Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
664 FXCA62 TJSJ 100836 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 436 AM AST Mon Jun 10 2024 .SYNOPSIS... Hot conditions return today. Excessive Heat Warnings are in effect from 9 AM to 6 PM AST for all lower elevations and coastal areas of Puerto Rico. Heat Advisories are in effect from 9 AM to 6 PM AST for Vieques, Culebra, and the US Virgin Islands.Due to the likelihood of these extreme heat conditions continuing, an Excessive Heat Watch is now in place for Tuesday. Weather conditions remain relatively stable before an increased moisture reaches the area by Wednesday due to the proximity of a tropical wave. Small craft should exercise caution today for areas of the nearshore and offshore Atlantic waters due to increasing winds. Seas up to 4 feet, occasionally up to 5 feet. Saharan dust particles also promoting hazy conditions. && .SHORT TERM...Today through Wednesday... An overnight radar and satellite imagery analysis indicated that clear to partly cloudy skies dominated the region. A few light passing showers moved inland over the US Virgin Islands, Vieques, Culebra, and eastern Puerto Rico, leaving minimal rainfall totals. Reports from official sites indicate that overnight minimum temperatures stayed above 80 degrees across coastal areas of the San Juan metropolitan area, northeastern and southwestern Puerto Rico, and the local islands. In higher elevations, temperatures dropped to around 67-69 degrees. Winds were mainly light to calm and variable. Weather conditions throughout the short-term forecast should remain relatively stable, mainly due to consistent mid-level ridging across the region and prolonged drier-than-normal periods. East-to-east- southeast trade winds will persist throughout most of the forecast period, with peak daytime wind speeds ranging from 15 to 20 mph, driven by a high-pressure system over the central Atlantic. Winds will begin to weaken and slowly turn from the east-northeast by Wednesday night. Intermittent patches of drier- and wetter-than- normal patches will cause precipitable water levels to fluctuate between 1.6 and 2.0 inches today, followed by an abrupt drop to around 1.3 inches on Tuesday afternoon and back to typical values on Wednesday. Despite these moisture fluctuations, limited shower activity is likely throughout the forecast period, primarily generated by daytime heating over the far western-to-northwestern sections of Puerto Rico. Passing shower frequency may increase by Wednesday due to the proximity of a tropical wave. However, no flooding impacts are anticipated with any of the expected rains. In terms of temperatures, dangerously hot conditions will return today. As a result, Excessive Heat Warnings are in effect from 9 AM to 6 PM AST for all lower elevations and coastal areas of Puerto Rico, posing a threat to anyone without effective cooling and/or adequate hydration. Meanwhile, Heat Advisories have been issued for Vieques, Culebra, and the US Virgin Islands, posing a risk to most individuals sensitive to heat. Remember to take extra precautions when outside. Wear lightweight and loose-fitting clothing. Try to limit strenuous activities to early morning or evening. It is essential to stay hydrated and watch for signs of heat exhaustion. Due to the likelihood of these extreme heat conditions continuing, an Excessive Heat Watch is now in place for Tuesday. .LONG TERM...Thursday through Monday... Current model guidance suggests normal to below normal Precipitable Water (PWAT) values as a tropical wave will be southwest of the area to start the period. However, an area of normal to above normal PWAT will start to approach the islands from the northeast increasing PWAT values through Friday. This is due to the remnants of a past frontal boundary being pushed towards the area by a high pressure system over the Atlantic. High pressure aloft will also strengthen over the Western Caribbean through the period. Winds through Friday are forecast to be more east to east northeasterly, which could bring some slight relief in terms of warm temperatures although model guidance continues to suggest above normal 925 mb temperatures. Winds are forecast, however, to become more southeasterly by the weekend and through the rest of the period. This will help promote warm temperatures once again. PWAT values return to normal for the weekend with another plume of moisture with above normal to normal values possibly reaching the area by next week. Most available moisture will remain below 850 mb, with only a slight increase in moisture through the mid-levels for the weekend. Saharan dust particles will linger to start the forecast period. && .AVIATION... (06Z TAFS) VFR conditions will likely prevail across all terminals during the next 24 hours. Between 10/13 and 22Z, afternoon VCSH/SHRA may briefly impact operations across TJSJ, TJBQ, and the USVI terminals. Light to calm, variable winds will turn from the E-ESE at 12-16 knots between 10/13-22Z, accompanied by higher gusts and sea breeze variations. && .MARINE... A mid to upper level ridge is promoting generally stable conditions across the local waters. Surface high pressure extending from the northeastern to central Atlantic and north of the area will continue to promote up to moderate to fresh east-southeasterly winds through midweek. A tropical wave is expected to increase the potential for showers and isolated thunderstorms mainly across the Caribbean waters and local passages on Wednesday. && .BEACH FORECAST... Moderate risk of rip currents for most of St. Croix`s coasts today and tonight. Moderate risk forecast for southwestern and southeastern PR tonight. Low risk elsewhere. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...Excessive Heat Warning from 9 AM this morning to 6 PM AST this evening for PRZ001>003-005-007-008-010-011. Excessive Heat Watch from Tuesday morning through Tuesday afternoon for PRZ001>003-005-007-008-010>013. Heat Advisory from 9 AM this morning to 6 PM AST this evening for PRZ012-013. VI...Excessive Heat Watch from Tuesday morning through Tuesday afternoon for VIZ001-002. Heat Advisory from 9 AM this morning to 6 PM AST this evening for VIZ001-002. AM...None. && $$ SHORT TERM...ICP LONG TERM....MRR