Small Craft Advisory 17, NWS JSJ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1119 PM AST MON MAY 4 2009

.UPDATE...
CLOUDINESS AND CONVECTIVE ACTIVITY ACROSS PUERTO RICO...CULEBRA
AND VIEQUES CONTINUED TO DIMINISH DURING THE LATE EVENING HOURS.
HOWEVER...LATEST SATELLITE IMAGERY AS WELL AS THE DOPPLER WEATHER
RADAR INDICATED SHOWERS AND ISOLATED THUNDERSTORMS MOVING ACROSS
THE LOCAL WATERS NORTHEAST OF PUERTO RICO...AND JUST EAST OF THE
U.S. VIRGIN ISLANDS. THIS ACTIVITY IS ALONG THE TRAILING EDGE OF
THE SURFACE TROUGH AXIS WHICH WILL CONTINUE TO DRIFT WESTWARDS
ACROSS THE LOCAL AREA THROUGH TUESDAY. THE PROXIMITY OF A MID TO
UPPER LEVEL TROUGH AND A JET SEGMENT WILL CONTINUE TO ENHANCE THE
CONVECTIVE ACTIVITY OVER THE NEXT 24-48 HOURS. THIS WILL MAINTAIN
A VERY ACTIVE WEATHER PATTERN ACROSS THE REGION AT LEAST THROUGH
WEDNESDAY...BEFORE THE MID TO UPPER TROUGH AND ASSOCIATED JET
SEGMENT WEAKENS AND LIFTS NORTHWARDS.

THEREAFTER AND THROUGH THE END OF THE WEEK...THE CENTRAL ATLANTIC
SURFACE HIGH PRESSURE RIDGE WILL SINK FURTHER SOUTHWARD ACROSS THE
NORTHEAST CARIBBEAN...AND THE PREVAILING SOUTHEAST WIND FLOW WILL
MAINTAIN THE INFLUX OF TROPICAL MOISTURE ACROSS THE REGION. THIS
COMBINED WITH DIURNAL AND LOCAL EFFECTS WILL ENHANCE SHOWER AND
THUNDERSTORM ACTIVITY ACROSS THE LOCAL ISLANDS. THEREFORE THE
POTENTIAL FOR FLASH FLOODING AS WELL AS FOR MUDSLIDES WILL REMAIN
HIGH THROUGH THE END OF THE WEEK. ONLY MINOR ADJUSTMENT MADE TO
THE INHERITED SHORT TERM FORECAST FOR NOW...AS SHOWER ACTIVITY
SIGNIFICANTLY DIMINISHED ACROSS PUERTO RICO...CULEBRA AND VIEQUES.

&&

.AVIATION...
THUNDERSTORM ACTIVITY HAS DIMINISHED OVER PUERTO RICO...BUT
REMAINS ACTIVE OVER THE U.S. VIRGIN ISLANDS AND WATERS IMMEDIATELY
EAST. EXPECT MOMENTARY IFR CONDITIONS WITH TSRA OVER TIST AND TISX
LIKELY BETWEEN 04Z AND 12Z. THESE CELLS ARE EXTREMELY SLOW MOVING
AND STORM MOTION IS TRICKY. FOR TUESDAY...EXPECT THUNDERSTORM
ACTIVITY TO CONTINUE LIKELY PRODUCING MVFR TO IFR CIGS/VSBYS OVER
AT LEAST TJBQ AND TJMZ IN PUERTO RICO...AND ALL SITES IN THE U.S.
VIRGIN ISLANDS AND LEEWARD ISLANDS.

&&

.PREV DISCUSSION... /ISSUED 423 PM AST MON MAY 4 2009/

DISCUSSION...SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS
AFFECTED THE ISLANDS OF ST JOHN AND ST THOMAS....PRODUCING
RAINFALL ACCUMULATIONS OF AROUND 2 INCHES. ALSO SCATTERED TO
NUMEROUS SHOWERS AND THUNDERSTORMS DEVELOPED ALONG THE THE INTERIOR
SECTIONS OF PUERTO RICO...THESE SHOWERS MOVED SLOWLY NORTHWARD
AFFECTING MOST OF THE NORTHERN HALF OF PUERTO RICO. AT THIS
MOMENT...AN AREA OF SHOWERS CONTINUE TO AFFECT WESTERN PORTIONS OF
PUERTO RICO. THESE SHOWERS WILL LINGER THROUGH LATE EVENING.

A MID TO UPPER LEVEL TROUGH WILL CONTINUE TO PRODUCE A VERY
UNSTABLE ATMOSPHERE THROUGH THE INCOMING WEEKEND. A 70 KNOTS JET
STREAK OVER THE LOCAL AREA IS ALSO CONTRIBUTING ON THE SHOWER AND
THUNDERSTORM ENHANCEMENT. THESE WEATHER FEATURES PROMISE TO
GENERATE NUMEROUS SHOWERS AND THUNDERSTORMS THROUGH AT LEAST
FRIDAY. SATURATED SOILS AND INCREASING SHOWERS THROUGH THE WEEK
WILL INCREASE THE FLOODING POTENTIAL FOR PUERTO RICO AND THE USVI
THE NEXT SEVERAL DAYS.

RESIDENTS AND VISITORS OF PUERTO RICO SHOULD REMAIN ALERT TO THE
LATEST FORECASTS AS FLASH FLOOD WATCHES AND WARNINGS WILL LIKELY
BE REQUIRED AT SOME POINT THIS WEEK.

AVIATION...EXPECT MVFR OR EVEN IFR CONDITIONS ACROSS TIST AND TISX
DURING THE REST OF THE AFTERNOON AND THE EVENING HOURS. SHOWER
ACTIVITY WILL DIMINISH ACROSS TJBQ AND TJMZ THIS EVENING WITH MAINLY
VFR CONDITIONS THIS EVENING AND OVERNIGHT. HOWEVER AN INCREASE IN
LOW LEVEL MOISTURE ACCOMPANYING THE PREVAILING EAST TO SOUTHEAST
WIND FLOW FOR TOMORROW AFTERNOON...WILL BRING PERIODS OF MVFR
CONDITIONS ACROSS TJBQ AND TJMZ. LATEST TJSJ 12Z SOUNDING INDICATED
A LIGHT AND VARIABLE WIND FLOW FROM THE SURFACE TO AROUND 10K
FEET...BECOMING WESTWARD AND STRONGER ABOVE 10K FEET.

MARINE...NORMAL MARINE CONDITIONS ARE EXPECTED TO PREVAIL FOR THE
REST OF THE WEEK BUT MARINERS SHOULD EXERCISE CAUTIONS FOR
THUNDERSTORMS MOVING ACROSS THE LOCAL WATERS. THESE SHOWERS AND
THUNDERSTORMS COULD PRODUCE LOCALLY HIGHER WAVES...LIGHTNING
STRIKES...AND HEAVY DOWNPOURS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  84  75  85 /  40  60  50  70
STT  75  83  75  86 /  70  60  60  70

&&

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

93/09

HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN
ISLANDS
NATIONAL WEATHER SERVICE SAN JUAN PR
1210 PM AST MON MAY 4 2009

AMZ710>745-PRZ001>013-051615-
SAN JUAN AND VICINITY-NORTHEAST-SOUTHEAST-EASTERN INTERIOR-
NORTH CENTRAL-CENTRAL INTERIOR-PONCE AND VICINITY-NORTHWEST-
WESTERN INTERIOR-MAYAGUEZ AND VICINITY-SOUTHWEST-CULEBRA-VIEQUES-
THE NEARSHORE AND OFF SHORE ATLANTIC AND CARIBBEAN COASTAL WATERS-
1210 PM AST MON MAY 4 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE
ADJACENT COASTAL WATERS.

.DAY ONE...THIS AFTERNOON AND TONIGHT

PERIODS OF MODERATE TO HEAVY SHOWERS AND ISOLATED THUNDERSTORMS
WILL PRODUCE LOCALIZED FLOODING OF URBAN AREAS AND SMALL STREAMS
AS HEAVY RAIN BANDS CONTINUE TO MOVE IN FROM THE SOUTH AND EAST.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A NEARLY STATIONARY AREA OF LOW PRESSURE IN THE MID LEVELS OF THE
ATMOSPHERE LOCATED NORTH OF HISPANIOLA WILL COMBINE WITH A VERY
MOIST EAST SOUTHEAST FLOW TO GENERATE WIDESPREAD HEAVY RAINS AND
THE POTENTIAL FOR FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

AMZ715-725-VIZ001-002-051615-
ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX-
NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS-
1210 PM AST MON MAY 4 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS AND
THE ADJACENT COASTAL WATERS.

.DAY ONE...THIS AFTERNOON AND TONIGHT

PERIODS OF MODERATE TO HEAVY SHOWERS AND ISOLATED THUNDERSTORMS
WILL PRODUCE LOCALIZED FLOODING OF URBAN AREAS AND SMALL STREAMS
AS HEAVY RAIN BANDS CONTINUE TO MOVE IN FROM THE SOUTH AND EAST.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A NEARLY STATIONARY AREA OF LOW PRESSURE IN THE MID LEVELS OF THE
ATMOSPHERE LOCATED NORTH OF HISPANIOLA WILL COMBINE WITH A VERY
MOIST EAST SOUTHEAST FLOW TO GENERATE WIDESPREAD HEAVY RAINS AND
THE POTENTIAL FOR FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...