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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1537Z Oct 28, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1137 AM EDT TUE OCT 28 2014

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

MODEL DISCUSSION (VALID FROM OCTOBER 28 AT 00UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS CONTINUE IN GOOD AGREEMENT ON FORECAST
EVOLUTION. SOME DIFFERENCES ARISE OFF SOUTHERN CHILE IN SHORT WAVE
PERTURBATIONS STREAMING FROM THE SOUTH/SOUTHEAST BY LATE CYCLE.

ACROSS SOUTHERN CHILE...EXPECTING ACTIVE PATTERN OF CONVECTION
EARLY IN THE CYCLE AS UPPER TROUGH AND ASSOCIATED SURFACE FRONTS
CROSS THE ANDES. THIS WILL LEAD TO ISOLATED TO SCATTERED MAXIMUM
ACCUMULATIONS OF 10-15MM/DAY SOUTH OF TEMUCO INTO THE MAGALLANES
REGION THROUGH THURSDAY MORNING. A COLD ADVECTIVE PATTERN WILL
GRADUALLY ESTABLISH AS A POTENT RIDGE ORGANIZES IN THE EASTERN
PACIFIC. THIS WILL DRAW A MASS OF ANTARCTIC ORIGINS NORTHWARD
ACROSS SOUTHERN CHILE...TO SUSTAIN SNOWFALL MOSTLY IN THE
MAGALLANES REGION AND IN HIGHER ELEVATIONS OF THE AYSEN REGION.
EXPECTING SNOW SHOWERS TO DEVELOP LATE ON TUESDAY AND PEAK DURING
WEDNESDAY EVENING. LARGEST ACCUMULATIONS ARE EXPECTED DURING
WEDNESDAY EVENING WITH MAXIMA OF 00-05CM OF SNOW. PRECIPITATION IS
TO DECREASE AFTERWARDS AND A WARMING TREND WILL ESTABLISH AFTER
THURSDAY.

UPPER TROUGH IN SOUTHEASTERN BRAZIL CONTINUES INTERACTING WITH
MOIST AND UNSTABLE AIRMASS IN THE REGION. THIS...IN INTERACTION
WITH OROGRAPHY...WILL CONTINUE SUSTAINING HEAVY RAINFALL AMOUNTS
IN PARTS OF ESPIRITO SANTO AND EASTERN MINAS GERAIS. THROUGH
WEDNESDAY MORNING EXPECTING MAXIMA OF 40-80MM/DAY. BY WEDNESDAY
INTO THURSDAY ACCUMULATIONS ARE TO DECREASE AFTERWARDS.

OTHER REGION OF INTEREST WILL BE CENTRAL ARGENTINA. SEVERAL SHORT
WAVE TROUGHS ARE TO CROSS THE ANDES AND INTERACT WITH MOIST AND
UNSTABLE AIR MASS ACROSS CENTRAL PORTIONS OF ARGENTINA. AN UPPER
TROUGH IS CROSSING TODAY TUESDAY AND WILL CONTINUE ENHANCING THE
DEVELOPMENT OF SEVERE WEATHER AHEAD OF A DEVELOPING SURFACE FRONT.
EXPECTING ACCUMULATIONS OF 40-80MM/DAY WITH STRONGEST
THUNDERSTORMS TO EXTEND ACROSS MOST OF THE BUENOS AIRES PROVINCE
INTO THE RIO DE LA PLATA REGION. CONVECTION IS TO CONTINUE
REDEVELOPING DURING WEDNESDAY. THIS WILL LEAD TO LARGEST
ACCUMULATIONS FROM ENTRE RIOS/CORRIENTES INTO URUGUAY/WESTERN RIO
GRANDE DO SUL...WITH MAXIMA OF 50-100MM/DAY. ISOLATED HIGHER
AMOUNTS ARE EXPECTED IN STRONGEST THUNDERSTORMS. DURING THURSDAY
INTO FRIDAY...STRONGEST CONVECTION WILL CONCENTRATE ACROSS THE
UPPER MESOPOTAMIA REGION TO PRODUCE MAXIMA OF 20-35MM/DAY FROM
SOUTHEASTERN PARAGUAY INTO MISIONES AND THE INTERIOR OF SOUTHERN
BRASIL. LATER IN THE CYCLE...AS THE BOLIVIAN HIGH RESTRUCTURES
FROM SOUTHERN PERU INTO SOUTHERN BOLIVIA...VENTILATION WILL
INCREASE IN THE REGION. FURTHERMORE...AN INTENSIFICATION OF THE
CHACO LOW BY THURSDAY INTO FRIDAY WILL LEAD TO THE ADVECTION OF
MOISTURE AND INSTABILITY FROM SOUTHWESTERN BRASIL INTO THE CHACO
PARAGUAYO AND EASTERN BOLIVIA. THIS PATTERN IS TO INCREASE THE
COVERAGE OF THUNDERSTORMS IN THE REGION WITH SCATTERED MAXIMA OF
20-45MM/DAY. MODELS ARE THEN UNDULATING A SURFACE FRONT ACROSS
SOUTHERN BOLIVIA DURING FRIDAY INTO SATURDAY. THIS WILL LEAD TO
ENHANCED MOISTURE CONVERGENCE ACROSS EASTERN BOLIVIA/SOUTHERN PERU
INTO RONDONIA/ACRE AND MATO GROSSO. AS VENTILATION WILL REMAIN
FAVORABLE ALONG NORTHERN PERIPHERY OF SUBTROPICAL HIGH...EXPECTING
STRONG THUNDERSTORMS OVER A LARGE AREA TO PRODUCE RAINFALL AMOUNTS
IN THE ORDER OF 40-80MM/DAY. ENHANCED VENTILATION WILL ALSO
DOMINATE THE CENTRAL ANDES IN PERU AND BOLIVIA TO SUSTAIN
SCATTERED MAXIMA OF 15-25MM/DAY.

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