Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 200130
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
930 PM AST Thu Oct 19 2017

.UPDATE/ NEAR TERM...A dry and stable air mass will continue to
prevail across the forecast area through at least early next week
under ridge pattern aloft. Therefore a fair weather pattern is
expected to prevail tonight and into the upcoming weekend.

Shower activity, if any, will be focused across western areas of
Puerto Rico each afternoon. Maximum temperatures are expected to
remain warm to hot particularly across the northern slopes of
Puerto Rico.

&&

.AVIATION...Mostly VFR conds expected to prevail at all TAF sites
through the forecast period. Brief periods of MVFR conds still
possible due to reduced visibilities. Light and variable winds
overnight. &&

.MARINE...A trade wind surge will continue to produce choppy and
hazardous seas particularly across the offshore waters and local
passages through at least Saturday. Saharan dust over the local
area will continue to cause reduced visibility due to haze tonight
and Friday.

&&

.PREV DISCUSSION... /issued 354 PM AST Thu Oct 19 2017/

SYNOPSIS...Upper level ridge will continue to dominates the local
region through the weekend. A TUTT low will dig south across the
northeast Caribbean early next week.

SHORT TERM...Thursday through Sunday...Very dry, hazy and hot
conditions prevailed across Puerto Rico and the U.S.Virgin Islands
this afternoon. A very dry air mass has moved across the region,
limiting any shower development across the area. 19/12Z TJSJ
sounding showed precipitable water of only 1.35 inches, and local
models indicated it could get even drier tonight and tomorrow.
Therefore, no shower activity is expected. In addition, a Saharan
Air Layer has moved across the area since late yesterday night,
which has produced very hazy skies across the local islands. No
changes in this weather pattern in expected through Sunday.

LONG TERM...Monday through Thursday...Relative dry weather
conditions are expected to continue Monday as Upper level ridge
maintains control of the weather locally. However, as upper level
trough dig south across the area, better chances for showers are
expected from Tuesday through the rest of the work week.

AVIATION...VFR conds mainly expected but Haze will occasionally
cause MVFR visibility due to its high concentration of Saharan dust.
This dust will improve slightly tonight, which should cause
prevailing VFR conds across all of the local terminals. Easterly
winds expected for the rest of today at 10-15KT with gusts 20-25KT.
Winds and haze improving slightly after 20/00Z, continued easterly
but at around 10KT. Fair weather expected for the next 24 hours.

MARINE...Seas up to 7 feet and winds up to 20 knots are expected
across the local waters through at least Friday. Small Craft
advisories continue in effect for most coastal waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  79  89  79  89 /   0   0  10  20
STT  80  85  80  85 /   0   0  30  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through Friday afternoon for Central
     Interior-Northeast-Ponce and Vicinity-Southeast-Southwest-
     Vieques.

     Small Craft Advisory until 8 AM AST Friday for Southeast.

VI...High Rip Current Risk through Friday afternoon for St Croix.

     Small Craft Advisory until 8 AM AST Friday for St.Thomas...St.
     John...and Adjacent Islands.

AM...High Rip Current Risk through Friday afternoon for Coastal
     Waters OF Southwestern Puerto Rico out 10 NM-Coastal Waters
     of Southern Puerto Rico out 10 NM.

     Small Craft Advisory until 8 AM AST Friday for Coastal Waters of
     Southern Puerto Rico out 10 NM-Coastal Waters of Southern
     USVI Vieques and Eastern Puerto Rico out 10 NM.

     Small Craft Advisory until 8 PM AST Saturday for Caribbean
     Waters of Puerto Rico from 10 NM to 17N-Mona Passage
     Southward to 17N.

     Small Craft Advisory until 2 PM AST Friday for Anegada Passage
     Southward to 17N-Atlantic Waters of Puerto Rico and USVI
     from 10 NM to 19.5N.

&&

$$

NEAR TERM...OM
AVIATION....OM


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