146  
FXSA20 KWBC 251701  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
100 PM EDT TUE MAR 25 2025  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/DATA/NCCF/COM/GFS/PROD/  
 
SOUTH AMERICAN FORECAST BULLETIN FROM 25 MARCH 2025 AT 1700 UTC  
 
AN UPPER LOW CENTERED NEAR 34S/73W IS DRIFTING SOUTHEAST AND IS  
EXPECTED TO MOVE EAST OF NORTHERN PATAGONIA BY THURSDAY MORNING.  
MEANWHILE, AN UPPER TROUGH WILL APPROACH THE COAST OF CHILE BY  
THURSDAY AFTERNOON. HIGH PRESSURE CURRENTLY OVER SOUTHERN CHILE  
INTO CENTRAL PATAGONIA IS SHIFTING EAST-NORTHEAST INTO THE  
ATLANTIC, WEAKENING INTO AN UPPER RIDGE BY WEDNESDAY AFTERNOON  
OVER THE WESTERN SOUTH ATLANTIC. FURTHER NORTH, THE BOLIVIAN HIGH  
WILL REMAIN CENTERED OVER EASTERN BOLIVIA THROUGH THURSDAY,  
MAINTAINING UPPER-LEVEL DIVERGENCE CONDUCIVE TO CONVECTIVE  
DEVELOPMENT ACROSS TROPICAL SOUTH AMERICA.  
 
THE MID-LEVEL PATTERN MIRRORS UPPER-LEVEL DYNAMICS, WITH A  
MID-LEVEL LOW NEAR 33S/74W GRADUALLY DRIFTING SOUTHEAST. A  
MID-LEVEL HIGH OVER SOUTHERN CHILE INTO CENTRAL PATAGONIA WILL  
MOVE EAST-NORTHEAST TODAY, AHEAD OF AN APPROACHING MID-LEVEL  
TROUGH SET TO REACH THE COAST OF CHILE BY THURSDAY AFTERNOON. OVER  
THE TROPICAL REGION, A BROAD MID-LEVEL HIGH PRESSURE SYSTEM  
EXTENDS FROM EASTERN BOLIVIA INTO NORTHERN PARAGUAY AND THE  
PANTANAL REGION OF BRAZIL.  
 
LOW-LEVEL MOISTURE WILL REMAIN NEAR NORMAL ACROSS MOST OF BRAZIL,  
WHILE BEING BELOW NORMAL ACROSS NORTHEASTERN BRAZIL AND MOST OF  
VENEZUELA THROUGH THURSDAY. HOWEVER, SLIGHTLY ABOVE-NORMAL  
MOISTURE WILL PERSIST OVER BOLIVIA AND PARAGUAY, SUPPORTING  
LOCALIZED CONVECTIVE ACTIVITY. MORE SIGNIFICANTLY, WELL  
ABOVE-AVERAGE MOISTURE IS OBSERVED OVER ARGENTINA TODAY AND  
WEDNESDAY, SHIFTING INTO URUGUAY BY LATE WEDNESDAY. THIS IS DRIVEN  
BY NORTH LOW-LEVEL WINDS ADVECTING TROPICAL MOISTURE INTO THE  
REGION. MEANWHILE, A COLD FRONT WILL MOVE INTO SOUTHERN AND  
AUSTRAL CHILE BY WEDNESDAY AFTERNOON, BRINGING DRIER AIR BEHIND IT.  
 
ACROSS TROPICAL SOUTH AMERICA, DIURNAL HEATING WILL ENHANCE  
SHOWERS AND THUNDERSTORMS OVER CENTRAL BRAZIL, WESTERN ECUADOR,  
AND COLOMBIA, WHERE PERSISTENT ONSHORE FLOW INTERACTS WITH THE  
MOUNTAIN RANGE. ACROSS BOLIVIA & SOUTHERN PERU, LOW-LEVEL  
CONVERGENCE EAST OF THE ALTIPLANO, COUPLED WITH SLIGHTLY ANOMALOUS  
MOISTURE, WILL SUPPORT DAILY CONVECTIVE DEVELOPMENT. IN ARGENTINA,  
STRONG THUNDERSTORMS ARE EXPECTED LATE TONIGHT INTO WEDNESDAY  
MORNING, ESPECIALLY ACROSS LA PAMPA AND BUENOS AIRES, WHERE HIGHER  
THAN NORMAL MOISTURE INTERACTS WITH UPPER-LEVEL DIVERGENCE. IN  
CHILE, THE APPROACHING COLD FRONT WILL BRING DRIER AIR AND  
POTENTIALLY SUPPRESS CONVECTIVE DEVELOPMENT IN THE SOUTH.  
 
IN TERMS OF RAINFALL, THE MODEL GUIDANCEâ€INCLUDING DYNAMIC,  
ENSEMBLE, AND AI-DRIVEN FORECASTSâ€SHOWS GOOD AGREEMENT ON THE  
HEAVIEST RAINFALL LOCATIONS FROM TODAY INTO WEDNESDAY MORNING.  
MATO GROSSO INTO PARA, CENTRAL BOLIVIA, AND SOUTHERN PERU COULD  
OBSERVE 20-50MM DAILY DUE TO PERSISTENT CONVECTIVE ACTIVITY.  
WESTERN LA PAMPA INTO CUYO (ARGENTINA), UP TO 50MM, WITH POTENTIAL  
FOR STRONG THUNDERSTORMS DUE TO ENHANCED UPPER DIVERGENCE. SOME  
MODELS SUGGEST THAT WESTERN ECUADOR AND COLOMBIA CAN OBSERVE UP TO  
80MM IN TODAY, WITH 3-DAY ACCUMULATIONS REACHING 100-150MM IN  
ISOLATED AREAS.  
 
FOR ASSOCIATED QPF GRAPHICAL INFORMATION:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/INTERNATIONAL/SAM_DAY1-3.SHTML  
 
ALAMO...(WPC)  
 
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