Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 180155 AAA

Area Forecast Discussion...UPDATED
National Weather Service San Juan PR
955 PM AST Sun Feb 17 2019

.UPDATE...Updated grids with latest models, for some changes to
temperatures, winds and dew points. Dry conditions continue to be
expected so no real change to synoptic idea or discussions.


.AVIATION...VFR conditions expected to prevail thru 18/22Z. Some mtn
tops likely obscured aft 18/16Z. Isold SHRA ern PR til 18/14Z.
Isold SHRA wrn PR aft 18/18Z. Sfc winds 10 kt or less til 18/14Z.
Aft 18/14Z sfc winds east 12 to 18 kt with hir gusts. Winds NE-E
up thru FL370. Max wind ENE 30-40 kt btwn FL210-340.


.MARINE...Wind are set to increase tomorrow and will bring higher
seas with them. Conditions will become hazardous beginning Monday
night when small craft advisories are set to begin in the
Caribbean waters. Expect wind 15 to 25 knots and seas of 5 to 7
feet there beginning Monday night. Conditions spread into the
Atlantic on Tuesday and will continue through at least the end of
the week.


.PREV DISCUSSION... /issued 425 PM AST Sun Feb 17 2019/

SYNOPSIS...A generally fair and mainly stable weather pattern
is expected to prevail across the local isles much of this week.

SHORT TERM...Tonight thru Tuesday...

A building mid to upper level ridge will continue to dominate the
local weather regime through the forecast cycle. This feature is
expected to erode the available moisture resulting in precipitable
water values below one inch by Monday. At lower levels, a surface
high pressure across the east central Atlantic will yield easterly
winds through Monday, becoming more east northeast on Tuesday as
another surface high pressure builds north of the area. The local
pressure gradient is in fact expected to tighten as the surface
high builds north of the area and across the western Atlantic.
Having said that, continue to expect fair and stable weather
conditions with limited shower activity each day.

LONG TERM...Wed thru Mon /issued 437 AM AST Sun Feb 17 2019/

Fair weather is expected to prevail in the long term forecast. Dry
airmass is expected to persist and only a few brief patches of
moisture are expected to move through, which may bring some brief
shower to the local area. The mid and upper levels will maintain a
stable atmosphere as well. Latest forecast soundings still
indicate a strong inversion and very dry mid levels, which is
consistent with the mid and upper level ridges and low
precipitable water values. East to east northeast winds of 15 to
20 mph are expected across the local waters and coastal areas. So
given the stable atmosphere, dry air, and breezy conditions,
mainly fair weather conditions are to be expected with moments of
brief showers during the night and morning hours. That said, the
marine conditions are expected to deteriorate starting midweek,
more on that in the marine section below.

AVIATION...VFR conds at all terminals durg prd excpt for VCSH at
TJNR/TJSJ/TJMZ/TJBQ...ovr coastal waters en route btw Ern PR and
Northern Leeward islands til 17/22Z. SFC wnds mainly fm E except for
sea breeze variations and ocnly hir gust...bcmg LGT/VRB AFT 17/22Z.
L/LVL wnds mainly fm E-NE 5-15 kts blo FL200...then backing and incr
w/ht ABV. No sig operational AVN wx impacts attm.

MARINE...Seas below Small Craft Advisory criteria through midweek.
As a result, continue to expect seas 3 to 5 feet across the offshore
waters, ranging between 2 and 4 feet nearshore. Marine conditions
are expected to deteriorate by Wednesday with a northerly swell
and fresh east northeast winds.


SJU  74  85  74  84 /  10   0  30  30
STT  73  85  73  85 /  10   0  20  20


AM...Small Craft Advisory from 6 PM Monday to 6 PM AST Friday for
     Caribbean Waters of Puerto Rico from 10 NM to 17N-Mona
     Passage Southward to 17N.



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