Areal Flood Warning 70, NWS JSJ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
1056 PM AST FRI NOV 25 2011

.UPDATE...HAD A RATHER BUSY EVENING WITH NUMEROUS SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS THE INTERIOR AND NORTH SECTIONS OF
PUERTO RICO. PERIODS OF HEAVY RAIN OCCURRED IN SEVERAL LOCATIONS
AND CURRENTLY THE LEVELS OF RIO GRANDE DE MANATI AT MANATI ARE
ABOVE FLOOD STAGE AND STILL RISING...WITH OTHER RIVERS AND STREAMS
AT WELL ABOVE NORMAL LEVELS. EXPECT VARIABLY CLOUDY SKIES ACROSS
THE LOCAL ISLANDS OVERNIGHT. ISOLATED TO SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS WILL CONTINUE...ESPECIALLY OVER THE U.S.
VIRGIN ISLANDS...CULEBRA...VIEQUES...THE NORTH AND EAST SECTIONS
OF PUERTO RICO AND ACROSS THE COASTAL WATERS. INHERITED SHORT
TERM GRIDS AND ZFP HAD A PRETTY GOOD HANDLE ON EXPECTED
CONDITIONS OVERNIGHT BUT SENT A QUICK UPDATE TO BOTH TO ALTER THE
WEATHER...SKY COVER...POPS AND WINDS IN SEVERAL ZONES. FOR THE
COASTAL WATERS...MADE A COUPLE OF SEMANTIC ALTERATIONS TO THE
PREVIOUS CWF...MAINLY TO THE SYNOPSIS...OTHERWISE NO CHANGES.

&&

.AVIATION...PREVAILING VFR AT LOCAL TAF SITES. SHRA AND OBSCD
MTNS WILL CONTINUE GRADUALLY DIMINISHING OVER INTERIOR PR THIS
EVE. BUT BRIEF MVFR PSBL TJSJ/TIST/TISX/TNCM/TKPK AS SHRA CONT
COMING FROM E. WNDS BLO FL200 BE LESS THAN 20 KTS THRU
SAT...MAINLY E BLW FL100.

&&

.PREV DISCUSSION... /ISSUED 258 PM AST FRI NOV 25 2011/

SYNOPSIS...MID TO UPPER LEVEL HIGH PRESSURE RIDGE ACROSS THE
AREA...WILL CONTINUE TO ERODE OVERNIGHT THROUGH SATURDAY. THIS
WILL EVENTUALLY GIVE WAY TO A MID TO UPPER LEVEL TROUGH WHICH IS
FORECAST TO SETTLE ACROSS THE REGION BY EARLY SUNDAY. THIS
UNFOLDING PATTERN WILL BE SUPPORTED BY A BROAD INVERTED SURFACE
TROUGH WHICH WILL SET UP ACROSS THE NORTHEAST CARIBBEAN BY
SUNDAY...AS STRONG HIGH PRESSURE OVER THE WEST ATLANTIC SPREADS
FURTHER EAST...AND ANOTHER AREA OF HIGH PRESSURE REMAINS ANCHORED
ACROSS THE NORTHEAST ATLANTIC. FURTHER EAST...A TROPICAL WAVE AND
ASSOCIATED MOISTURE JUST EAST OF THE WINDWARD ISLANDS WILL
CONTINUE TO MOVE WEST NORTHWEST AND ENTER THE EASTERN CARIBBEAN BY
SATURDAY MORNING. IT IS THEN EXPECTED TO BE ABSORBED BY THE BROAD
SURFACE TROUGH WHICH WILL DEVELOP ACROSS THE EASTERN CARIBBEAN AND
LIFT NORTHWARDS ACROSS THE LOCAL AREA BY SUNDAY.

DISCUSSION...FAIRLY LIGHT EASTERLIES CONTINUED TO TRANSPORT SMALL
PATCHES OF TRADE WIND MOISTURE ACROSS THE REGION TODAY. THIS LEAD
TO INCREASED CLOUDINESS WITH THE DEVELOPMENT OF SHOWERS AND ONE OR
TWO ISOLATED THUNDERSTORMS ACROSS PARTS OF THE ISLANDS AND
SURROUNDING WATERS. SO FAR NO WIDESPREAD RAINFALL WAS OBSERVED
OVER THE ISLANDS.

FOR TONIGHT AND THROUGH SATURDAY...ALTHOUGH CLOUDINESS AND
SHOWERS ACTIVITY WILL DIMINISH OVER LAND...EXPECT A GRADUAL
INCREASE IN TROPICAL MOISTURE AS THE AFOREMENTIONED SURFACE TROUGH
DEVELOPS NORTHWARDS AND SURFACE PRESSURE GRADIENT TIGHTENS ACROSS
THE REGION. IN ADDITION...THE DEVELOPING TROUGH WILL INDUCING AN
EAST TO SOUTHEAST LOW LEVEL WIND FLOW AND THIS IN TURN WILL
INCREASE THE CHANCES OF PASSING SHOWERS ACROSS THE REGION.

MODELS SUGGEST CONTINUED INCREASE IN DEEP LAYERED MOISTURE AND
INSTABILITY BEGINNING LATE SATURDAY AND CONTINUING THROUGH THE
EARLY PART OF NEXT WEEK. THIS IS IN RESPONSE TO AFOREMENTIONED MID
TO UPPER LEVEL TROUGH. THERE STILL HOWEVER REMAINS SOME
UNCERTAINTY FOR THE LONG TERM FORECAST ESPECIALLY FOR THE EARLY
PART OF NEXT WEEK...AS SOME MODELS SUGGESTS THAT THE DEEP LAYERED
MOISTURE WILL BE FOCUSED MAINLY ACROSS THE EASTERN HALF OR PUERTO
RICO AND ACROSS THE VIRGIN ISLANDS THROUGH AT LEAST MID WEEK. THE
PWAT VALUES ARE HOWEVER EXPECTED TO JUMP TO 2.00 INCHES OR MORE IN
SOME AREAS AT LEAST THROUGH WEDNESDAY. WITH THIS IN MIND...DECIDED
TO MAINTAIN CONSISTENCY WITH THE PRESENT FORECAST PACKAGE AND LOOK
FOR INCREASINGLY UNSETTLED WEATHER CONDITIONS BEGINNING LATE
SATURDAY AND CONTAINING THROUGH THE EARLY PART OF NEXT WEEK. BASED
ON OVERALL MODEL GUIDANCE...THERE IS GOOD POTENTIAL FOR
SIGNIFICANT RAINFALL ACCUMULATIONS ACROSS ALL OR PARTS OF THE
FA...BUT ALL DEPEND ON HOW MUCH AND EXACTLY WHERE THE DEVELOPING
SURFACE TROUGH INTERACTS WITH THE UPPER TROUGH OVER THE NEXT FEW
DAYS. STAY TUNED AS FURTHER ADJUSTMENTS TO THE FORECAST WILL BE
NECESSARY AS THIS EXPECTED WETTER PATTERN UNFOLDS.

AVIATION...PREVAILING VFR CONDS EXPECTED AT MOST OF THE LOCAL TAF
SITES THROUGH THE FORECAST AREA. ISOLD TO SCT SHRA/TSRA WILL
CONTINUE TO DEVELOP OVER THE INTERIOR AND WEST SECTIONS OF PR AS
WELL AS PARTS OF THE USVI TIL 25/22Z. PERIODS MVFR CONDS ARE PSBL
ACROSS TJMZ...TIST AND TISX AS SHRA/TSRA MOVE SLOWLY TO THE WNW.
SJU AIRCRAFT(AMDAR) SOUNDING AT 1730Z SHOWED 0-6 KM AVG WIND AT
145DEG/6KTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  84  74  84 /  40  50  50  70
STT  75  84  75  85 /  40  40  70  70

&&

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