226 FXCA62 TJSJ 110900 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 500 AM AST Mon Feb 11 2019 .SYNOPSIS...Surface high pressure moving across the western Atlantic will result in breezy conditions through midweek. Fragments of low-level moisture embedded within the trade wind flow will continue to result in occasional trade wind showers. A mid to upper-level trough will move near the region by the end of the work week into early next weekend, resulting in an increase in moisture and showers. A return to a fair weather pattern is expected by late next weekend through early the following week as another mid to upper-level ridge builds overhead. && .SHORT TERM...Today through Wednesday... A strong surface high pressure over the western Atlantic will cause breeze east to east-northeast trades through at least Tuesday across the region. Sustained winds between 15-20 mph with higher gusts are expected during this period. A cold front is expected to stall around 24N during the next day or so with no significant impact on the local weather conditions. The surface high will shift into the north central Atlantic by Wednesday and winds will turn more from the east-southeast, but moderate to locally fresh trades will prevail through the short term period. At upper levels, a ridge is forecast to build over the region from southwestern Atlantic into the northeastern Caribbean, keeping a fairly stable atmosphere through at least Wednesday. Therefore, shower activity will be limited to trade wind showers across the USVI and PR through the short term period. Hi res models suggest best rainfall amounts between the west coast of PR and the Mona Passage today and from an area of scattered showers that was moving from the Leeward islands into the USVI earlier this morning. .LONG TERM...Thursday through Monday... The mid to upper-level ridge axis will shift eastward as a mid to upper-level shortwave trough approaches from the west later Thursday into the day on Friday. At the lower-levels, the flow will be completely from the southeast as a frontal system moves across the western and central Atlantic. The low-level flow from the southeast will increase the low-level moisture transport. Therefore, an increase in shower activity can be expected across the area Friday and Saturday. At this point, confidence is low on how much rainfall can be expected as it will all depend on how much moisture will be available and where the best upper-level forcing sets up. By Sunday, as the mid to upper-level trough moves away and weakens, another mid to upper ridge will rapidly build across the region and hold through at least the first part of the following week. Therefore, a return to a fair weather pattern with limited shower activity can be expected. && .AVIATION...Mainly VFR conditions are expected to prevail during the next 24 hours across all terminals. However, trade wind showers could result in tempo MVFR cigs at TNCM/TIST/TISX through Monday morning. SHRA over western PR could also cause tempo MVFR cigs at TJMZ btw 16z-22z. East winds will prevail at 15-20 kt with higher gusts after 14z. && .MARINE...A surface high pressure moving across the western Atlantic will to continue to build north of the region and tighten the local pressure gradient, resulting in moderate to fresh easterly trade winds between 15 and 20 knots. This will create choppy and hazardous marine conditions across most of the regional waters through mid week with seas ranging between 5 and 8 feet. Therefore, small craft advisories are in effect. Along with the hazardous seas, a high risk of rip currents is in effect for the north facing beaches of PR, Culebra, and Saint Croix and for the north facing beaches of Saint Thomas starting tonight. && FIRE WEATHER...Even though some showers occurred across the southern coastal plains and the western foothills of Puerto Rico on Sunday, not enough rain has fallen to significantly change the vegetation state. Given that the flow will continue from the east northeast today with winds increasing to between 15 and 20 mph with higher gusts, relative humidity values are likely to drop into the mid 40s for a couple of hours during the late morning into the early afternoon hours. Therefore, the fire danger threat will remain elevated and a fire weather discussion (RFDSJU) has been issued for the southern coastal plains as well as the western foothills of Puerto Rico. && .PRELIMINARY POINT TEMPS/POPS... SJU 84 73 85 72 / 40 40 10 10 STT 83 73 84 73 / 50 40 20 40 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through late Tuesday night for Culebra- North Central-Northeast-Northwest-San Juan and Vicinity- High Rip Current Risk from this evening through late Tuesday night for Mayaguez and Vicinity. VI...High Rip Current Risk through late Tuesday night for St Croix. High Rip Current Risk from this evening through late Tuesday night for St.Thomas...St. John...and Adjacent Islands. AM...Small Craft Advisory until 2 PM AST Wednesday for Atlantic Waters of Puerto Rico and USVI from 10 NM to 19.5N-Mona Passage Southward to 17N. Small Craft Advisory from 8 PM this evening to 2 PM AST Wednesday for Coastal Waters of Northern Puerto Rico out 10 NM. Small Craft Advisory from 4 AM Tuesday to 2 PM AST Wednesday for Anegada Passage Southward to 17N-Caribbean Waters of Puerto Rico from 10 NM to 17N. Small Craft Advisory from 4 AM Tuesday to 2 AM AST Wednesday for Coastal Waters OF Northwestern Puerto Rico out 10 NM- Coastal Waters of Northern USVI and Culebra out 10 NM. && $$ SHORT TERM...DS LONG TERM....GL