SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
303 PM EST FRI JAN 10 2025

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

SOUTH AMERICAN FORECAST BULLETIN FOR 10 JAN 2025 AT 2000 UTC:

ON FRIDAY...THE SOUTH ATLANTIC CONVERGENCE ZONE (SACZ) IS EXPECTED
FROM RIO DE JANEIRO TO MATO GROSSO DO SUL BY THE EVENING HOURS.
THE MOISTURE CONTENT TO THE NORTH OF THE SACZ IS BEGINNING TO
DECREASE YET MODERATE TO HEAVY PRECIPITATION IS STILL EXPECTED IN
BRASIL DUE TO THE UPPER LEVEL DIFFLUENCE. THE UPPER LEVEL TROUGH
IN EAST BRASIL CONTINUES TO PROPAGATE TO THE EAST...WHILE
INTERACTING WITH THE BOLIVIAN HIGH TO ITS WEST. THE REGION OF
INTERACTION IS EXPECTED IN NORTHEAST BRASIL AND INTO THE SOUTHEAST
REGIONS ON FRIDAY. BY SATURDAY...THE BASE OF THE UPPER LEVEL
TROUGH MOVES INTO THE ATLANTIC OCEAN...SO THE BOLIVIAN HIGH BEGINS
TO ENTER THE EASTERN REGIONS OF BRASIL. THIS SHIFT IN THE UPPER
LEVEL CONDITIONS WILL BEGIN TO WEAKEN THE SACZ BEGINNING ON
SATURDAY...AND THE WEAKENING IS EXPECTED TO CONTINUE INTO SUNDAY.
THE AMOUNT OF AVAILABLE MOISTURE CONTINUES PRESENT IN NORTH AND
CENTRAL BRASIL...ASSISTING IN THE MODERATE TO HEAVY PRECIPITATION
EXPECTED ON SATURDAY. ON SUNDAY...A MID TO UPPER LEVEL TROUGH
ENTERS BRASIL FROM THE SOUTH AND EXTENDS INTO SOUTHEAST BRASIL BY
SUNDAY EVENING. THIS NEW UPPER TROUGH WILL INTERACT WITH THE
PERIPHERY OF THE BOLIVIAN HIGH AND PROVIDE VENTILATION FOR DEEP
CONVECTION IN EAST AND CENTRAL BRASIL. THE SACZ CONTINUES OVER
CENTRAL BRASIL FROM BAHIA TO GOIAS. IN TERMS OF PRECIPITATION...ON
FRIDAY...FROM SOUTH BAHIA TO NORTH MINAS GERAIS EXPECT MAXIMA OF
35-70MM. WHILE THE NORTH BAHIA...THROUGH TOCANTINS...AND MATO
GROSSO/SOUTH PARA EXPECT MAXIMA OF 20-45MM. FROM EASTERN PARA TO
PIAUI EXPECT MAXIMA OF 20-35MM. ON SATURDAY...EXPECT MAXIMA OF
35-70MM IN EAST BAHIA. WHILE THE REST OF BAHIA TO EAST MATO GROSSO
EXPECT MAXIMA OF 25-50MM. FROM NORTHERN REGIONS OF MATO GROSSO TO
NORTHEAST BRASIL EXPECT MAXIMA OF 20-35MM. ON
SUNDAY...BAHIA...PIAUI...SOUTH TOCANTINS...AND NORTH GOIAS CAN
EXPECT MAXIMA OF 25-50MM. A SURFACE TROUGH RESPONDING TO THE MID
TO UPPER LEVEL TROUGH ENTERING SOUTH BRASIL WILL FAVOR MOIST
SOUTHEASTERLY ONSHORE FLOW INTO RIO DE JANEIRO...WHERE EXPECT
MAXIMA OF 35-70MM.

TO THE WEST...A MID LEVEL TROUGH EXTENDS OVER SOUTH PERU INTO
WESTERN BOLIVIA...PROVIDING ASCENT IN THE REGION ON FRIDAY. IN
ADDITION TO THE FEATURE IN THE MID LEVELS...MOISTURE FROM THE
NORTHERN TROPICAL REGION IS BEING TRANSPORTED ALONG THE EASTERN
PRECORDILLERA OR FOOTHILLS OF THE ANDES MOUNTAINS...WHERE THEY ARE
CONVERGING. THE OROGRAPHIC EFFECTS IS FAVORING LIFT FROM SOUTH
PERU INTO BOLIVIA...PROVIDING A FAVORABLE ENVIRONMENT FOR HEAVY
PRECIPITATION ON FRIDAY AND SATURDAY. BY SUNDAY...THE ENTRANCE OF
A SHORT WAVE TROUGH IN THE MID TO UPPER LEVELS CONTRIBUTES TO THE
ASCENTS IN THE REGION...WHERE MODERATE TO HEAVY PRECIPITATION IS
EXPECTED TO CONTINUE INTO SUNDAY FROM SOUTH PERU THROUGH NORTH
ARGENTINA. ON FRIDAY...MAXIMA OF 30-60MM FROM NORTH LA PAZ THROUGH
WEST SANTA CRUZ-BOLIVIA. THERE IS A POTENTIAL FOR LOCALLY HIGHER
AMOUNTS. MAXIMA OF 20-35MM ARE EXPECTED IN NORTHERN BOLIVIA...AND
FROM SOUTH CENTRAL BOLIVIA TO JUJUY-ARGENTINA...AS WELL AS EAST
BOLIVIA TO NORTH PARAGUAY. MAXIMA OF 15-25MM ARE EXPECTED IN WEST
BOLIVIA. ON SATURDAY...THE CENTRAL REGION OF BOLIVIA CAN EXPECT
MAXIMA OF 40-80MM...HOWEVER LOCALIZED HIGHER TOTALS ARE EXPECTED
IN THE REGION. EASTERN BOLIVIA CAN EXPECT MAXIMA OF 20-45MM. ALONG
THE ANDES MOUNTAINS FROM PERU TO NORTH ARGENTINA EXPECT MAXIMA OF
15-25MM. BY SUNDAY...EXPECT MAXIMA OF 25-50MM IN NORTH BOLIVIA
INTO SOUTHERN PERU.

IN THE SOUTHERN REGION OF THE CONTINENT...CONDITIONS ARE EXPECTED
TO REMAIN DRIER AS AN UPPER RIDGE IS DEVELOPING THAT IS EXTENDING
FROM CENTRAL CHILE INTO CENTRAL ARGENTINA. HOWEVER...THE PASSING
OF SOME FRONTAL BOUNDARIES ON FRIDAY WILL BRING TRACE AMOUNTS OF
PRECIPITATION TO THE AUSTRAL REGION OF CHILE THAT ARE NOT EXPECTED
TO EXCEED 20MM. HOWEVER ON SATURDAY...AN ATMOSPHERIC RIVER IS
EXPECTED TO ENTER SOUTHERN CHILE BY THE AFTERNOON ON SATURDAY WITH
PRECIPITABLE WATER AMOUNTS OF OVER 30MM...WITH STRONG WINDS IN THE
LOWER LEVELS THAT WILL ENHANCE THE MOISTURE CONVERGENCE AS IT
INTERACTS WITH THE TERRAIN. IN THE UPPER LEVELS...A THE DIVERGENT
SIDE OF A MID TO UPPER LEVEL TROUGH IS INTERACTING WITH WITH THE
FEATURES IN THE LOWER LEVELS...ENHANCING THE VENTILATION FOR HEAVY
PRECIPITATION IN THE REGION. THIS WILL BE ACCOMPANIED BY AN UPPER
LEVEL JET THAT WILL PROVIDE FURTHER ASSISTANCE. ALTHOUGH THE
SYSTEM IS PROGRESSIVE...MAXIMA OF 25-50MM ARE EXPECTED IN SOUTH
AYSEN AND NORTH MAGALLANES-CHILE...WITH A CHANCE OF LOCALLY HIGHER
AMOUNTS. IN SOUTH MAGALLANES...EXPECT MAXIMA OF 15-20MM. A CHANCE
OF THUNDERSTORM ACTIVITY IS POSSIBLE. ON SUNDAY...ANOTHER MOIST
PLUME IS EXPECTED TO ENTER SOUTH CHILE...HOWEVER IT IS EXPECTED TO
BE MUCH WEAKER AND DRIER. EXPECT MAXIMA OF 20-35MM IN SOUTH
AYSEN/NORTH MAGALLANES.

CASTELLANOS...(WPC)