Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 310830
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
430 AM AST THU JUL 31 2014

.SYNOPSIS...TUTT LOW NORTH OF THE AREA WILL RETROGRESS TOWARD THE
BAHAMAS OVER THE NEXT FEW DAYS. INVEST 93L LIKELY TO DEVELOP INTO
A TROPICAL CYCLONE IN THE NEXT 48 HRS AND MOVE OVR NE PR SAT EVENING.

&&

.DISCUSSION...TUTT LOW WILL CONTINUE TO DOMINATE THE WX PATTERN
THROUGH FRI AND MAINTAIN UNSTABLE CONDITIONS WITH THE RISK OF
AFTERNOON CONVECTION OVR INLAND SECTIONS OF PR. INCREASING
SUBSIDENCE FRI AFTERNOON AHEAD OF INVEST 93L WILL RESULT IN A
DECREASE IN AREAL CVRG OF CONVECTION WITH RED FLAG CONDITIONS
LIKELY OVER VIEQUES AND ST. CROIX.

RECENT SATELLITE IMAGERY INDICATES INVEST 93L HAS DEVELOPED SOME DEEP
CONVECTION IN THE LAST 6 HRS AND THIS HAS PROMPTED NHC TO RAISE
THE GENESIS POTENTIAL TO 60% OR LIKELY CATEGORY. ALL GUIDANCE NOW
PRETTY MUCH ONBOARD INDICATING A WELL-DEFINED MID LEVEL
CIRCULATION POSSIBLE WEAK TROPICAL CYCLONE WILL PASS OVER
NORTHEAST PR SAT EVENING. AN ASCAT PASS AROUND 0111Z SHOWED A FEW
WIND BARBS IN THE 30-35 KT RANGE NORTH OF THE CENTER OF
CIRCULATION. EXPECT A SWATH OF HEAVY RAINS ALONG TRACK OF MID-
LEVEL CIRCULATION AFFECTING THE LEEWARDS...USVI AND NORTHEAST PR
SATURDAY AND SATURDAY EVENING. RAINS EXPECTED TO REACH ST. CROIX
BY 12Z SAT AND SPREAD OVER THE ERN THIRD OF PR AROUND MIDDAY SAT
AND CONTINUE THROUGH MIDNIGHT SAT NIGHT. A 6-HR PERIOD OF VERY
INTENSE RAIFNALL APPEARS LIKELY OVR THESE AREAS. LATEST GFS
SUGGESTS A SWATH OF 4 TO 6 INCHES WILL AFFECT THE USVI. FOR A
6-HR PERIOD RAINFALL AMOUNTS TYPICALLY AVERAGE AROUND FIVE INCHES
SO THINK A RANGE OF THREE TO SEVEN INCHES OF RAIN IS POSSIBLE WITH
THIS SYSTEM WITH THE HIGHEST ACCUMULATIONS OVR NE PR/EL YUNQUE
AREA WHERE BEST OROGRAPHIC ENHANCEMENT IS EXPECTED. REST OF PR
WILL SEE MUCH LESSER AMOUNTS. SHOWERS WILL DIMINISH IN CVRG AND
INTENSITY AFTER 06Z SUN AS SYSTEM DEPARTS AND WINDS AND SFC
CONVERGENCE DIMINISH.

TURNING MUCH DRIER EARLY PART OF NEXT WEEK AS STRONG RIDGE BUILDS
IN. AREAS THAT DO NOT RECEIVE SUFFICIENT RAINS SAT WILL HAVE A
SIGNIFICANT FIRE WEATHER THREAT MON-TUE OF NEXT WEEK. THESE ARE
LIKELY TO BE SOUTHWEST PR.


&&

.AVIATION...VFR CONDS AT ALL TAF SITES FOR THE REST OF THE MORNING
HOURS. THEN...SHRA/ISOLD TSRA FM 31/16-31/22Z W/BRIEF MVFR CIGS
EXPECTED ACROSS THE CENTRAL INTERIOR AND NORTHWESTERN SECTIONS OF PR
AFFECTING MAINLY TJBQ AND TJMZ...VCTS LIKELY AT ALL OTHER TERMINALS.
LOW LEVEL WINDS FM THE SE AT 5-15 KTS.


&&

.MARINE...POSSIBLE TS CONDITIONS SAT-SAT NIGHT AS INVEST 93L
TRACKS WNW AROUND 15 KT. GUIDANCE SUGGESTS MINIMAL TS CONDITIONS
WITH WINDS 35-40 KT.


&&

.FIRE WEATHER...SIG DRYING EXPECTED OVR VIEQUES AND ST. CROIX FRI
AHEAD OF TROPICAL SYSTEM. ACCORDING TO THE LATEST GFS...THE DRY
AIR IS NOT EXPECTED TO COINCIDE WITH PEAK HEATING OVR MAINLAND PR.
FOR THIS REASON ONLY INCLUDED VIEQUES AND ST. CROIX IN A FIRE WX
WATCH.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  90  79  90  80 /  40  10  10  10
STT  88  81  88  81 /  40  10   0  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...FIRE WEATHER WATCH FROM FRIDAY MORNING THROUGH FRIDAY AFTERNOON
     FOR VIEQUES.

VI...FIRE WEATHER WATCH FROM FRIDAY MORNING THROUGH FRIDAY AFTERNOON
     FOR ST CROIX.

COASTAL WATERS...NONE.
&&

$$

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