663 FXCA62 TJSJ 281055 CCA AFDSJU Area Forecast Discussion...CORRECTED National Weather Service San Juan PR 655 AM AST Sun Jun 28 2020 .SYNOPSIS...Saharan dust will remain over the local area today and therefore hazy skies are expected. Surface high pressure will cause east to east northeast winds today, becoming mainly easterly by Monday. An upper trough will cause instability and thunderstorm activity through the first half of the workweek and a weak tropical wave could approach the local islands by Thursday. && .SHORT TERM...Today through Tuesday... The presence of Saharan dust over the region will maintain relatively tranquil weather today. However, there is some low level moisture that could combine with the local effects, resulting in shower activity in the afternoon across central to southwestern PR due to an ENE wind flow. For Monday, the pattern changes, an upper-level trough and induced surface perturbation will approach the northeastern Caribbean. These features will enhance upward motion and will increase the shower and thunderstorm activity. Therefore, starting on Monday, isolated to scattered showers are expected mostly over eastern sections of Puerto Rico and the U.S. Virgin Islands in the morning. Then, afternoon convection with moderate to heavy showers and isolated thunderstorms are expected over the interior and western sections of Puerto Rico in the afternoon. Also, showers will not be ruled out across the San Juan Metro area. Urban and small stream flooding is expected with the heaviest showers. This instability due to the upper trough, is expected for the first few days of the workweek, therefore a similar pattern in expected on Tuesday. In term of temperatures, warmer than normal temperatures are expected aross the coastal sections and urban areas with heat index values that could be in the 100 to 105 degree range. .LONG TERM...Wednesday through Monday... A slot of dry air is expected on Wednesday, ahead of a tropical wave that could reach the local islands on Thursday. That said, there may still be the influence of the upper trough, which will help develop showers and thunderstorms across central to NW-PR on Wednesday afternoon. The weak tropical wave that could reach the area on Thursday may cause a significant enough increase in moisture to cause showers and a few thunderstorms across a more generalized area, with the latest GFS guidance favoring development across the north half of PR. This pattern however is trending differently than what the model was suggesting yesterday, so not too much confidence is put in the long range forecast. For the next weekend, patches of moisture will be moving through, but by then, the upper low may not be positioned in a location to provide good dynamics for generalized convection over the local islands, so locally induced convection would be favored starting on Friday and Saturday. However, some deeper moisture could cause an increase in shower activity again on Sunday and Monday. && .AVIATION...Some haze is expected to continue today with visibilities staying P6SM across all TAF sites. VFR conditions are expected across the local TAF sites, but SHRA is possible at TJPS after 28/18Z. Winds out of the E-ENE between 10 and 15 kt with sea breeze variations and occasional gusts. && .MARINE...Winds of 10 to 15 knots are expected today with choppy seas up to 6 feet. However, from this afternoon onward, most of the local waters are expected to have wave heights up to 5 feet as seas gradually subside. There is a moderate risk of rip currents today across many of the local beaches, especially across northern and southeastern Puerto Rico, Vieques and Culebra, west and south Saint Thomas, south Saint John, as well as north, eastern and southeastern Saint Croix. && .PRELIMINARY POINT TEMPS/POPS... SJU 90 79 87 77 / 30 40 40 50 STT 91 78 88 77 / 20 40 40 60 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM...LIS LONG TERM....JA PUBLIC DESK...99