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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1907Z Aug 08, 2018)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
307 PM EDT WED AUG 08 2018

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

MODEL DISCUSSION (VALID FROM AUG 08 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN GOOD AGREEMENT ON THE EVOLUTION THE
FORECAST THROUGH THE FORECAST CYCLE. DISCREPANCIES START TO APPEAR
ONLY AFTER 120HRS. ECMWF SOLUTION HAS CORRECTED FROM PREVIOUS
FORECASTS...AND NOW ECMWF AND GFS SOLUTIONS ARE ALMOST THE SAME
THROUGHOUT THE ENTIRE CYCLE. THE ONLY MODEL SHOWING SOME
DISCREPANCIES IS THE UKMET MODEL...WHICH STARTS TO DIFFER AFTER
96HRS.

A WIDE UPPER LEVEL TROUGH IS APPROACHING THE COAST OF
CHILE...ASSOCIATED WITH A FRONT...EXTENDING FROM 40S-80W TO THE
SOUTHERN TIP OF TIERRA DEL FUEGO. AS IT CROSSES THE
CONTINENT...DUE TO LOW AVAILABILITY OF MOISTURE...IT WILL ONLY
PRODUCE LIGHT PRECIPITATION IN SOUTHERN CHILE. 05-10MM
ACCUMULATION AMOUNTS ARE EXPECTED FOR WEDNESDAY. BUT LATER THIS
WEEK...A SECOND FRONT IS EXPECTED TO CROSS THE SAME REGION. THIS
ONE WILL BE ACCOMPANIED BY SLIGHTLY HIGHER AMOUNTS OF PRECIPITABLE
WATER AS A SUBTROPICAL MOISTURE CONNECTION ARRIVES TO THE COASTS
OF CENTRAL CHILE. ACCUMULATION AMOUNTS OF 15-20MM ARE EXPECTED FOR
COASTAL CENTRAL CHILE ON SUNDAY...AND 10-15MM FOR MONDAY.

AT MID-LATITUDES...A ROBUST SURFACE CYCLONE IS INTENSIFYING AND IS
FORECAST TO EXIT THROUGH THE COASTS OF URUGUAY AND SOUTHERN BRASIL
LATE ON WEDNESDAY/EARLY THURSDAY. AS IT DOES...THE OCCLUDED LOW
WILL SUSTAIN PRECIPITACION OVER PROVINCIA DE BUENOS
AIRES...URUGUAY AND SOUTHERN BRASIL...EXPECTING MAXIMA AROUND
15-25MM...WITH A LOCAL PEAKS OF 25-50MM OVER THE COASTS OF RIO DE
LA PLATA FOR THURSDAY...ESPECIALLY ALONG SOUTHERN URUGUAY. ON
FRIDAY...THIS WILL DECREASE TO 15-20MM IN COASTAL URUGUAY AND
SOUTHERN BRASIL. ALSO ASSOCIATED WITH THIS CYCLONE...A SURFACE
FRONT WILL CROSS OVER PARAGUAY AND SOUTHERN BRASIL FROM THURSDAY
TO SATURDAY...TO FINALLY REMAIN STATIONARY OVER RIO DE JANEIRO
UNTIL THE END OF THE CYCLE. THIS...ALONG WITH FAVORABLE UPPER
DYNAMICAL FORCING IN ASSOCIATION WITH AN UPPER LEVEL JET... WILL
SUSTAIN PRECIPITACION OVER THE REGION. THIS WILL PEAK ON
WEDNESDAY-EARLY THURSDAY TO PRODUCE MAXIMA OF 20-35MM IN
SOUTHEASTERN PARAGUAY INTO PARTS OF SOUTHERN BRASIL. DECREASING
RAPIDLY ON THURSDAY.

NORTH OVER THE CONTINENT...PRECIPITATION IS FORECASTED FOR THE
AMAZON DELTA FROM THURSDAY TO SATURDAY...WITH ACCUMULATIONS OF
05-10MM...DECREASING TO 00-05MM FOR SATURDAY. SHOWERS ARE ALSO
EXPECTED FOR PERU AND WESTERN BOLIVIA ON THURSDAY...ACCUMULATING
GENERALLY 05-10MM. IN THE AMAZON...A SHEAR LINE WILL DEVELOP ON
THURSDAY FROM THE SURFACE FRONT THAT CROSSES PARAGUAY. BY THURSDAY
EVENING...THE SHEAR LINE WILL EXTEND INTO WESTERN
AMAZONAS-BRASIL...TOP ENHANCE PRECIPITATION AND PRODUCE MAXIMA OF
10-15MM/DAY FROM THURSDAY TO FRIDAY. FURTHER NORTHWEST ALONG THE
FOOTHILLS OF ECUADOR/SOUTHERN COLOMBIA EXPECTING MAXIMA OF 20-35MM.
FOR THE REST OF THE PERIOD...AMAZONAS...COLOMBIA...AND VENEZUELA
WILL GENERALLY ACCUMULATE BETWEEN 10-25MM/DAY.

SANCHEZ...SMN (ARGENTINA)
SALAZAR...SENAMHI (BOLIVIA)
GALVEZ...WPC (USA)