150 FXCA62 TJSJ 070804 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 404 AM AST Sat Jun 7 2025 .KEY MESSAGES... * Increasing surface winds will likely generate moderate to locally fresh winds, resulting in wind-driven seas. Therefore, small craft operators should exercise caution. Small Craft Advisories may be needed across the offshore waters. * Warmer-than-normal temperatures are likely to continue through the weekend across most coastal and lower elevations of the islands.A heat advisory could needed on Monday. * Above-normal moisture associated with a tropical wave, along with increasing instability, might result in a rise in showers and thunderstorms by midweek next week. && .SHORT TERM...Today through Monday... Isolated morning showers will drift across the local waters, primarily affecting the eastern portions of Puerto Rico and the surrounding island, but are not expected to produce significant rainfall accumulations through at least mid morning. Showers amd cloud cover are expected to increase later this morning as available moisture combines with daytime heating and local sea breeze convergence, generating sufficient instability for convective development by early afternoon. the main area of activity will be over the western interior and northwestern Puerto Rico. Additionally, CU line may develop over La Sierra de Luquillo and drift westward, potentially impacting the San JUan Metro area later this afternoon. A surface high pressure system over the central Atlantic will maintain an easterly wind flow, gradually shifting to an east- southeasterly direction later today. As the high pressure strengthens over the region, wind speeds are expected to increase, resulting in breezy to locally windy conditions across the forecast area. On Monday, a southerly component of the winds will increase the potential for high temperatures...a Heat Advisory could be issue. .LONG TERM...Tuesday through Friday... Current model guidance has precipitable water (PWAT) values at up to above normal to start the long term period as moisture, in part from a tropical wave over the Caribbean Sea, is steered into the local islands under east-southeast flow. However, a Saharan Air Layer (SAL) will also reach the islands, promoting hazy skies. While PWAT values will gradually decrease, a more notable mass of drier air is forecast to arrive by Friday. A surface high pressure over the Atlantic will continue building during the period, promoting breezy to locally windy easterly to east-southeasterly steering flow. A mid- level ridge will be present to start the period, but it will gradually weaken as a mid-level low moves into the central Atlantic. The typical diurnal pattern will continue with patches of moisture and showers reaching windward sectors of the islands, especially during the mornings and overnight hours, and with afternoon showers and thunderstorms mainly over interior to western Puerto Rico due to sea breeze convergence, diurnal heating and local effects. Lines of showers can also develop downwind of the local islands and El Yunque. An elevated flood potential will persist over interior to western Puerto Rico. Highs will be in the upper 80s to low 90s at lower elevations and coastal areas , with heat indices over 100 degrees. A limited heat risk will persist for most coastal and lower elevation areas. Lows will be in the 60s for higher elevations of Puerto Rico and in the 70s to around 80 over lower elevations of the islands. Although moisture will gradually decrease, the frequency of showers could be higher due to an upper level trough from the northeast, and another tropical wave moving into the Caribbean Sea by the end of the forecast period. && .AVIATION... (06Z Taf) Mainly VFR conditions are expected to prevail across all terminals during the next 24 hours. Any SHRA that develops will be brief, ESE winds and local effects can produce VCSH near TJBQ/TJSJ through 07/22Z, no impacts to operations expected. Winds from the ESE at 15- 20kts, with higher gusts, through 07/23Z when they are expected to decrease. Winds will increase to similar values again after 08/13Z. && .MARINE...A surface high pressure system over the central Atlantic will continue to support moderate to locally fresh trade winds, shifting from the east to southeast over the weekend. This will generate choppy conditions across the local waters mainly during the peak of sea breeze wind speed enhancement. Isolated thunderstorms are expected to develop each afternoon over the western waters of Puerto Rico. Additionally, a tropical wave is forecast to move across the eastern Caribbean around Tuesday. && .BEACH FORECAST...Increasing winds across the region will continue to elevate the threat of rip currents along most beaches in Puerto Rico and USVI through the reminder of the weekend. As wind driven seas build, hazardous swimming conditions will become more widespread. Even when the rip currents threat is categorized as low , dangerous rip currents can still form unexpectedly, especially near structures such a piers, reefs, and jetties. Beachgoers are reminded to remain vigilant and exercise caution when entering the waters, regardless of the daily risk level. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM...MRR LONG TERM....EM AVIATION...EM
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