textproduct: San Juan

KEY MESSAGES

Issued at 241 PM AST Thu Nov 12 2026

- A Heat Advisory is in effect until 5 PM today. Hot and humid conditions will persist across the islands over the next few days. Sensitive individuals should remain hydrated and seek indoors during peak daytime heating hours.

- Generally fair-weather conditions will prevail across the US Virgin Islands over the next few days. - Moisture content at low-levels, diurnal heating and topographic effects will still support isolated shower and thunderstorm activity over the next few days each afternoon over southern and northern portions today into the weekend, and western to northwestern portions from Sunday onwards.

- A moderate risk for life-threatening rip currents will continue through Sunday across most local beaches, improving by Monday onwards.

Short Term(This evening through Saturday)

Issued at 241 PM AST Thu Nov 12 2026

Calm conditions have prevailed across the islands today with passing showers developing across the offshore waters. This amenable weather pattern will persist throughout the short-term period. A surface high pressure positioned over the central Atlantic Ocean is promoting breezy conditions across the forecast region. By Friday into Saturday winds will increase further due to the tightening of the pressure gradient. These breezy conditions will impede developing convection to linger, lowering the chances for flooding associated to isolated rainfall events. Mid-level (700-500 mb) ridging over the region will continue to warm the temperatures and weaken the lapse rates at these levels throughout the forecast period as well as promote subsidence and dry air aloft. This will act as a limiting factor for the development of deep convective cells. Today, a passing shortwave through incoming from the west will slightly weaken the mid-level ridging. This will allow for moistening of the lower-to-mid levels which will favor the development of passing showers along the eastern and southern portions of Puerto Rico as well as the US Virgin Islands during the afternoon and evening. For the remainder of the short-term period the available moisture will remain below-to-around seasonal ranges with precipitable water (PWAT) remaining below 2 inches and low relative humidity at mid-levels (700-500 mb). The combination of these features will lead to generally calm weather over the next days. Nonetheless, the combination of daytime heating, available moisture and local effects will lead to localized showers and thunderstorms across northwest and interior sectors of Puerto Rico during the afternoons. Whereas, advective showers during the mornings and nights as well as streamers from El Yunque and the smaller Islands during the afternoon will also affect the US Virgin Islands and eastern Puerto Rico during the mornings and nights.

The predominant risk for the period remains the excessive heat. Model guidance indicates that the 925 mb temperatures will be two standard deviations above average. In combination with the available moisture and decreased cloud cover heat associated risks can not be ruled out. Thus, a heat advisory remains in effect until 5 PM this afternoon. This will lead to a level of heat that affects most individuals sensitive to heat, especially those without effective cooling and/or adequate hydration. Individuals are invited to remain weather ready and updated with the latest forecasts as they become available.

Long Term(Sunday through Thursday)

Issued at 345 AM AST Thu Nov 12 2026

No major changes were introduced to the long-term forecast. The interaction with a surface high pressure over the Central Atlantic and a frontal boundary north of the CWA should slightly weaken local pressure gradient, maintaining a E-SE wind flow. Aloft, a mid-level ridge in the vicinity should dominate most of the weather pattern, as model guidance suggest slightly warmer than normal mid-level temperatures throughout most of the forecast period. Sunday should be the less active day of the long-term, as model guidance suggest well below normal moisture content in the low and mid levels. Shower activity (if any) during the afternoon should remain isolated and short-lived. On Monday, model guidance suggest the arrival of a patch of moisture in the early morning, increasing frequency of showers over windward areas. From the latest model solutions, it seems that PWATs may push back into normal values, however, it mainly concentrates in the 1000-850 and 300 - 200 mb layers, while the mid-levels remain dry. Additionally, the latest NASA AOT suggest low concentrations of SAL lingering in the CWA. Although these conditions will limit deep convection, daytime heating and local effects will trigger afternoon convection across interior and western/northwestern Puerto Rico. Rainfall accumulations could increase the likelihood of ponding of water over roadways and poorly drained areas, though the urban and small stream flood should remain isolated. A similar weather pattern can be expected on Tuesday and Wednesday, though the flood threat should remain low.

AVIATION

(18Z TAFS) Issued at 241 PM AST Thu Nov 12 2026

Mainly VFR conditions to prevail across the terminals. SE flow up to around 15 kts, with higher gusts and sea breeze variations, will steer VCSH/-SHRA towards the southern terminals. VCSH/-SHRA can also develop in and around, mainly TJBQ through 12/22Z. This could result in brief MVFR conditions. After 12/22Z, SE flow over the Caribbean will gradually increase and can result in winds to around 10 to 13 kts, especially across TJPS/TIST/TISX, with locally higher gusts.

MARINE

Issued at 241 PM AST Thu Nov 12 2026

A surface high pressure over the central Atlantic Ocean will strengthen east- southeast winds through Saturday, with winds of 15 to 20 knots and gusts up to 30 knots, particularly tomorrow. This will induce wind-driven seas, producing choppy to locally rough conditions, with seas between 3 to 6 feet, occasionally reaching up to 8 feet across offshore waters and local passages. The most hazardous conditions for small craft operators are expected tomorrow. Shower and isolated thunderstorm activity may produce locally higher winds and seas. These conditions should improve by Sunday into early next week.

BEACH FORECAST

Issued at 241 PM AST Thu Nov 12 2026

A moderate risk of life-threatening rip currents will persist across most local beaches until Sunday. Beginning Monday, an improvement is expected as the risk decreases over most southern beaches.

Beachgoers should remain cautious as life-threatening rip currents are possible in the surf zone across most local beaches until early next week. In addition, while on Monday onwards the risk of life-threatening rip currents decreases over most southern beaches, isolated stronger rip currents may occur along these beaches.

In addition, regardless of the low chance of thunderstorm development for the next days, isolated activity producing lightning pose another beach hazard, particularly during the afternoon hours. If thunder is heard, get out of water and seek shelter immediately.

SJU WATCHES/WARNINGS/ADVISORIES

PR...Heat Advisory until 5 PM AST this afternoon for PRZ001>013.

VI...Heat Advisory until 5 PM AST this afternoon for VIZ001-002.

AM...None.