791  
FXCA62 TJSJ 260135  
AFDSJU  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN JUAN PR  
935 PM AST THU MAY 25 2017  
   
UPDATE
 
A FEW LIGHT SHOWERS PERSISTED ACROSS WESTERN PR THROUGH  
THE EARLY EVENING HOURS. WHILE ISOLATED SHOWERS FROM STREAMERS  
FROM THE NORTHERN USVI MADE IT INLAND ACROSS CULEBRA AND EASTERN  
PR. ALSO, LIGHT TRADE WIND SHOWERS WERE NOTED OVER THE CARIBBEAN  
WATERS AND OVER PORTIONS OF ST. CROIX. HOWEVER, NO SIGNIFICANT  
RAINFALL ACCUMULATION'S WERE OBSERVED. OVERALL, FAIR WEATHER  
CONDITIONS SHOULD PREVAIL OVERNIGHT WITH A FEW SHOWERS MOVING FROM  
TIME TO TIME ACROSS THE USVI/EASTERN PORTIONS OF PR. MINOR CHANGES  
WERE MADE TO SHORT TERM GRIDS.  
 

 
 
   
AVIATION
 
MAINLY VFR ACROSS ALL TERMINALS THROUGH THE FORECAST  
PERIOD. LIGHT TRADE WIND SHOWERS COULD BRIEFLY AFFECT THE  
LEEWARD/USVI/EASTERN PR TERMINALS THROUGH EARLY FRIDAY MORNING.  
HZ DUE TO SAHARAN DUST WILL CONTINUE BUT VSBY P6SM. LATEST 26/00Z  
TJSJ UPPER AIR SOUNDING INDICATED E WINDS BELOW FL100 AT 7-20  
KTS...BCMG N ABOVE.  
 

 
   
MARINE
 
NO CHANGE FROM PREVIOUS DISCUSSION. HIGH RIP CURRENT  
RISK CONTINUES OVERNIGHT ACROSS THE NORTHWEST TO NORTH CENTRAL  
COAST OF PR. MODERATE RISK OF RIP CURRENTS EXPECTED ON FRIDAY  
ACROSS MUCH OF THE BEACHES OF THE ISLANDS.  
 

 
   
PREV DISCUSSION
 
/ISSUED 449 PM AST THU MAY 25 2017/  
 
SHORT TERM...TODAY THROUGH SATURDAY...  
MOSTLY SUNNY AND HAZY SKIES PREVAILED ACROSS THE REGION ONCE AGAIN  
TODAY. ONLY A FEW LIGHT SHOWERS WERE NOTED OVER THE WEST INTERIOR  
OF PUERTO RICO DURING THE LATE AFTERNOON HOURS. HOWEVER, THE ACTIVITY  
WAS OF SHORT DURATION. EXPECT MOSTLY CLEAR SKIES DURING THE OVERNIGHT  
HOURS WITH LITTLE OR NO MEASURABLE PRECIPITATION EXPECTED ACROSS THE  
FORECAST AREA.  
 
A VERY DRY AND STABLE AIRMASS WILL CONTINUE TO DOMINATE THE LOCAL  
REGION FOR THE NEXT FEW DAYS AS A STRONG LOW TO MID LEVEL RIDGE  
WILL DOMINATE THE REGION. SAHARAN DUST WILL CONTINUE ACROSS THE  
REGION DURING THE REST OF THE EVENING BUT LESSER CONCENTRATIONS IS  
EXPECTED DURING THE NEXT FEW DAYS. AN EAST TO SOUTHEAST WIND FLOW  
WILL PREVAIL THROUGH SATURDAY PROMOTING NEAR OR SLIGHTLY ABOVE NORMAL  
TEMPERATURES ALONG THE NORTHERN SLOPES OF PUERTO RICO. ELSEWHERE TEMPERATURES  
WILL BE NEAR NORMAL. ON FRIDAY, THE UPPER LEVEL RIDGE WILL GRADUALLY  
ERODE ALLOWING FOR A SLIGHT INCREASE IN LOW LEVEL MOISTURE TRANSPORT  
THROUGH SATURDAY. THIS SHOULD ALLOW A BETTER CHANCE FOR EARLY MORNING  
SHOWERS FOLLOWED BY SOME AFTERNOON SHOWERS AND POSSIBLY ISOLATED THUNDERSTORM  
DEVELOPMENT MAINLY OVER THE INTERIOR AND WEST SECTIONS OF PUERTO RICO.  
 
LONG TERM...SUNDAY THROUGH FRIDAY...  
AN UPPER LEVEL LOW AND AN ASSOCIATED TROUGH JUST EAST NORTHEAST OF THE  
REGION IS FORECAST TO RETROGRESS NORTH NORTHWEST ACROSS THE AREA  
WHILE WEAKENING SUNDAY THROUGH MONDAY. HOWEVER, ANOTHER SHORT WAVE  
TROUGH IS EXPECTED TO DEVELOP AND MOVE ACROSS THE SOUTHWESTERN ATLANTIC  
AND REINFORCE THE PREVIOUSLY MENTIONED LINGERING TROUGH. SURFACE  
HIGH PRESSURE ACROSS THE CENTRAL ATLANTIC IS FORECAST TO MAINTAIN  
MODERATE TRADE WINDS ACROSS THE REGION THROUGH EARLY. HOWEVER,  
WINDS ARE TO BECOME EAST TO NORTHEAST BY MID WEEK AND ONCE AGAIN  
EAST SOUTHEAST FOR THE REST OF THE PERIOD. ALL IN ALL, EXPECT  
RELATIVELY DRY WEATHER PATTERN ACROSS THE LOCAL ISLANDS DURING  
MOST OF THE WEEKEND WITH TYPICAL DIURNALLY AND LOCALLY INDUCED  
AFTERNOON CONVECTION MAINLY OVER PARTS OF THE INTERIOR AND WEST  
SECTIONS OF PUERTO RICO. A TROPICAL WAVE IS STILL FORECAST TO  
APPROACH TO THE LESSER ANTILLES SUNDAY AND MONDAY AND MOVE ACROSS  
THE EASTERN CARIBBEAN TUESDAY THROUGH WEDNESDAY. THIS FEATURE IN  
COMBINATION WITH THE PROXIMITY OF AN UPPER TROUGH SHOULD BRING AN  
INCREASE IN TROPICAL MOISTURE TRANSPORT AND CONSEQUENTLY INCREASE  
THE CHANCE FOR SHOWERS AND THUNDERSTORMS OVER THE LOCAL ISLANDS  
AND SURROUNDING WATERS EARLY NEXT WEEK.  
 
AVIATION...SUSPENDED SAHARAN DUST WILL RESULT IN SLIGHT HZ WITH  
SLANT VSBY BTWN 6-9 NM DURG PRD. SOME SHRA/-SHRA ARE POSSIBLE IN  
THE VCTY OF TJMZ BTWN 25/18-23Z, THEN VFR CONDITIONS WILL PREVAIL  
DURING THE NEXT 24 HOURS. SURFACE WINDS E-ESE AT 10-20 KNOTS WITH  
HIGHER GUSTS. LIGHT AND VARIABLE OVERNIGHT.  
 
MARINE...A NORTHERLY SWELL AT 3 TO 5 FEET CONTINUED TO MOVE ACROSS  
THE LOCAL ATLANTIC WATERS. THIS SWELL WILL CONTINUE TO SUBSIDE  
DURING THE REST OF THE EVENING HOURS. THE NEARSHORE BUOYS  
CONTINUED TO SUGGESTS EASTERLY WINDS AT 15 TO 20 KNOTS. MARINERS  
CAN THEREFORE EXPECT SEAS BETWEEN 3 AND 6 FEET AND WINDS AT 15  
KNOTS OR LESS.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SJU 78 89 77 89 / 10 40 40 40  
STT 78 87 77 88 / 10 40 40 40  
 

 
   
SJU WATCHES/WARNINGS/ADVISORIES
 
 
PR...HIGH RIP CURRENT RISK UNTIL 6 AM AST FRIDAY FOR NORTH CENTRAL-  
NORTHWEST-WESTERN INTERIOR.  
 
VI...NONE.  
AM...NONE.  

 
 

 
 
SHORT TERM...DS  
LONG TERM....RAM  
 
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