Area Forecast Discussion
Issued by NWS San Juan, PR
Issued by NWS San Juan, PR
817 FXCA62 TJSJ 021830 AFDSJU Area Forecast Discussion National Weather Service San Juan PR 230 PM AST Fri Oct 2 2026 ...New SHORT TERM, AVIATION, MARINE, BEACH FORECAST... .KEY MESSAGES... Issued at 230 PM AST Fri Oct 2 2026 - Showers and thunderstorms will continue to develop this afternoon across interior, western, and northwestern Puerto Rico. Streamer activity will also bring scattered showers and isolated thunderstorms to the San Juan metro area and eastern sections. - Locally heavy rainfall may lead to urban and small-stream flooding, as well as rapid river rises, especially in areas with already saturated soils. - Strong showers and thunderstorms remain possible through the weekend. Remember: seek shelter immediately whenever you hear thunder or see frequent lightning. - High temperatures and humid conditions will persist over the next few days, with elevated heat risk from Sunday into early next week across the islands. - A moderate risk of rip currents continues along the northern and eastern beaches of Puerto Rico, as well as portions of the U.S. Virgin Islands. && .Short Term(This evening through Sunday)... Issued at 230 PM AST Fri Oct 2 2026 The short term period will be characterized by a seasonal weather pattern with advective showers and streamers developing from the morning into the afternoon across the US Virgin Islands and eastern Puerto Rico, and in the afternoons across the interior and western Puerto Rico. Nonetheless, a couple of synoptic features will be enhancing the observed shower activity. The upper-level low pressure system currently positioned to the northeast of the US Virgin Islands that had been promoting upper-level convergence in the vicinity of the islands will depart the region by Saturday afternoon. From Saturday into Sunday a low pressure system currently located over the west Atlantic Ocean will move southward and position itself over La Hispanola. While the enhanced weather from this system will likely remain to the west of Puerto Rico, it will continue to promote cooling of the mid-tropospheric temperatures further steepening the lapse rates at those levels. This will increase the potential for the development of deep convective cells. While a surface-induced perturbation is currently over La Hispanola, the associated precipitable water (PWAT) will serve as one of the main drivers for shower and thunderstorm activity today. Furthermore, the atmospheric column will moisten towards the afternoon, especially over the western sector of Puerto Rico. The mid-tropospheric temperatures will also undergo cooling into the afternoon hours further steepening the lapse rates. Breezy ESE conditions will prevail, aiding in the development of streamers from El Yunque and the smaller islands. These features combined with local effects, and the ESE wind flow will also lead to showers and thunderstorms across the interior, western and northwestern Puerto Rico during the afternoon. Given the rainfall received since yesterday and the current streamflows, where frequent downpours occur there is a chance for flooding along urban areas, roads, small streams, and washes along with a small chance for flash floods. For Saturday, there will be slightly above seasonal PWAT values across western Puerto Rico. There is some disagreement between the models with some showing a deep moisture profile while others show drier low-levels (around 700 mb). Nonetheless, there is higher agreement in the column moistening during the afternoon hours. The upper-level level low pressure system will begin approaching La Hispanola continuing to promote cooling at the mid-levels and steep lapse rates. The steering flow will remain locally breezy and form the ESE. This will continue to promote streamers from el Yunque and the smaller islands during the morning and afternoons with impacts to the US Virgin Islands and eastern Puerto Rico. Combined with local effects, these conditions will also lead to the development of showers and thunderstorms across the interior, western and northwestern sectors of Puerto Rico during the afternoon. Similar flooding risks to those seen for today will persist on Saturday. Model guidance suggest that drier low-levels (around 700 mb) will prevail on Sunday. Nonetheless, there will be similar favorable conditions to those seen on Saturday making the development of convection possible, especially over western Puerto Rico. The upper- level low will finally settle over La Hispanola further promoting cooler mid-levels and steep lapse rates. Thus, associated to advective showers may be expected over eastern Puerto Rico during the night and early morning, while rainfall from streamers can be expected over the region during the afternoon. Similarly, local effects coupled with favorable conditions will lead to showers and thunderstorms across the interior and western Puerto Rico during the afternoon. Similar flooding risks to those seen for today will persist on Sunday. With seasonal PWAT and low-level temperature values from normal-to- above normal levels for the season the heat risk is expected to be limited for today and Saturday, with an elevated risk expected by Sunday. These levels of heat may affect individuals sensitive to heat, without effective cooling and adequate hydration. Citizens and visitors are invited to remain alert of the changing weather conditions. && .Long Term(Monday through Friday)... Issued at 440 AM AST Fri Oct 2 2026 Generally, the long-term period will be characterized by a seasonal weather pattern. A building high-pressure system over the central Atlantic will be the main weather feature for the long term period, enhancing an easterly wind flow from Monday through Tuesday. Under this pattern, the latest model guidance suggests seasonal precipitable water (PWAT). Despite the moisture lingering at the low levels, a mid-level ridge established over the region will promote stable conditions with warmer temperatures at 500 MB rounding between -6 and -4 degrees. That stability combined with some slightly drier mid-levels will inhibit some of the shower development during these days. Under these conditions, low-level lingering moisture, daytime heating, and local effects will be the primary drivers for shower and thunderstorm activity through Tuesday. A more southeasterly wind flow is forecast from Tuesday evening into Wednesday, as the broad building high pressure over the Central Atlantic deep into the area. An upcoming tropical wave and the associated moisture field will move south of the CWA, enhancing convection from late evening Tuesday into Wednesday. Although the bulk of the moisture associated with this wave is expected to remain over Caribbean waters, local effects, diurnal heating, and the available moisture will enhance strong convection along the islands. Due to the shift of winds to an east-southeasterly flow, the activity will shift more toward the interior and northwestern portions. Given the expected conditions, there is a chance to observe a limited to elevated flooding threat with the heaviest shower activity, especially on Tuesday and Wednesday. As a result, urban and small-stream flooding is possible over roadways and poorly drained areas, and flash flooding cannot be ruled out. In addition, an elevated heat risk from Monday is expected due to more stability anticipated and seasonal moisture levels. For those sensitive to the heat, staying hydrated and avoiding outdoor activities during peak heating hours is highly recommended. && .AVIATION... (18Z TAFS) Issued at 230 PM AST Fri Oct 2 2026 Mainly VFR conditions are expected to prevail across all terminals during the fcst period. SHRA/TSRA will continue to develop across the interior and western PR, resulting in VCTS at TJBQ/TJPS thru 02/22-23Z. Brief MVFR/IFR conds are possible in heavier SHRA/TSRA, along with mtn obsc across the interior. Additional SHRA developing across the northeastern quadrant of PR will result in VCSH/SHRA at TJSJ/TIST/TISX thru 02/22Z. E-ESE winds btw 10-15 kt, with higher gusts and sea breeze variations thru 02/22Z. Winds are expected to diminish aft 02/23Z, to 10 kt or less with land breeze variations thru 03/13-14Z. && .MARINE... Issued at 230 PM AST Fri Oct 2 2026 Surface high pressure north of the region will maintain moderate to locally fresh easterly trade winds through at least early tonight, producing up to choppy conditions. The pressure gradient will then relax over the weekend, promoting more moderate winds. This will in turn result in a more moderate chop through early next week. Lingering moisture behind yesterday`s disturbance and a trough that will move to the west and northwest of the local area will support showers and thunderstorms into the weekend. Thunderstorms may produce locally hazardous conditions for small craft, including gusty winds, higher seas, lightning, and reduced visibility. && .BEACH FORECAST... Issued at 230 PM AST Fri Oct 2 2026 A moderate rip current risk (rip currents are possible in the surf zone) will continue across most exposed north- and east-facing beaches of Puerto Rico and the U.S. Virgin Islands through the weekend and at least through midweek. Even in areas where the risk of rip currents is low, life-threatening rip currents can often occur in the vicinity of groins, jetties, reefs, and piers. Always swim near a lifeguard and follow beach patrol guidance and posted warning flags. Afternoon thunderstorms are more likely to develop across western Puerto Rico this weekend. If you hear thunder, leave the water immediately and seek shelter inside a substantial building or enclosed vehicle. && .SJU WATCHES/WARNINGS/ADVISORIES... PR...None. VI...None. AM...None. && $$ SHORT TERM...RVM LONG TERM...JCP/LIS KEY MESSAGES/AVIATION...GRS MARINE/BEACH FORECAST...MRR