Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
641 FXCA62 TJSJ 082017 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 417 PM AST Sat Jun 8 2024 .SYNOPSIS... A stable weather pattern is expected for the next several days under the presence of a low to upper ridge dominating the region. The islands will be mostly dominated by an east-southeasterly wind flow at the surface. Under this wind pattern, a warm spell will prevail for the next two days. As a result, an Excessive Heat Watch is in effect for most of the coastal areas on Sunday, and warmer conditions are expected for Monday. && .SHORT TERM...Tonight through Monday: A stable weather pattern prevailed across the islands today, with warmer temperatures and no rainfall activity for any sector of the island. According to some unofficial stations across the islands, heat index values reached 112 Fahrenheit degrees across the northwestern quadrant and between 105 to 110 Fahrenheit degrees in the north-central areas of Puerto Rico. According to the official climate site at the Luis Munoz Marin Airport in Carolina, the maximum temperature reached 95 F at around 1 PM AST with a maximum heat index of 105 Fahrenheit. The forecast remains on track. At the mid to upper levels, the presence of a ridge will continue to provide subsidence, inducing stable weather conditions and drier air aloft, resulting in mostly a drying pattern with minimal or no rain activity. This pattern in the upper level will hold for most of the period, leaving the islands dominated by a building surface high pressure extending from the eastern Atlantic to the Central Atlantic. This surface feature will interact over the central Atlantic by Sunday, inducing more east-southeasterly winds across the region. Embedded in these winds, some brief patches of tropical moisture will filter in, causing an increase in the potential for convective showers in the afternoon hours each day. Although showers are still forecasted, widespread shower activity is not anticipated. By late Sunday into Monday, model guidance continues to suggest the passage of a tropical wave well south of the islands, leaving the bulk of the moisture over the Caribbean Sea. That said, the islands might experience some pulses of moisture, increasing the pesky passing showers. .LONG TERM...Tuesday through Saturday...from previous discussion issued at 450 AM AST Saturday June 8 2024... A surface high pressure extending from the eastern to central Atlantic will continue to promote southeasterly winds throughout the upcoming week. We foresee a change in the weather pattern to begin Tuesday afternoon into Wednesday as patches of moisture associated with an approaching tropical wave. The latest Precipitable Water (PW) models suggest values increasing to normal climatological levels, around 1.6 to 1.9 inches from Tuesday night into Wednesday. That moisture field could increase the frequency or intensity of the showers across the regional waters resulting in better rain chances, especially across the Caribbean waters and portions of the islands. By Thursday, the low-level southeasterly winds will push a drier airmass, which probably will briefly limit rain development that day. However, at the end of the week, models agree that additional moisture from another surface disturbance will also reach the island along with an upper-level trough and further enhance the chance of showers through the weekend. Temperature-wise, even tho temperatures should improve, limited to elevated excessive heat risk is anticipated to continue across lower elevations and coastal areas of Puerto Rico and the rest of the islands. && .AVIATION... VFR conds at all terminals and en route btw islands. Few low clds btw FL028...FL050...FL100. Isold -SHRA ovr local waters and passages. Brief late aftn SHRA psbl ovr ctrl interior and NW PR til 23Z. SFC wnd fm SE 8-12 kts and brief gusts with some sea breeze variations...bcmg calm to lgt/vb aft 23Z. No sig operational wx impacts attm. && .MARINE... A surface high pressure extending from the central Atlantic into the eastern Atlantic will continue to promote a moderate east- southeasterly wind flow across the region. Tranquil seas will continue for the rest of the weekend into the upcoming workweek with seas up to 5 feet for most of the CWA local waters. From Monday into Tuesday, a tropical wave now located just over the Lesser Antilles might result in localized shower activity due to strong showers. && .BEACH FORECAST... There will be a low to moderate rip current risk across the exposed local beaches for several days. For most of the northern local beaches, the risk will remain low for tonight. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...Excessive Heat Warning until 6 PM AST this evening for PRZ001>003-005-007-008-010-011. Excessive Heat Watch from Sunday morning through Sunday afternoon for PRZ001>003-005-007-008-010>013. Heat Advisory until 6 PM AST this evening for PRZ012-013. VI...Excessive Heat Watch from Sunday morning through Sunday afternoon for VIZ001-002. Heat Advisory until 6 PM AST this evening for VIZ001-002. AM...None. && $$ SHORT TERM...ERG LONG TERM....LIS PUBLIC...RVT