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554
FXCA62 TJSJ 010243
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1043 PM AST TUE SEP 30 2014

.UPDATE...FORECAST ON TRACK...NO CHANGES WERE INTRODUCED. TROUGH
ALOFT WILL CONTINUE TO PREVAIL ACROSS THE TROPICAL ATLANTIC AND
INTO THE EASTERN AND CENTRAL CARIBBEAN WITH TWO AREAS OF LOW
PRESSURE DEVELOPING EAST OF THE LESSER ANTILLES AND SOUTH OF
JAMAICA. WEAKENING OF MID LEVEL RIDGE EXPECTED EARLY NEXT WEEK.
TROPICAL WAVE PASSAGE EXPECTED ON THURSDAY EVENING INTO FRIDAY
MORNING.

INCREASE IN LOW LEVEL MOISTURE EXPECTED TONIGHT AND INTO WEDNESDAY
REACHING ITS MAXIMUM...NEAR TWO INCHES...THURSDAY EVENING AND FRIDAY
MORNING ASSOCIATED WITH NEXT TROPICAL WAVE PASSAGE. BEHIND THIS
WAVE...A DRIER AIR MASS WILL MOVE IN FOR THE EAST.

THEREFORE UNDER THIS EVOLVING PATTERN...AFTERNOON CONVECTION EXPECTED
ACROSS THE CORDILLERA AND WEST PUERTO RICO WEDNESDAY AND THURSDAY
WITH A BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS THURSDAY
EVENING AND FRIDAY AS TROPICAL WAVE MOVES ACROSS THE AREA.

&&

.AVIATION...VFR CONDITIONS EXPECTED AT ALL TAF SITES DURING THE
FORECAST PERIOD. HOWEVER...PASSING -SHRA EMBEDDED IN THE TRADE WINDS
WILL CREATE VCSH AT TKPK AND TNCM DURING THE OVERNIGHT AND EARLY
MORNING HOURS AND COULD REACH TIST/TISX DURING THIS PERIOD.
AFTER...01/16Z VCSH EXPECTED AT TJBQ AND TJMZ WITH POSSIBLE MTN TOP
OBSCD OVER THE WESTERN INTERIOR OF PR. EAST SOUTHEAST WINDS AT 5-14
KTS BELOW 3 KFT.

&&

.MARINE...NO CHANGE TO PREVIOUS DISCUSSION.

&&

.PREV DISCUSSION... /ISSUED 257 PM AST TUE SEP 30 2014/

SYNOPSIS...MID-LEVEL RIDGE ACROSS THE EASTERN CARIBBEAN WILL
PREVAIL THROUGH WEDNESDAY....MAINTAINING A FAIR WEATHER PATTERN
ACROSS THE REGION UNTIL WEDNESDAY. A TROPICAL WAVE IS EXPECTED ACROSS
THE LOCAL AREA ON THURSDAY INTO FRIDAY MORNING...INCREASING THE
CHANCES OF SHOWERS AND THUNDERSTORMS ACROSS THE LOCAL ISLANDS.
AFTER THE TROPICAL WAVE PASSES...MUCH DRIER AND STABLE AIRMASS IS
EXPECTED AS A SURFACE HIGH MOVES IN THROUGH THE WEEKEND.

DISCUSSION...FAIRLY WARM DAY TODAY WITH TEMPERATURES REACHING 94
DEGREES SO FAR IN SAN JUAN...TYING THE RECORD SET BACK IN 2001. IT
WAS ALSO DRY WITH ONLY A FEW CLOUDS OBSERVED...ESPECIALLY ACROSS
THE NORTHWESTERN PORTIONS OF PR IN THE AFTERNOON...OTHERWISE
MOSTLY SUNNY SKIES WERE OBSERVED. THERE IS STILL A SLIGHT CHANCE
OF SHOWERS ACROSS NW PR IN THE AREAS WHERE CLOUDS ARE
DEVELOPING...BUT THESE ARE NOT EXPECTED TO PRODUCE SIGNIFICANT
ACCUMULATIONS IF THEY DEVELOP. THE REST OF THE LOCAL ISLANDS
SHOULD REMAIN DRY FOR THE REST OF THE DAY.

SLIGHTLY MORE MOISTURE IS EXPECTED TO MOVE IN FOR WEDNESDAY AND
INSTABILITY INCREASES SLIGHTLY AS WELL...SO THERE IS A BETTER
CHANCE FOR SHOWERS AND ISOLATED THUNDERSTORMS ON WEDNESDAY
AFTERNOON ACROSS THE NW PORTIONS OF PR. HOWEVER THE REAL INCREASE
IN MOISTURE AND INSTABILITY IS EXPECTED ON THURSDAY AS A TROPICAL
WAVE MOVES INTO THE LOCAL AREA. SCATTERED TO NUMEROUS SHOWERS AND
ISOLATED THUNDERSTORMS ARE FORECAST WITH THE PASSAGE OF THIS WAVE
ON THURSDAY INTO FRIDAY. BY LATE FRIDAY NIGHT...MUCH DRIER AIR IS
EXPECTED TO MOVE INTO THE LOCAL AREA AND REMAIN OVER THE ISLANDS
THROUGH THE WEEKEND. NAAPS MODEL INDICATES THAT SAHARAN DUST WILL
BE MOVING IN FOR SATURDAY ALONG WITH A SURFACE HIGH PRESSURE...SO DRY AND
HAZY CONDITIONS ARE VERY POSSIBLE THIS WEEKEND.

BEHIND THE SURFACE HIGH PRESSURE THERE ARE NORTHEASTERLY WINDS AND
MORE MOIST AIR...WHICH MAY MOVE INTO THE LOCAL ISLANDS ON TUESDAY
AFTER THE HIGH PRESSURE PASSES. THIS MAY LEAVE US WITH PASSING
SHOWERS AND SOME CLOUDS AS THE MOISTURE INCREASES.

AVIATION...VFR CONDS WILL PREVAIL AT ALL TAF SITES AND ACROSS THE
LOCAL FLYING AREA DURING THE PRD. LOW LEVEL WINDS WILL BE MAINLY
FROM THE ESE AT 5-15 KTS BLO FL150...BCMG FM NE-N ABV AND INCR TO
20-25 KTS NR FL350. FEW FAIR WX CU LINES W/NO SIG VERTICAL EXTENT EN
ROUTE BTW E PR AND VIRGIN ISLANDS. NO SIG OPERATIONAL WX IMPACTS
ATTM.

MARINE...SEAS ARE EXPECTED TO REMAIN AT 3 TO 4 FEET FOR THE NEXT
FEW DAYS WITH SEAS GENERALLY LESS THAN 17 KNOTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  92  78  91 /  20  20  30  30
STT  80  89  80  89 /  30  30  50  50

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...NONE.
&&

$$

13/23






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