SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1152 AM EDT THU MAY 09 2013

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

MODEL COMPARISON (VALID FROM 00 UTC MAY 09): GLOBAL MODELS AND
ENSEMBLE MEMBERS CONTINUE AGREEING IN FORECAST EVOLUTION WITH THE
EXCEPTION OF MINOR DETAILS IN EVOLUTION OF SHORT WAVE TROUGHS.
FORECAST CONFIDENCE IS HIGH THROUGH 84-96 HRS...AND REMAINS HIGH
THROUGH THE CYCLE IN THE EVOLUTION OF LARGE SCALE FEATURES.

MID-UPPER TROUGH IS APPROACHING SOUTHERN CHILE WITH ASSOCIATED
TRANS OF FRONTS. BEST MOISTURE CONVERGENCE WILL PRODUCE LOCALLY
MODERATE RAINFALL ACROSS SOUTHERN CHILE WITH ACCUMULATIONS OF
10-15MM/DAY BETWEEN LOS ANGELES/TEMUCO AND ISLA CHILOE TODAY.
AMOUNTS ARE TO DECREASE LATER IN THE CYCLE LEADING TO NUMEROUS
SHOWERS AND WINDY CONDITIONS PERSISTING THROUGH LATE CYCLE IN
REGIONS TO THE SOUTH OF ISLA CHILOE. COLD AIR MASS WILL ARRIVE IN
DAY 03. THIS WILL LEAD TO THE DEVELOPMENT OF SHOW SHOWERS IN
REGIONS TO THE SOUTH OF ISLA WELLINGTON INTO TIERRA DEL FUEGO
AND...TO A LESSER EXTENT...SOUTHERN PATAGONIA. SNOW SHOWERS AND
WINDY CONDITIONS ARE TO PERSIST ON DAYS 04 AND 05 WITH A
DECREASING TREND IN ACCUMULATIONS.

TROUGH IN THE NORTHERN STREAM WILL CROSS THE ANDES ON DAY 02.
HEIGHT FALLS WILL INDUCE FRONTOGENESIS ACROSS NORTH-CENTRAL
ARGENTINA...FROM CORDOBA/SANTIAGO DEL ESTERO INTO THE RIO DE LA
PLATA BASIN BY 48 HRS. FRONT WILL SLOWLY MOVE NORTHWARD INTO RIO
GRANDE DO SUL-RESISTENCIA BY 78 HRS TO THEN MEANDER IN THE REGION.
SHORT WAVE TROUGH WILL RAPIDLY EXIT INTO THE SOUTH ATLANTIC ON DAY
03 WHILE A BROADER TROUGH ORGANIZES TO THE WEST. BROAD TROUGH
PATTERN PERSISTING ACROSS THE SOUTHERN CONE WILL SUSTAIN ROUNDS OF
CONVECTION ALONG AND TO THE NORTH OF SURFACE FRONT. WET PATTERN IS
THUS TO ESTABLISH ACROSS MID-SECTIONS OF THE CONTINENT TO PERSIST
FROM DAY 03 INTO THE END OF THE FORECAST CYCLE. EXPECTING MODERATE
ACCUMULATIONS STARTING BY 36-60 HRS WITH AMOUNTS OF 15-25MM/DAY
ACROSS NORTHEASTERN ARGENTINA INTO THE RIO DE LA PLATA BASIN.
BETTER DYNAMICS AND MOISTURE AVAILABILITY WILL LEAD TO AN INCREASE
BY 60-84 HRS TO 25-50MM/DAY...MOSTLY ACROSS WESTERN/CENTRAL
PARAGUAY INTO CHACO/CORRIENTES AND WESTERN RIO GRANDE DO SUL.
AFTERWARDS...EXPECTING AMOUNTS IN THE 20-40MM/DAY RANGE WITH
STRONGEST CONVECTION TO CENTER MOSTLY ACROSS PARAGUAY/EXTREME
NORTHERN ARGENTINA AND WESTERN RIO GRANDE DO SUL/SANTA CATARINA.

INLAND IN TROPICAL SOUTH AMERICA...EXPECTING STRONGEST CONVECTION
ACROSS AMAPA/EASTERN PARA AND THE EASTERN GUIANAS ASSOCIATED WITH
AN ACTIVE ITCZ AND APPROPRIATE VENTILATION. INITIALLY...EXPECTING
ACCUMULATIONS OF 25-50MM/DAY DECREASING THROUGH THE CYCLE. ACTIVE
CONVECTION WILL ALSO PERSIST ACROSS THE NORDESTE INTERIOR TO THE
WEST OF CEARA INTO NORTHERN TOCANTINS/SOUTHEASTERN PARA...WHILE
PROPER VENTILATION PERSISTS. EXPECTING HEAVIEST AMOUNTS THROUGH 36
HRS...REACHING ACCUMULATIONS OF 20-40MM/DAY...DECREASING TO
15-30MM/DAY ON DAY 02. AMOUNTS ARE TO RAPIDLY DECREASE AFTERWARDS
AS STRONGEST CONVECTION REMAINS ACROSS NORTHERN BRASIL ALONG THE
NET. ACTIVE CONVECTION WILL ALSO DEVELOP ACROSS COASTAL BAHIA INTO
COASTAL PERNAMBUCO AHEAD OF STATIONARY FRONT. PRECIPITABLE WATER
WILL BE HIGH...AND A SOUTHEASTERLY JET WILL ENHANCE CONVERGENCE.
THIS WILL LEAD TO ACCUMULATIONS OF 20-45MM/DAY THROUGH 36
HRS...GRADUALLY DECREASING TO 15-20MM/DAY BY 84-108 HRS.

MAQUEDA...DINAC (PARAGUAY)
SILVA DE SOUZA...INMET (BRASIL)
DAVISON...WPC (USA)
GALVEZ...WPC (USA)