715  
FXSA20 KWBC 271855  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
154 PM EST THU FEB 27 2025  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/DATA/NCCF/COM/GFS/PROD/  
 
SOUTH AMERICA FORECAST BULLETIN 27 FEB 2025 AT 1900UTC:  
 
IN MID - LATITUDE SOUTH AMERICA...  
 
IN NORTH - CENTRAL ARGENTINA AND URUGUAY, IN THE UPPER LEVELS,  
SPEED DIVERGENCE CONTINUES TO DOMINATE IN THE REGION AHEAD OF THE  
PASSAGE OF A POTENT UPPER TROUGH, WITH AN AXIS AT 28S 83W AND 36S  
80W ON THURSDAY AFTERNOON. THIS TROUGH WILL TRAVERSE THE REGION  
STARTING FRIDAY MORNING THROUGH FRIDAY EVENING. THEREAFTER, EXPECT  
A RETURN IN SPEED DIVERGENCE ACROSS THE REGION THROUGH SUNDAY  
MORNING, WHEN A JET STREAK IS LIKELY TO FORM ACROSS CENTRAL  
ARGENTINA. THUS, DIVERGENCE WILL BE FAVORABLE FOR THE NEXT THREE  
DAYS IN THIS REGION. THE ACCELERATED UPPER FLOW WILL ALSO CONTINUE  
TO SUSTAIN MID - LEVEL SHORTWAVE TROUGHS AND MEANDERING SURFACE  
TROUGHS IN THE LOW LEVELS THROUGH THE NEXT THREE DAYS.  
 
THROUGH FRIDAY MORNING, THE LOW LEVEL MOISTURE TRANSPORT FROM  
BOLIVIA WILL CONTINUE TO FAVOR AN INCREASE OF MOISTURE THROUGH  
SATURDAY MORNING ACROSS THE AMAZON BASIN INTO NORTH ARGENTINA,  
URUGUAY, AND SOUTH BRASIL. MOISTURE CONVERGENCE WILL BE MOST  
FAVORABLE ALONG AND AHEAD OF A MEANDERING SURFACE TROUGH IN THIS  
REGION THROUGH THE NEXT THREE DAYS. FROM THURSDAY MORNING THROUGH  
FRIDAY MORNING, EXPECT A TOTAL PRECIPITATION MAXIMA OF 25 - 50MM  
ACROSS THE BUENOS AIRES REGION OF ARGENTINA, WHERE A MARGINAL RISK  
FOR SEVERE WEATHER IS POSSIBLE. FROM FRIDAY MORNING THROUGH  
SATURDAY MORNING, THERE WILL BE AN OVERALL INCREASE IN MOISTURE IN  
THE REGION, AND THUS YIELDING TO A GREATER TOTAL PRECIPITATION  
MAXIMA OF 30 - 60MM WITH A SLIGHT RISK FOR SEVERE WEATHER. AFTER  
SATURDAY MORNING, AN UPPER TROUGH LOCATED ACROSS SOUTH - EAST  
BRASIL WILL RETROGRADE WEST AND ENHANCE LOW LEVEL EASTERLY FLOW  
ACCOMPANIED BY DRY AIR ADVECTION INTO NORTH ARGENTINA, URUGUAY,  
AND SOUTH BRASIL. THOUGH SPEED DIVERGENCE WILL BE FAVORABLE DURING  
THIS PERIOD, EXPECT A DECREASE IN PRECIPITATION ACCUMULATIONS FROM  
SATURDAY MORNING THROUGH SUNDAY MORNING.  
 
IN CHILE, A SERIES OF MID - TO -UPPER LEVEL TROUGHS WILL CONTINUE  
TO IMPACT THE REGION. THE PERIOD OF GREATEST PRECIPITATION IMPACT  
WILL BE FROM SATURDAY MORNING THROUGH SUNDAY EVENING. A POTENT  
UPPER TROUGH WILL BE MOVING ACROSS THIS REGION THROUGH THIS PERIOD  
AND WILL BE ACCOMPANIED BY A LONG FETCH MOISTURE TONGUE IN THE  
LOWER LEVELS. IN THE LOWER LEVELS, AN INCREASE IN WIND SPEEDS WILL  
FAVOR OROGRAPHIC EFFECTS. THESE CONDITIONS WILL FAVOR A TOTAL  
PRECIPITATION MAXIMA OF 15 - 25MM DURING THIS PERIOD FOR NORTH  
AUSTRAL CHILE.  
 
IN TROPICAL SOUTH AMERICA...  
 
IN THE UPPER LEVELS, A SYSTEM OF INTEREST IS A POTENT UPPER TROUGH  
WITH AN AXIS 18S 44W ON THURSDAY AFTERNOON. THIS SYSTEM IS  
EXPECTED TO BROADEN AND RETROGRADE WESTWARD. BY SUNDAY MORNING,  
ITS AXIS SHOULD BE LOCATED AT 19S 53W. THIS FEATURE WILL FAVOR THE  
INCREASE OF LOW LEVEL EASTERLY WINDS ACROSS SOUTH BRASIL,  
PARAGUAY, AND SOUTHEAST BOLIVIA. NOTE, DIURNAL CONVECTION WILL  
PERSIST, ESPECIALLY ALONG ITS WEST PERIPHERY. OVERALL, THIS UPPER  
LEVEL FEATURE SHOULD YIELD TO A DECREASE IN PRECIPITATION ACROSS  
THIS REGION.  
 
ANOTHER FEATURE OF INTEREST IS THE RETURN OF UPPER LEVEL EASTERLY  
WINDS ACROSS COLOMBIA, ECUADOR, AND PERU STARTING SATURDAY  
MORNING, WHICH WILL FAVOR UUPER DIFFLUENCE AND UPPER DIVERGENCE  
THROUGH THE REST OF THE FORECAST CYCLE. IN THE LOW LEVELS, NORTH  
AND WESTERLY FLOW WILL CONTINUE TO IMPACT THE REGION, ENHANCING  
MOISTURE CONVERGENCE AND OROGRAPHIC EFFECTS ACROSS THE COAST. THE  
GREATEST PRECIPITATION IMPACT WILL OCCUR FROM THURSDAY MORNING  
THROUGH SATURDAY MORNING WHEN UPPER DIVERGENCE AND MOISTURE  
CONVERGENCE WILL BE MOST FAVORABLE, WHERE A DAILY TOTAL  
PRECIPITATION MAXIMA OF 30 - 60MM IS LIKELY.  
 
ELSEWHERE, IN THE NORTH - CENTRAL AMAZON BASIN, SPEED DIVERGENCE  
WILL BECOME FAVORABLE AFTER SATURDAY AFTERNOON. DURING THIS  
PERIOD, AN INCREASE IN MOISTURE ACROSS THE REGION IS EXPECTED,  
YIELDING TO A TOTAL PRECIPITATION MAXIMA OF 25 - 50MM FROM  
SATURDAY MORNING THROUGH SUNDAY MORNING.  
 
IN NORTHEAST BRASIL, A SERIES OF LOW LEVEL TROUGHS, ASSOCIATED  
WITH MOISTURE CONVERGENCE, AND THE ITCZ WILL CONTINUE TO FAVOR THE  
DEVELOPMENT OF CONVECTION. AS THE AFOREMENTIONED BRASILIAN UPPER  
TROUGH RETROGRADES, AN INCREASE IN UPPER DIFFLUENCE AND DIVERGENCE  
IS POSSIBLE IN THIS REGION. THE PERIOD OF GREATEST PRECIPITATION  
IMPACT WILL BE SATURDAY MORNING THROUGH SUNDAY MORNING, WHEN AN  
INTENSE MOISTURE PLUME IS EXPECT TO MIGRATE ACROSS THIS REGION.  
THESE CONDITIONS WILL YIELD A TOTAL PREICPITAITON MAXIMA OF 30 -  
60MM DURING THIS PERIOD.  
 
ELSEWHERE IN TROPICAL SOUTH AMERICA, THE ITCZ AND NET WILL  
CONTINUE TO FAVOR THE DIURNAL CONVECTION. LOW LEVEL TROUGHS WILL  
CONTINUE TO PROPAGATE ACROSS THE REGION AND WILL BE ACCOMPANIED BY  
MOISTURE CONVERGENCE, HELPING YIELD TO HIGHER TOTAL PRECIPITATION  
MAXIMA.  
 
MORALES...(WPC)  
 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.
The Nexlab HPC Page
Main Text Page