597  
FXSA20 KWBC 281931  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
230 PM EST FRI FEB 28 2025  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/DATA/NCCF/COM/GFS/PROD/  
 
SOUTH AMERICA FORECAST BULLETIN 28 FEB 2025 AT 1930UTC:  
 
IN MID - LATITUDE SOUTH AMERICA...  
 
IN CENTRAL ARGENTINA AND SOUTH URUGUAY, IN THE UPPER LEVELS,  
STARTING FRIDAY MORNING, AN UPPER SHORTWAVE TROUGH WILL TRAVERSE  
ACROSS THE REGION, EXITING INTO THE ATLANTIC BASIN BY FRIDAY  
EVENING, HELPING ENHANCE UPPER DIVERGENCE DURING THIS PERIOD.  
THEREAFTER, AN INCREASE IN UPPER LEVEL WIND SPEEDS IS ANTICIPATED  
AND WILL FAVOR SPEED DIVERGENCE THROUGH MONDAY MORNING. NOTE, THE  
ACCELERATION IN THE UPPER FLOW IS LIKELY DUE TO THE INTERACTIONS  
BETWEEN AN UPPER TROUGH ACROSS SOUTH BRASIL, FORMATION OF THE  
BOLIVIAN HIGH, AND THE FORMATION OF AN UPPER RIDGE IN THE  
ATLANTIC. THIS FLOW WILL FAVOR THE FORMATION AND PROPAGATION OF  
MID - LEVEL SHORTWAVE TROUGHS AND THE MAINTENANCE OF MEANDERING  
SURFACE TROUGHS. IN THE LOW LEVELS, THE SOUTH AMERICAN LOW LEVEL  
JET (SALLJ) WILL CONTINUE TO INFLUENCE THE TRANSPORT OF MOISTURE  
INTO THIS REGION THROUGH MONDAY MORNING, FAVORING MOISTURE  
CONVERGENCE DURING THIS PERIOD. THE SALLJ WILL BEGIN TO WEAKEN  
THEREAFTER DUE TO INCREASING SUBSIDENCE ASSOCIATED WITH THE UPPER  
TROUGH ACROSS SOUTH BRASIL. FROM FRIDAY MORNING THROUGH SATURDAY  
MORNING, A TOTAL PRECIPITATION MAXIMA OF 20 - 45MM IS LIKELY  
ACROSS LA PAMPA - BUENOS AIRES AND A MAXIMUM OF 20 - 35MM IN RIO  
DE LA PLATA, WHERE A MARGINAL RISK FOR SEVERE WEATHER IS POSSIBLE  
IN THESE REGIONS. NOTE, CONVECTION MAY BE MOST FAVORABLE DURING  
FRIDAY. ANOTHER PERIOD OF INTEREST WILL BE SUNDAY MORNING THROUGH  
MONDAY MORNING. ON SUNDAY, MID - LEVEL VORTICITY ADVECTION WILL BE  
MOST FAVORABLE, YIELDING TO A TOTAL PRECIPITATION MAXIMA OF 30 -  
60MM ACCOMPANIED WITH A MARGINAL RISK FOR SEVERE WEATHER ACROSS  
THE LA PAMPA - BUENOS AIRES REGION.  
 
IN CHILE, A SERIES OF UPPER TROUGHS AND JET STREAKS WILL CONTINUE  
TO DRIVE THE UPPER LEVEL DYNAMIC REGIME. SURFACE FRONTS  
ACCOMPANIED BY MOISTURE PLUMES WILL CONTINUE TO ENHANCE MOISTURE  
CONVERGENCE AND OROGRAPHIC EFFECTS ACROSS SOUTHERN CHILE, YIELDING  
TO HIGHER TOTAL PRECIPITATION MAXIMA IN THIS REGION THROUGH SUNDAY  
MORNING. FROM SUNDAY MORNING THROUGH MONDAY MORNING, A POTENT  
UPPER TROUGH, INCREASING MID - LEVEL VORTICITY ADVECTION, AN  
INCREASE IN LOW LEVEL MOISTURE CONVERGENCE, AND INCREASING WIND  
SPEEDS WILL ENHANCE OROGRAPHIC EFFECTS ACROSS THE REGION. THESE  
CONDITIONS WILL FAVOR A TOTAL PRECIPITATION MAXIMA OF 15 - 25MM  
WITH A RISK FOR THUNDERSTORMS.  
 
IN TROPICAL SOUTH AMERICA...  
 
IN THE UPPER LEVELS, A FEATURE OF INTEREST IS A POTENT UPPER  
TROUGH THAT HAS AN AXIS AT 17S 45W ON FRIDAY AFTERNOON. ITS AXIS  
IS EXPECTED TO BE AT 20S 54W BY SUNDAY EVENING AND WILL LIKELY  
LOSE ITS DEFINITION THEREAFTER. ELSEWHERE, ONGOING CONVECTION  
ACROSS BOLIVIA WILL BE A CONTRIBUTING FACTOR TO THE FORMATION OF  
THE BOLIVIAN HIGH BY SUNDAY MORNING, WHEN ITS AN AXIS WILL BE  
LOCATED AT 15S 71W. AFTER SUNDAY MORNING, THE INTERACTION BETWEEN  
THESE TWO FEATURES WILL ENHANCE UPPER DIFFLUENCE ACROSS THE NORTH  
- CENTRAL BRASIL, YIELDING TO A TOTAL PRECIPITATION MAXIMA OF 25 -  
50MM FROM SUNDAY MORNING THROUGH MONDAY MORNING.  
 
IN BOLIVIA, A MID - LEVEL TROUGH WILL DEVELOP ACROSS CENTRAL  
BOLIVIA ON FRIDAY AND WEAKEN BY SATURDAY MORNING. ALSO DURING THIS  
PERIOD, EXPECT AN INCREASE IN LOW LEVEL MOISTURE, YIELDING TO A  
TOTAL PRECIPITATION MAXIMA OF 30 - 60MM FROM FRIDAY MORNING  
THROUGH SATURDAY MORNING. MOISTURE CONVERGENCE WILL PERSIST  
THROUGH THE REST OF THE FORECAST CYCLE, HELPING SUSTAIN CONVECTION  
ACROSS THIS REGION.  
 
ANOTHER REGION OF INTEREST IS WEST ECUADOR AND PERU. THE PERIOD OF  
GREATEST PRECIPITATION IMPACT WILL BE FRIDAY MORNING THROUGH  
SATURDAY MORNING. DURING THIS PERIOD, MID - LEVEL WINDS ARE  
EXPECTED TO DECREASE, WHILE THE WESTERLY LOW LEVEL FLOW WILL  
CONTINUE TO FAVOR MOISTURE CONVERGENCE ACROSS THE COAST OF  
ECUADOR. THESE CONDITIONS WILL FAVOR A TOTAL PRECIPITATION MAXIMA  
OF 40 - 80MM DURING THIS PERIOD. STARTING SATURDAY EVENING, EXPECT  
AN INCREASE IN UPPER LEVEL EASTERLY WINDS, WHICH WILL HELP SUSTAIN  
DIFFLUENCE AND SPEED DIVERGENCE ACROSS THE REGION THROUGH MONDAY  
MORNING. A TOTAL PRECIPITATION MAXIMA OF 30 - 60MM IS POSSIBLE  
FROM SATURDAY MORNING THROUGH SUNDAY MORNING. BY SUNDAY MORNING  
THROUGH MONDAY MORNING, MOISTURE CONVERGENCE WILL PREVAIL IN THE  
REGION, HOWEVER, AN INCREASE IN MID LEVEL WIND SPEEDS WILL FAVOR  
AN INCREASE IN SHEAR, THUS YIELDING TO A RELATIVELY LOWER TOTAL  
PRECIPITATION MAXIMA FOR THIS PERIOD.  
 
IN NORTHEAST BRASIL, A SERIES OF LOW LEVEL TROUGHS ACCOMPANIED  
WITH MOISTURE CONVERGENCE WILL CONTINUE TO IMPACT THIS REGION  
THROUGH THE NEXT THREE DAYS. NOTE, UPPER LEVEL DIVERGENCE AND  
DIFFLEUNCE WILL BECOME FAVORABLE FOR SATURDAY MORNING THROUGH  
SUNDAY MORNING. FROM FRIDAY MORNING THROUGH SUNDAY MORNING, A  
DAILY TOTAL PRECIPITATION MAXIMA OF 30 - 60MM IS POSSIBLE.  
 
ELSEWHERE IN TROPICAL SOUTH AMERICA, THE ITCZ, NET, AND SOUTHERN  
ITCZ WILL CONTINUE TO FAVOR DIURNAL CONVECTION. A SERIES OF LOW  
LEVEL TROUGHS WILL PROPAGATE ACROSS THE REGION AND WILL BE  
ACCOMPANIED BY MOISTURE CONVERGENCE, HELPING YIELD TO HIGHER TOTAL  
PRECIPITATION MAXIMA ACROSS THE AMAZON BASIN.  
 
MORALES...(WPC)  
 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.
The Nexlab HPC Page
Main Text Page