779
FXCA62 TJSJ 260727
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
327 AM AST SUN JUL 26 2026
...NEW SHORT TERM, LONG TERM, AVIATION, MARINE, BEACH FORECAST, FIRE WEATHER...
KEY MESSAGES
UPDATED AT 327 AM AST SUN JUL 26 2026
* DANGEROUS HEAT WILL CONTINUE THROUGH TUESDAY FOR THE USVI AND
PR. HEAT ADVISORIES REMAIN IN EFFECT TODAY, AND ADDITIONAL HEAT
ADVISORIES OR EVEN EXTREME HEAT WARNINGS MAY BE NEEDED MONDAY
AND TUESDAY, ESPECIALLY WHERE RAINFALL IS LIMITED.
* A TROPICAL WAVE WILL INCREASE SHOWERS AND THUNDERSTORMS FROM
LATE SUNDAY THROUGH TUESDAY. THE GREATEST COVERAGE IS EXPECTED
MONDAY AND TUESDAY, BRINGING AN ELEVATED RISK OF URBAN AND
SMALL-STREAM FLOODING, WITH ISOLATED FLASH FLOODING POSSIBLE IN
AREAS OF PERSISTENT HEAVY RAINFALL.
* TODAY'S FLOODING THREAT WILL REMAIN LOCALIZED. SCATTERED
AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS MAY PRODUCE BRIEF
HEAVY RAIN, MAINLY ACROSS THE SAN JUAN METRO AREA, EAST PR, AND
INTERIOR TO NORTHWESTERN PUERTO RICO, LEADING TO PONDING OF
WATER AND ISOLATED URBAN FLOODING.
* BEACHGOERS SHOULD EXERCISE CAUTION DUE TO A MODERATE RISK OF
LIFE-THREATENING RIP CURRENTS ACROSS THE NORTH AND SOUTH COAST
OF PR AND THE ST CROIX.
SHORT TERM(TODAY THROUGH TUESDAY)
ISSUED AT 327 AM AST SUN JUL 26 2026
THE MODERATE CONCENTRATIONS OF SUSPENDED SAHARAN DUST LED TO
WARMER-THAN-NORMAL NIGHTS, WITH LOWS IN THE LOW 80S AND UPPER 70S
IN COASTAL AND URBAN AREAS OF THE USVI AND PR. A FEW SHOWERS
DEVELOPED AROUND MIDNIGHT AND EARLY IN THE MORNING NEAR THE
NORTHERN AND EASTERN COASTS OF PR, AND SOME MOVED INLAND ACROSS
THE USVI. HOWEVER, THIS ACTIVITY WAS BRIEFED. SKIES WERE MOSTLY
CLEAR, EXCEPT FOR THE CLOUDS ASSOCIATED WITH THE PASSING SHOWERS
AFFECTING THE WINDWARD LOCATIONS. WINDS WERE MAINLY FROM THE EAST
TO EAST-SOUTHEAST ACROSS MOST LOCAL STATIONS, AT 5 TO 15 MPH, WITH
LAND-BREEZE FLUCTUATIONS.
SUBSIDENCE AHEAD OF AN APPROACHING TROPICAL WAVE WILL PROMOTE
RELATIVELY QUIET WEATHER THROUGH MUCH OF SUNDAY MORNING, LIMITING
CONVECTION TO A FEW PASSING SHOWERS ACROSS THE WINDWARD COASTS.
ADDITIONALLY, WARMER-THAN-NORMAL OVERNIGHT TEMPERATURES AND THE
AVAILABLE MOISTURE WILL CONTRIBUTE TO DANGEROUS HEAT BETWEEN MID-
MORNING AND THE AFTERNOON. CONSEQUENTLY, A HEAT ADVISORY REMAINS
IN EFFECT FOR PORTIONS OF THE FORECAST AREA.
BY SUNDAY AFTERNOON, THE LEADING EDGE OF DEEPER TROPICAL MOISTURE
INTERACTING WITH A LINGERING MID- TO UPPER-LEVEL TROUGH WILL
SUPPORT SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. THE GREATEST
COVERAGE IS EXPECTED ACROSS THE U.S. VIRGIN ISLANDS SURROUNDING
WATERS, EXTENDING DOWNWIND OF VIEQUES AND THE LUQUILLO MOUNTAINS
INTO THE SAN JUAN METROPOLITAN AREA, AS WELL AS ACROSS THE
INTERIOR AND NORTHWESTERN PORTIONS OF PUERTO RICO. ALTHOUGH
LOCALLY HEAVY RAINFALL IS POSSIBLE, RELATIVELY DRY MID-LEVEL AIR
SHOULD LIMIT CONVECTIVE COVERAGE AND DURATION, RESULTING IN ONLY A
LIMITED FLOODING THREAT. LOCALIZED PONDING OF WATER ON ROADS AND
IN POOR-DRAINAGE AREAS WILL BE THE PRIMARY CONCERN, WITHOUT RULING
OUT ISOLATED URBAN FLOODING.
CONDITIONS BECOME INCREASINGLY FAVORABLE FOR MORE WIDESPREAD
CONVECTION BEGINNING LATE SUNDAY NIGHT AS DEEP TROPICAL MOISTURE
OVERSPREADS THE REGION. MOISTURE AND INSTABILITY WILL CONTINUE TO
INCREASE THROUGH MONDAY AND TUESDAY AS THE TROPICAL WAVE MOVES
WEST-NORTHWEST ACROSS THE NORTHEASTERN CARIBBEAN. THIS PATTERN
WILL FAVOR PERIODS OF SCATTERED TO NUMEROUS SHOWERS AND ISOLATED
TO SCATTERED THUNDERSTORMS, PARTICULARLY DURING THE OVERNIGHT AND
MORNING HOURS ON MONDAY AND AGAIN EACH AFTERNOON THROUGH TUESDAY.
THEREFORE, AN ELEVATED RISK OF FLOODING IS EXPECTED ON BOTH DAYS,
WITH URBAN AND SMALL-STREAM FLOODING BECOMING MORE LIKELY, AND A
LIMITED POTENTIAL FOR ISOLATED FLASH FLOODING WHERE HEAVIER, MORE
PERSISTENT CONVECTION DEVELOPS.
IN ADDITION TO THE RAINFALL THREAT, FORECAST 925-MB TEMPERATURES
REMAIN ANOMALOUSLY WARM. AREAS WITH LIMITED RAINFALL WILL LIKELY
SEE ABOVE-NORMAL DAYTIME HIGHS AND UNUSUALLY WARM OVERNIGHT LOWS.
COMBINED WITH THE INCREASING TROPICAL MOISTURE, THESE CONDITIONS
WILL PROMOTE ELEVATED TO POTENTIALLY SIGNIFICANT HEAT IMPACTS
ACROSS PORTIONS OF THE ISLANDS. ADDITIONAL HEAT ADVISORIES AND
POSSIBLY EXTREME HEAT WARNINGS MAY BE REQUIRED ON MONDAY AND
TUESDAY, DEPENDING ON OBSERVED TEMPERATURES AND HEAT INDEX VALUES.
LONG TERM(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 327 AM AST SUN JUL 26 2026
RECENT MODEL GUIDANCE CONTINUES TO SUGGEST ABUNDANT MOISTURE ACROSS
PUERTO RICO AND THE U.S. VIRGIN ISLANDS AS A TROPICAL WAVE MOVES
THROUGH THE REGION EARLY IN THE PERIOD. THE LATEST PRECIPITABLE
WATER (PWAT) VALUES ARE NEAR 2.0 INCHES, REFLECTING NORMAL TO ABOVE-
NORMAL MOISTURE FOR THIS TIME OF YEAR. UNDER THIS SCENARIO,
SCATTERED TRADE WIND SHOWERS REMAIN POSSIBLE DURING THE MORNING,
FOLLOWED BY AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS ACROSS
CENTRAL AND NORTHWESTERN PUERTO RICO DRIVEN BY DAYTIME HEATING AND
LOCAL EFFECTS.
HOWEVER, THESE CONDITIONS WILL BE SHORT-LIVED AS A DRIER AIR MASS
QUICKLY MOVES INTO THE AREA BY WEDNESDAY NIGHT. AT THE SURFACE, A
STRENGTHENING HIGH-PRESSURE SYSTEM WILL TIGHTEN THE PRESSURE
GRADIENT, PROMOTING BREEZY CONDITIONS THROUGH THE REST OF THE
PERIOD. STABILITY ALOFT WILL BE FURTHER SUPPORTED BY A BUILDING MID-
TO-UPPER LEVEL RIDGE, LIMITING OVERALL SHOWER ACTIVITY ACROSS THE
ISLANDS THROUGH THE SECOND HALF OF THE WEEK AS PWAT VALUES DROP
BELOW NORMAL TO 1.25-1.30 INCHES. NONETHELESS, QUICK PATCHES OF
MOISTURE EMBEDDED IN THE TRADE WINDS WILL BRING OCCASIONAL FAST-
MOVING SHOWERS WITH MINIMAL TO NO IMPACT. MOISTURE LEVELS SHOULD SEE
A SLIGHT INCREASE BY LATE SATURDAY INTO SUNDAY AS ANOTHER TROPICAL
WAVE APPROACHES THE REGION. NEAR TO ABOVE-NORMAL TEMPERATURES WILL
PERSIST DAILY, WITH DAYTIME HIGHS REACHING THE UPPER 80S TO LOW 90S
ACROSS COASTAL AND URBAN AREAS.
AVIATION
(06Z TAFS)
ISSUED AT 327 AM AST SUN JUL 26 2026
MOSTLY VFR CONDITIONS WILL PREVAIL TODAY. EXPECT E-ESE WINDS AT
10–20 KT WITH GUSTS UP TO 30 KTS, BTWN 26/13-23Z. SHRA/TSRA ARE
POSSIBLE NEAR IST/ISX/JSJ BTWN 26/14-18Z, SPREADING TO THE
INTERIOR AND NW-PR BTWN 26/16-23Z, BRINGING BRIEF MVFR/IFR
CONDITIONS AND MOUNTAIN OBSCURATIONS. ACTIVITY WILL SLOWLY
INCREASE AFT 26/23Z WITH THE ARRIVAL OF A TROPICAL WAVE, CREATING
AN UNSTABLE AND WET PATTERN.
MARINE
ISSUED AT 327 AM AST SUN JUL 26 2026
MODERATE TO LOCALLY FRESH EASTERLY WINDS WILL CONTINUE TO PRODUCE
CHOPPY SEAS AND HAZARDOUS CONDITIONS FOR SMALL CRAFT ACROSS PORTIONS
OF THE ATLANTIC WATERS, OFFSHORE CARIBBEAN WATERS, AND LOCAL
PASSAGES THROUGH SUNDAY. AN APPROACHING TROPICAL WAVE WILL INCREASE
SHOWERS AND ISOLATED THUNDERSTORMS LATE SUNDAY INTO MONDAY, CREATING
LOCALLY HIGHER WINDS AND SEAS, FREQUENT LIGHTNING, AND REDUCED
VISIBILITY IN AND NEAR CONVECTION. MARINE CONDITIONS ARE EXPECTED TO
IMPROVE BRIEFLY EARLY NEXT WEEK AS WINDS AND SEAS SUBSIDE BEFORE
DETERIORATING AGAIN BY MIDWEEK AS EASTERLY WINDS STRENGTHEN.
LINGERING LOW CONCENTRATIONS OF SAHARAN DUST MAY RESULT IN
OCCASIONAL HAZY SKIES BUT ARE NOT EXPECTED TO BECOME A SIGNIFICANT
MARINE HAZARD.
BEACH FORECAST
ISSUED AT 327 AM AST SUN JUL 26 2026
A MODERATE RISK OF RIP CURRENTS CONTINUES ACROSS NORTHERN AND
EASTERN PUERTO RICO, VIEQUES, CULEBRA, AND ST. CROIX. AS WINDS
DECREASE EARLY NEXT WEEK, THE RIP CURRENT RISK SHOULD GRADUALLY
LESSEN, RESULTING IN IMPROVING BEACH CONDITIONS THROUGH MIDWEEK.
HOWEVER, LIFE-THREATENING RIP CURRENTS WILL REMAIN POSSIBLE NEAR
REEFS, JETTIES, GROINS, AND PIERS. THE RIP CURRENT RISK IS EXPECTED
TO INCREASE AGAIN LATER IN THE WORKWEEK AS EASTERLY WINDS
STRENGTHEN. BEACHGOERS SHOULD ALSO REMAIN ALERT FOR THUNDERSTORMS
AND HEAT.
FIRE WEATHER
ISSUED AT 327 AM AST SUN JUL 26 2026
DESPITE RELATIVE HUMIDITY VALUES REMAINING ABOVE CRITICAL
THRESHOLDS, CRITICALLY DRY FUELS CONTINUE TO PERSIST ACROSS
SOUTHERN PUERTO RICO AND ST. CROIX. THEREFORE, MARGINAL FIRE
WEATHER CONDITIONS WILL CONTINUE, PARTICULARLY WHERE LOCALLY
BREEZY WINDS DEVELOP DURING THE AFTERNOON.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HEAT ADVISORY FROM 10 AM THIS MORNING TO 5 PM AST THIS AFTERNOON
FOR PRZ001>005-007-008-010>013.
VI...HEAT ADVISORY FROM 10 AM THIS MORNING TO 5 PM AST THIS AFTERNOON
FOR VIZ001-002.
AM...NONE.
KEY MESSAGE/SHORT TERM/AVIATION/FIRE...CAM
LONG TERM....GRS
MARINE/BEACH FORECAST...ICP
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