545  
FXSA20 KWBC 051935  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
234 PM EST WED MAR 05 2025  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/DATA/NCCF/COM/GFS/PROD/  
 
SOUTH AMERICA FORECAST BULLETIN 5 MAR 2025 AT 1945UTC:  
 
IN MID - LATITUDE SOUTH AMERICA...  
 
IN CENTRAL ARGENTINA, IN THE LOW LEVELS, A STRONG SOUTH AMERICA  
LOW LEVEL JET (SALLJ) WILL BEGIN DOMINATING CENTRAL SOUTH AMERICA,  
HELPING CHANNEL INTO CENTRAL ARGENTINA, YIELDING ABOVE AVERAGE  
PRECIPITABLE WATER FOR THE NEXT THREE DAYS. IN THE UPPER LEVELS,  
SPEED DIVERGENCE AND UPPER DIFFLUENCE WILL REMAIN FAVORABLE AHEAD  
OF THE PASSAGE OF AN UPPER TROUGH, WHICH WILL BEGIN MOVING ACROSS  
THE CHILEAN ANDES AND INTO WEST - CENTRAL ARGENTINA BY WEDNESDAY  
AFTERNOON. THIS TROUGH IS EXPECTED TO EXIT INTO THE ATLANTIC BASIN  
BY THURSDAY MORNING. DURING THIS PERIOD, ANTICIPATE A SURFACE  
STATIONARY FRONT TO BE PRESENT ACROSS THE LA PAMPA - BUENOS  
AIRES, SOUTH CORDOBA - SANTA FE, AND EAST CUYO PROVINCES. ALONG  
AND AHEAD OF THIS FRONT, LOW LEVEL MOISTURE CONVERGENCE WILL BE  
FAVORABLE, YIELDING TO A TOTAL PRECIPITATION MAXIMA OF 25 - 50MM  
FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING.  
 
STARTING THURSDAY EVENING, ANOTHER SLOW MOVING POTENT UPPER AND  
STACKED MID LEVEL TROUGH WILL BEGIN TO PROPAGATE ACROSS THE  
CENTRAL CHILEAN ANDES. THE INCREASE OF UPPER LEVEL WIND SPEEDS  
WILL ALSO FAVOR THE ROTATION OF THE ATMOSPHERE IN THE LOWER  
LEVELS, AND HELP INDUCE FRONTOGENESIS ACROSS CENTRAL ARGENTINA.  
AFTER THURSDAY EVENING, EXPECT THE DEVELOPMENT OF A FAST MOVING  
COLD FRONT ACROSS CENTRAL ARGENTINA. BY FRIDAY EVENING, THE FRONT  
WILL BE ACROSS NORTH - CENTRAL ARGENTINA. AHEAD AND ALONG THE  
FRONT, EXPECT AN INCREASE IN MOISTURE CONVERGENCE, WHICH IS BEING  
ENHANCED BY THE SALLJ. THESE CONDITIONS WILL YIELD A TOTAL  
PRECIPITATION MAXIMA OF 35 - 70MM FROM THURSDAY MORNING THROUGH  
FRIDAY MORNING ACROSS SOUTH - CENTRAL ARGENTINA WITH A SLIGHT RISK  
FOR SEVERE WEATHER. BY FRIDAY MORNING THROUGH SATURDAY MORNING, A  
TOTAL PRECIPITATING MAXIMA OF 30 - 60MM IS POSSIBLE, WITH A SLIGHT  
RISK FOR SEVERE WEATHER ACROSS CENTRAL ARGENTINA.  
 
IN CHILE, AT THE UPPER LEVELS, THROUGH THURSDAY EVENING, EXPECT AN  
INCREASE IN WIND SPEEDS, WHICH IS ASSOCIATED WITH A STRENGTHENING  
UPPER JET STREAK THAT IS AHEAD OF A POTENT UPPER TROUGH. THIS WILL  
FAVOR AN INCREASE IN UPPER DIVERGENCE ACROSS CENTRAL CHILE THROUGH  
THURSDAY EVENING. AT THE LOW LEVELS, A LONG FETCH MOISTURE PLUME  
WILL CONTINUE TO IMPACT THIS REGION, WITH WINDS SPEEDS BEING  
FAVORABLY STRONG THROUGH THURSDAY MORNING. THIS MOISTURE PLUME  
WILL WEAKEN THEREAFTER AS IT QUICKLY PROPAGATES NORTHWARD. THROUGH  
THURSDAY MORNING, A TOTAL PRECIPITATION MAXIMA OF 20 - 45MM IS  
POSSIBLE. THEREAFTER ON THURSDAY THROUGH FRIDAY MORNING, THE  
AFOREMENTIONED PROPAGATING POTENT UPPER TROUGH WILL ALSO BE  
ACCOMPANIED BY MID - LEVEL VORTICITY ADVECTION. A SLIGHT INCREASE  
IN MOISTURE, ASSOCIATED WITH A WEAK MOISTURE PLUME, WILL ENHANCE  
MOISTURE CONVERGENCE AND FAVOR OROGRAPHIC EFFECTS ON THURSDAY  
EVENING. THESE CONDITIONS WILL YIELD TO A TOTAL PRECIPITATION  
MAXIMA OF 20 - 45MM FROM THURSDAY MORNING THROUGH FRIDAY MORNING.  
 
IN TROPICAL SOUTH AMERICA...  
 
IN THE UPPER LEVELS, A FEATURE OF INTEREST IS A BROAD RIDGE  
RESEMBLING THE BOLIVIA HIGH CENTERED AT 14S 81W ON WEDNESDAY  
AFTERNOON. THIS RIDGE WILL FAVOR SPEED DIVERGENCE FOR THE NEXT  
THREE DAYS ACROSS EAST PERU AND BOLIVIA. IN CENTRAL BOLIVIA, A  
PRE-EXISTING SURFACE TROUGH WILL PERSIST THROUGH FRIDAY MORNING  
AND FAVOR AN INCREASE IN MOISTURE CONVERGENCE. THESE CONDITIONS  
WILL YIELD A DAILY TOTAL PRECIPITATION MAXIMA OF 20 - 45MM.  
 
ANOTHER REGION OF INTEREST IS ECUADOR AND COLOMBIA, WHERE AT THE  
UPPER LEVELS, EXPECT AN INCREASE IN EASTERLY WIND SPEEDS, FAVORING  
SPEED DIVERGENCE FOR THE NEXT THREE DAYS. IN THE MID - LEVELS, THE  
WIND FLOW DIRECTION WILL ALSO BEGIN TO SHIFT TO A MORE WESTERLY  
DIRECTION AFTER WEDNESDAY EVENING. EXPECT SHEAR AFTER THURSDAY  
MORNING, LIMITING THE POTENTIAL FOR DEEP CONVECTION. IN THE LOW  
LEVELS, MOISTURE CONVERGENCE WILL BE MOST FAVORABLE THROUGH  
THURSDAY EVENING, BEFORE THE WIND DIRECTION BEGINS SHIFTING TO A  
MORE EAST AND WEST DIRECTION. THUS, EXPECT THE GREATEST TOTAL  
PRECIPITATION MAXIMA TO OCCUR FROM WEDNESDAY MORNING THROUGH  
THURSDAY MORNING, WITH A MAXIMUM OF 30 - 60MM POSSIBLE.  
 
IN NORTHEAST BRASIL, THE INTERACTION BETWEEN THE EASTERLY TRADES  
AND ITCZ WILL CONTINUE TO FAVOR CONVERGENCE ACROSS THIS REGION.  
ALSO, SERIES OF LOW LEVEL TROUGHS AND ASSOCIATED MOISTURE  
CONVERGENCE WILL FURTHER INCREASE PRECIPITATION POTENTIALS. THESE  
CONDITIONS, COUPLED WITH UPPER DIVERGENCE, WILL FAVOR DAILY TOTAL  
PRECIPITATION MAXIMA OF 25 - 50MM FROM WEDNESDAY MORNING THROUGH  
FRIDAY MORNING.  
 
ELSEWHERE IN TROPICAL SOUTH AMERICA, THE ITCZ AND NET WILL  
CONTINUE TO FAVOR DIURNAL CONVECTION ACROSS THE REGION. IN THE  
LOW, MID, AND UPPER LEVELS, ANTICIPATED AN OVERALL INCREASE IN  
EASTERLY WINDS AFTER THURSDAY MORNING, WHICH WILL FAVOR A  
MOISTENING OF THE ATMOSPHERE. FOR THE NEXT THREE DAYS, EXPECT A  
SERIES OF LOW LEVEL TROUGHS, ACCOMPANIED BY MOISTURE CONVERGENCE,  
TO FAVOR HIGHER PRECIPITATION TOTALS ACROSS NORTH BRASIL AND THE  
AMAZON BASIN.  
 
TINOCO - MORALES...(WPC)  
LEDESMA...(WPC)  
 

 
 
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