455 FXCA62 TJSJ 101556 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 1156 AM AST Wed Oct 10 2018 .UPDATE... TJSJ 12z RAOB showed a slight decrease in the available moisture (1.85 in PW) with a wind mind flow from the northeast at 14 knots. While periods of sunshine with passing clouds will prevail across most of the islands, local effects and diurnal heating will result in afternoon convection across the southwest quadrant of PR today. Therefore, periods of moderate to heavy rain could lead to urban and small stream flooding across the interior and southwest quadrant of Puerto Rico. The eastern sections could expect periods of moderate showers at times. No changes were introduced to the forecast package. && .AVIATION... VFR conditions are forecast to prevail today. SHRA will affect TJSJ/TIST/TISX/TNCM/TKPK from time to time. The strongest activity is expected across SW-PR and could affect TJMZ and the vicinity of TJPS. Therefore VCTS are expected at TJPS and brief periods of MVFR are forecast for TJMZ between 10/17-23z. && .MARINE... A northerly swell around 6 feet was detected at San Juan buoy (41053). This swell will create hazardous rip currents along the north and east facing beaches of Puerto Rico. Seas will range between 1 and 5 feet across the Caribbean waters, except across the Offshore waters where could reach up to 6 feet. && .PREV DISCUSSION... /issued 521 AM AST Wed Oct 10 2018/ SYNOPSIS...A slightly drier airmass will reduce the rainfall coverage during the day today through early Thursday. A wetter and more unstable weather pattern is expected starting later on Thursday and continuing into the early portions of next week as an upper-level low will combine with deep tropical moisture associated with a developing surface low-pressure area and also from a tropical wave that will be moving from the east. SHORT TERM...Today through Friday... The available moisture will decrease somewhat through the day today, particularly for the northern portions of the forecast area. There is also an upper ridge over the local area today, but an upper trough will gradually develop to the west of the local area by Friday, which will gradually dig to the west southwest for the next couple of days after that. Even though moisture will decrease slightly this afternoon, there will still be enough moisture that will combine with the local effects to cause the development of showers and thunderstorms across the interior, western and southwestern PR this afternoon. There is also a chance of showers across eastern Puerto Rico and the northern USVI. Even though the upper trough is expected to develop by Friday to the west of the local area, the chances of thunderstorm continues in the short term. Not to mention the fact that the available moisture will start to increase once again on Thursday afternoon and we will continue to have higher than normal moisture on Thursday afternoon and Friday and for the next several days after that, with precipitable water values near 2 inches. So given the current setup, we expect a somewhat rainy pattern for the next few days, with the thunderstorms mainly in areas of convergence, such as sea breeze convergence and also downstream from the islands and the Luquillo Mountain Range into the San Juan metro area, especially for Thursday and Friday. Little change in the temperatures is expected, with the max temps in the mid to upper 80s across the lower elevations and in the low 80s across the higher elevations. LONG TERM...Saturday through Thursday... The wet and unstable weather pattern will prevail across the region during the weekend into early next week as the upper-level trough, which will be situated north of the region, will combine with deep tropical moisture not only associated with a developing surface low-pressure area over the central Caribbean, but also from a tropical wave that will be moving in into the forecast area late Sunday into Monday. This will provide a favorable environment for enhanced shower and thunderstorm activity across the forecast area during this time period. A return to drier weather conditions is expected by the middle to latter half of next week as a drier airmass will be moving in from the northeast, therefore, limiting the shower activity. AVIATION... VFR conds expected across the local terminals through 10/17Z, due to SHRA/TSRA possibly affecting TJMZ thereafter. However there will be SHRA in the general area that may cause VCSH across most of the local terminals through the forecast period. Winds will be mainly from the east to ENE at 15KT and gusty with sea breeze variations past 10/14Z. MARINE...Seas will continue to range between 4 to 6 feet across the Atlantic waters and local Caribbean passages. Therefore, small craft operators are urged to exercise caution across these waters. Elsewhere, seas of 3 to 5 feet are expected to prevail. Northerly swell associated with Hurricane Leslie, located across the central Atlantic Ocean, will continue to produce a high risk of rip currents across the northern beaches of PR and Culebra for today. && .PRELIMINARY POINT TEMPS/POPS... SJU 87 79 90 79 / 40 20 60 40 STT 91 81 87 81 / 40 20 50 40 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...High Rip Current Risk through Thursday afternoon for North Central-Northeast-Northwest-San Juan and Vicinity-Southeast- Western Interior. High Rip Current Risk until 6 PM AST this evening for Culebra. VI...None. AM...None. && $$ UPDATE...CAM AVIATION...CAM