379 FXCA62 TJSJ 140841 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 441 AM AST Sun Feb 14 2021 .SYNOPSIS... Fair weather will prevail across the area over the next several days with occasional patches of low-level moisture advecting across the local islands. Low-level moisture will induce a few isolated to scattered showers and light rainfall amounts. A trough north of Puerto Rico will cause a slight uptick in showers during the middle of the week before lifting northeast of Puerto Rico. A surface high will continue to promote brisk easterly trade winds and choppy to rough maine condtions through Wednesday. && .SHORT TERM...Today through Tuesday... A surface high pressure across the central Atlantic will cause an easterly breeze for the next few days. Winds are expected to be at 10 to 20 mph, especially during the daytime hours, with lighter winds late in the night. Mid level high pressure will persist over the next few days as well, which will cause subsidence and any rain that develops should be shallow. That said, a tilted upper level trough appears to show signs of developing starting on Tuesday, but we will be in the subsident side of its axis by Tuesday night. Mainly dry air is expected over the next few days, with brief patches of moisture. Therefore fair weather is to be expected most of the time, but brief isolated to scattered showers will move in from time to time, mainly affecting the local waters, USVI, and eastern PR. This air mass of drier air will have precipitable water values of an inch or less, with the brief patches of moisture bumping precipitable water to around 1.5 inches, but again those patches of moisture will be brief. The forecast soundings show a rather stable atmosphere through Tuesday. The forecast therefore is for fair weather with brief isolated showers this morning, followed by isolated to scattered showers this afternoon. A similar pattern can be expected on Monday. && .LONG TERM...Wednesday through Monday... The global models are in agreement with the long-term period relatively tranquil due to the surface and mid-level ridge anchoring themselves across the area. The ridging will keep the mid-levels of the atmosphere mostly stable and dry. Brisk easterly winds will push patches of moisture occasionally over the region and produce brief, shallow convection. Global models continue to keep the moisture confined between the 1000 to 700 mb levels of the atmosphere. The devoid moisture in the mid to upper-levels of the atmosphere will inhibit the development of organized convection and significant rainfall. The GFS and ECMWF keep 500 mb heights around -7 to -9 throughout the period due to a weak trough developing north of Puerto Rico. The trough will lift to the northeast of Puerto Rico Tuesday afternoon. Meager moisture content and ridging at the surface and aloft will off set the the upper-level instability over the region thus leading to development of shallow convection. Precipitable water will remain remain above 1.0 inches throughout the long- term period due to the trough northeast of Puerto Rico and the easterly tradewinds advecting moisture into the area. The increase in low- level moisture will increase rain chances across the region late in the period. Forecast confidence is medium. && .AVIATION... VFR conds expected for the next 24 hours with fair weather. VCSH is possible at TJBQ after 14/18Z. Winds will increase to around 15 knots, gusting to around 25 knots after 14/14Z. Winds will be from the east, but with sea breeze variations. && .MARINE... Choppy to rough wind driven seas will prevail across most of the regional waters through Wednesday. Easterly trade winds will range from 15 to 20 kts with higher gusts. Small Craft Advisories are in effect for most of the regional and local waters due to seas being up to 8 feet. There is a high risk of rip currents for the northern beaches of PR, Culebra, USVI, Saint Thomas and Saint John. && .PRELIMINARY POINT TEMPS/POPS... SJU 85 74 84 74 / 20 30 30 20 STT 85 73 83 74 / 20 30 30 20 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through late Tuesday night for Culebra- North Central-Northeast-Northwest-San Juan and Vicinity- Southeast. VI...High Rip Current Risk through late Tuesday night for St Croix. High Rip Current Risk through late Monday night for St.Thomas...St. John...and Adjacent Islands. AM...Small Craft Advisory until 8 AM AST Thursday for Caribbean Waters of Puerto Rico from 10 NM to 17N-Anegada Passage Southward to 17N-Atlantic Waters of Puerto Rico and USVI from 10 NM to 19.5N-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. High Rip Current Risk through late Monday night for Coastal Waters of Southern USVI Vieques and Eastern Puerto Rico out 10 NM. Small Craft Advisory from 8 AM this morning to 8 AM AST Thursday for Mona Passage Southward to 17N. && $$ SHORT TERM...JA LONG TERM....TW PUBLIC DESK...JA