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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1713Z Apr 06, 2015)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
113 PM EDT MON APR 06 2015

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

MODEL DISCUSSION (VALID FROM APRIL 06 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN GOOD AGREEMENT ON FORECAST EVOLUTION
THROUGH 96-120 HRS OVER THE ATLANTIC...AND ONLY THROUGH 84-96 HRS
OVER THE PACIFIC.

NORTHERN STREAM TROUGH AND SURFACE FRONTS OFF THE COAST OF
SOUTH-CENTRAL CHILE WILL CONTINUE WEAKENING WHILE ROBUST MID-UPPER
RIDGE DOMINATES THE SOUTHERN CONE. FIRST TRAIN OF FRONTS TO ARRIVE
INTO SOUTHERN CHILE WILL DO SO EARLY TUESDAY INTO WEDNESDAY. THIS
WILL LEAD TO SCATTERED CONVECTION WITH MAXIMA OF 10-15MM/DAY WITH
ACCUMULATIONS DECREASING AFTER. A NEW SURFACE TROUGH WILL APPROACH
THE REGION DURING THURSDAY TO PRODUCE ACCUMULATIONS OF 10-15MM/DAY
BETWEEN PUERTO AYSEN AND PUERTO NATALES.

TO THE NORTH...DEEP-LAYER MOISTURE WILL REMAIN TO THE NORTH OF 25S
TO LIMIT ACCUMULATIONS ACROSS ARGENTINA/URUGUAY AND SOUTHERN
BRASIL. AN UPPER TROUGH ALREADY OVER THE ATLANTIC IS SUSTAINING A
TRAIN FRONTS THAT WILL ENHANCE ACTIVITY ACROSS PARTS OF
SOUTHEASTERN AND EASTERN BRASIL. THE SURFACE FRONT WILL EXTEND
INTO THE COASTS OF SAO PAULO/WESTERN RIO DURING LATE
MONDAY...SOUTHERN ESPIRITO SANTO/SOUTHERN MINAS GERAIS DURING
TUESDAY...AND NORTHERN ESPIRITO SANTO DURING WEDNESDAY. EXPECTING
ACCUMULATIONS OF 20-35MM/DAY THROUGH EARLY TUESDAY INCREASING TO
25-50MM/DAY BY TUESDAY THROUGH EARLY THURSDAY WHEN INSTABILITY AND
LOW-LEVEL CONVERGENCE ARE EXPECTED TO PEAK. AMOUNTS WILL START
DECREASING DURING FRIDAY AS REGION OF STRONGEST CONVECTION CENTERS
OVER BAHIA.

ACROSS TROPICAL SOUTH AMERICA...THE SUBTROPICAL RIDGE IS STARTING
TO LOSE DEFINITION. YET...UNSEASONABLY ACTIVE CONVECTION IN
TROPICAL WESTERN SOUTH AMERICA WILL CONTINUE SUSTAINING AN
ILL-DEFINED RIDGE OVER THE WESTERN TIER OF THE CONTINENT. THIS
WILL CONTINUE SUSTAINING NEST VENTILATION OVER PARTS OF THE
NORTHWESTERN AMAZON WHERE EXPECTING MOST ACTIVE CONVECTION.
INITIALLY...A WEAKENING SOUTHERLY SURGE WILL CONVECTION OVER
PERU/WESTERN BRASIL TO PRODUCE SCATTERED MAXIMA OF 30-60MM/DAY.
AMOUNTS ARE TO DECREASE TO MAXIMA OF 20-35MM/DAY AFTERWARDS. A
SURGE IN ACTIVITY IS EXPECTED DURING THURSDAY...STIMULATED BY AN
UPPER TROUGH APPROACHING SOUTHERN PERU/NORTHERN BOLIVIA. THIS WILL
LEAD TO ACCUMULATIONS INCREASING ONCE AGAIN TO SCATTERED MAXIMA OF
30-60MM/DAY IN LOW-LYING AREAS...AND 10-15MM/DAY IN THE ANDEAN
REGIONS OF PERU/BOLIVIA AND NORTHERN CHILE.


SCHNEIDER...INMET (BRASIL)
CALLE...UNALM (PERU)
CHARPENTIER...DMC (CHILE)
DAVISON/GALVEZ...WPC (USA)