Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 060300
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1100 PM AST TUE MAY 5 2015

.UPDATE...SHORT WAVE TROUGH JUST WEST OF THE REGION AND THE
GRADUALLY ERODING RIDGE ALOFT ALLOWED FOR THE DEVELOPMENT OF
AFTERNOON CONVECTION ACROSS PORTIONS OF WESTERN PUERTO RICO INTO
THE EARLY EVENING HOURS. SOME SHOWERS WERE MODERATE TO LOCALLY
HEAVY AT TIMES ESPECIALLY IN AND AROUND UTUADO...LARES AND SAN
SEBASTIAN. BY LATE EVENING...ALL SHOWER ACTIVITY HAD DISSIPATED
LEAVING MOSTLY CLEAR SKIES. DURING THE OVERNIGHT HOURS...EXPECT NO
PRECIPITATION OVER LAND... AS A SLOT OF EVEN DRIER AIR WILL MOVE
ACROSS THE REGION. RECENT TJSJ 06/00Z UPPER AIR SOUNDING AS WELL
AS SATELLITE DERIVED PRECIPITABLE WATER PRODUCE BOTH SUGGESTS PWAT
VALUES NOW NEAR AN INCH OR SO ACROSS THE REGION...WITH VERY DRY
CONDITIONS ALOFT...AND ONLY A FEW SHALLOW PATCHES OF LOW LEVEL
MOISTURE NOTED ACROSS THE NORTHEASTERN CARIBBEAN. EXPECTED ANOTHER
HOT AND FAIRLY DRY WEATHER PATTERN ON WEDNESDAY WITH ONLY A SLIGHT
CHANCE OF ISOLATED SHOWERS ACROSS PORTIONS OF THE WEST INTERIOR
SECTION OF PUERTO RICO. STILL NOW SIGNIFICANT CHANGES IN THE
OVERALL WEATHER PATTERN AT LEAST UNTIL THE UPCOMING WEEKEND...WHEN
THE RIDGE ALOFT FLATTENS IN RESPONSE TO AN UPPER TROUGH BECOMING
AMPLIFIED ACROSS THE SOUTHWESTERN ATLANTIC...AND A SURGE OF LOW
LEVEL MOISTURE IS FORECAST TO MOVE ACROSS THE REGION. THIS WILL
INCREASE THE CHANCES FOR SHOWERS AND THUNDERSTORM ACTIVITY ACROSS
THE ISLANDS DURING THE ENTIRE WEEKEND. FOR NOW NO CHANGES MADE TO
THE INHERITED SHORT TERM FORECAST BUT WILL CONTINUE TO MONITOR AND
SEE HOW THE WEATHER PATTERN UNFOLDS DURING THE NEXT COUPLE OF
DAYS.

&&

.AVIATION UPDATE...VFR CONDITIONS EXPECTED ACROSS THE LOCAL
FLYING AREA FOR THE NEXT 24 HOURS...IN HAZY CONDITIONS. OCCASIONAL
GUSTY WINDS ARE STILL POSSIBLE OVERNIGHT...WITH EASTERLY WINDS AT
5 TO 12 KT. AFT 06/12Z WINDS WILL INCREASE...15 TO 20 KT WITH
GUSTS UP TO 25 KT.

&&

.FIRE WEATHER...HIGH PRESSURE ALOFT AND PERSISTENT SURFACE HIGH
NORTH OF THE REGION WILL HELP MAINTAIN OVERALL DRY CONDITIONS AND
CONTINUE TO DESICCATE FUELS. AS A RESULT...ELEVATED FIRE DANGER
CONDITIONS EXPECTED ON WEDNESDAY AND ON THURSDAY WITH EXTREMELY
CRITICAL FIRE WEATHER CONDITIONS POSSIBLE. FOR THIS REASON A RED
FLAG WATCH OR WARNING MAY BE REQUIRED FOR SOME AREAS ACROSS PUERTO
RICO...PARTICULARLY IN AND AROUND SALINAS. STAY TUNED FOR
ADDITIONAL UPDATES.

&&

.MARINE UPDATE...MARGINAL SMALL CRAFT ADVISORY CONDITIONS WILL
CONTINUE FOR AT LEAST THE MONA PASSAGE UNTIL WEDNESDAY AFTERNOON.
THE EASTERLY TRADE WINDS WILL BE MODERATE TO FRESH THROUGHOUT THE
PERIOD TO MAINTAIN CHOPPY SEA CONDITIONS ACROSS MOST OF THE REGIONAL
WATERS WITH SEAS FLUCTUATING TO 6 TO 7 FEET IN SOME PLACES...HIGHEST
SOUTH AND SOUTHWEST OF PR AND IN PORTIONS OF THE MONA PASSAGE.

&&

.PREV DISCUSSION... /ISSUED 338 PM AST TUE MAY 5 2015/

DISCUSSION...CONTINUED DRY CONDITIONS ACROSS THE AREA THOUGH A
FEW FAIRLY INTENSE SHOWERS HAS DEVELOPED THIS AFTERNOON FOR
WESTERN PR AND CAN AGAIN DURING AFTERNOON NEXT SEVERAL DAYS. BUT
THESE WILL NOT LAST LONG AS DRY AIR ALOFT MIXES DOWN AND CLOUDS
INCREASE TO MINIMIZE SUNSHINE. PRECIPITABLE WATER BARELY MORE
THAN AN INCH WILL CONTINUE THIS WEEK AND MAKE SHOWERS ALMOST NON-
EXISTENT AT NIGHT. TEMPERATURES TO REMAIN ABOVE NORMAL BUT NOT AS
MUCH AS THEY HAVE BEEN.

LITTLE CHANGE EXPECTED UNTIL SAT...MORE LIKELY SUNDAY. GFS SHOWS
A 700 MB TROUGH CURRENTLY NEAR 15N/30W (HARD TO SEE ON SATELLITE)
TO MIGRATE WESTWARD AND HELP TO DIRECT MOISTURE WELL NORTH OF
ANTILLES ABOUT 25N TOWARDS PR/USVI. THIS MOISTURE WILL BEGIN
MOVING THIS WAY ONCE THE 700 MB RIDGE AT 19N/45W DISSIPATES AND
THE WESTWARD MOVING TROUGH ARRIVES.

AVIATION...MOSTLY VFR CONDITIONS EXPECTED AT ALL TAF SITES THE NEXT
24 HOURS. HOWEVER FEW CLOUDS AND ISOLATED SHOWERS WILL CONTINUE
UNTIL 05/22Z IN THE VICINITY OF TJBQ AND TJMZ. A SAHARAN AIR MASS
WILL REMAIN ACROSS THE LOCAL FLYING AREA...PRODUCING HAZY SKIES FOR
THE NEXT 24 HOURS. EAST SOUTHEAST WINDS OF 15 TO 20 KT ARE EXPECTED
WITH GUSTS UP TO 25 KT UNTIL AT LEAST 05/22Z...DIMINISHING AFTER
THAT.

MARINE...MARGINAL SMALL CRAFT ADVISORY CONDITIONS TO CONTINUE AT
LEAST INTO WED. TRADE WINDS TO BE MAINLY IN FRESH CATEGORY WHICH
WILL KEEP SEAS CHOPPY AND FLIRTING AROUND 6 FEET SOME PLACES...
HIGHEST SOUTH AND SOUTHWEST OF PR AND TOWARDS CENTRAL CARIBBEAN.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  90  76  92 /   0   0  10  20
STT  77  87  77  87 /   0   0  20  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
AM...SMALL CRAFT ADVISORY UNTIL 8 PM AST WEDNESDAY FOR MONA PASSAGE
     SOUTHWARD TO 17N.

&&

$$

15/09


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