Area Forecast Discussion

FXCA62 TJSJ 230951

AFDSJU

Area Forecast Discussion

National Weather Service San Juan PR

551 AM AST Fri Feb 23 2018

.SYNOPSIS...High pressure will fade in the western Atlantic just

north of the local area over the weekend and into early next

week allowing winds to diminish and hazardous marine conditions

to subside. Moisture will peak on Sunday with increasing showers

until then. A gradual drying trend will then continue through next

Thursday.

.SHORT TERM...Today through Sunday...

Satellite imagery detected patches of clouds approaching the islands

from the northeast. As these clouds approached, the Terminal Doppler

radar indicated showers with periods of moderate to locally heavy

rain. Through the morning hours, most of the activity is expected to

affect the local Atlantic Waters, the U.S. Virgin Islands, Vieques,

Culebra as well the northern and eastern sections of Puerto Rico.

Although rainfall amount are expected to be minimal, brief periods

of heavy showers could produce hazardous driving conditions. Showers

are forecast to develop across the interior and western sections

around noon, but some brief trade wind showers will remain possible

across the St Thomas, Culebra, the north and east Puerto Rico.

A strong but fading surface high pressure over the western

Atlantic will continue to dominate the local weather conditions

through at least the upcoming week. An upper level trough will

extend southwest over Hispanola through the weekend. Although the

surface moisture is not significant, the surface high pressure

will continue to push patches of moisture across the local

islands, which will result in scattered to numerous showers mostly

during the overnight and early morning hours. Then during the

afternoon hours, this moisture will combine with the upper level

dynamic to result in showers over the western portions of Puerto

Rico as well as downwind from the U.S. Virgin Islands each

afternoon.

.LONG TERM...Monday through Saturday...

Surface high pressure will fade in the western Atlantic just

north of the local area early next week, but will be replaced by a

second high moving out of the eastern United States Wednesday

through Friday. The rumpled remains of a cold front will pass

through the area Monday through Tuesday next week with continued

shower activity, even while precipitable water values trend

downward from Sunday's peak. This will be due to drying at the top

of the lower levels of the atmosphere. A drier and much more

stable air mass will be ushered in behind the remnants of the cold

front passage on Tuesday. This will limit shower activity area-

wide. Moist air behind a second front on Friday of next week will

prepare the area for possibly more shower activity and a more

vigorous pre-frontal trough early in the week after next.

.AVIATION...SHRA will continue to move across TJSJ/TIST/TNCM/TKPK

through the morning hours. Some of these SHRA will produce brief BKN

ceilings btwn FL020-FL050 at these sites. VFR conds are expected

elsewhere. SHRA will develop near TJMZ and in the VCTY of TJPS

during the afternoon (btwn 23/16-23z). ENE winds 10-15 kt

increasing at 15-20 knots with higher gusts aft 23/12z.

.MARINE...Seas are expected to subside slowly this evening through

Sunday, such that by Sunday night all small craft advisories

should be down. Swell from a strong low in the northern Atlantic

mid week next week will send another surge of swell into the area

Wednesday night and Thursday when small craft advisories will

again be needed for the Atlantic waters and passages.

.PRELIMINARY POINT TEMPS/POPS...

SJU 81 73 82 73 / 60 60 60 60

STT 83 72 83 72 / 60 60 60 60

.SJU WATCHES/WARNINGS/ADVISORIES...

PR...High Rip Current Risk through late Saturday night for Culebra-

Mayaguez and Vicinity-North Central-Northeast-Northwest-San

Juan and Vicinity-Vieques-Western Interior.

High Surf Advisory until 6 AM AST Saturday for Culebra-Mayaguez

and Vicinity-North Central-Northeast-Northwest-San Juan and

Vicinity-Southeast-Western Interior.

High Rip Current Risk through late tonight for Central Interior-

Southeast.

High Surf Advisory until 6 PM AST this evening for Vieques.

VI...High Rip Current Risk through late Saturday night for St Croix.

High Surf Advisory until 6 AM AST Saturday for St Croix-

St.Thomas...St. John...and Adjacent Islands.

Small Craft Advisory until 8 PM AST this evening for

St.Thomas...St. John...and Adjacent Islands.

High Rip Current Risk through Saturday afternoon for

St.Thomas...St. John...and Adjacent Islands.

AM...Small Craft Advisory until 8 PM AST this evening for Coastal

Waters of Southern Puerto Rico out 10 NM.

Small Craft Advisory until 8 AM AST Sunday for Caribbean Waters

of Puerto Rico from 10 NM to 17N-Coastal Waters of Northern

Puerto Rico out 10 NM-Coastal Waters of Northern USVI and

Culebra out 10 NM-Coastal Waters of Southern USVI Vieques

and Eastern Puerto Rico out 10 NM-Mona Passage Southward to

17N.

Small Craft Advisory until 2 PM AST Sunday for Anegada Passage

Southward to 17N-Atlantic Waters of Puerto Rico and USVI

from 10 NM to 19.5N.

Small Craft Advisory until 2 AM AST Sunday for Coastal Waters OF

Northwestern Puerto Rico out 10 NM.

$$

SHORT TERM...CAM

LONG TERM....WS