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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1604Z Oct 08, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1204 PM EDT WED OCT 08 2014

GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/

MODEL DISCUSSION (VALID FROM OCTOBER 08 AT 00UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS CONTINUE IN GOOD AGREEMENT ON FORECAST
EVOLUTION. CONFIDENCE IS HIGH.

POSITIVELY TILTED TROUGH IS GRADUALLY CROSSING THE ANDES. AS IT
CROSSES INTO ARGENTINA...TROUGH WILL INTERACT WITH MOISTER AND
WARMER AIRMASS AND INDUCE CYCLOGENESIS SURFACE LOW IS ALREADY
STARTING TO FORM IN THE CUYO REGION. BY WEDNESDAY EVENING IT IS
FORECAST TO CENTER NEAR BAHIA BLANCA EXTENDING A COLD FRONT ALONG
SOUTHERN CORDOBA/NORTHERN MENDOZA. BY THURSDAY EVENING LOW WILL BE
WELL OFF THE COASTS OF ARGENTINA WITH FRONT EXTENDING ALONG
CENTRAL URUGUAY/SANTA FE/SANTIAGO DEL ESTERO...AIDED BY A PAMPERO
JET. BY FRIDAY EVENING FRONT WILL EXTEND ALONG NORTHERN RIO GRANDE
DO SUL/SERRA GAUCHA INTO SOUTHERN PARAGUAY...EXTREME SOUTHERN
BOLIVIA TO THEN START LOSING DEFINITION OVER THE CONTINENT.
THROUGH EARLY THURSDAY...EXPECTING ACCUMULATIONS OF 05-10MM/DAY
ACROSS NORTHERN PATAGONIA. A SECOND AREA WITH THE POTENTIAL FOR
THUNDERSTORM DEVELOPMENT WILL STRETCH FROM TUCUMAN/CORDOBA INTO
THE RIO DE LA PLATA/URUGUAY WITH ISOLATED TO SCATTERED MAXIMUM
ACCUMULATIONS OF 15-20MM/DAY. BY THURSDAY INTO EARLY
FRIDAY...CONVECTION WILL ORGANIZE ALONG AND BEHIND ADVANCING COLD
FRONT. UPPER DIVERGENCE AND LOW-LEVEL CONVERGENCE WILL REACH ITS
PEAK. THIS WILL LEAD TO STRONG THUNDERSTORMS WITH ACCUMULATIONS OF
40-80MM/DAY AND THE RISK FOR MCS FORMATION. BY FRIDAY INTO EARLY
SATURDAY...EXPECTING ISENTROPIC LIFT TO STRENGTHEN ACROSS
NORTHEASTERN ARGENTINA/SOUTHERN BRASIL. THIS WILL LEAD TO POST
FRONTAL CONVECTION WITH MAXIMA OF 20-45MM/DAY ACROSS
CORRIENTES/NORTHERN URUGUAY/RIO GRANDE DO SUL. BY SATURDAY INTO
EARLY SUNDAY...ISENTROPIC LIFT PATTERN IS TO CONTINUE...WITH
MAXIMA DECREASING TO 15-30MM/DAY OVER THE SAME AREA. BY SUNDAY
INTO MONDAY...THE ARRIVAL OF A WEAK SHORT WAVE UPPER TROUGH WILL
ENHANCE CONVECTION ACROSS THE REGION. EXPECTING SCATTERED
THUNDERSTORMS WITH ACCUMULATIONS INCREASING TO MAXIMA OF
20-40MM/DAY.

NORTH OVER THE CONTINENT...SUBTROPICAL HIGH IS WELL ESTABLISHED
OVER CENTRAL PERU. THE HIGH IS FORECAST TO GRADUALLY MEANDER
WESTWARD TO CENTER AT 13S 84W BY SATURDAY. IN THE MEANTIME...THE
HIGH WILL PROVIDE DECENT VENTILATION TO SUSTAIN ACTIVE PATTERN OF
CONVECTION ACROSS MOST OF WESTERN AMAZONIA AND THE PERUVIAN AND
ECUADORIAN ANDES. THROUGH THURSDAY MORNING...EXPECTING MAXIMA OF
20-40MM/DAY ACROSS THE WESTERN AMAZON BASIN...AND 15-30MM/DAY
ALONG THE ANDES OF ECUADOR AND NORTHERN PERU. BY THURSDAY INTO
EARLY SUNDAY EXPECTING SCATTERED DIURNAL THUNDERSTORMS TO PRODUCE
ACCUMULATIONS OF 15-30MM/DAY FROM NORTHERN AMAZONAS IN BRASIL INTO
LORETO IN PERU AND MOST OF ECUADOR. A TRANSIENT ENHANCEMENT OF
ACTIVITY ACROSS THE PERUVIAN AMAZON IS EXPECTED FRIDAY INTO EARLY
SATURDAY...WITH MAXIMA OF 15-20MM/DAY.

CHILE WILL CONTINUE LIMITED BY MOISTURE. STARTING
THURSDAY...ACTIVITY WILL LIMIT TO REGIONS BETWEEN PUERTO MONTT AND
PUNTA ARENAS/PUERTO WILLIAMS. EXPECTING ACCUMULATIONS TO LOMIT TO
THE 05-10MM/DAY RANGE.

CAROCA...DMC (CHILE)
DURAN...SENAHMI (PERU)
GALVEZ...WPC (USA)