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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1448Z Oct 09, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1048 AM EDT THU OCT 09 2014

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

MODEL DISCUSSION (VALID FROM OCTOBER 09 AT 00UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS CONTINUE IN GOOD AGREEMENT ON FORECAST
EVOLUTION. CONFIDENCE IS HIGH...WITH THE EXCEPTION OF AREAS SOUTH
OF 45S AFTER 108-120 HRS.

UPPER TROUGH IS CROSSING THE ANTES AND NOW EXITING INTO THE
SOUTHERN ATLANTIC. THE TROUGH IS SUSTAINING A SURFACE COLD FRONT
THAT HAS RAPIDLY CROSSED THE RIO DE LA PLATA ACCOMPANIED BY A
PRE-FRONTAL SQUALL LINE. TO THE NORTH...A MOIST LOW-LEVEL JET IS
FEEDING MOISTURE TO THE SYSTEM WITH PRECIPITABLE WATER VALUES
FORECAST TO APPROACH 50MM LATER TODAY. STABILITY INDICES ALSO
SUGGEST UNSTABLE AIRMASS TO CONTINUE FAVORING STRONG THUNDERSTORMS
THROUGH FRIDAY MORNING. EXPECTING MAXIMUM ACCUMULATIONS OF
40-80MM/DAY STRETCHING FROM CHACO/FORMOSA INTO CORRIENTES/ENTRE
RIOS/MOST OF URUGUAY AND SOUTHERN RIO GRANDE DO SUL. ISOLATED
HIGHER AMOUNTS ARE EXPECTED IN STRONGER THUNDERSTORMS.

SYSTEM WILL START WEAKENING DURING FRIDAY...AS IT LOSES UPPER
SUPPORT. EXPECTING STILL ISOLATED STRONG THUNDERSTORMS ACROSS RIO
GRANDE DO SUL/CORRIENTES TO PRODUCE ISOLATED MAXIMA OF
25-50MM/DAY. BY SATURDAY INTO EARLY SUNDAY...STILL EXPECTING A FEW
ISOLATED TO SCATTERED THUNDERSTORMS NEAR/SOUTH OF THE MEANDERING
FRONT ACROSS SOUTHERN BRASIL. EXPECTING ACCUMULATIONS OF
15-30MM/DAY. NEW SHORT WAVE TROUGH IS TO APPROACH THE REGION
DURING THE PERIOD. THIS WILL STIMULATE THUNDERSTORM DEVELOPMENT
DURING SUNDAY INTO EARLY MONDAY...LEADING TO MAXIMA OF 20-40MM/DAY
IN PARTS OF SOUTHERN BRASIL. DURING MONDAY INTO EARLY
TUESDAY...WEAKENING SYSTEM WILL LEAD TO ISOLATED ACCUMULATIONS OF
15-20MM/DAY ACROSS PARANA IN BRASIL.

NORTH OVER THE CONTINENT...SUBTROPICAL HIGH IS MEANDERING BETWEEN
PERU AND EXTREME WESTERN BRASIL WHILE THE CAVADO DO NORDESTE
RETROGRESSES. AS THE CAVADO ENTERS CENTRAL/WESTERN BRASIL AND DRY
STABLE AIR MASS CONTINUES LINGERING IN THE AREA...EXPECTING
SCATTERED DIURNAL THUNDERSTORM ACTIVITY TO CONSTRAIN TO AREAS
NORTH OF 10S AND...FOR THE MOST PART...WEST OF 60. IN TERMS OF
ACCUMULATIONS...LARGEST AMOUNTS ARE EXPECTED ACROSS NORTHERN
AMAZONAS IN BRASIL INTO ECUADOR/EXTREME NORTHERN PERU WITH MAXIMA
OF 15-30MM/DAY THROUGH SUNDAY MORNING WITH A DECREASING TREND
AFTERWARDS. ENHANCED MOISTURE CONVERGENCE ALONG THE PERUVIAN
AMAZON WILL LEAD TO SCATTERED ACCUMULATIONS OF 15-30MM/DAY DURING
FRIDAY INTO EARLY SATURDAY.

ACROSS CHILE...SEASONALLY QUIET PATTERN CONTINUES. MOST FREQUENT
ACTIVITY IS EXPECTED TO THE SOUTH OF PUERTO MONTT...WHERE
SCATTERED SHOWERS ARE TO PRODUCE MAXIMUM ACCUMULATIONS OF
05-10MM/DAY.

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