Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 030138 CCA
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
932 PM AST SUN AUG 2 2015

.DISCUSSION...SHOWERS APPROACHING ACROSS USVI AND ANEDAGA PASSAGE
HAVE SO FAR BEEN NOT WIDESPREAD AND UNIMPRESSIVE THOUGH SOME ARE
THERE ALONG WITH ISOLATED THUNDER...CURRENTLY NORTH OF THE ISLANDS.
PRECIPITABLE WATER IN THIS PLUME IS NEAR 2 INCHES AND POTENTIAL
FOR MORE SHOWERS CERTAINLY EXISTS AT ANY TIME THOUGH CLEARLY NO
UPPER LEVEL SUPPORT IS AVAILABLE FOR DEVELOPMENT AND THE MOISTURE
IS COINCIDENT WITH SOME SAHARAN AIR. WRF SUGGESTS ACTIVITY TO
INCREASE OVERNIGHT. SHOWERS WITH NO MORE COVERAGE THAN SCATTERED
APPEARS RIGHT AND HAVE LEFT FORECAST GRIDS WITHOUT MODIFYING THEM.

&&

.AVIATION...SHRA ARE EXPECTED TO INCREASE AS MOISTURE ASSOCIATED
WITH A TROPICAL WAVE IS EXPECTED TO REACH THE LOCAL ISLANDS
OVERNIGHT. AS A RESULT...MVFR CONDITIONS MAINLY OVER TIST TISX TJSJ
ARE POSSIBLE. AFTER 03/12Z DRY AIR ADVECTION WITH LESS SHRA ACTIVITY
IS EXPECTED. DURING THE AFTERNOON SHRA ARE STILL POSSIBLE ACROSS THE
WESTERN/INTERIOR SECTIONS OF PR. WINDS AT 5 TO 15 KT LOCALLY HIGHER
IN SHRA...AFT 03/12Z INCREASING AT 10 TO 20 KT WITH HIGHER GUSTS AND
SEA BREEZE VARIATIONS.

&&

.MARINE...NO CHANGE. STRONG WINDS IN THE SOUTHEAST FLOW ALOFT ARE
NOT MIXING TOWARDS SURFACE AND WILL BE INCREASINGLY DIFFICULT FOR
THEM TO AS SAHARAN AIR BEGINS TO ARRIVE LATE TONIGHT. BUT LOCAL
WINDS TO 20 KT AND SEAS LOCALLY TO 6 FT...POTENTIALLY HIGHER IN
THUNDERSTORMS.

&&

.PREV DISCUSSION... /ISSUED 321 PM AST SUN AUG 2 2015/

SYNOPSIS...TUTT WILL LINGER ACROSS THE REGION OVER THE NEXT FEW
DAYS. ANOTHER TUTT LOW WILL RELOCATE OVER PR BY THE END OF THE
WORK WEEK. A TROPICAL WAVE WILL EXIT THE LOCAL AREA OVERNIGHT.
DRY AND STABLE AIR MASS WITH SAHARAN DUST WILL MOVE OVER THE
REGION LATE MONDAY INTO TUESDAY. TRADE WIND SHOWERS ARE FORECAST
FOR THE SECOND PART OF THE WEEK.

DISCUSSION...SHOWER AND THUNDERSTORM ACTIVITY WAS OBSERVED TODAY
ACROSS THE FORECAST AREA. PASSING SHOWERS WERE NOTED EARLY IN THE
MORNING HOURS ACROSS PORTIONS OF EASTERN PR AND THE USVI...THEN BY
EARLY AFTERNOON...SCATTERED TO NUMEROUS SHOWERS AND ISOLATED
THUNDERSTORMS DEVELOPED ACROSS PARTS OF WESTERN PR. BY MID
AFTERNOON...MAX RAINFALL TOTALS WERE BETWEEN 1 TO 2 INCHES OF
RAIN WITH THE HEAVIEST SHOWERS.

LOW LEVEL MOISTURE WILL CONTINUE ACROSS THE LOCAL ISLANDS AS THE
BACK EDGE OF A TROPICAL WAVE WILL CONTINUE TO MOVE ACROSS THE AREA
THIS EVENING INTO MONDAY MORNING. SHOWERS WITH ISOLATED
THUNDERSTORMS WILL AFFECT THE EASTERN PORTIONS OF PUERTO RICO AND
THE USVI THROUGH THE OVERNIGHT HOURS.

STABLE AIR AND SAL IS EXPECTED TO FILL OVER THE REGION BY LATE
MONDAY MORNING AND CONTINUE THRU TUESDAY...KEEPING THE CHANCES OF
RAIN LOW FOR MOST OF THE AREA. HOWEVER...BY THE SECOND PART OF THE
WEEK A WETTER PATTERN IS FORECAST...AS FAVORABLE UPPER LEVEL
DYNAMICS AND EARLY TRADE WIND SHOWERS WILL FAVOR AFTERNOON
CONVECTION OVER THE INTERIOR/WESTERN PR AND TRADE SHOWERS OVER
EASTERN PR/USVI DURING THE EARLY MORNING HOURS.

AVIATION...SHRA W PR TIL 02/22Z. AS A RESULT...MVFR CIGS IN TJMZ
 TO VCTY SHRA.  FEW CU EN ROUTE BTW E PR AND USVI WITH PASSING SHRA.
ANOTHER AREA OF SHOWERS WILL MOVE ACROSS THE LOCAL REGION THIS
EVENING GENERATING MVFR CONDITIONS MAINLY OVER TIST TISX TJSJ AND
TJPS. SHOWERS WILL LINGER AROUND THROUGH THE OVERNIGHT HOURS.

MARINE...NEAR SHORE BUOYS ARE INDICATING SEAS OF 3-5 FEET ACROSS
THE USVI AND PR WATERS. EAST WINDS ARE AROUND 15 KNOTS WITH GUSTS
IN THE LOW 20S. SEAS UP TO 6 FEET ARE EXPECTED ACROSS THE OFFSHORE
ATLANTIC AND CARIBBEAN WATERS AS TROPICAL WAVE CONTINUES TO EXIT
THE LOCAL AREA.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  79  90  79  90 /  40  30  30  30
STT  80  89  79  90 /  50  20  30  30

&&

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

$$

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