698 FXCA62 TJSJ 062132 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 532 PM AST Wed Nov 6 2024 .SYNOPSIS... Wet and unstable weather conditions are expected to continue into the next few days. The main feature will be a deepening upper- level trough and plenty of moisture across the islands. The National Hurricane Center is monitoring a low within a trough with a low chance of formation in the next two days that would affect the local pattern tomorrow into Friday. Hazardous marine and coastal conditions are in effect with several small craft advisories and high risk of rip currents in effect through at least the end of the week. For more information visit www.weather.gov/sju/marine. && .SHORT TERM...Tonight through Friday... Rain showers and thunderstorms began developing during the morning, particularly in the metropolitan area and eastern parts of Puerto Rico. Throughout the day, persistent bands of showers moved across the region. Radar estimates indicated rainfall totals ranging from 1 to 3 inches in the northern and eastern sections of Puerto Rico, as well as in St. Thomas in the U.S. Virgin Islands. While temperatures were generally moderated by cloud cover and showers, they reached the low 90s in the far southwest of Puerto Rico. In contrast, temperatures in the highest elevations remained in the lower 70s. The wet and unstable wet pattern is expect to continue particularly the rest of tonight into early afternoon hours of tomorrow Thursday. Through the rest of the afternoon and into the overnight hours, enhanced shower activity is expected as a new pulse of moisture, associated with the lingering remnants of a frontal boundary, approaches the region. Also a trough of low pressure is also forecast to pass over the area between Thursday morning and Friday maintaining enough instability. The National Hurricane Center is monitoring this system due to its low potential for development over the next 48 hours to 7 days. As a result, tonight and tomorrow could bring potential impacts across the forecast area, including urban and small stream flooding, flash flooding in flood-prone areas, and rapid river rises. With soils already saturated, there is also an elevated risk of landslides in steep terrain. The flooding risk is expected to range from moderate to significant, particularly in the northern and eastern parts of Puerto Rico. We advise residents and visitors to closely monitor the forecast for any advisories, or warnings that may be issued by our local office related to the expected rain. && .LONG TERM...Saturday trough Wednesday... ./FROM PREV DISCUSSION...Issued at 512 AM AST Mon Nov 6 2024/ The long-term forecast will start wet and unstable. At the upper levels, a low pressure located over the western Atlantic will keep instability aloft, due to moisture between 500-700 MB being above normal by two standard deviations on Saturday and colder temperatures at 500 MB of minus 7 degrees Celsius. These unstable conditions, combined with plenty of tropical moisture will be in place due to the passage of a low pressure. This trough of low pressure is now being monitored by the National Hurricane Center and has a low chance of formation in the next two & seven days. A low pressure is expected to develop and move westward to result in a east-southeasterly wind flow across the region. The surface wind will inject the islands with abundant tropical tropical moisture trapped between the 700 to 300 MB. Given the actual forecast pattern, the islands can expect widespread shower activity with the bulk of the showers across northeastern, interior and northwestern sections of Puerto Rico. The U.S. Virgin Islands can expect a similar pattern with showers affecting the islands in the early morning hours. From Sunday through the rest of the long term, the instability of the upper-level low moves more into the southwestern Atlantic, and the islands will remain under the influence of a mid to upper- level ridge. The mid to upper-level ridge will induce warmer temperatures at 500 MB and create a more stable atmosphere, limiting the total development of the most vigorous shower activity. Some dry intrusion is forecast for Sunday, resulting in less coverage in the afternoon showers. However, for Monday, tropical moisture from previous systems and a tropical wave moving westward will increase the moisture available for the development of the daily showers. Surface winds will change under the influence of a strong building surface high pressure from the western Atlantic extending into the Central Atlantic becoming more east-northeasterly on Sunday, easterly on Monday, and southeasterly TUesday and beyond, as the ridge moves eastward into the north-central Atlantic. This change in the winds will affect the presence of showers in the same areas of Puerto Rico during that period. && .AVIATION... (18Z TAFS) Mostly VFR conds will prevail, however sporadic showers and thunderstorms in the NE flow will continue to pop up bringing MVFR conds and some mtn obscurations. Sfc wind flow is NE 5-12 kt but by FL005-015 increases to 15-25 kt. These winds are expected to cont thru 07/14Z then turn to the SE thru 07/21Z. Max winds NNW 57-67 kt btwn FL405-465. && .MARINE... A surface high pressure across the western to central Atlantic and the proximity of a trough of low pressure will promote fresh to locally strong northeasterly winds. In combination with pulses of northerly swells will result in hazardous seas. Also, increased thunderstorm activity is expected over the next few days. Small Craft Advisories are in effect across most of the regional and local waters and passages through at least Friday. && .BEACH FORECAST... Tonight, the risk of the rip currents will increase to high, particularly for beaches along the northern coast of Puerto Rico, Culebra and the U.S. Virgin Islands, persisting through the end of the workweek due to the proximity of a trough of low pressure and some long-period waves reaching the islands. For more details, please consult the Surf Zone Forecast (SRFSJU). && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through Friday afternoon for PRZ001-002- 005-008-012. High Rip Current Risk from Thursday morning through Friday afternoon for PRZ010. VI...High Rip Current Risk through late Thursday night for VIZ001. High Rip Current Risk from Thursday morning through late Thursday night for VIZ002. AM...Small Craft Advisory until 2 PM AST Friday for AMZ711-712-716- 741. Small Craft Advisory until 6 AM AST Friday for AMZ723-742. Small Craft Advisory from midnight tonight to 6 PM AST Thursday for AMZ726. && $$ SHORT TERM...YZR/DS LONG TERM....LIS AVIATION...WS/DS PUBLIC...MNG
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