124
FXCA62 TJSJ 190751
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
351 AM AST TUE NOV 19 2024
SYNOPSIS
COOLER THAN NORMAL TEMPERATURES AND DRY CONDITIONS WILL PERSIST
AT LEAST UNTIL EARLY THURSDAY. THEN, SHOWERS AND THUNDERSTORMS
WILL INCREASE FOR THE END OF THE WORKWEEK AND EARLY NEXT WEEK.
MARINE CONDITIONS HAVE IMPROVE, BUT ACROSS THE BEACHES, THE RIP OF
RIP CURRENTS REMAIN MODERATE.
SHORT TERM...TODAY THROUGH THURSDAY
IT WAS A COOL NIGHT OVER THE ISLANDS WITH REPORTED OVERNIGHT LOWS
WERE IN THE LOW TO MID 60S AT HIGHER ELEVATIONS OF PUERTO RICO, IN
THE UPPER 60S TO MID 70S AT LOWER ELEVATIONS OF PUERTO RICO, AND IN
THE MID 70S TO AROUND 80 AT THE USVI. SINCE MIDNIGHT, ONLY LIGHT
SHOWERS HAVE BEEN MOVING OVER THE NORTH AND NORTHWESTERN WATERS.
CURRENT SATELLITE DERIVED PRECIPITABLE WATER (PWAT) VALUES SHOWS DRY
AIR OVER THE REGION. DURING THE OVERNIGHT HOURS, PWAT VALUES OVER
PUERTO RICO WERE AROUND 1 TO 1.2 INCHES, WELL BELOW NORMAL TO BELOW
NORMAL, INCREASING EASTWARD. BELOW NORMAL PWAT VALUES WERE ALSO
OBSERVED OVER OTHER REGIONS, VIEQUES, CULEBRA AND THE NORTHERN USVI
SAW BETWEEN 1.27 TO 1.29 INCHES, AND ST. CROIX SAW AROUND 1.35 IN.
COOL AND DRY AIR WILL CONTINUE TO MOVE OVER THE ISLANDS UNDER
NORTHERLY FLOW THROUGH WEDNESDAY. CURRENT MODEL GUIDANCE HAS PWAT
VALUES OF 0.9 TO 1.3 INCHES THROUGH WEDNESDAY, WELL BELOW TO BELOW
NORMAL VALUES FOR THIS TIME OF THE YEAR. MID TO UPPER LEVEL RIDGING
WILL MAINTAIN A TRADE WIND CAP INVERSION AROUND 850 MB, WITH ALL THE
LOW LEVEL MOISTURE TRAPPED BELOW THIS LEVEL. LOW LEVEL MOISTURE
ITSELF, AS WELL AS 925MB TEMPERATURES, ARE FORECAST TO BE BELOW
NORMAL THROUGH MOST OF THE PERIOD BUT BEGINNING TO CLIMB BACK UP ON
THURSDAY. GENERALLY LOW PROBABILITY OF PRECIPITATION (POP) WILL
REMAIN THROUGH WEDNESDAY, WITH SOME SHOWERS MOVING IN AT TIMES FROM
THE WATERS TOWARDS WINDWARD SECTIONS. 500 MB TEMPERATURES WILL BE
WARM, FURTHER DIMINISHING DEEP CONVECTIVE ACTIVITY POSSIBILITIES,
HOWEVER LOCAL EFFECTS CAN HELP PRODUCE LIMITED AFTERNOON CONVECTION
OVER THE INTERIOR. GENERALLY STABLE CONDITIONS WILL PREVAIL DURING
MOST OF THE PERIOD WITH TEMPERATURES COOLING DOWN TO BELOW
CLIMATOLOGICAL VALUES. HIGHS WILL BE IN THE THE MID 80S ACROSS MOST
COASTAL AREAS OF THE ISLANDS, EXCEPT IN SOUTHERN PR WHERE IT CAN
REACH THE LOW 90S. COOL LOWS SIMILAR TO LAST NIGHT WILL ALSO
CONTINUE. SURFACE WINDS WILL BE GENERALLY NORTHEASTERLY, BECOMING
MORE EASTERLY ON LATE WEDNESDAY AND THURSDAY, AS A SURFACE HIGH
GRADUALLY MOVES IN FROM OUR NORTHWEST. INCREASING MOISTURE WILL THEN
BE EXPERIENCED THURSDAY WITH PWAT VALUES CLIMBING BACK TO LOW END
NORMAL VALUES. THE CHANGE IN WIND WILL BRING IN A MOISTURE PLUME
FROM THE EAST AND SOUTH, INCREASING THE POTENTIAL FOR SHOWERS AND
SETTING THE STAGE FOR A WETTER LONG TERM PERIOD.
LONG TERM...FRIDAY THROUGH TUESDAY
A HIGH PRESSURE SYSTEM OVER THE EASTERN ATLANTIC AND A POLAR
TROUGH EXITING THE EASTERN COAST OF THE UNITED STATES WILL SWITCH
THE WINDS FROM THE SOUTH FOR THE END OF THE WEEK. THE PRESSURE
GRADIENT WILL WEAKEN TOO, MEANING THAT THE WIND FLOW WILL BE
LIGHT. UNDER THIS FLOW, MOISTURE WILL BE PULLED FROM THE CARIBBEAN
SEA INTO THE ISLANDS, INCREASING THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS. THIS WILL ELEVATE THE RISK OF FLOODING FOR THE
ISLANDS THROUGH THE WEEKEND. THEN, EARLY NEXT WEEK, THE RIDGE WILL
REBUILD, BUT PRECIPITABLE WATER VALUES WILL REMAIN ABOVE NORMAL.
THE TRADE WINDS WILL RECOVER TOO, COMING FROM THE EAST AROUND 15
KNOTS. UNDER THIS FLOW, PATCHES OF LOW-LEVEL CLOUDS WILL STILL
REACH THE ISLANDS, WITH PASSING SHOWERS ACTIVITY FOR EASTERN
PUERTO RICO AND THE VIRGIN ISLANDS.
AVIATION
(06Z TAFS)
MAINLY VFR CONDITIONS ARE FORECAST TO PREVAIL ACROSS THE TERMINALS.
VCSH WILL BE BROUGHT IN BY NORTHEASTERLY FLOW, PARTICULARLY TOWARDS
TJBQ TO START THE MORNING. AFTER 18Z, CONVECTIVE VCSH CAN ALSO
POSSIBLY AFFECTING TJPS. BELOW FL050, NE WINDS WILL BE UP TO AROUND
10 KTS WITH HIGHER GUSTS AND SEA BREEZE VARIATIONS.
MARINE
GENTLE TO MODERATE NORTHERLY WINDS WILL PREVAIL THROUGH LATE WEDNESDAY
WHEN EASTERLY WINDS RETURN. ANOTHER PULSE OF THE NORTHERLY SWELL WILL
ARRIVE TOMORROW, BUT CONDITIONS ARE LIKELY TO REMAIN BELOW SMALL
CRAFT ADVISORY CRITERIA. ANOTHER SMALL LONG-PERIOD NORTHERLY SWELL IS
EXPECTED FOR THE WEEKEND.
BEACH FORECAST
COASTAL CONDITIONS HAVE IMPROVE ACROSS PUERTO RICO AND THE VIRGIN
ISLANDS, BUT THE RISK OF RIP CURRENTS CONTINUE TO BE MODERATE.
THERE IS ANOTHER PULSE OF NORTHERLY SWELL THAT COULD ARRIVE
TOMORROW, INCREASING THE RISK TO HIGH AGAIN.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM...MRR
LONG TERM....ERG
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