Hurricane Season runs from June 1-November 30
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000 FXCA62 TJSJ 270800 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 400 AM AST Sat Apr 27 2024 .SYNOPSIS... Unsettled weather conditions are expected to prevail today, with an elevated risk of flooding, especially for the interior and southwestern Puerto Rico. Some improvement is anticipated for the first couple of days of the workweek, but the pattern will turn wet again after Tuesday, with additional periods of showers and thunderstorms. Marine and coastal conditions are expected to deteriorate Monday onward as a northerly swell arrives. && .SHORT TERM...Today through Monday... Isolated to scattered showers affected the local waters of Puerto Rico and the U.S. Virgin Islands overnight. Some of these showers reached the eastern coast of Puerto Rico, leaving minor accumulations over Humacao, Las Piedras and San Lorenzo. Similar weather conditions are expected to persist through at least the mid- morning hours. Low temperatures were observed in the mid to upper 60s across the mountains, and around the mid 70s along the coastal and urban areas. Light winds from the east prevailed through most of the night. Another active day is anticipated as a plume of moisture moves into the region, promoting moderate to locally heavy showers and isolated thunderstorms. The latest model guidance are showing an increase in moisture content by the mid-morning hours through the afternoon with precipitable water values ranging from 1.90 to 2.20 inches. This moisture content in combination with diurnal heating, local orographic effects, and sea breeze may lead to deep convective activity over Puerto Rico. Therefore, the rainfall risk is elevated today for the eastern, central interior and southwestern portions of Puerto Rico, including the San Juan metro area. Due to previous rains, soils are very saturated and additional rains could lead to flash flooding, river rises, and mudslides. We encourage residents and visitors to stay aware and monitor the weather forecast in your location to plan your weekend accordingly. A strong surface high pressure located over the Carolinas in the U.S. eastern coast will promote moderate northeast winds today. Winds are expected to increase on Sunday, resulting in breezy conditions during the first days of the week. Model guidances continue to show an above-than-normal moisture through the rest of the period, with a slight improvement on Monday. Prepare for a wet and unstable weather pattern to persist for the next several days. .LONG TERM...Tuesday through Saturday... A high pressure system at the lower levels of the atmosphere will drive the winds from the east at the surface, and from the northeast a little bit aloft. This feature will maintain the moisture trapped in the lower levels of the atmosphere. In general, Tuesday looks like the driest day of the forecast period, but moisture will still remain at seasonal levels, triggering convection in the interior and southwestern Puerto Rico. The pattern will turn wet again for the rest of the workweek as yet another mid and upper level trough digs into the western Caribbean. This trough will pull plenty of moisture from the Caribbean Sea into the local islands, and precipitable water values will be above normal. On Wednesday, the steering flow will be from the southeast, so local effects should trigger for the interior, north and northwest of Puerto Rico, as well as around the Virgin Islands and local waters. Then, on Thursday, as the trough further approaches, the steering winds will collapse, with very light winds anticipated. Additionally, the mean flow will be from the southwest, so activity could switch focus for the eastern interior, the San Juan metro area, and then the Virgin Islands. One thing that could delay the development of rain, however, is that if a thick cloud layer get established, then local effects will be milder. Also, temperatures could be below normal for a change, except for the southern coast of Puerto Rico, where values are still expected to reach the low 90s. On the other hand, if there are breaks of sunshine, then the risk for showers and thunderstorms will be elevated, likely producing urban and small stream flooding, water surges along rivers, as well as mudslides. By Friday, the influence of the mid and upper level trough diminishes, but a surface reflection remains, maintaining enough moisture, and a light wind flow from the northeast. More moisture will also be added into the mixture from another trough approaching the eastern Caribbean from the east. Thus, another active afternoon is anticipated for the interior of Puerto Rico, with activity then spreading toward the coastal areas. Since some drier air will filter at the mid and upper levels, temperatures will warm up again to more seasonal values, reaching the mid and upper 80s, and even the low 90s. On Saturday, the pressure gradient begins to recover as a surface high pressure exits the eastern coast of the United States. The winds will be around 10 knots, and out of the southeast. Lingering moisture around the northeastern Caribbean will maintain a showery pattern, with another active afternoon and an elevated risk for flooding and mudslides. && .AVIATION... (06z TAFs) Mainly VFR conds expected across all terminals through the forecast period. However, areas of SHRA/TSRA could produce tempo MVFR/IFR conds and mtn obsc, mainly over TJPS/TJBQ aft 27/14z. VCSH expected at TJSJ/TIST/TISX terminals after 27/13z. ENE winds btw 9 to 14 knots with by higher gusts and sea breeze variations aft 27/13z. && .MARINE... A small northwesterly swell will continue to spread across the local waters today into the rest of the weekend. Winds will prevail from the east and becoming northeast today under the influence of a surface high pressure moving off the eastern coast of the United States. A northerly swell is anticipated to spread across the local waters early next week deteriorating coastal and marine conditions. Therefore, building seas are forecast from Sunday into Monday across the offshore Atlantic waters, with seas up to 7 feet. Small craft operators are urge to stay tune for further advisories. Additionally, showers and thunderstorms will continue to affect the local waters for the next several days as lingering moisture from a surface trough/old frontal boundary remains over the local area. && .BEACH FORECAST... Breaking waves around 5 feet will maintain the risk of rip currents moderate through Sunday along the north facing beaches of the islands. A northerly swell will be arriving on Monday, increasing the risk for these beaches to high through at least late Wednesday. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM & AVIATION...GRS LONG TERM & BEACH FORECAST....ERG MARINE ...LIS
