northern and eastern coastal
areas through Thursday. Another upper trof and associated surface
boundary are forecast to move north of the area by late Sunday
enhancing shower activity once again.
AVIATION...SCT SHRA will affect the flying area thru 14Z. As a
result, MVFR cigs are possible in passing SHRA across TJBQ,TJSJ and
TIST. VFR conds are expected after 14Z...with limited shower
activity over the region. West winds of 10-15 kt will continue below
MARINE...Small pulses of northerly swell are forecast to reach
the regional waters for the next few days. Swell is expected to
peak on Friday morning between 4-6 feet. There is a moderate risk
of rip currents along the northern beaches of the islands.
West to northwest winds between 10-15 knots will continue today as
weak frontal boundary moves across the local area.
.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 83 71 / 20 20 20 30
STT 82 74 82 72 / 50 20 20 30
PR...High Rip Current Risk until 6 PM AST this evening for Mayaguez
and Vicinity-North Central-Northeast-Northwest-San Juan and