Leeward Islands Offshore Forecast
| Today...E Winds 15 To 20 Kt. Seas 5 To 7 Ft In E Swell. |
| Tonight...E Winds 15 To 20 Kt. Seas 5 To 7 Ft. |
| Fri...E Winds 15 To 20 Kt. Seas 5 To 7 Ft In E Swell. |
| Fri Night...E Winds 15 To 20 Kt. Seas 5 To 7 Ft. |
| Sat...E Winds 15 To 20 Kt. Seas 5 To 7 Ft. |
| Sat Night...E Winds 15 To 20 Kt. Seas 5 To 7 Ft. |
| Sun...E Winds 15 To 20 Kt. Seas 5 To 7 Ft. |
| Sun Night...E Winds 15 To 20 Kt. Seas 5 To 7 Ft. |
| Mon...E Winds 15 To 20 Kt. Seas 5 To 7 Ft. |
| Mon Night...E Winds 15 To 20 Kt. Seas 5 To 7 Ft. |
| Area Forecast Discussion ...CORRECTED National Weather Service San Juan PR 339am AST Thu May 21 2026 .Short Term(Today through Saturday)... Issued at 325am AST Thu May 21 2026 Calm weather conditions prevailed overnight across Puerto Rico and the U.S. Virgin Islands under clear to partly cloudy skies. Doppler radar and satellite imagery observed pockets of fast-moving passing showers across the local Atlantic and Caribbean waters; however, only a few of these showers reached portions of Vieques and eastern Puerto Rico during the early morning hours. Overnight lows ranged from the low to mid-70s across coastal and urban areas, and from the low to mid-60s in the higher elevations. Easterly winds prevailed at 5 to 10 mph, with occasional higher gusts and land breeze variations. A mid to upper-level trough located over the western Atlantic (near the Bahamas) is expected to continue weakening over the next few days as a mid-level ridge builds across the area. At the lower levels, a surface high pressure system over the central Atlantic will continue to strengthen and tighten the local pressure gradient. This setup will promote fresh to locally strong east-southeasterly winds through at least next week. During the short-term period, precipitable water (PWAT) content will generally remain at seasonal values between 1.5 and 2.0 inches. However, PWAT (Precipitable Water) values will briefly dip slightly below normal today to around 1.30 inches before increasing again by Friday. Under this pattern, passing showers will continue to move over portions of the U.S. Virgin Islands and eastern Puerto Rico, including Vieques and Culebra with minimal impacts. During the afternoon hours, daytime heating combined with local effects will induce convection across western Puerto Rico, triggering showers and a few isolated thunderstorms. Because breezy conditions will persist, these showers are expected to move quickly, keeping the risk of flooding limited over the next few days. Warm to hot temperatures will persist daily through early next week. Maximum temperatures are expected to range from the upper 80s to low 90s along coastal areas, and from the low to mid-80s in the higher elevations. Heat indices will rise between 100 and 105 degrees Fahrenheit. Residents and visitors are urged to stay hydrated, seek shade, and monitor local conditions to ensure safety during peak heating hours. .Long Term(Sunday through Thursday)... Issued at 325am AST Thu May 21 2026 Small changes were introduced to the long-term forecast, as variable conditions may persist early next week, becoming wetter by the end of the period. The wind pattern will continue from the E-ESE as a surface high pressure building in the western Atlantic, maintaining breezy to windy conditions from Sunday through Tuesday, peaking on Monday. However, the high pressure may migrate eastward and linger over the Central Atlantic, weakening and veering winds from the SE Tuesday onward. Moisture content should remain seasonal, with PWAT (Precipitable Water) values ranging between 1.5 and 1.75 inches on Sunday and Monday, but it should gradually increase as abundant moisture pools into the region. According to the latest model guidance, PWAT (Precipitable Water) values could increase up to 2.0 inches, near the climatological normal, with low and mid-level moisture increasing well above normal and sounding models showing skinny profiles. Due to the proximity of the upper- level trough, mid-level temperatures should briefly cool both Sunday and Monday (around -8 degrees Celsius), gradually warming as a mid- level ridge north of the CWA (County Warning Area) weakens the trough. Although shower activity is expected each day of the forecast, for Sunday and Monday, fast-moving showers are expected over half of eastern Puerto Rico and the U.S. Virgin Islands, with afternoon convection over interior and western Puerto Rico. Additionally, streamers should develop by midday, moving over portions of Vieques, Culebra, and eastern Puerto Rico, including the San Juan Metropolitan Area. Rainfall accumulations could result in ponding of water over roadways and poorly drained areas, along with minor flooding, with a limited flooding threat. Besides flooding, these areas can experience gusty winds and lightning. As winds shift and moisture content increases, the flood threat may remain limited, but an elevated threat (including urban and small stream flooding) over localized areas cannot be ruled out. With abundant moisture and seasonal temperatures across the region, heat indices over localized areas (particularly urban and coastal) of the islands may reach and exceed 100 degrees Fahrenheit. Nevertheless, the heat will remain limited, likely to impact those sensitive to heat. Stay hydrated and avoid long sun exposure. Marine Issued at 325am AST Thu May 21 2026 Moderate to fresh easterly winds will continue across the regional waters through the next several days due to strong high pressure over the Atlantic. Choppy to rough seas will persist at times, especially across the offshore Atlantic waters where Small Craft Advisories remain in effect through at least Thursday afternoon. Isolated afternoon thunderstorms may develop near the western coastal waters of Puerto Rico each day, producing locally higher winds and seas. Beach Forecast Issued at 325am AST Thu May 21 2026 Moderate rip current risk conditions will continue across most local beaches through the next several days due to persistent breezy conditions and ongoing wind-driven seas. The highest risk will remain along north and east-facing beaches of Puerto Rico, Culebra, and the U.S. Virgin Islands. Beachgoers should exercise caution, as life-threatening rip currents remain possible. .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...Small Craft Advisory until 6pm AST this evening for AMZ711. |