508
FXCA62 TJSJ 010832
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
432 AM AST TUE JUL 1 2025
KEY MESSAGES
* SAHARAN DUST WILL GRADUALLY DECREASE TODAY, BUT HIGH
CONCENTRATIONS OF DUST ARE AGAIN EXPECTED THIS WEEKEND, JUST
AFTER THE PASSAGE OF A WEAK TROPICAL WAVE.
* WINDS WILL BE BREEZY, WITH CHOPPY SEAS AND A MODERATE RIP
CURRENT RISK ANTICIPATED.
* HIGH HEAT INDICES, ABOVE 102 DEGREES ARE EXPECTED EACH DAY FOR
ALL THE COASTAL AND URBAN AREAS OF PUERTO RICO AND THE VIRGIN
ISLANDS.
SHORT TERM...TODAY THROUGH THURSDAY
SINCE MIDNIGHT, THE HIGHEST RADAR ESTIMATED RAINFALL ACCUMULATIONS
OVER LAND RANGED FROM 0.10 TO 0.20 INCHES, MAINLY OVER ISABELA,
AGUADILLA, VIEQUES, ST. THOMAS, ST. JOHN AND EASTERN PR. LOWS HAVE
RANGED FROM THE UPPER 60S AT HIGHER ELEVATIONS OF PUERTO RICO TO THE
UPPER 70S AND LOW 80S AT LOWER ELEVATIONS ACROSS THE ISLANDS.
CURRENT SATELLITE-DERIVED PRECIPITABLE WATER (PWAT) VALUES INDICATE
UP TO AROUND 1.3 TO (LOCALLY) 1.5 INCHES OVER THE AREA.
A MID-LEVEL RIDGE OVER THE ISLANDS, CONTINUES TO PROMOTE DRY AIR
BETWEEN 850 AND 700 MB. AT THE SURFACE, HIGH PRESSURE OVER THE
CENTRAL ATLANTIC WILL CONTINUE TO PROMOTE BREEZY CONDITIONS. A WEAK
TROPICAL WAVE WILL MOVE WELL SOUTH OF THE ISLANDS TODAY, OVER THE
CARIBBEAN SEA. SAHARAN DUST CONCENTRATIONS WILL CONTINUE TO
DECREASE, WITH LINGERING LOW AMOUNTS PERSISTING THROUGH THE PERIOD.
THE MID-LEVEL RIDGE WILL HOLD THROUGH AT LEAST TUESDAY, MAINTAINING
A TRADE WIND INVERSION AROUND 850 MB. THIS WILL LIMIT WIDESPREAD
RAINFALL DEVELOPMENT, WITH ONLY ISOLATED AFTERNOON CONVECTION
POSSIBLE OVER W-SW PUERTO RICO (UNDER ENE STEERING FLOW) TODAY AND
OVER W-NW PUERTO RICO (UNDER ESE STEERING FLOW) TOMORROW AND
THURSDAY. A SURGE OF MOISTURE (A WEAK SURFACE DISTURBANCE) WILL
ARRIVE LATE TONIGHT INTO TOMORROW AND THEN ON THURSDAY PERIPHERAL
MOISTURE FROM A NEARBY TROPICAL WAVE WILL CAUSE PRECIPITABLE WATER
VALUES TO REACH AROUND 1.5 TO 1.80 INCHES. HOWEVER, PATCHES OF DRIER
AIR WILL ALSO FILTER IN. THE DIURNAL PATTERN OF PASSING
MORNING/OVERNIGHT SHOWERS AND AFTERNOON SHOWERS AND ISOLATED
THUNDERSTORMS OVER W-NW PR, WHERE A LIMITED FLOODING RISK WILL
REMAIN, WILL CONTINUE. TOMORROW, THE MID-LEVEL RIDGE WILL BEGIN TO
GIVE WAY TO A MID-TO-UPPER-LEVEL LOW NORTHEAST OF THE AREA THAT WILL
DEEPEN AND APPROACH THE REGION. HOWEVER, RELATIVE HUMIDITY IN THE
700-500 MB LAYER WILL REMAIN BELOW NORMAL, POSSIBLY LIMITING
WIDESPREAD CONVECTION. A LIMITED HEAT THREAT WILL REMAIN ACROSS
URBAN AND COASTAL AREAS DURING THE LATE MORNING TO AFTERNOON HOURS.
LONG TERM...FRIDAY THROUGH TUESDAY
A WEAK TROPICAL WAVE WILL APPROACH THE ISLANDS ON FRIDAY. THE BULK
OF THE WAVE WILL REMAIN OVER THE CARIBBEAN SEA, BUT ENOUGH
MOISTURE SHOULD TRIGGER SOME SHOWERS OVER THE VIRGIN ISLANDS AND
PUERTO RICO, WITH STRONGER CONVECTION DEVELOPING ACROSS WESTERN
PUERTO RICO IN THE AFTERNOON. JUST LIKE THE LAST WAVE THAT MOVED
OVER THE REGION, THIS ONE ALSO COMES WITH A LOT OF SAHARAN DUST,
SO SKIES WILL BE HAZY LATE ON FRIDAY AND ON SATURDAY. LATER ON THE
WEEKEND AND EARLY NEXT WEEK, A SERIES OF SURFACE TROUGHS WILL
ALSO MOVE INTO THE REGION, BUT THEY WILL ALSO BE EMBEDDED IN
SAHARAN DUST. THE PATTERN ALOFT WILL NOT FAVOR DEEP CONVECTION,
BUT OCCASIONAL SHOWERS WILL MOVE INTO THE ISLANDS AT TIMES, WITH
ADDITIONAL SHOWERS AND ISOLATED THUNDERSTORMS EACH AFTERNOON
ACROSS THE WEST. THE WINDS WILL BE DRIVEN BY A SURFACE HIGH
PRESSURE OVER THE EASTERN ATLANTIC, AT 10 TO 16 KTS. IT WILL BE
HOT TOO, AS IT IS EXPECTED FOR JULY, WITH HEAT INDICES ABOVE 102
DEGREES ALONG ALL COASTAL AND URBAN AREAS IN THE REGION.
AVIATION
(06Z TAFS)
MAINLY VFR CONDITIONS EXPECTED. SAHARAN DUST WILL CONTINUE TO
DECREASE TODAY. ENE STEERING FLOW UP TO AROUND 15 TO 20 KTS WITH
HIGHER GUSTS WILL STEER VCSH TOWARDS THE TERMINALS. AFTERNOON
CONVECTION FORECAST TO CONCENTRATE WEST OF TJPS'S VCTY. WINDS
DECREASING AT AROUND 01/22Z
MARINE
MARINERS CAN EXPECT CHOPPY SEAS ACROSS THE LOCAL ATLANTIC AND
CARIBBEAN WATERS DUE PERSISTENT MODERATE TO FRESH EASTERLY WINDS.
SMALL CRAFT SHOULD EXERCISE CAUTION OVER MOST LOCAL WATERS. A WEAK
TROPICAL WAVE IS FORECAST TO MOVE OVER THE LOCAL WATERS ON FRIDAY,
INCREASING SHOWER AND THUNDERSTORM CHANCES. SAHARAN DUST WILL FOLLOW
THE TROPICAL WAVE, WITH HAZY SKIES RETURNING ON SATURDAY.
BEACH
BREEZY CONDITIONS WILL MAINTAIN A MODERATE RIP CURRENT RISK FOR
MOST OF THE BEACHES OF PUERTO RICO AND THE VIRGIN ISLANDS.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM...MRR
LONG TERM....ERG
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