Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 280120
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
920 PM AST MON APR 27 2015

.UPDATE....NO CHANGES FROM PREVIOUS DISCUSSION...FORECAST ON
TRACK. DOPPLER WEATHER RADAR DETECTED MOSTLY CLEAR SKIES ACROSS
THE REGION THIS EVENING. NOT PRECIPITATION WAS DETECTED OVER THE
LOCAL ISLANDS OR COASTAL WATERS. A FAIR AND STABLE WEATHER
PATTERN WILL CONTINUE TO PREVAIL ACROSS THE LOCAL ISLANDS OVER THE
NEXT SEVERAL DAYS...UNDER A MID TO UPPER LEVEL RIDGE AND LIMITED
LOW LEVEL MOISTURE. SHOWER ACTIVITY...IF ANY...WILL BE SHALLOW
AND FOCUSED EACH AFTERNOON ACROSS THE NORTHERN SLOPES OF PUERTO
RICO. THE SOUTHEAST LOW LEVEL WIND FLOW WILL CONTINUE TO PROMOTE
ABOVE NORMAL TEMPERATURES ACROSS THE AREA...BUT ESPECIALLY ALONG
THE NORTHERN SLOPES OF PUERTO RICO. THE SOUTHERLY WIND FLOW
IS EXPECTED TO CONTINUE ACROSS THE LOCAL ISLANDS UNTIL THE END OF
THE WEEK.

&&

.AVIATION...MOSTLY VFR CONDITIONS WILL CONTINUE ACROSS THE LOCAL
FLYING AREA THRU AT LEAST WEDNESDAY AS HOT/DRY AIR STREAMS FROM
THE SOUTHEAST ACROSS THE REGION. ONLY ISOLATED SHRA (AT MOST) ARE
POSSIBLE OVER THE NORTHERN HALF OF PUERTO RICO AFTER 28/17Z
AFFECTING TJBQ AND TJSJ.

&&

.MARINE...TRANQUIL MARINE CONDITIONS WILL CONTINUE WITH A GENTLE
TO MODERATE SOUTHERLY WINDS PREVAILING ACROSS THE REGIONAL WATERS
OVERNIGHT AND TUESDAY. SEAS OF 4 FEET OR LESS AND WINDS OF 15
KNOTS OR LESS ARE EXPECTED WITH POSSIBLE GUSTS UP TO 20 KNOTS
ALONG THE COASTS.

&&

.PREV DISCUSSION... /ISSUED 254 PM AST MON APR 27 2015/

SYNOPSIS...HOT AND DRY CONDITIONS EXPECTED DURING THE DAYTIME
FOR MUCH OF PUERTO RICO WHILE THE USVI REMAINS NOT QUITE AS HOT.
HIGH PRESSURES AT THE LOW...MID...AND UPPER LEVELS DOMINATING THE
LOCAL REGION. SOUTH TO SOUTHEAST WIND FLOW DUE TO THE HIGH
PRESSURE ACROSS THE EASTERN ATLANTIC AND THE SURFACE LOW TO THE
NORTH OF THE LOCAL AREA. THE HIGH PRESSURES IN THE MID AND UPPER
LEVELS WILL KEEP A STABLE ATMOSPHERE CAUSING SUBSIDENCE AND DRY
CONDITIONS. SAHARAN DUST EXPECTED TO MOVE IN BY MIDWEEK.

DISCUSSION...IT HAS BEEN A HOT DAY TODAY ACROSS MOST OF PUERTO
RICO...IN PARTICULAR FOR THE SAN JUAN METRO AREA WHERE THE
TEMPERATURE REACHED 94 DEGREES...BREAKING THE OLD RECORD OF 93 SET
IN 2010. THE 12Z SOUNDING INDICATED A PRECIPITABLE WATER OF ONLY
1.22 INCHES WITH A STRONG TEMPERATURE INVERSION. LITTLE TO NO RAIN
IS EXPECTED LATER IN THE AFTERNOON AND NO RAIN WAS OBSERVED DURING
THE MORNING AND EARLY AFTERNOON HOURS.

INTERESTING WIND FLOW PATTERN WAS OBSERVED TODAY WHEN THE WIND
FROM THE SOUTH SOUTHEAST ENCOUNTERED MAINLAND PUERTO RICO THEN
BECAUSE OF THE LOCAL TERRAIN...A SHADOW OF WIND IS OBSERVED ACROSS
NORTH CENTRAL AND NORTHWESTERN PR...WHILE THE GENERAL WIND FLOW
THEN CAUSES AN EDDY AND LOOPS BACK TO THE WEST AND INTO ARECIBO
TO AGUADILLA...GIVING THEM A NORTHERLY WIND AND ABOUT 10 DEGREES
COOLER TEMPS THAN THE SAN JUAN METRO. THE SEA BREEZE DID NOT
DEVELOP OVER THE SAN JUAN AREA.

THIS SOUTH SOUTHEAST WIND FLOW IS EXPECTED TO CONTINUE THROUGH
THIS WEEK. THERE IS NO SIGNIFICANT CHANGE IN THE WEATHER PATTERN
ACCORDING TO GUIDANCE. SO WE DO EXPECT NEAR RECORD TEMPS AT LEAST
THROUGH THURSDAY WHILE THE TEMPS OVERNIGHT WILL ALSO BE ON THE
WARM SIDE...CLOSE TO 80 DEGREES IN THE LOWER ELEVATIONS.
ALSO...LITTLE TO NO RAIN IS EXPECTED AS CONTINUED DRY AIR IS
MOVING IN. IN FACT...NAAPS MODEL SUGGESTS THAT SOME SAHARAN DUST
IS MOVING IN FOR WEDNESDAY THROUGH FRIDAY...WHICH WILL HELP KEEP
THE CHANCES OF SIGNIFICANT RAINFALL VERY LOW.

AVIATION...VFR CONDS DURG ENTIRE PRD. LIGHT SRLY WIND FLOW BLO
FL100 BCM FM N AND INCR W/HT TO MAX WND 25-30 KTS NR FL450. NO SIG
OPERATIONAL IMPACTS ATTM. FEW FAIR WX CU EN ROUTE BTW ISLAND FM
ERN PR TO NRN LEEWARDS. LATEST SATELLITE IMAGERY SHOWED SAHARAN
AIR LAYER W/SUSPENDED DUST PARTICULATES NOW SPREADING NORTHWARDS
ACROSS THE SE CARIBBEAN AND CROSSING THE WINDWARD ISLANDS.

MARINE...GENTLE TO MODERATE SOUTHERLY WINDS PREVAILED
ACROSS THE REGIONAL WATERS WITH FAIRLY TRANQUIL SEAS OF 4 FEET OR
LESS AND WINDS 15 KNOTS OR LESS EXCEPT FOR OCCASIONAL GUSTS UP TO
20 KNOTS NEAR THE COASTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  80  94  80  94 /   0  20  10  10
STT  81  88  79  88 /  20  20  10  10

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
AM...NONE.
&&

$$

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