AFDSJU Area Forecast Discussion National Weather Service San Juan PR 1243 PM AST Sat Dec 6 2025 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 1243 PM AST Sat Dec 6 2025 * Mostly fair and stable weather will continue for Puerto Rico, with a few quick showers at times, especially overnight and in the morning across eastern areas. * The U.S. Virgin Islands will also see fair weather, with occasional brief showers mainly during the night and early morning hours. * Winds will gradually increase by the end of the workweek, leading to breezier conditions over the islands and coastal waters. * A northerly swell expected by the middle and later part of next week, combined with increasing winds, may lead to rougher seas and a higher risk of life-threatening rip currents, though some uncertainty remains regarding its timing and strength. && .Short Term(This evening through Monday)... Issued at 1243 PM AST Sat Dec 6 2025 Mostly sunny skies have prevailed during the day under a southeast breeze of 15 to 20 knots. Some showers were observed in the area, but impacts to land were minimal. The rest of the afternoon will be fair, with a slight chance of showers for western Puerto Rico due to diurnal heating. These showers are not expected to lead into flooding and should be brief in nature. For tonight, a small perturbation in the trade winds will move in. This feature will bring near normal moisture levels, hence an increase in showers will be anticipated for the Virgin Islands and portions of southern and eastern Puerto Rico. With the enhanced moisture, showers are expected tomorrow for the Cordillera Central, western Puerto Rico and portions of the San Juan metro area. Again, the flooding threat will be very limited, but there could be some impacts to people enjoying outdoors activities. Even with the small perturbation moving in, the mid and upper level atmosphere are dominated by a ridge, maintaining moisture trapped closer to the surface. Also, a surface high pressure over the eastern Atlantic will maintain the trade winds coming from the southeast, at 10 to 20 knots. All these factors work against the formation of any strong showers. It will be even drier on Monday, with a drier air mass also reaching the lower levels of the atmosphere. Any shower that reach the island will be short lived, limited to portions of the Virgin Islands and eastern Puerto Rico. && .Long Term(Tuesday through next Friday).../from prev discussion/ Issued at 1243 PM AST Sat Dec 6 2025 A persistent mid-level ridge will dominate the period, maintaining below- to near-normal mid-level relative humidity and generally stable conditions. Climatology comparisons keep 700-500 mb relative humidity in the lower to mid percentiles, but periodic patches of low-level moisture will still move through, producing brief PWAT increases and allowing isolated to scattered showers mainly across eastern PR and the USVI during the nighttime and morning hours. Afternoon showers over western Puerto Rico remain possible whenever moisture deepens toward 700 mb. Even with the ridging aloft, 500 mb temperatures are expected to remain cool enough for seasonal 700-500 mb lapse rates to support limited afternoon convection. Any storms that develop will be short-lived and shallow, but a few brief thunderstorms cannot be ruled out. At the surface, southeast winds start out light early in the period due to a weak pressure gradient. By the end of the workweek, winds will strengthen and shift slightly east-southeast as the gradient tightens across the northeastern Caribbean. Temperatures will remain above normal, particularly early in the period under a southeasterly wind flow, supported by 925 mb temperatures and 1000-850 mb thickness values running near to above normal. Highs will generally reach the mid to upper 80s at lower elevations. Overall, the pattern favors stable conditions with passing shallow moisture, occasional brief convection, increasing winds late in the workweek, and continued warm temperatures. && .AVIATION... (18Z TAFS) Issued at 1243 PM AST Sat Dec 6 2025 Mainly VFR conditions expected to prevail through the forecast period. Isolated SHRA are observed along the Caribbean and Atlantic waters, but no impacts to operations are expected. After 06Z, SHRA will increase in the vicinity of the USVI terminals, and brief periods of reduced VIS and low ceilings can be anticipated. Winds will be from the ESE at 13-16 kts, with stronger gusts. && .MARINE... Issued at 1243 PM AST Sat Dec 6 2025/from prev discussion/ An east to northeast 4 to 5 ft swell at around 10 seconds and moderate trades will promote choppy seas across most offshore waters and local passages today. A building surface high pressure north of the area will maintain moderate to locally fresh trades (easterlies) on Sunday before subsiding early next week. && .BEACH FORECAST... Issued at 1243 PM AST Sat Dec 6 2025 Enhanced trade winds will maintain a moderate rip current risk through mid-week. A northerly swell is expected to reach the islands by mid-week, that along with breezy conditions should rise the risk of rip currents to high. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$