416  
FXCA62 TJSJ 230333  
AFDSJU  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN JUAN PR  
1133 PM AST THU FEB 22 2018  
   
UPDATE
 
BUOYS HAVE CONSISTENTLY REPORTED A SECOND SPIKE OF  
ENERGY AT WITH PERIODS OF 16 TO 18 SECONDS ALMOST AS STRONG AS  
THE 10 TO 12 SECOND SEAS THAT ARE COMING IN. THIS WILL BOOST THE  
BREAKING WAVE HEIGHTS TO AS HIGH AS 19 FEET IN THE MOST EXPOSED  
AND FAVORABLE AREAS. NO REPORTS HAVE BEEN RECEIVED OF COASTAL  
FLOODING AT THIS TIME AND BUOYS IN SAN JUAN AND ARECIBO (THAT  
REPORT WATER LEVELS) ARE SHOWING LEVELS SLIGHTLY LOWER THAN  
FORECAST WITH ONLY MODERATE HIGH TIDES THAT ARE EXPECTED BETWEEN 2  
AND 3 AM AST, THEREFORE HAVE UPDATED SURF ZONE FORECAST AND  
COASTAL HAZARDS AND MARINE ZONES WITH NEW MODEL RUNS BUT WILL NOT  
ISSUE COASTAL FLOOD ADVISORY. NO CHANGE TO WEATHER GRIDS OR  
REASONING AT THIS TIME.  
 

 
 
   
PREV DISCUSSION
 
/ISSUED 924 PM AST THU FEB 22 2018/  
 
UPDATE...MOSTLY FAIR WEATHER PREVAILED ACROSS THE LOCAL ISLANDS  
THROUGH THE AFTERNOON HOURS WITH ONLY A FEW SHOWERS BEING DETECTED  
ACROSS NORTHERN AND WESTERN PR AND ACROSS THE USVI, LEAVING  
MINIMAL ACCUMULATIONS. HOWEVER, A PATCH OF MOISTURE MOVED IN AND  
THE SHOWERS INCREASED ACROSS THE AREA IN THE EVENING HOURS. THIS  
SHOWER ACTIVITY IS EXPECTED TO CONTINUE THROUGH TONIGHT. THE AREAS  
AFFECTED WILL BE MOSTLY THE NORTHERN HALF OF PR AND THE EASTERN  
SECTIONS AS WELL AS THE NORTHERN USVI. EVEN THOUGH THE SHOWERS MAY  
BE LOCALLY NUMEROUS, THE ACCUMULATIONS ARE EXPECTED TO BE  
GENERALLY LESS THAN A QUARTER OF AN INCH OF RAIN WITH ISOLATED  
AREAS WITH HIGHER AMOUNTS.  
 
THE SCATTERED TO NUMEROUS SHOWER ACTIVITY IS EXPECTED TO CONTINUE  
INTO FRIDAY ACROSS THE SAME AREAS AS TONIGHT, BUT IN THE AFTERNOON  
HOURS THE SHOWERS MAY PROGRESS INTO THE CENTRAL AND WESTERN SECTIONS  
OF PR. EXPECT A RAINY PATTERN WITH RAINFALL ACCUMULATIONS THAT  
WOULD CAUSE PONDING OF WATER ON ROADWAYS AND POOR DRAINAGE AREAS.  
 
AVIATION...PREVAILING VFR CONDS WITH BRIEF SHRA ACROSS THE LOCAL  
TERMINALS TONIGHT, WITH THE EXCEPTION OF TJMZ AND TJPS WHERE FAIR  
WEATHER IS EXPECTED THROUGH THE NIGHT. WINDS WILL CONTINUE FROM  
THE ENE-NE AT 15 KT OR SO WITH OCCASIONAL GUSTS TONIGHT,  
INCREASING AFTER 23/14Z UP TO 20KT SUSTAINED WITH GUSTS NEAR 30K.  
 
MARINE...NO CHANGES FROM THE PREVIOUS DISCUSSION. THE LOCAL  
MARINE CONDITIONS WILL CONTINUE TO BE HAZARDOUS INTO THE UPCOMING  
WEEKEND. SEAS ARE STILL EXPECTED TO REACH WAVE HEIGHTS OF UP TO 12  
FEET AND THE COASTAL BREAKING WAVES ACROSS THE NORTHERN SHORES  
COULD BE UP TO 13 FEET OR SO. HIGH RISK OF RIP CURRENTS ACROSS  
MANY OF THE LOCAL BEACHES FOR THE NEXT SEVERAL DAYS. THERE IS A  
HIGH SURF ADVISORY IN EFFECT AND ALSO A SMALL CRAFT ADVISORY.  
 
PREV DISCUSSION... /ISSUED 411 PM AST THU FEB 22 2018/  
 
SYNOPSIS...STRONG SURFACE HIGH PRESSURE OVER THE WESTERN  
ATLANTIC JUST NORTH OF THE REGION WILL CONTINUE TO RESULT IN  
BREEZY CONDITIONS ACROSS THE REGION THROUGH AT LEAST FRIDAY.  
TRADE WIND SHOWER PATTERN WILL CONTINUE TO BRING AREAS OF SHOWERS  
ACROSS THE USVI AND THE NORTHERN SECTIONS OF PR EACH DAY. UPPER  
LEVEL TROUGH AND ASSOCIATED JET MAXIMA WILL MOVE OVER THE REGION  
FRIDAY THROUGH SATURDAY. THIS WILL INCREASE THE CHANCES OF SHOWERS  
ACROSS THE REGION.  
 
SHORT TERM...TONIGHT THROUGH SATURDAY...  
TERMINAL DOPPLER RADAR INDICATED ISOLATED TO SCATTERED PASSING  
SHOWERS MOVING SOUTHWESTWARD FROM THE ATLANTIC WATERS, AFFECTING  
MOSTLY THE U.S. VIRGIN ISLANDS, VIEQUES, CULEBRA AS WELL THE  
NORTHERN AND EASTERN SECTIONS OF PUERTO RICO. THIS ACTIVITY IS  
EXPECTED TO CONTINUE TONIGHT. HOWEVER, RAINFALL AMOUNTS HAVE BEEN  
MINIMAL IF ANY. THE REMNANTS OF A WEAK FRONTAL BOUNDARY WILL  
CONTINUE TO DISSIPATE ACROSS THE CARIBBEAN WATERS JUST SOUTH OF  
THE REGION. STRONG SURFACE HIGH PRESSURE WILL HOLD ACROSS THE  
WESTERN ATLANTIC THROUGH AT LEAST TUESDAY, NEXT WEEK. AN UPPER  
LEVEL TROUGH EXTENDS SOUTHWEST FROM AN UPPER LEVEL LOW ACROSS THE  
CENTRAL ATLANTIC, SEVERAL HUNDRED MILES TO OUR NORTH AND IS  
ACCOMPANIED ON ITS SOUTHERN PERIPHERY BY A STRENGTHENING JET. THIS  
JET WILL CROSS THE AREA FROM THE SOUTHEAST FRIDAY INTO SATURDAY  
MORNING BRINGING STRONG UPPER WINDS OVER THE REGION. THE STRONG  
SURFACE HIGH PRESSURE ACROSS THE WESTERN ATLANTIC WILL CONTINUE TO  
BRING PATCHES OF LOW LEVEL MOISTURE ACROSS THE LOCAL ISLANDS FOR  
THE NEST SEVERAL DAYS. THIS MOISTURE WILL COMBINE WITH THE STRONG  
UPPER LEVEL WINDS AND UPPER TROUGH TO ALLOW SHOWER ACTIVITY TO  
INCREASE FRIDAY AND SATURDAY. THERE IS ALSO A POSSIBILITY OF  
THUNDERSTORMS DEVELOPING OVER PUERTO RICO FRIDAY AND SATURDAY.  
ALTHOUGH THE SHOWERS IN THE THUNDERSTORMS COULD BE HEAVY FLOODING  
IS NOT EXPECTED DUE TO THE RAPID MOVEMENT THE SHOWERS. IN SUMMARY,  
SHOWERS WILL CONTINUE ACROSS THE WINDWARD SLOPES OF PUERTO RICO  
AND AT LEAST THE NORTHERN U.S. VIRGIN ISLANDS TONIGHT AND INCREASE  
THROUGH FRIDAY NIGHT AIDED BY THE TROUGH AND JET JUST MENTIONED.  
SHOWERS SHOULD ALSO BE FORCED ACROSS MOST OF PUERTO RICO NORTH OF  
THE CORDILLERA CENTRAL IN THE MODERATE TO FRESH TRADE WINDS THAT  
WILL PERSIST THROUGH AT LEAST SATURDAY.  
 
LONG TERM...SUNDAY THROUGH THURSDAY...FROM PREVIOUS DISCUSSION...  
HIGH PRESSURE NORTH OF THE REGION WILL HOLD THROUGH TUESDAY  
MAINTAINING A MODERATE TO LOCALLY FRESH EAST TO NORTHEAST TRADE  
WIND FLOW ACROSS THE AREA. TRADE WIND SHOWERS WILL CONTINUE TO  
MOVE AND INCREASE IN FREQUENCY DURING THE FIRST PART OF NEXT WEEK.  
MEANWHILE, UPPER LEVEL TROUGH OVER THE CENTRAL CARIBBEAN WILL  
CONTINUE TO AID IN THE DEVELOPMENT OF SHOWERS WITH POSSIBLE  
THUNDERSTORM DEVELOPMENT THROUGH TUESDAY. URBAN AND SMALL STREAM  
FLOODING IN ISOLATED AREAS WILL BE POSSIBLE WITH THE HEAVIEST  
SHOWERS DURING THE LONG TERM PERIOD.  
 
AVIATION...VFR CONDS ARE EXPECTED TO PREVAIL THROUGH THE FORECAST  
CYCLE WITH VCSH AT THE LEEWARD AND USVI TERMINALS AS WELL AS  
JSJ/JBQ. ENE WINDS 15-20 KNOTS WITH HIGHER GUSTS, BECOMING AT AROUND  
10-12 KNOTS OVERNIGHT.  
 
MARINE...ROUGH SEAS CONTINUE ACROSS THE REGIONAL WATERS EXCEPT  
IN THE COASTAL SOUTHWESTERN WATERS OF PR. SEAS WILL RANGE BETWEEN  
8-12 FEET AND EAST TO NORTHEAST TRADES AT 15-25 KNOTS WILL  
CONTINUE ACROSS THE REGION. WINDS WILL GRADUALLY DECREASE THROUGH  
THE WEEKEND AS WELL AS THE SEAS. HOWEVER, SCA ARE IN EFFECT  
THROUGH THE WEEKEND DUE TO SEAS STILL REACHING 7-8 FEET. HIGH  
SURF ADVISORY CONTINUES FOR THE NORTHERN BEACHES OF PR AND THE  
USVI THROUGH FRIDAY AFTERNOON. HIGH RISK OF RIP CURRENTS WILL  
CONTINUE THROUGH THE WEEKEND ACROSS THE NORTHERN BEACHES OF THE  
ISLANDS.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SJU 74 82 73 81 / 70 70 60 60  
STT 72 82 72 83 / 60 50 40 30  
 

 
   
SJU WATCHES/WARNINGS/ADVISORIES
 
 
PR...HIGH RIP CURRENT RISK THROUGH SATURDAY AFTERNOON FOR CULEBRA-  
MAYAGUEZ AND VICINITY-NORTH CENTRAL-NORTHEAST-NORTHWEST-SAN  
JUAN AND VICINITY-VIEQUES-WESTERN INTERIOR.  
 
HIGH SURF ADVISORY UNTIL 6 PM AST FRIDAY FOR CULEBRA-MAYAGUEZ  
AND VICINITY-NORTH CENTRAL-NORTHEAST-NORTHWEST-SAN JUAN AND  
VICINITY-SOUTHEAST-VIEQUES-WESTERN INTERIOR.  
 
HIGH RIP CURRENT RISK THROUGH LATE FRIDAY NIGHT FOR CENTRAL  
INTERIOR-SOUTHEAST.  
 
SMALL CRAFT ADVISORY UNTIL 8 PM AST FRIDAY FOR SOUTHEAST.  
 
VI...HIGH RIP CURRENT RISK THROUGH SATURDAY AFTERNOON FOR ST CROIX-  
ST.THOMAS...ST. JOHN...AND ADJACENT ISLANDS.  
 
HIGH SURF ADVISORY UNTIL 6 PM AST FRIDAY FOR ST CROIX-  
ST.THOMAS...ST. JOHN...AND ADJACENT ISLANDS.  
 
SMALL CRAFT ADVISORY UNTIL 8 PM AST FRIDAY FOR ST.THOMAS...ST.  
JOHN...AND ADJACENT ISLANDS.  
 
SMALL CRAFT ADVISORY FROM 6 PM SATURDAY TO 8 AM AST SUNDAY FOR  
ST.THOMAS...ST. JOHN...AND ADJACENT ISLANDS.  
 
AM...HIGH RIP CURRENT RISK THROUGH SATURDAY AFTERNOON FOR COASTAL  
WATERS OF NORTHERN USVI AND CULEBRA OUT 10 NM-COASTAL  
WATERS OF SOUTHERN USVI VIEQUES AND EASTERN PUERTO RICO OUT  
10 NM.  
 
HIGH SURF ADVISORY UNTIL 6 PM AST FRIDAY FOR COASTAL WATERS OF  
NORTHERN USVI AND CULEBRA OUT 10 NM-COASTAL WATERS OF  
SOUTHERN USVI VIEQUES AND EASTERN PUERTO RICO OUT 10 NM.  
 
HIGH RIP CURRENT RISK THROUGH LATE FRIDAY NIGHT FOR COASTAL  
WATERS OF SOUTHERN PUERTO RICO OUT 10 NM.  
 
SMALL CRAFT ADVISORY UNTIL 8 PM AST FRIDAY FOR COASTAL WATERS OF  
SOUTHERN PUERTO RICO OUT 10 NM.  
 
SMALL CRAFT ADVISORY UNTIL 6 PM AST SATURDAY FOR CARIBBEAN  
WATERS OF PUERTO RICO FROM 10 NM TO 17N-MONA PASSAGE  
SOUTHWARD TO 17N.  
 
SMALL CRAFT ADVISORY UNTIL 8 AM AST SUNDAY FOR COASTAL WATERS OF  
NORTHWESTERN PUERTO RICO OUT 10 NM-COASTAL WATERS OF  
NORTHERN PUERTO RICO OUT 10 NM-COASTAL WATERS OF NORTHERN  
USVI AND CULEBRA OUT 10 NM-COASTAL WATERS OF SOUTHERN USVI  
VIEQUES AND EASTERN PUERTO RICO OUT 10 NM.  
 
SMALL CRAFT ADVISORY UNTIL 2 PM AST SUNDAY FOR ANEGADA PASSAGE  
SOUTHWARD TO 17N-ATLANTIC WATERS OF PUERTO RICO AND USVI  
FROM 10 NM TO 19.5N.  
 

 
 

 
 
SHORT TERM...WS  
LONG TERM....CAM  
 
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