583  
FXSA20 KWBC 041921  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
221 PM EST TUE MAR 04 2025  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/DATA/NCCF/COM/GFS/PROD/  
 
SOUTH AMERICA FORECAST BULLETIN 4 MAR 2025 AT 1930UTC:  
 
IN MID - LATITUDE SOUTH AMERICA...  
 
IN CENTRAL ARGENTINA, STARTING TUESDAY EVENING THROUGH THURSDAY  
MORNING, TWO SHORTWAVE UPPER TROUGHS WILL TRAVERSE THE REGION,  
FAVORING UPPER DIVERGENCE AND DIFFLUENCE. DURING THIS TIME, A  
SERIES OF SHORTWAVE TROUGHS AND A SURFACE STATIONARY FRONT WILL  
HELP TRIGGER CONVECTION ACROSS THIS REGION. AT THE 850 HPA LEVEL,  
THE SOUTH AMERICAN LOW LEVEL JET (SALLJ) WILL CONTINUE TO  
STRENGTHEN, HELPING DRIVE MOISTURE INTO CENTRAL ARGENTINA THROUGH  
THE NEXT THREE DAYS. AHEAD AND ALONG THIS FRONT, THE SUBTLE  
INCREASE IN MOISTURE WILL ENHANCE MOISTURE CONVERGENCE IN THE  
REGION. THESE CONDITIONS WILL FAVOR A TOTAL PRECIPITATION MAXIMA  
OF 20 - 40MM FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING, AND A  
TOTAL PRECIPITATION MAXIMA OF 25 - 50MM FROM WEDNESDAY MORNING  
THROUGH THURSDAY MORNING. SEVERE WEATHER RISKS EXIST DURING THIS  
PERIOD. AFTER THURSDAY EVENING, A POTENT UPPER TROUGH WILL BEGIN  
TO PROPAGATE ACROSS THE CHILEAN ANDES AND EXIT INTO THE ATLANTIC  
BASIN BY SATURDAY AFTERNOON. DURING THIS PERIOD, EXPECT AN  
INCREASE IN DIVERGENCE DURING ITS PASSAGE. FRONTOGENESIS IS ALSO  
ANTICIPATED ACROSS CENTRAL ARGENTINA, WHICH WILL HELP IN THE  
INITIATION OF PRECIPITATION. MOISTURE CONVERGENCE WILL BE MOST  
FAVORABLE AHEAD AND ALONG THE COLD FRONT, YIELDING TO A TOTAL  
PRECIPITATION MAXIMA OF 30 - 60MM FROM THURSDAY MORNING THROUGH  
FRIDAY MORNING WITH A SLIGHT RISK FOR SEVERE WEATHER.  
 
IN CHILE, FROM TUESDAY MORNING THROUGH THURSDAY MORNING, A SERIES  
OF UPPER JET STREAKS WILL CONTINUE TO FAVOR UPPER DIVERGENCE  
ACROSS CENTRAL CHILE. THE PERIOD OF GREATEST PRECIPITATION IMPACT  
IS WEDNESDAY MORNING THROUGH THURSDAY MORNING, WHEN A TOTAL  
PRECIPITATION MAXIMA OF 20 - 40MM IS POSSIBLE. DURING THIS PERIOD,  
EXPECT A JET STREAK TO MOVE ACROSS CENTRAL CHILE AHEAD OF THE  
PASSAGE OF A POTENT UPPER TROUGH ON THURSDAY, WHICH WILL YIELD TO  
AN INCREASE IN UPPER DIVERGENCE. AT THE LOWER LEVELS, A LONG FETCH  
MOISTURE PLUME, ACCOMPANIED BY STRONG WIND SPEEDS, WILL BEGIN TO  
IMPACT CENTRAL CHILE BY WEDNESDAY MORNING THROUGH THURSDAY  
AFTERNOON, YIELDING TO AN INCREASE IN MOISTURE CONVERGENCE AND  
OROGRAPHIC EFFECTS.  
 
IN TROPICAL SOUTH AMERICA...  
 
IN BOLIVIA, THE BOLIVIAN HIGH APPEARS TO BE DEVELOPING ACROSS  
NORTHWEST BOLIVIA AND SOUTH PERU, WHERE ITS AXIS IS ESTIMATED TO  
BE LOCATED AT 15S 70W ON TUESDAY AFTERNOON. IT IS ANTICIPATED TO  
STRENGTHEN TOWARDS THE END OF THE FORECAST CYCLE. THIS RIDGE WILL  
BE INTERACTING WITH A WEAKENING UPPER TROUGH, WITH AN AXIS AT 18S  
57W ON TUESDAY AFTERNOON, THROUGH THE NEXT THREE DAYS. ACROSS  
SOUTH - EAST BOLIVIA, EXPECT SPEED DIVERGENCE AND DIFFLUENCE TO BE  
MOST FAVORABLE FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING.  
THEREAFTER, THE UPPER LEVEL FLOW SPEED WILL DECREASE, BUT,  
DIVERGENCE WILL CONTINUE BEING FAVORABLE ACROSS THIS REGION FOR  
THE REMAINDER OF THE FORECAST CYCLE. AT THE LOWER LEVELS, A  
STATIONARY LOW LEVEL TROUGH WILL REMAIN ACROSS CENTRAL BOLIVIA,  
HELPING ENHANCE MOISTURE CONVERGENCE. THE GREATEST PRECIPITATION  
IMPACT WILL BE FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING,  
WHERE A TOTAL PRECIPITATION MAXIMA OF 30 - 60MM IS LIKELY IN THIS  
REGION. FROM WEDNESDAY MORNING THROUGH FRIDAY MORNING, EXPECT A  
DAILY TOTAL PRECIPITATION MAXIMA OF 20 - 40MM.  
 
IN ECUADOR AND BOLIVIA, UPPER LEVEL EASTERLIES WILL DOMINATE FOR  
THE NEXT THREE DAYS, ENHANCING UPPER DIVERGENCE AND DIFFLUENCE. AT  
THE MID - LEVELS, WEAK WIND SPEEDS WILL PERSIST THROUGH WEDNESDAY  
EVENING AND INCREASE AFTER, STIMULATING AN INCREASE OF SHEAR AFTER  
WEDNESDAY. AT THE LOW LEVELS, THE WIND DIRECTION WILL BE MOSTLY  
FROM THE WEST AND NORTH THROUGH TUESDAY AFTERNOON. THIS WILL FAVOR  
MOISTURE CONVERGENCE AND OROGRAPHIC EFFECTS. THUS, THESE  
CONDITIONS WILL YIELD TO A DAILY TOTAL PRECIPITATION MAXIMA OF 25  
- 50MM FROM TUESDAY MORNING THROUGH THURSDAY MORNING. AFTER  
WEDNESDAY, DAILY TOTAL PRECIPITATION MAXIMA WILL DECREASE SLIGHTLY  
IN ECUADOR.  
 
ELSEWHERE IN TROPICAL SOUTH AMERICA, DIURNAL CONVECTION WILL  
REMAIN FAVORABLE ALONG THE ITCZ AND NET THROUGH THE NEXT THREE  
DAYS. ALSO, A SERIES OF LOW LEVEL TROUGHS, ACCOMPANIED BY MOISTURE  
CONVERGENCE, WILL CONTINUE TO TRAVERSE NORTH BRASIL AND THE AMAZON  
BASIN, YIELDING TO HIGHER DAILY PRECIPITATION MAXIMA. IN NORTHEAST  
BRASIL, ALONG THE AMAZON DELTA, EXPECT THE PERIOD OF GREATEST  
PRECIPITATION IMPACT FROM TUESDAY MORNING THROUGH WEDNESDAY  
MORNING, WHEN THE MID LEVEL WINDS WILL BE WEAKEST. A TOTAL  
PRECIPITATION MAXIMA OF 25 - 50MM IS POSSIBLE DURING THIS PERIOD.  
 
TINOCO - MORALES...(WPC)  
 
 
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