Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
767 FXCA62 TJSJ 111613 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 1213 PM AST Tue Aug 11 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER... .KEY MESSAGES... Issued at 1204 PM AST Tue Aug 11 2026 - Shower activity will continue this afternoon and tomorrow, with drier conditions and concentrations of Saharan dust likely to limit shower activity across the islands Thursday onward. - Heat remains the main threat as warm to hot conditions are likely to continue across the islands for the rest of the week. - Marine and coastal conditions will deteriorate by the end of the workweek into the weekend as stronger trade winds build seas and increase the risk of life-threatening rip currents. - NHC continues to monitor multiple Atlantic disturbances. It remains too early to determine any potential impacts to Puerto Rico or the U.S. Virgin Islands. && .Short Term(This evening through Thursday)... Issued at 1204 PM AST Tue Aug 11 2026 Ample moisture remains entrenched across the region today, with atmospheric soundings and satellite-derived total precipitable water imagery indicating values between 1.90 and 2.25 inches. East-southeast steering winds, coupled with diurnal heating and sea breeze convergence, will trigger convective development by early afternoon. Heavy localized downpours and isolated thunderstorms are anticipated across the interior and western portions of Puerto Rico. At the same time, scattered activity with periods of moderate to locally heavy rainfall will prevail across the U.S. Virgin Islands and the eastern half of PR. Urban and small stream flooding, localized flash flooding, and mudslides in steep terrain remain the primary hazards with the strongest activity. Meanwhile, in areas without cloud coverage, the sunshine and elevated ambient humidity will combine to drive heat indices into the 102F to 108F range across low-elevation and coastal urban areas before the onset of afternoon showers. A brief transition in the atmospheric profile will begin late tonight as a strong Saharan Air Layer (SAL) spreads across the northeastern Caribbean. Aerosol optical depth modeling indicates moderate to high concentrations of suspended particulates moving overhead, resulting in widespread haze and diminished air quality across the islands through early Wednesday. Shower activity on Wednesday will be noticeably reduced compared to today. Still, another surge in low-level moisture is expected to gradually increase PWAT content to around 2.00 inches by midday into the evening hours. Therefore, expect limited to brief early morning trade wind showers across the windward areas, followed by an enhancement in diurnally induced afternoon showers across the islands. By Thursday, dry and stable conditions will return across the local area. Columnar moisture is projected to drop well below seasonal climatological normals as the Saharan dust air mass (with lesser concentrations) remains firmly anchored across the region. Convective development will be almost entirely suppressed, keeping rain chances low for most island locations, aside from a few shallow, fast-moving passing showers across the local waters and the typical afternoon showers over western PR. In general, the heat threat will increase on Wednesday and Thursday, and heat advisories could be required each day. Hazy conditions will also be of concern to those with respiratory issues. && .Long Term(Friday through next Monday)... Issued at 145 AM AST Tue Aug 11 2026 A tightening pressure gradient associated with the Atlantic high is expected to support breezy to locally windy east to northeast winds through much of the long-term period. Gusty conditions could affect unsecured outdoor items, particularly across exposed coastal and higher-elevation areas. Winds could approach advisory criteria at times, although confidence in the magnitude and duration of the strongest winds remains limited. Saharan dust and a relatively dry air mass should otherwise dominate much of the period, with precipitable water values generally remaining below normal near 1.3 inches. Intermittent patches of low-level moisture may support passing windward showers and highly localized afternoon convection. Elevated heat risk will also persist, with locally significant heat impacts possible across the warmer urban and coastal areas. Warm overnight temperatures will continue to provide limited relief. Forecast uncertainty increases considerably late in the period as the National Hurricane Center continues to monitor a tropical disturbance over the central Atlantic. While development is possible as the system moves generally westward, considerable uncertainty remains regarding its eventual track, intensity, timing, and whether it could have any direct or indirect influence on Puerto Rico and the U.S. Virgin Islands early next week. Continue to monitor subsequent forecasts and Tropical Weather Outlooks from the National Hurricane Center as the forecast evolves. && .AVIATION... (18Z TAFS) Issued at 1204 PM AST Tue Aug 11 2026 SHRA/TSRA will continue to increase across the local area as a tropical wave moves across the region through late tonight. Tempo MVFR to brief IFR conds are possible across all terminals thru at least 12/00z. Mtn top obscd and BKN cigs nr FL025 expected across the eastern interior of PR. Mainly east winds btw 20-30 kt expected blo FL100, with sea/land breeze variations. && .MARINE... Issued at 1204 PM AST Tue Aug 11 2026 A tropical wave moving across the region will continue to bring showers and isolated thunderstorms across the regional waters and Caribbean passages, with periods of heavy rainfall, gusty winds, and isolated lightning. The broad Atlantic ridge extending from the western into the central Atlantic will continue to promote moderate easterly winds across the local waters for the rest of today and Wednesday. Marine conditions will deteriorate toward the end of the workweek as the local pressure gradient tightens and easterly winds strengthen. Fresh to locally strong winds and building seas across portions of the offshore waters and local passages could lead to choppy to rough seas, hazardous conditions for small craft. Small Craft Advisories will likely be required for some of these waters. Pulses of Saharan dust will also persist throughout the week, occasionally reducing visibility. && .BEACH FORECAST... Issued at 1204 PM AST Tue Aug 11 2026 The moderate risk of rip currents continues today, particularly across the northern and eastern beaches of Puerto Rico, including Vieques and Culebra, and the U.S. Virgin Islands; low elsewhere. As mentioned in previous discussions, beachgoers must pay attention to the beach conditions as life-threatening rip currents are possible along the surf zone. The risk should persist on Wednesday, however, winds will gradually strengthen on Wednesday night into Thursday, with breezy to windy conditions across the islands, leading to hazardous coastal conditions. With building seas, the likelihood of life-threatening rip currents across exposed beaches is expected to increase as well. Hence, the risk of rip currents will likely be high for most beaches of Puerto Rico and the U.S. Virgin Islands from Thursday into the weekend; Rip Current Statements will likely be issued. Residents and visitors are encouraged to check the beach forecast before going out and follow the advice from the local beach patrol and the flag warning systems. Aside from rip currents, beachgoers should remain weather alert as showers and isolated thunderstorms may move near coastal areas, particularly this afternoon and Wednesday. Seek shelter whenever you hear thunder. && .FIRE WEATHER... Issued at 1204 PM AST Tue Aug 11 2026 In the morning hours, shower activity associated with a tropical wave increased, with isolated to scattered showers and isolated thunderstorms across the islands. As of 12 PM AST, most of the rainfall accumulations are across the interior and the eastern side of Puerto Rico, with WSR-88D estimates up to 2.5 inches. Across the U.S. Virgin Islands, non-official stations reported up to 0.35 - 0.40 inches. RAWs stations reported breezy to locally windy conditions across the southern coastal plains of Puerto Rico, between 15 - 20 mph and gusts up to 30 mph. Although RH values dropped during the morning, RAWs stations reported values above thresholds (> 55%). Given the current conditions and the expected forecast, the fire danger will remain low today, though residents and visitors are encouraged to avoid outdoor burning and very dry fuels and drought conditions across the area could support fire growth. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM/AVIATION...DSR KEY/MARINE/BEACH/FIRE...MNG LONG TERM....MRR